Presentation on theme: "A Review of Orthokeratology Across Three Ophthalmology Practices Introduction Non-surgical corneal reshaping, also known as orthokeratology, has been available."— Presentation transcript:
A Review of Orthokeratology Across Three Ophthalmology Practices Introduction Non-surgical corneal reshaping, also known as orthokeratology, has been available since the 1960’s. Early lenses were made from polymethyl methacrylate (PMMA), a hard plastic with low oxygen permeability or an early gas permeable material. While practiced on a limited basis until the 1980’s, orthokeratology declined in popularity because of limited lens designs and variable refractive results. Materials used to manufacture contact lenses and the introduction of computer lathes that can create sophisticated contact lens shapes have renewed interest in corneal reshaping. These key features along with an increase in oxygen permeability, allow for the manufacturing of reverse geometry designs and the ability to wear these lenses overnight. Modern orthokeratology designs create a flat central corneal zone and a steepening in the mid-periphery allowing for improved centration and increased effectiveness (Figure 1). Space in the mid-periphery created by the steepened curve allows epithelial cell redistribution creating thickening in the mid-periphery and central flattening 1. Corneal reshaping lenses are worn overnight by the patient, allowing the patient to be correction free during his or her waking hours. The Corneal Refractive Therapy (CRT) system used was developed by Paragon Vision Sciences and FDA approved in 2002 2. Bruce Koffler, MD, James Sears, Lance Forstot,MD, Lisa Wohl, MD Figure 1. Fluorescein image of an eye while wearing an orthokeratology lens. Most important is the apparent bulls eye pattern indicative of proper centration.
A Review of Orthokeratology Across Three Ophthalmology Practices Variation Among Different Age Groups A wide range of ages were treated, the youngest patient being 9 years old and the oldest being 59 years old. A total number of 239 eyes were treated of 145 patients. 85% of patients achieved 20/20 and 99% achieved 20/40 (Figure 2). No outcome differences were observed in the various age groups. The youngest patients, best called pre-teen (9-13), 92% and 95% achieve UCVA of 20/20 and 20/25, respectively, one patient failed to improve beyond 20/40. The next age group, adolescents (14-21), 93%, 95% and 100% achieved UCVA’s of 20/20, 20/25, and 20/30, respectively. In young adults (22-37), there are similar results: 88% achieve UCVA 20/20, 98% achieve 20/25, and 100% reach 20/30. Pre-presbyopia patients (38-42) showed slight worse outcomes with 74%, 92%, and 95% achieving UCVA’s of 20/20, 20/25, and 20/30 or better. One patient failed treatment in this group. However, this trend was not continued as patients best characterized as early-presbyopia (43-48) performed slightly better, with 82% achieving UCVA 20/20, 95% achieving UCVA 20/25, and 100% achieving 20/30 or better. Older, presbyopic patients (49-59) achieved similar results as the previous groups with 78%, 94%, and 100% of patients achieving UCVA of 20/20, 20/25, and 20/30 or better. Only two patients across all age ranges failed to achieve UCVA of 20/30 but were successful in continuing with CRT. (Figure 3) Figure 3. Graph that shows the age groups discussed below and the percent of patients that achieved each visual acuity. Each column adds up to be 100% of the patients. Majority of the patients achieved a visual acuity of 20/40 or greater. Bruce Koffler, MD, James Sears, Lance Forstot, MD, Lisa Wohl, MD Figure 2. Percentage of patients achieving a final visual acuity of 20/20 and 20/40 on a Snellen eye chart.
A Review of Orthokeratology Across Three Ophthalmology Practices Final Visual Acuity vs. Severity of Myopia Correction All patients requiring less than 1.0 diopter of correction achieved 20/20 vision, with 60% of this group achieving UCVA of 20/15. In the next group of patients (-1.25 to -2.00), 93% of patients achieved UCVA of 20/20 or better and 99% of the patients achieved UCVA of 20/30 or better. One patient in this group failed to respond to therapy. Increasing the refractive error to moderate myopia (-2.25 to -3.00), there are high levels of success: 80% achieve UVCA 20/20, 97% achieve UCVA 20/25 and 100% achieve 20/30 or better. In the next two groups of increasing moderate myopia (-3.25 to -4.00) and (-4.25 to -5.00), there is a similar outcome: 77% and 71% achieve UCVA of 20/20 and 94% in each group achieve UCVA of 20/25 or better. One hundred percent of both these groups achieve 20/30 or better uncorrected vision. Approaching high myopia (-5.25 to -7.00), the benefit of CRT begins to decline. However, 70% of these patients achieve an uncorrected 20/20 and only 20% fail to achieve UCVA of 20/40 or better. The high myopia group had only 5 patients (10 eyes) enrolled, whereas the other groups had a substantially higher number of participants. The smaller sample size may be responsible for the decrease in efficacy (Table 1). Table 1. Severity of initial myopia vs. the final visual acuity of patients receiving treatment.. Each column in the table adds up to be 100%. The range of myopia for each severity group is at the top and total number in each severity group is at the bottom of the table. Final visual acuity is displayed to the left of the table. Bruce Koffler, MD, James Sears, Lance Forstot, MD, Lisa Wohl, MD
A Review of Orthokeratology Across Three Ophthalmology Practices Conclusion References Yoon, JH, Swarbrick, HA. Posterior Corneal Shape Changes in Myopic Overnight Orthokeratology. Optometry and Vision Science. 2013 Mar; 90(3):196-204 Food and Drug Administration. Summary of Safety and Effectiveness Data of Paragon CRT. Available at: http://www.accessdata.fda.gov/cdrh_docs/pdf/P870024S043b.pdf. Accessibility verified: December 13, 2012. http://www.accessdata.fda.gov/cdrh_docs/pdf/P870024S043b.pdf Special thanks: William E. Meyers, PhD for providing the statistical interpretation of our data http://www.kofflervisiongroup.com/ Bruce Koffler, MD, James Sears, Lance Forstot, MD, Lisa Wohl, MD Corneal refractive therapy was a safe and effective modality for corneal reshaping and flattening. Patients were observed for extended periods of time, up to 4 years, with a mean follow-up of 20 months. Patients achieved results of 20/20 eighty-five percent of the time and 20/40 ninety-nine percent of the time. Younger patients (pre-teens) responded as well as presbyopic patients. No significant adverse events were recorded throughout the study. Emphasis on education and close follow up may have prevented adverse events. All three ophthalmology offices involved, were successful in fitting CRT lenses even though this was their first experience with CRT.