The following studies are provided for patients and parents for references regarding Ortho-K or CRT and myopia treatment:
LORIC (Long Term Ortho-K Research In Children) Pauline Cho showed that axial length increase was 50% in Ortho-K patients compared to the control group in glasses. Although Ortho-K slowed myopia, the effect couldn't be predicted for individuals.
Current Eye Research, 30:71;80, 2005
CLAMP (Contact Lens And Myopia Progression) Jeff Walline studied 59 RGP eyes versus 57 soft lens eyes. There was no difference in axial length growth. RGPs flattened the cornea .5D, while soft lenses steepened it .5D. RGPs slowed progression but only a small amount.
Walline JJ, Jones LA, Mutti DO, and Zanik K: A Randomized Trial of the Effect of Rigid Contact
Lenses on Myopia Progression. Arch Ophthalmol 122: 1760-1766, 2004
COMET (Correction of Myopia Evaluation Trial) Progressive Addition Lenses slowed myopic progression by .13D over five years, an effect considered negligible.
Gwiazda J, Hyman L, Hussein M, Everett D, Norton TT, Kurtz D, Leske MC, Manny R, Marsh-Tootle W, Scheiman M, and the COMET Group: A randomized clinical trial of progressive addition lenses versus single vision lenses on the progression of myopia in children. IOVS 44: 1492-1500, 2003.
CRAYON (Corneal Reshaping and Yearly Observation of Nearsightedness) An update to the LORIC study by Jeff Walline. Ortho-K slows axial growth over the study length of two years. Not yet published. Walline, Jeffrey J., Slowing Myopia Progression with Lenses, Contact Lens Spectrum, June
COOKI (Children's Overnight Orthokeratology Investigation) essentially proved that Ortho-K works overnight for children in the 8-11 year old group.
Invest Ophthalmol Vis Sci 2003;44:
SMART (Stabilization of Myopia through Accelerated Reshaping Technologies) A five year study where after each year of wear the patient is allowed to normalize without wearing their molding lenses after which they start wearing their lenses again. Preliminary results show stability after one year.
CANDY (Controlling Astigmatism and Nearsightedness in Developing Youth) showed myopic progression of -.37D per year in normally corrected myopes and -.03D per year in Ortho-K patients. Patients were allowed to normalize at various times during their Ortho-K wear. The graph below summarizes the data.
Over the 3 year period, children who corrected their vision with glasses and soft contact lenses on average had a 1.5 diopter increase of their myopia. The children who wore the Ortho-k correction had a myopic increase of only .37 diopters over the same 3 year period.
Glasses and soft contact lenses Ortho-k lenses
The last two studies (SMART and CANDY) are attempting to answer the question of whether the stabilization is just a temporary phenomenon that would disappear on cessation of lens wear. It appears that the Ortho-K effect is such that patients regress back to their starting point of Ortho-K wear, not partially regress or even progress to where they might have been if not wearing Ortho-K lenses.
The studies are not definitive. It will be a long time before such data is recognized as clinical fact. But the overwhelming evidence at this time is that Ortho-K is a very good alternative for young myopes.
Title: FDA Study Summary of Safety and Effectiveness, Premarket Approval Application (PMA) Abstract: The main objective of this study was to assess the safety and effectiveness of the Euclid Systems Orthokeratology Contact Lenses in the temporary;reduction of myopia, when worn overnight. This investigation was a multi-center study consisting of 9 investigational sites; which included 14 investigators participating. The study was initiated on;September 21, 1998 and ended on June 2, 2000. There were 191 patients (378 ;eyes) enrolled into the study including 4 monocular subjects. There were; ineligible eyes enrolled but not dispensed lenses. The subjects were at least 18;years old. Clinical investigators and investigational sites were selected in an effort to provide sufficient diversity in geographic access, climate and elevation, and urban and rural living for a resultant study population thaL represents the intended ;population to be treated. The study period was 9 months.
The results of the data provided from this clinical study revealed no major complications or slit lamp findings and 12 adverse events which resolved. Additionally, the results show that 95 % of the eyes completing the study in the core group achieved visual acuity of 20/40 or better at nine months and 99% demonstrated a reduction in pretreatment myopia. As shown in Table 15, the results of the clinical study provide reasonable;assurance of the safety and effectiveness of the device for the subject population, refractive conditions and specified wearing modality.
Title: The SMART Study - Clinical Evaluation of Stablizing Myopia by Accelerated Reshaping Technique
DATE: 5 year study in progress. First year results published January 09
LINK: Not published as study still in progress
Barry Eiden, OD, FAAO, Robert L Davis, OD, FAAO, principle investigators Ed Bennett,OD, FAAO, Cary Herzberg, OD, FAAO Michael Lipson OD, FAAO, LaMar Zigler, OD FAAO Doug Becherer, OD, FAAO Bruce Koffler, MD Rob Gerowitz, OD, FAAO, Lisa Wohl, MD " EyeVis"- Eye & Vision Research Institute: Giving Vision Through Research
Abstract: The use of Orthokeratology for overnight wear raises many questions of safety, efficacy and the effects of myopia stabilization. Orthokeratology or corneal reshaping produces a temporary reduction of myopia by changing the shape (flattening) of the cornea, which is elastic in nature. Flattening the cornea reduces the focusing power of the eye, and if the amount of corneal flattening is properly controlled, it is possible to bring the eye into correct focus and compensate for myopia. Upon removal of the contact lens, the cornea retains its altered shape for a period of time. The global prevalence of myopia is increasing significantly in the school age population. It is estimated that one billion of the six billion people in the world are myopic. (3) Not only is the prevalence increasing but the degree of myopia has also increased. The prevalence of myopia in the United States is estimated to be 25%, in India to be 19% and in the Asian nations the rates of myopia are greater than 75%(1,2,3).
Studies have shown that complications from myopia, such as chorioretinal degeneration and retinal detachment will increase with increasing myopia. The application of corneal reshaping or orthokeratology may potentially stabilize the progressive nature of myopia throughout the adolescent years. Additionally, if wearing corneal reshaping lenses controls the progression of myopia, there also may be a reduction in the rates of adverse effects of advancing myopia. The fact that myopia is on the rise indicates that although the wearing of spectacles clears the vision, it does nothing to control the progression of myopia and its adverse effects.
Conclusions: The initial recruitment phase, fitting statistics, and demographics provide the structure for the five year SMART investigation. Initial dispensing data for corneal reshaping test subjects showed a high first lens success rate to achieve 20/20 unaided acuity. Long term results of this study will provide fitting information, myopia progression comparative data, anatomical differences, and subjective responses to each lens modality. 80.5% of the test group were fit able to use the initial empirically fit lens and did not require a lens change.
Year 1 Interim Results: 138 subjects in the test group and 90 from the control group completed the first year. The findings from the first year showed that overall mean prescription change in control group was almost 0.50 diopters whereas there was no change in the test group. The study continues.
Title: CLAMP Study - To examine the effects of rigid gas permeable contact lenses on the progression of myopia (nearsightedness) in children.
Abstract: Rigid gas permeable (RGP) contact lenses provide clear, comfortable vision with relatively few ocular health risks and are a standard management option for correcting nearsightedness. While RGP contact lenses are used to correct myopic refractive error, they may also slow the progression of myopia. A definitive study that could provide guidance regarding the effects of rigid gas permeable contact lenses on myopia (nearsightedness) progression may define the standard of care for slowing the progression of myopia in young children. An eye care practitioner first reported that hard contact lenses may slow or stop the progression of nearsightedness in 1956. Other anecdotal clinical reports with similar results soon followed. Previous review papers have suggested that rigid contact lenses slow the progression of myopia in children, and several studies have attempted to prove this.
Two studies in the past twenty years have shown that rigid gas permeable contact lenses slow the progression of nearsightedness in children, however both studies failed to provide proper attention to many important variables. While these earlier works produced intriguing results for scientists and clinicians, they contain many problems that challenge the significance of the studies findings. The faults of the previous studies can be summarized in four categories: 1) high losses to follow-up, 2) inadequate control group, 3) incomplete ocular component measurements, and 4) inadequate or poorly selected entry criteria. Positive results in previous studies also failed to exclude alternate possibilities which may explain why rigid gas permeable contact lenses may slow the progression of myopia.
For example, the studies found that rigid contact lenses slow the progression of myopia and that corneal flattening accounts for some of the treatment effect, but none of the studies was able to definitively answer other mechanisms that may slow myopia advancement. A need for a controlled study of rigid contact lenses which measures all of the components that may affect myopia progression still exists. The CLAMP Study examines all of these components and addresses the problems encountered in previous studies. The CLAMP Study uses a run-in period to enroll only children who are able to adapt to rigid contact lens wear into the study. This decreases the number of children who drop-out of the study because they cannot adapt to rigid contact lens wear. Once children show that they are able to wear rigid contact lenses, they are enrolled in the study and randomly assigned to wear rigid gas permeable contact lenses or soft contact lenses. Both groups are then examined each year for three years to determine which group progresses the most in nearsightedness.
Annual examinations include assessment of the children's ability to focus their eyes, their eye glass prescription, detailed maps of the shape and thickness of their corneas, and the curvature of the lens inside the eye. Their eye glass prescription is determined when the children's eyes are dilated. We examined 222 children for eligibility. Out of the 222 children, 148 were eligible to participate in the run-in period. Of the 148 eligible children, 116 (78.5%) were able to adapt to rigid gas permeable contact lens wear. All of the children were examined at The Ohio State University College of Optometry.
the treatment is used on children. The aim of this paper is to provide a comprehensive guide to practitioners to improve their Orthokeratology practice and minimize unnecessary complications. The fundamental requirement for starting Orthokeratology practice is to have proper education in the area and to equip the practice appropriately.
Title: FERRIS STATE STUDY - SEEOMC- Safety and efficacy of overnight Orthokeratology in myopic children
Date: May 2007 Source: www.sciencedirect.com
Renée Mika, O.D., Bruce Morgan, O.D., Michael Cron, O.D., Josh Lotoczky, O.D., and John Pole, O.D., M.S.; Michigan College of Optometry, Ferris State University, Big Rapids, Michigan.
Abstract: BACKGROUND: This prospective case series was conducted to describe the safety and efficacy of ;Orthokeratology with the Emerald Contact Lens for Overnight Orthokeratology; Euclid ;Systems Corporation, Herndon, Virginia) among young myopes. ;METHODS: Twenty subjects (ages 10 to 16) were enrolled in the 6-month pilot study. Subjects were ;empirically with overnight Orthokeratology lenses and evaluated at 1 day, 1 week, 1 month, 2 months, 3 months, and 6 months.
RESULTS: Sixteen subjects completed the study. The mean baseline spherical equivalent refraction SER) was 06 diopters (D) (0.75). The mean SER at 6 months was 0.16 D 0.38). The mean ;baseline uncorrected acuity was 0.78 (0.28) logarithmic minimum angle of esolution (logMAR) equivalent (20/100 Snellen). The mean logMAR equivalent at 6 months was 0.03 0.12 (20/20 Snellen). On average, 40% of eyes showed some type of corneal staining between the 1-week and 6-month visits. No serious adverse events occurred during the study.
Conclusions: In contrast to previously published studies that reported maximum results at 2 weeks,subjects reached maximum reduction in myopia at the 1-week visit and, on average, obtained a 92.2% reduction in spherical equivalent refractive error at 6 months. This pilot study lends to a growing body of evidence that short-term correction of mild to moderate myopia with overnight orthokeratology is safe and ef cacious in children and adolescents. Optometry 2007;78:225-231
Title: Orthokeratology Review and Update
Date: Feb 2006 Source: www.optometrists.asn.au
Helen A Swarbrick PhD School of Optometry and Vision Science, University of New South Wales, Sydney, Australia Clinical Experimetal Optometry
Abstract: Orthokeratology (OK) is a clinical technique that uses specially designed rigid contact lenses to reshape the cornea to temporarily reduce or eliminate refractive error. This article reviews the history of traditional daily-wear OK (1960s to 1980s) and discusses the reasons for the recent resurgence in interest in the new modality of overnight OK, using reverse-geometry lens designs (1990s to the present). The clinical effecacy of the current procedure is examined and outcomes from clinical studies in terms of refractive error change and unaided visual acuity are summarised.
Onset of the effects of overnight OK lens wear is rapid, with most change after the rst night of lens wear and stability of refractive change after seven to 10 days. Mean reductions in myopic refractive error of between 1.75 and 3.33 D and individual reductions of up to 5.00 D have been reported. There appear to be slight reductions or minimal changes in astigmatism with the use of reverse-geometry lenses and most patients are reported to achieve 6/6 unaided vision or better. The induction of higher order aberrations, in particular, spherical aberration, has been reported and this may affect subjective vision under conditions of low contrast and pupil dilation. Patient satisfaction with overnight OK has been reported as similar to or better than with other popular modalities of contact lens wear.
Available evidence suggests that the corneal changes induced by overnight OK are fully reversible. The refractive effect in OK is achieved by central epithelial thinning and this has raised concerns about compromise of the epithelial barrier to microbial infection. Recent reports of microbial keratitis in the modality are reviewed and the overall safety of the procedure is examined critically. Recent research on stromal contributions to the OK effect, particularly relating to overnight oedema, is summarised. Emerging issues in OK, including myopic control, correction of other refractive errors and permanency of the OK effect, are discussed.
Title: Microbial Flora of Tears of Orthokeratology Patients, and Microbial Contamination of Contact Lenses and Contact Lens Accessories.
Date: June 2005
BOOST, MAUREEN V. PhD, FIBMS; CHO, PAULINE PhD, FAAO
Abstract: Purpose. The purpose of this study is to determine if there are changes in the ocular flora of overnight orthokeratology (ortho-k) patients, and the levels of contamination of their lenses and lens accessories, and to correlate compliance with levels of contamination.
Method. Normal ocular flora of 41 subjects was determined twice before commencing ortho-k lens wear by culture of the lower conjunctiva. Further specimens were collected on six follow-up visits after beginning lens wear, as were samples from their lenses, cases, and suction holders. A questionnaire on lens care was administered after the fifth visit. Results. Three subjects provided conjunctival samples yielding Staphylococcus aureus on one occasion before lens wear, one being positive for this organism after beginning lens wear. Of 38 subjects yielding no growth or only normal eye flora before use, 28 remained free of ocular pathogens after beginning lens wear. Only four subjects had positive cultures on more than one occasion after lens wear. There was no significant difference in isolation levels of pathogens with lens wear (p = 0.423) culture of 54% of subjects yielded no growth or normal flora only; lenses of 16 subjects yielded potential pathogens, including three subjects contaminated on more than one occasion. Lens isolates did not match the organisms transiently colonizing the eye. Lens case, the most frequently contaminated item, was associated with lens contamination (p < 0.001), the same organism being isolated from both items in 11 subjects. Lens suction holder was less frequently contaminated.Neither lens case nor suction holder contamination was associated with isolates from the eye. Reported good compliance correlated with lack of contamination in all but one subject. The most frequent breaches in the lens care protocol were failure to clean, disinfect, and replace the lens case.
Conclusion. Ocular flora was not altered by ortho-k lens wear over an extended period, and patients remained free of infection. Contaminants identified were generally of a transient nature.Most patients had significant contamination of at least one item, most frequently the lens case. Lens case isolates were significantly associated with those from the lens. The majority of patients reporting good compliance had low or no contamination of their lenses and accessories. (C) 2005 American Academy of Optometry
Title: COOKI - The Children's Overnight
Orthokeratology Investigation Pilot Study
Date: June 2004
Optometry and Vision Science. Walline , Jeffrey j. OD,Phd, FAAO; RAH, Majorie J. OD, PhD, FAAO; Jones Lisa A. PhD, FAAO Lippincott Williams & Wilkins
Abstract: Purpose. Innovations in contact lens materials and designs allow patients to wear contact lenses during sleep to flatten the cornea and temporarily to reduce myopic refractive error and improve unaided visual acuity. We conducted the Children's Overnight Orthokeratology Investigation (COOKI) pilot study, a case series, to describe the refractive error and visual changes, as well as the slitlamp observations associated with overnight orthokeratology in children, over a period of 6 months.
Methods. Twenty-nine 8- to 11-year-old children with myopia between -0.75 and -5.00 D and <-1.50 D corneal toricity were fitted with corneal refractive therapy contact lenses (Paragon Vision Sciences, Mesa, AZ). They were examined within 1 hour of awakening and about 6 hours later at 1 day, 1 week, 2 weeks, 1 month, 3 months, and 6 months after the first night of contact lens wear. At each visit, the logarithm of the minimum angle of resolution (logMAR) visual acuity, manifest refraction, slitlamp examination, and corneal topography were performed.
Results. Twenty-three subjects completed the 6-month study. Three subjects decided not to wear contact lenses, two did not achieve acceptable fits, and one moved from the area. At the 6-month afternoon visit, the mean +/- SD uncorrected high-contrast visual acuity was +0.08 +/- 0.15 logMAR (Snellen equivalent, 20/24), and the mean +/- SD spherical equivalent refraction was -0.16 +/- 0.66 D. The corneas of three-fifths of the subjects showed mild staining at the morning visit, and one-third of the patients showed mild corneal staining at the afternoon visit. The most common type of stain was central punctate staining. No subjects experienced lasting adverse visual effects from cornea-reshaping contact lens wear during the study period.
Conclusions. Overnight cornea-reshaping contact lenses are efficacious for young myopic patients, and no children experienced a serious adverse event during the study. (C) 2004 American Academy of Optometry
Title: LORIC - The Longitudinal Orthokeratology Research in Children (in Hong Kong: A Pilot Study on Refractive Changes and Myopic Control
Date: July 2004 , Pauline Cho, Sin Wan Cheung and Marion Edwards
Purpose: Myopia is a common ocular disorder, and progression of myopia in children is of increasing concern. Modern overnight orthokera- tology (ortho-k) is effective for myopic reduction and has been claimed to be effective in slowing the progression of myopia (myopic control) in children, although scientific evidence for this has been lacking. This 2 year pilot study was conducted to determine whether ortho-k can effectively reduce and control myopia in children. Methods: We monitored the growth of axial length (AL) and vitreous chamber depth (VCD) in 35 children (7-12 years of age), under- going ortho-k treatment and compared the rates of change with 35 children wearing single-vision spectacles from an earlier study (control). For the ortho-k subjects, we also determined the changes in corneal curvature and the rela- tionships with changes of refractive errors, AL and VCD.
Results: The baseline spherical equivalent refractive errors (SER), the AL, and VCD of the ortho-k and control subjects were not statistically different. All the ortho-k subjects found post-ortho-k unaided vision acceptable in the daytime. The residual SER at the end of the study was -0.18 0.69 D (dioptre) and the reduction (less myopic) in SER was 2.09 1.34 D (all values are mean SD). At the end of 24 months, the increases in AL were 0.29 } 0.27 mm and 0.54 0.27 mm for the ortho-k and control groups, respectively (unpaired t test; p = 0.012); the increases in VCD were 0.23 0.25 mm and 0.48 0.26 mm for the ortho-k and control groups, respectively (p = 0.005). There was signicant initial corneal ;attening in the ortho-k group but no signi;cant relationships were found between changes incorneal power and changes in AL and VCD.
Conclusion: Ortho-k can have both a corrective and preventive/control effect in childhood myopia. However, there are substantial variations in changes in eye length among children and there is no way to predict the effect for individual subjects.
Current Eye Research, 30:71-80, 2005 Copyright:Taylor & Francis Inc. ISSN: 0271-3863 print / 1460-2202 online DOI: 10.1080
Corneal reshaping and myopia progression
J J Walline, L A Jones, L T Sinnott
Accepted 25 February 2009 Published Online First 4 May 2009
Background/aims: Anecdotal evidence indicates that corneal reshaping contact lenses may slow myopia progression in children. The purpose of this investigation is to determine whether corneal reshaping contact lenses slow eye growth.
Methods: Forty subjects were fitted with corneal reshaping contact lenses. All subjects were 8 to 11 years and had between −0.75 D and −4.00 D myopia with less than 1.00 D astigmatism. Subjects were age-matched to a soft contact lens wearer from another myopia control study. A-scan ultrasound was performed at baseline and annually for 2 years.
Results: Twenty-eight of 40 (70%) subjects wore corneal reshaping contact lenses for 2 years. The refractive error and axial length were similar between the two groups at baseline. The corneal reshaping group had an annual rate of change in axial lengths that was significantly less than the soft contact lens wearers (mean difference in annual change = 0.16 mm, p = 0.0004). Vitreous chamber depth experienced similar changes (mean difference in annual change = 0.10 mm, p = 0.006).
Conclusion: Results confirm previous reports of slowed eye growth following corneal reshaping contact lens wear.
Orthokeratology for Controlling Myopia:
Two practitioners obtain results similar to that in the literature for controlling myopia with ortho-k.
By Peter A graduate of the University of Alabama at Birmingham School of Optometry, Dr. Wilcox completed a Primary Care residency at Pennsylvania College of Optometry. He is in private practice in
Hayes, Va. He can be reached at doc@wilcoxeye
A graduate of Illinois College of Optometry, Dr. Bartels is in group practice in Buffalo, N.Y. He can be reached at firstname.lastname@example.org.
E. Wilcox, OD, & David P.F
For more than 30 years, researchers worldwide have
been studying myopia in children and experimenting
with modalities to slow or stop its progression. Some of the tactics employed have been unpredictable and, at times, inconvenient. For example, the use of atropine eye drops is one of the most successful forms of intervention, but the side effects greatly outweigh the outcomes (Gimbel, 1973; Lee et al, 2006). Spectacles with bifocal or progressive lenses have only minimal effect, and they are cumbersome for active children (Paluru et al, 2005; Leung and Brown, 1999). GP lenses worn during the day may slightly reduce myopia progression but at rates that are of limited value to patients (Walline et al, 2004; Katz et al, 2003). More recently, researchers have turned their attention to the potential of orthokeratology to control myopia in children.
Why Ortho-k Shows Promise Patients undergoing overnight orthokeratology,also known as corneal molding and corneal reshaping, wear custom-made GP contact lenses that Bartels, OD reshape the cornea and provide clear unaided vision during the day. What makes ortho-k a promising treatment for childhood myopia? Researchers feel that hyperopic blur in the equatorial and peripheral retina may be a significant stimulus for increased axial length, which results in myopia progression (Hung et al, 1995; Smith et al, 2005).
Smith and colleagues reported exciting findings and provided intriguing images of axial lengthening (Figure 1) in their 2009 study of monkey eyes, designed to determine whether refractive development in primates is mediated by local retinal mechanisms. They reported:
“The main findings of our study were that hemiretinal form deprivation altered refractive development in a regionally selective manner, typically producing myopia in the treated hemifields of infant monkeys, and that these treatment-induced changes in refractive error were associated with local, region-specific alterations in vitreous chamber depth in the treated hemiretina.”
In our opinion, the clinical significance of this study is powerful, suggesting that eyes may become more myopic due to local deprivation of properly focused light. In the case of a myopic eye, conventional spectacles and contact lenses focus light at the fovea with Figure 1. Hemiretinal form deprivation in infant monkey eyes resulted in myopia development in the treated areas. hyperopic defocus in the midperipheral retina. This relative hyperopia may act as a local signal to stimulate axial elongation of the globe. The axial elongation results in a more myopic condition, which, when corrected, recreates the hyperopic midperiphery.
The cycle ensues and the eye continues to become
It could be theorized that a child who becomes myopic may have had a hyperopic peripheral refractive error that caused the eye to lengthen locally and become myopic. The rationale for the uncorrected myopic eye to progress is that the blur in the macula causes the local lengthening to occur in the macula. Studies are underway to explore these theories. Interrupting this blur-lengthening cycle may be a key factor in the myopia stabilization effect attributed to orthokeratology. Following ortho-k treatment for myopia, the typical molded cornea is flattened centrally and remains unchanged outside of the central 7mm or so. The annular zone, located between 5mm and 7mm, must, therefore, be relatively steeper to align with the unaffected cornea outside of the 7mm zone. This steeper zone results in more clearly focused light in the previously hyperopic midperiphery. Thus, the central zone of flattened cornea provides excellent Snellen acuity, and the red ring (Figure 2) may provide stability in the absolute refractive error. The panretinal stimulation of focused light from orthokeratology may slow myopic eye growth, whereas the spherical and/or aspherical focusing from spectacles and traditional daytime contact lenses is linked with progressing refractive errors from advancing axial lengths. These factors have been the impetus for recent studies of ortho-k for myopia control in children.
Promising Initial Study Results
The Longitudinal Orthokeratology Research in Children (LORIC) study (Cho et al, 2005), a two-year pilot study conducted in Hong Kong, suggests
that ortho-k can have a corrective and preventive/ control effect in childhood myopia. The researchers cautioned, however, that predicting the effect for individual patients is impossible because of substantial variations in eye length changes among
In 2007, Walline reported myopia stabilization via ortho-k in the Corneal Reshaping and Yearly Observation of Nearsightedness (CRAYON) two-year results. In a subsequent study, Walline and colleagues (2009) confirmed previous reports of slowed eye growth following corneal reshaping lens wear.
Also in 2007, Eiden and Davis initiated the Stabilization of Myopia by Accelerated Reshaping Technique (SMART) trial, a five-year ortho-k/myopia
control study of 300 children, ages 8 through 14. Interim results are being prepared for publication.
As we followed the literature and read about researchers’ promising results, we began to take a closer look at our own practices, specifically at our young ortho-k patients. Interestingly, we found that our outcomes did more than mirror what the reserchers were reporting. Ortho-k seemed to stop the progression of myopic refractive error in our young patients, although other controlled investigations have reported only a slowing (not stopping) of eye growth and unpredictable results for individuals.
We retrospectively evaluated five patient cases
ages 9 to 15 who were myopic with or without astigmatism for periods ranging from 19 to 62 months. During this period, their myopic/astigmatic spherical equivalent had progressed by 0.46D per year. Their pretreatment spherical refractive errors ranged from –1.00D to –4.25D, and their cylindrical refractive errors ranged from plano to –1.00DC. Before ortho-k lens fitting, the mean spherical equivalent of the 10 eyes was –2.57D. During their 13 to 37 months of
ortho-k wear, these patients either remained in their initial contact lenses or wore duplicate replacements for lost or broken lenses. All five patients achieved 20/20 vision during ortho-k treatment.
We wanted to find out whether there had been any progression in their baseline refractive error. Therefore, we asked them to cease lens wear until their topographies had returned to baseline or for a maximum of 14 days. Because corneal curvature may not return completely to baseline after long-term ortho-k in children (Wu et al, 2009), corneal unmolding was considered complete when patients’ flat simulated K readings were within 0.50D of their pretreatment simulated K readings. A study by Hiraoka and colleagues (2009) confirmed that “the effect of orthokeratology is completely reversible in light of optical quality of the eye and quality of vision as well as refraction and visual acuity.”
During the regression process, we performed noncycloplegic refractions at three- to seven-day intervals until reversal was complete or 14 days had elapsed. The results showed that the patients had essentially returned to their pretreatment refractive error, as the rate of progression of their spherical equivalent refractive error was only 0.03D per year. These are encouraging although anecdotal outcomes, and we are now designing a study to validate them.
Topography is Key to Ortho-k Success Given the promising results of our pilot study, we will continue to recommend our ortho-k for myopia control program (see “Marketing the CANDY
Plan”) and to use the following ortho-k technique.
We fit our ortho-k patients in custom Wave (Wave Contact Lenses) ortho-k lenses. These lenses are software-designed based on topography data, with the Wave Design Software currently optimized for the Keratron family of topographers including the Scout Topographer (EyeQuip), which was used to generate the maps. Before proceeding with contact lens fitting, we educate and inform all patients and parents about theMarketing the CANDY Plan
Reviewing the clinical histories of some of our young orthokeratology patients has not only
provided encouraging information about the use of this modality for stopping myopia progression in children, but it has also spawned a successful new internal marketing tool in our practices. Over the past year, we devised the “Controlling Astigmatism and Nearsightedness in Developing Youth” program, better known as the CANDY Plan.
The CANDY Plan introduces the concept of orthokeratology to patients and parents through posters and displays in the office, as well as through videos that play in the reception area. Simple statements and intriguing questions such as: “Would you like to participate in our CANDY Plan?” and “CANDY is good for your child’s vision. Ask us why!” are designed to start a dialogue, and people frequently inquire about the CANDY Plan.
With the conversation started, we discuss the details of orthokeratology. We present our graphic (Figure 3), which helps condense a lengthy conversation into a few moments of targeted communication. The myopia stabilization aspect of the therapy is always of great interest to parents. We present the concept of myopia and astigmatism stabilization through
ortho-k as a plan, not a guarantee. We have found, however, that most, if not all, of the children who participate in this process in our practices routinely achieve our predicted goals.
Of course, additional education ensues as needed, but the usually lengthy conversation
about an infrequently recognized vision correction and stabilization process is short and sweet—just like candy.
Figure 3. This graph of our case patients shows that in our practices, ortho-k treatment of myopia has successfully controlled the progression of myopia.
associated pros/cons and risks/rewards of ortho-k treatment. Patients/parents sign the appropriate consent forms once they have read and comprehend the process and the variables. We also inform patients/ parents that although the Wave lenses are similar in design and material to FDA-approved lenses, they are in fact used in an off-label manner (although the lenses we use are now approved for overnight wear under FDA guidelines for ortho-k).
Once we decide to pursue orthokeratology, capturing baseline topography is extremely important. Topography data are the foundation for the custom software-designed Wave ortho-k lenses, so patience and thoroughness are imperative for precise image capture. The lens material used for these patients was Boston XO (Bausch + Lomb). Other considerations when designing an accurate ortho-k contact lens include: refractive error, horizontal visible iris diameter, pupil size, pachymetry, tear quality, and interpalpebral fissure opening. We electronically submit the Wave corneal mold design data to the lab’s CN lathe to manufacture each unique contact lens.
At the dispensing visit, we teach patients proper lens care and handling, including how to apply and remove the lenses. After this training, we apply the lenses and measure unaided visual acuities. Then we have patients recline with their eyes closed for 20 to 30 minutes. At the end of that time, we measure visual acuities and assess the fit with both
white light and fluorescein (Figure 4). We then remove the lenses, measure unaided visual acuities and perform topography.
Our patients and their parents have been satisfied with this experience. Any doubt or resistance disappears as the unaided visual acuities improve after lens removal, despite the brief period of closed-eye wear. We’ve had patients with unaided visual acuity of 20/200 read the 20/40 line after this brief wearing time. We then ask patients to initiate nighttime wear. We’ve found that they routinely enjoy great unaided vision after their first night of wear. Repeating the nighttime wearing process provides them with day time non-surgical freedom from glasses and contact lenses. We typically schedule follow-up visits at one week, one month, and six months, scheduling any additional visits as needed.
Many clinicians are familiar with the benefits of orthokeratology for adults. A significant added value of orthokeratology for young patients, which is supported by a growing number of initial studies, is the possible reduced rate of myopic progression. A recent study (Vitale et al, 2009) reported a 66 percent increase in myopia prevalence over a recent 30-year period. These facts address one of the oldest concerns that parents have held for their children: how to keep their eyes from getting worse every year. We may now have an answer. Learn it, promote it, and provide it. CLS For references, please visit www.clspectrum.com/references.asp and click on document #174.
Eye & Contact Lens: Science & Clinical Practice:
doi: 10.1097/ICL.0b013e318298ee76 Article: PDF Onl
Corneal Reshaping Influences Myopic Prescription Stability (CRIMPS): An Analysis of the Effect of Orthokeratology on Childhood Myopic Refractive Stability
Downie, Laura E. B.Optom., Ph.D., F.A.C.O., P.G.Cert.Oc.Ther., Dip.Mus.(Prac), A.Mus.A.; Lowe, Russell B.Sc.Optom., F.A.A.O.
Objective: To determine whether overnight orthokeratology (OK) influences the progression rate of the manifest refractive prescription in myopic children, when compared with an age- and refraction-matched spectacle-wearing control group, over a period up to 8 years.
Methods: The right eyes of control (n=30) and OK (n=26) children were compared. Treatment groups were matched for baseline age and refractive error. At baseline, children were younger than 16 years and showed manifest spherical refractive error more than -0.50 diopters. The minimum period of evaluation for each child was 2 years. Changes to manifest refractive prescription were compared between the groups in 2 yearly intervals up to 8 years.
Results: On the whole, OK eyes showed a significantly (P<0.05) more stable myopic refractive prescription than control eyes over all of the 2-year treatment intervals. A subpopulation (n=18; 64%) of OK eyes demonstrated an apparent total arrest of manifest myopic refractive change. Symmetry in the vertical meridian of baseline corneal topography was associated with a greater degree of refractive stability in OK eyes.
Conclusions: This retrospective study provides evidence that OK can reduce the rate of progression of childhood myopia over the long term. In addition, these findings offer some early insight into a potential indicator that may help predict the extent of refractive stability in individual eyes undergoing OK.
(C) 2013 Lippincott Williams & Wilkins, Inc.
High Myopia-Partial Reduction Ortho-k: A 2-Year Randomized Study
Charm, Jessie; Cho, Pauline
Purpose. To investigate if the combination of partial reduction (PR) orthokeratology (ortho-k) and spectacles for residual refractive errors in the daytime was effective to slow myopic progression in high myopic children.
Methods. High myopic children (aged 8 to 11 years) with spherical equivalent refraction at least -5.75 diopters (D) and myopia -5.00 D or more myopic were recruited and randomly assigned into PR ortho-k and control groups. Subjects in the PR ortho-k group were fitted with custom made four-zone ortho-k lenses with target reduction of 4.00 D for both eyes, and the residual refractive errors were corrected with single-vision spectacles for clear vision in the daytime. Control subjects were fully corrected with single-vision spectacles. Axial length of each eye of all subjects was measured with the IOLMaster at 6-month intervals by a masked examiner. This study was registered at www.clinicaltrial.gov with the identifier NCT00977236.
Results. Fifty-two subjects were recruited and randomized to the PR ortho-k and control groups. Twelve PR ortho-k and 16 control subjects completed the study. Compared with the residual refractive errors at the 1-month visit (after stabilization of ortho-k treatment), the median increase in noncycloplegic residual myopia at the 24-month visit was 0.13 D. In the control group, the median increase in myopia was 1.00 D at the end of the study. The mean +/- SD increases in axial length were 0.19 +/- 0.21 mm in the PR ortho-k group and 0.51 +/- 0.32 mm in the control group (95% confidence interval, -0.55 to -0.12; unpaired t test, p = 0.005).
Conclusions. This single-masked randomized study showed that PR ortho-k effectively slowed myopic progression in high myopes. Axial length elongation was 63% slower in PR ortho-k-treated children compared with children wearing spectacles.
(C) 2013 American Academy of Optometry
An Update on Orthokeratology
New technology and lens designs are expanding the applications for orthokeratology treatment.
By Cary M. Herzberg, OD, FOAA Issue: March 2010
This first decade of the new millennium could well be described as a decade of medical technological breakthroughs. Like the medical field in general, orthokeratology (or corneal reshaping) has seen its share of advances. Ten years ago many of us could not have anticipated all that would emerge as the modern practice of ortho-k progressed. Indeed, the process and tools that make up corneal reshaping today hardly resemble what I used in my ortho-k practice just a quarter of a century ago.
It is not my purpose to endorse a particular ortho-k fitting style or lens design. It is also not feasible to cover all of the many different designs and their variations. In addition, please note that I will review many new areas of corneal reshaping practice in this article, some of which are not approved by the U.S. Food and Drug Administration. For example, utilizing corneal reshaping in correcting high myopia (>6.00D) would be considered an “off-label” use.
Safety and Efficacy
Practitioners and patients alike want the answer to one question in particular. How do we determine whether corneal reshaping is safe? Media coverage, clinical studies, and scientific papers can be a good place to initiate this process.
Reports have surfaced periodically in the media concerning incidents of microbial keratitis (MK) with ortho-k use. These reports primarily pertained to children in Asia and, unfortunately, some of these cases resulted in vision loss. A review of the literature failed to determine whether these children were actually fit by practitioners with ortho-k lenses. Questions were also raised pertaining to poor lens hygiene and lack of regulation of the modality (Jacobson, 2005). Furthermore, the preponderance of reported MK cases (69 percent) occurred around 2001, and a large segment of all of the reported cases (38 percent) were due to Acanthamoeba (Watt and Swarbrick, 2008).
A number of studies have been conducted that address the safety of orthokeratology including the Children's Overnight Orthokeratology Investigation (COOKI, Walline, 2008), Longitudinal Orthokeratology Research in Children (LORIC, Cho et al, 2005), Corneal Reshaping And Yearly Observation Of Nearsightedness (CRAYON, Walline, 2008), Stabilizing Myopia by Accelerating Reshaping Technique (SMART, Eiden et al, 2009), Overnight Corneal Reshaping (OCR, Lipson, 2009), and a study conducted at The Ohio State University (Bullimore, 2009). Each of these studies suggests that under controlled circumstances, ortho-k is safe. The results from the COOKI and CRAYON studies have concluded that 75 percent of children are capable of wearing corneal reshaping lenses. The SMART study is ongoing and will provide results for children ages 7 to 14 wearing ortho-k lenses for a five-year period.
The Ohio State study found that “the risk of MK with overnight reshaping lenses is similar to other overnight modalities” (Bullimore, 2009). The researchers obtained data from 86 randomly selected practitioners and 1,317 patients fitted during 2005 and 2006. The patients contributed 2,593 patient years of wear divided almost evenly between adults (49 percent) and children. Fifty event forms were submitted with 11 reporting corneal infiltrates. Two of these were MK, resulting in an estimated incidence of 7.7 per 10,000 years of wear. What does this all mean? That in all likelihood your corneal reshaping patients have a slightly higher risk of developing MK than your daily wear soft contact lens wearers do. Also, the risk of MK in ortho-k wearers may be as high as that for silicone hydrogel lenses worn overnight (Schein, 2005). Additional studies are needed to more completely address this issue.
When it comes to corneal reshaping safety, scientists commonly study corneal compromise during ortho-k lens wear. Does ortho-k compromise the epithelial barrier function and predispose the cornea to MK? Choo et al (2008) at the Institute for Eye Research set out to determine this by soaking ortho-k lenses in high concentrations of Pseudomonas aeruginosa and then placing them on cats' eyes for overnight wear. Pseudomonas aeruginosa is thought to be the leading causative organism (38 percent) in ortho-k infections worldwide (Watt and Swarbrick, 2008). The results of the study supported evidence that in cat eyes, ortho-k designs worn overnight do not compromise the epithelial barrier of the cornea.
Does the design of ortho-k lenses combined with overnight wear somehow make the lenses more susceptible to bacterial binding, which can lead to corneal compromise? Results so far from one study have shown that bacterial binding to ortho-k lenses had minimal short-term effects (Swarbrick, 2008).
The safety and efficacy of corneal reshaping will continue to be a hot topic in the years ahead. The many reports that have appeared in the media headlines have pertained primarily to “old” news and may reflect the lack of ortho-k knowledge and care in Asia 10 years ago rather than any unusual risks associated with corneal reshaping compared to other contact lens modalities.
Reports do continue to surface of MK incidence and corneal reshaping, requiring all of our due diligence. The eye health of your patients is your responsibility, making it mandatory that you seek to remain current in the practice of corneal reshaping. There are simple steps you can follow to maintain the health and safety of your ortho-k wearers' eyes. These include careful fitting of the ortho-k lenses, using a corneal topographer (essential in monitoring and troubleshooting), educating patients to not use tap water on their lenses and to replace lens cases monthly, patient compliance through education, and continuing with regular aftercare (Swarbrick, 2008).
What Happens to the Cornea During Ortho-k?
With the success of ortho-k, even for high myopes, questions arise regarding how such changes can be accomplished with movement of the corneal epithelium alone. Many studies have been conducted to attempt to explain the corneal changes that occur in ortho-k. A popular explanation for myopic refractive changes is that they result from movement of the corneal epithelium away from the center of the cornea and towards the periphery. With the corneal epithelial layer measuring approximately 50 microns, correcting myopia greater than 6.00D is mathematically not possible with epithelial thinning alone because an approximate 7 to 8 micron change in the epithelial depth accounts for approximately 1.00D of refractive change. So if the central epithelium alone were responsible for the refractive change, then correcting 7.00D of myopia with corneal reshaping would cause changes into the stroma (Berke, 2009).
Many theories have been presented to explain the changes in corneal tissue that result in the refractive changes in ortho-k. They attempt to explain corneal tissue changes as a result of epithelial cell compression, central thinning versus midperipheral thickening, midperipheral hyperplasia, increased cell retention, or decreased epithelial sloughing. So what exactly are we changing in the cornea itself that produces the ortho-k effect? Results from studies performed by Berke and colleagues may surprise you. Berke (2009) suggests that the central epithelial cells do not compress, thin, or migrate. “It appears as though the paracentral region thickens thus flattening the central cornea undergoing corneal reshaping. The induced minus lens sits on top of the pre-existing cornea, not embedded within it. The paracentral thickening appears to be essentially stromal hypertrophy rather than epithelial.” This new theory may well lead to many new lens designs including perhaps an optimum one. While this theory is a possibility, Cheah et al (2008) report that the changes are due to epithelial cell compression in the central cornea, so this issue needs to be further investigated.
Myopia Progression and Ortho-k
The National Eye Institute has just released new data on myopia which is sure to be of interest to even the most conservative practitioners. A current NIH study reported that in individuals aged 12 to 54, the frequency of myopia increased from 25 percent in 1972 to 41.6 percent in the five-year period studied (1999 to 2004). The study included people who had myopia ranging from mild to severe (Roan, 2009).
Reim and colleagues (2003) first reported the potential for myopia control with ortho-k lenses in a retrospective study reporting that patients corrected with corneal reshaping experienced about a 60-percent reduction in myopia progression. The LORIC study was conducted in Asia and reported a much slower rate of myopia progression and axial elongation (47 percent) among young progressive myopes who underwent corneal reshaping compared to those who wore eyeglasses. The CRAYON study also found lower rates of myopia progression and axial elongation (57 percent). Both the LORIC and CRAYON studies were small in scale, involving fewer then 40 subjects. The SMART study, a large-scale (300 subject), five-year, longitudinal multicenter evaluation of the effectiveness of corneal reshaping for young progressive myopes, is now underway.
Image Shells and Ortho-k: Preventive Care With the discovery of the phenomenon of form deprivation myopia, research has demonstrated that ocular growth and refractive development are regulated by visual feedback associated with the eye's refractive status. The conclusions of Dr. Earl Smith and colleagues (2009) point to the peripheral retina in primates as being more influential for controlling eye growth than previously thought possible. When susceptible visual systems are corrected with myopic lenses, it creates an image shell described as a positive curvature of field. These visual systems, while being corrected centrally, suffer from a relative hyperopia peripherally that causes conflicting visual stimulus. The result is elongation of the eye to correct the peripheral hyperopia. If, however, the peripheral retina is experiencing a relative myopia effect (negative curvature of field), then elongation may slow. The measurement of this discrepancy between peripheral and central retina is performed via peripheral refraction (Mutti, 2007).
Unlike conventional methods of correcting myopia such as glasses or regular contact lenses, myopia-correcting corneal reshaping lenses create a negative image shell on the retina of a treated patient (Figure 1). It is not yet apparent what ortho-k design is optimal to accomplish the best image shell. It may also be possible to track changes in peripheral refraction through corneal topography. Future research will include the optimization of orthokeratology to correct peripheral refractive error and the development of testing equipment that can measure a patient's susceptibility to develop myopia based on peripheral refraction (Mutti, 2007). This could lead to early treatment with corneal reshaping of those patients most susceptible to axial elongation of the eye (Cross, 2008). It is with great optimism that I look forward to a future of improved, efficient, and efficacious delivery of corneal reshaping products to solve our patients' corneal and refractive conditions.
Figure 1. Negative image shell post-orthokeratology treatment.
Getting Started With Ortho-k
The FDA has approved ortho-k for the treatment of up to 6.00D of myopia correction. With the advancement in computer driven lathing systems that have a tolerance of 0.0001mm, incredible accuracy is now available. With the advent of no polish blends, this accuracy and repeatability have risen to levels never before seen. This has allowed for advanced computer programs with data collected over thousands of fits to design for best results.
Today, even a novice ortho-k practitioner can attain success rates that were previously achieved only by contact lens design experts. Supplying keratometry values, manifest refraction, horizontal visible iris diameter (HVID), and, in some cases, corneal eccentricity values are all that is needed to successfully fit a low-to-moderate myope. Early results from the SMART study using the Euclid Emerald ortho-k lens indicated a first-fit success rate of 80.5 percent. In addition, the researchers reported a 95-percent success rate with only one additional lens fit. Very effective empirically fit designs are available throughout the industry that require only keratometry values, manifest refraction, and HVID values including lenses from Bausch + Lomb's Vision Shaping Treatment (Contex, DreamLens, Euclid, Wave), Paragon Vision Sciences (Paragon CRT), and Global OK (GOV).
If at first you don't succeed, laboratories have extremely competent consultants to answer questions and troubleshoot any problems that you may have. But sometimes even they need the ‘expert.’ As an example, TruForm Optics will ask Dr. Tom Reim, who designed the DreamLens, to consult with them on challenging cases.
Practitioners can now use the SureFit (Paragon) dispensing system to provide increased initial fitting success rates by utilizing a multiple (three) diagnostic lens pack. The lenses are chosen based on data from thousands of successful lens fit outcomes. This system can help reduce chair time and patient adaptation during the initial wearing schedule. Diagnostic sets can also offer added convenience and instant gratification with a greater range and availability of lens parameters. You can order small, medium, or large sets ranging from 10 to more than 100 lenses designed either by the laboratory or by you. With powerful computer-driven programs such as OrthoTools (www.orthotools.com), an optimum fitting set may be designed based on a number of factors including corneal eccentricity and optimum tear film thickness. The data can be integrated with diagnostic lens fitting to achieve a best fit lens design.
Using Topography Software to Design Ortho-k Lenses
Paralleling the meteoric rise in lathing technology have been advancements in topographical analysis of the cornea. Modern topographers have reached a level of acceptable accuracy and repeatability. The limitations on acquiring good topography images have more to do with the operator maintaining focus and alignment during their acquisition.
While topographer designs have improved in this regard, the greatest advances have come from topography software (Dave, 2008). Powerful computer programs can now analyze topographical maps to design corneal reshaping lenses. This computer design process can also involve a small fitting set of lenses to facilitate the outcome.
The topography-based software from BE Vision Shaping Treatment (B+L) chooses the first lens, and patients return after wearing the lenses overnight to determine how close the “bulls-eye” pattern is to optimum. The best bulls-eye results may come from the initial trial lens or from a new lens selected by the program from the fitting set. Another popular program from Wave Contact Lenses is a CAD/CAM system that integrates several features working together for optimum outcomes. Along with corneal topography, one program is used to manipulate design features, then another software program is used to send the design features as a numerical file to a CNC lathe. This allows you to custom design a patient's ortho-k lens to meet the data supplied through the topography in a precise and accurate manner.
High Myopia No Longer Out of Reach
Progressive myopia is on the rise and is causing a greater incidence of severe myopia. With this demand have come new corneal reshaping designs and philosophies including five-curve lenses, double reverse curves and dual geometric (DG) designs (Figure 2). Performing corneal reshaping safely and effectively beyond 5.00D of myopia with good all-day vision requires more manipulation of the corneal surface. That may mean a design that not only induces central flattening but also creates midperipheral thickening to sustain the visual outcome.
Figure 2. Bulls-eye corneal topography of a −10.75D myopic patient who achieved 20/15 unaided vision with orthokeratology.
In addition to enhanced lens designs, high myopes may also require additional lens fittings during the treatment phase for optimum results. It should be emphasized that corneal reshaping on prescriptions beyond 6.00D will result in much smaller treatment zones (Munnerlyn's Formula). This may result in night vision problems. Inform your patients of any possible complications that may result from corneal reshaping before you begin treatment. This should include any night vision problems that may result from glare or flare due to small treatment zones.
Presbyopic Corneal Molding
Corneal reshaping specialists have a secret weapon when it comes to correcting presbyopia. Due to a pinhole effect created by the corneal reshaping process, wearers who are early-to-moderate presbyopes can often still see adequately during close work. In the past, to supplement this effect, orthokeratologists could under-correct the non-dominant eye and create a monovision effect. Today, progressive molding designs offer more options.
One design was born from past experiences of fitting lenses too flat and creating superior decentration. This positioning, combined with central flattening, would create an inferior steep crescent or ‘smiley face.’ Patients gazing down through the steepened zone would experience a bifocal effect. To utilize this concept without the need for lens decentration, an additional aspheric zone was added to a traditional myopic design. This procedure flattens the central cornea for improved distance vision, but it also steepens the paracentral cornea, thereby creating a built-in bifocal or multifocal zone right on the cornea (Figure 3).
COURTESY OF PATRICK J. CAROLINE, FAAO
Figure 3. OK Multifocal (Contex).
Another design offers options such as a central reading button with a relatively flat outer ‘plateau’ zone that reshapes the cornea into an annular zone for distance vision. This design (Global OK) centers well due to an aspheric alignment zone. These designs have brought a whole new area of focus to corneal reshaping practice.
Correcting Astigmatism With Ortho-k
The model of forces acting in ortho-k makes it difficult to fully correct high levels of “bowtie” with-the-rule astigmatism. In fact, limbus-to-limbus astigmatism has been one of the few contraindications to ortho-k treatment (Mountford, 2004).
But how times have changed! New lathe technologies and powerful computer programs make it possible to customize lenses like never before. Need a toric alignment curve or an oval pupil in response to corneal astigmatism? Many designs now offer these options and more to solve challenging astigmatism fits. Going further, we now have available the Paragon CRT Dual Axis design (Paragon), a later-generation lens based on the original design that maintains its profile with the return zone depth (RZD) and landing zone angle (LZA) over 360 degrees. The Dual Axis, while not a true toric design, has two separate RZDs and perhaps two different LZAs 90 degrees apart (Figures 4 and 5).
COURTESY OF PATRICK J. CAROLINE, FAAO
Figure 4. Fluorescein pattern of a standard spherical Paragon CRT lens and of a Paragon CRT Dual Axis lens on a toric cornea.
Figure 5. Dual Axis design patient topography.
Ortho-k for Hyperopia
Some of the most effective early designs for ortho-k correction were products of aspheric technology. Posterior-aspheric designs of 0.8 eccentricity or greater commonly found in rigid lenses designed for correcting presbyopia generated significant reading adds, particularly on steep corneas. A negative side effect of such designs was central corneal steepening, which caused a myopic shift in the prescription.
This is the case with hyperopic ortho-k. A steeper central cornea is created by gently and precisely squeezing the midperipheral cornea. These designs are 100 percent aspheric while providing adequate tear exchange. They tend to work more slowly when compared to myopic ortho-k. A good lens fit must exhibit central clearance over the optical zone and progress to midperipheral touch while maintaining adequate edge lift. Like all ortho-k lenses, such a design must center well.
Another alternative is to adapt a Paragon CRT design. Lens selection is similar as that for myopic correction, but the sagittal depth of the RZD is reduced by 50 microns while maintaining the same landing angle. The base curve radius and power are adjusted to create the desired steepness in the central cornea.
Several designs or systems are available that can effectively correct up to 3.00D of hyperopia (Figures 6 to 8). It is now possible to even design a hyperopic progressive molding lens. How about a dual geometric bifocal design? The Global OK lens features a steep-flat-steep-flat design from the center to the periphery. It has central steepening for distance vision and a relatively flat outer plateau second zone. Aspheric curves can fine-tune the fit.
Figure 6. Dual Geometric Design (Global OK).
COURTESY OF PATRICK J. CAROLINE, FAAO
Figure 7. Hyperopic Multifocal Design (Contex).
Figure 8. Corneal topography of hyperopic molding.
Corneal Rehabilitation Post-LASIK and for Keratoconus
With the increasing popularity of Laser-Assisted In Situ Keratomileusis (LASIK) vision correction, the number of potential patients needing solutions to less-than-optimal outcomes is likewise increasing exponentially. This need has created specialty practices in corneal rehabilitation of post-surgical corneas. Ortho-k fitting of such corneas is a natural extension of these practices (Williams, 2006) (Figure 9). In fact, ortho-k fitting is preferable to enhancements in part because these corneas are already thinner as a result of the original LASIK surgery. The added incentive for these patients is the freedom from wearing correction during waking hours that ortho-k can provide, especially after they have already made a significant investment to gain freedom from contact lenses or glasses.
Figure 9. Topography of post-PK ectasia treated with Paragon CRT.
Typically a conventional ortho-k design is successful, but modifications such as increased treatment zone sizes can be beneficial for night vision issues. As with most ortho-k fits, one of the key factors is selecting the appropriate overall lens diameter. Because of the oblate surface that is being treated, the best results will occur when the overall lens diameter covers about 90 percent of the cornea. If you have the pre-surgical keratometry readings and manifest refraction, you can select the best-fitting lens as if the patient had never undergone LASIK. If those findings are not available, diagnostic lenses will usually resolve any questions.
Not long ago, keratoconus was on the list of absolute contraindications for corneal reshaping (Mountford, 2004). Today, fascinating results are being attained in correcting mild-to-moderate keratoconus with ortho-k (Yamada et al, 2005). A study sponsored by Hadassah Medical Organization is exploring the safety and efficacy of treating moderate keratoconus with ortho-k lenses (Landau, 2008).
Keratoconus has its own set of unique characteristics when it comes to corneal molding. The exact apical curvature of the cone and how far it's decentered from the geometric center of the eye are very important. Another challenge is to determine the best alignment curve for the ortho-k lens, which can typically be performed using accurate corneal topography. If the moderate cone has caused extensive corneal distortion, diagnostic fitting for the best alignment curve may be necessary. As in post-LASIK rehabilitation, it is important to have the optimum overall diameter, for which an accurate measurement of HVID is required. Determine the final base curve radius and power through diagnostic fitting. Often your most valuable tools in fitting keratoconus with ortho-k is accurate corneal topography and an ortho-k diagnostic set (Figure 10).
Figure 10. Bulls-eye fluorescein pattern in keratoconus (Global OK design).
A Tale of Two Countries: A Global View
China and the Netherlands appear, in general, to have little in common. When it comes to ortho-k, however, the world's most populous country may have taken some lessons from one of the smallest. The Netherlands model is a working success story for corneal reshaping. It certainly helps that the Netherlands is home to a number of ortho-k innovations and that practitioners from there have a history of fitting a high percentage of their patients with GP lenses. Ortho-k had its roots in the United States, but came to the European continent and to the Netherlands in 2003. In the Netherlands, right from the start the perception was that ortho-k fitters needed training and that no practitioner should fit these lenses without a corneal topographer (Beerten, 2004). In fact, the systems that came forth (NKL, Procornea) were topography-based. A fitter would submit refractive and corneal topography data from which lenses were designed.
The most likely candidate for ortho-k in the Netherlands is a young adult, and 6 percent of all contact lenses fit in the Netherlands are for ortho-k (van der Worp, 2008).
China, conversely, had a slightly different experience. China's ortho-k community is a small but dedicated group of researchers, educators, and practitioners who—until recently—were based mostly in Hong Kong. China banned ortho-k after citing the dangers posed to the population from an unregulated and unsupervised industry. This ban lasted until 2007 when the Chinese government approved an ortho-k design for overnight wear.
These were some hard lessons for the most populous country in the world. The lack of regulation and training was a disaster for all concerned. More recently, steps have been taken to emphasize education, training, and tighter regulation with regard to ortho-k.
With more than a 70-percent frequency of myopia among elementary age children in China, the driving force behind ortho-k implementation is myopia control (Fan, 2004). Also impacting ortho-k is a change in demographics in China over the last 10 years. Unlike a decade ago when there were almost no private hospitals or clinics, today they play a much more important role in the healthcare delivery system.
New Ortho-k Applications
New areas of research in myopic ortho-k involve semi-scleral ortho-k designs and the use of soft contact lenses for corneal reshaping (Caroline, 2008). I presented a paper at the 2004 Global Orthokeratology Symposium on using corneal-scleral lenses with ortho-k (Herzberg, 2004) (Figure 11). I still have well over 100 patients wearing the lenses successfully. At the time I used the Macrolens (C&H Contact Lens) mini-scleral design, which ranges in overall diameter from 13.6mm to 15.3mm. Mini-scleral lens designs are a very safe and useful medium for ortho-k correction, and they almost always create a well-centered treatment zone.
Figure 11. Corneal-scleral lens design.
The discovery of improved vision in high myopes who had mistakenly worn Night & Day (Ciba Vision) silicone hydrogel lenses everted for extended periods of time has led to new research in this area. The flexure of these materials appears to be optimum for reshaping the cornea. Currently, the total maximum correction is about 2.00D with new designs on the way (Caroline, 2009). This may offer an alternative for low myopes who have a problem with the initial lens awareness of rigid corneal reshaping lens designs.
Future Applications: Crosslinking
When we look back at the first decade of our millennium, we may conclude that it was the time when the promise of genetic engineering and smart drug delivery systems started becoming a reality. Although not quite as much of a paradigm shift, orthokeratology has its own great story to tell. With corneal crosslinking we are on the doorstep of a great new era in corneal reshaping. Crosslinking is a process that improves corneal rigidity by increasing the chemical bonds between the collagen fibers. It is a physiological procedure that causes the corneal stroma to become less flexible, thus making it stiffer by increasing the biomechanical strength of its tissue structure. It shows great promise in reducing the need for enhancement procedures following LASIK. It can control the progression of ectasia in keratoconus. It can prolong the correction achieved by corneal molding.
One way to crosslink the cornea is to add a photo-reactive reagent to the stroma and “cure” it with ultraviolet A light. Early results have concluded that the procedure is safe, with some patients showing a reduced dependence on wearing corneal reshaping lenses (El Hage, 2009). Another way is to use decorin (Stableyz, Euclid Systems) as a natural cross-linking molecule. Preliminary results are very encouraging with several patients not having to wear their moldings after the initial treatment for up to a year. The product will be taken to the FDA with a request to initiate clinical trials in the United States in 2010.
Sharing an Exciting Future
Today's eyecare practices face many challenges as they strive to grow into the new decade. The economic downturn is causing many of our patients to delay eyecare decisions or to seek cost cutting alternatives to eyecare services and products.
Corneal reshaping is an area that offers an incredible growth opportunity for practice. With a well thought out internal marketing program accompanied by staff and practitioner training, a practice can reasonably and quickly “turn on” their existing patient base to corneal reshaping.
The Orthokeratology Academy of America's (www.okglobal.org) annual education meeting will take place Oct. 20 to 24, 2010 near Chicago and offers a comprehensive program for practitioners and staff entirely on corneal reshaping. Included in the program is an all-day “boot-camp” for first-time or inexperienced ortho-k fitters.
With the emergence of the ortho-k specialty and all of the ways you can utilize its many applications, you have many new and innovative answers to the challenging marketplace we all live in. The question is, will you take the time to educate your patients about the benefits of corneal reshaping or potentially lose out on its exciting future because they hear about it somewhere else? The choice is yours. CLS
I would like to thank Dr. Bruce Williams (Seattle, WA), Jonathan Jacobson (Menicon), Marcel Kopito (Bausch + Lomb), Steven Ernst (Contex), Dr. Tung Hsiao-Ching (Global OK), PM Hawkins (Paragon Vision Sciences), Dr. Bruce H. DeWoolfson (Euclid Systems), Dr. Mark Bullimore (The Ohio State University), and Joann Simonsen (Euclid Systems) for taking time away from their busy schedules to provide information and support for this article.
For references, please visit www.clspectrum.com/references.asp and click on document #172
Respectively in Contact Lens & Anterior Eye and in Optometry & Vision Science, the experimental design and 2-year follow up results were presented of a study investigating whether the combination of partial reduction orthokeratology with spectacles for residual refractive errors was effective to slow myopia progression. High myopic children (aged 8 to 11 years) with spherical equivalent refraction of at least -5.75D were recruited and randomly assigned into a partial reduction orthokeratology group and a control group. Subjects in the partial reduction orthokeratology group were fitted with custom-made four-zone ortho-k lenses with target reduction of 4.00D. This single-masked randomized study showed that partial reduction orthokeratology effectively slowed myopia progression in the high myopes participating in the study. Axial length elongation was 63% slower in partial reduction orthokeratology-treated children compared with children wearing spectacles.
For more information or shedule for a Ortho-K and CRT evaluation, please call 781-676-2020 for Lexington (MA) office or 603-8988252 for Salem (NH) office.