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Jason Marsack, Chi Nguyen, Darren Koenig, Anita Ticak, James Elswick, Raymond Applegate; Visual Performance and Residual Aberration in Keratoconus Subjects Wearing Custom Scleral Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5466.
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© ARVO (1962-2015); The Authors (2016-present)
After decades of being all but obsolete, scleral contact lenses (SCLs) are re-emerging and being applied to vision correction in the eye disease keratoconus (KC). These lenses replace the aberrated first refracting surface of the KC eye and reduce high-order aberration (HOA) through an index-matching tear lens. However, reduction of HOA is not complete. The rigid, stable nature of scleral contact lenses makes them ideal for customization with wavefront-guided optics to target the residual HOA specific to an individual patient.
Six eyes of three subjects have completed data collection and data analysis to date. Each eye was fit with a predicate scleral contact lens from a custom scleral lens fitting set. For each eye, the fitting process identified a predicate lens design that provided acceptable corneal vault, limbal clearance and blood flow at the margin of the scleral lens, consistent with current clinical paradigms. Using the parameters for the predicate lens as a baseline, two additional lenses were designed and built for each eye: a scleral contact lens designed to correct low-order aberration (loSCL) and a wavefront-guided scleral contact lens (wfSCL) designed to correct both low-order and high-order aberration. Each scleral lens was allowed to settle on the eye for a minimum of 30 minutes. Residual ocular aberration through the 10th radial order and logMAR visual acuity (scored to the letter) were recorded for each lens tested.
Of the 6 eyes enrolled in the study, 4 continued to exhibit HORMS at levels above an age-matched mean during loSCL wear. During wfSCL 6 of 6 eyes achieved HORMS levels below an age-matched mean. Mean change in HORMS was from 0.372±0.128µm with loSCL wear to 0.152±0.049µm with wfSCL wear (57% reduction). Acute logMAR visual acuity in these eyes improved by 7 letters or more in 3 eyes.
While traditional low-order aberration compensating scleral lenses reduce HOA compared to the uncorrected condition, they, like gas permeable corneal lenses, can leave behind levels of HOA that exceed normal levels. Targeted HOA compensation provides a mechanism to further reduce HOA in KC eyes. Acute gain in visual performance is subject-dependent. The literature suggests further improvement in visual performance with adaptation to the better images.
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