Abstract
Purpose :
Recent evidence shows that in addition to providing a refractive correction for myopia, orthokeratology/Corneal Refractive Therapy (CRT) also acts to slow myopia progression. Understanding where CRT lenses are positioned on-eye, relative to the primary line of sight (pupil center) may help understand treatment effectiveness. It is not possible to measure lens position during overnight wear due to lid closure, however refractive change maps can identify the corneal treatment zone location created by lens position during overnight treatment. The current project evaluates CRT lens decentration on first-time wearers following 1 day, 1, 2 and 4 weeks of nightly treatment.
Methods :
Aberrometry data from both eyes of 10 participants was collected following lens removal along the primary line of sight with monocular, distance fixation in a dark room (< 3 cd/m2). All eyes were randomized to wear Paragon CRT lenses (paflufocon B, CooperVision) of either 5- or 6-mm optical zone diameters, one lens design in each eye. Manufacturer’s fitting guide was followed to determine lens parameters. Custom software was used to calculate refractive state maps from which treatment zone centration was measured.
Results :
Participants (7 Asian) were 22-30 years old, (average±stdev 24.5±2.1years) with spherical equivalent of -2.44±1.54D. Following 1 night of wear, corneal treatment zones centered well inferiorly (-0.14±0.21mm) and temporally (-0.07±0.20mm). Following 1 week of nightly lens wear, CRT lenses remained in similar positions as seen at 1 day, inferiorly (-0.10±0.17mm) and temporally (-0.18±0.15mm). Lens positions similar to 1 day were also seen following 2 and 4 weeks of nightly lens wear (2 weeks: -0.12±0.16mm inferior and -0.21±0.15mm temporal; 4 weeks: -0.11±0.13mm inferior and -0.19±0.16mm temporal). No significant difference was found in treatment zone centration between lenses with 5 or 6mm back optic zone diameter.
Conclusions :
During initial lens fitting clinicians aim to fit CRT lenses so they center well relative to the cornea. Refractive state maps derived from aberrometry data confirm that the CRT treatment zones also generally centered well on the pupil following 1 night of closed-eye lens wear, and treatment patterns remain stable over 4 weeks of nightly lens wear. These results confirm that clinical procedures to achieve lens-cornea centration with open eyelids, achieve central corneal flattening relative to the pupil center.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.