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Sujata Rijal, Gareth D Hastings, Lan Chi Nguyen, Matthew J. Kauffman, Raymond A Applegate, Jason D Marsack; Simulated optical and visual impact of wavefront-guided scleral lens misalignment. Invest. Ophthalmol. Vis. Sci. 2019;60(9):594.
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Scleral lenses tend to exhibit patient-specific inferio-temporal displacement on-eye. The wavefront-guided optics (WGO) in a wavefront-guided scleral lens (WGSL) must be well-aligned to the underlying pupil for maximum visual benefit. The purpose of this study was to simulate the resultant degradation in visual image quality and optical and visual performance when the optics of a WGSL are misaligned.
Residual aberration and decentration data obtained from a previous study including 10 subjects (20 eyes) with corneal ectasia wearing conventional scleral lenses were used to simulate WFO. The mean±SD decentration (mm) x: 0.47±0.15 and y: 0.46±0.29 was used as a common location for placement of WFO for all eyes. A second condition, where the WGO were placed at the geometric center of the lens was also studied. The impact of these purposeful misalignments of the WGO were assessed as change from the aligned position in higher order root mean square (HORMS) wavefront error and the change in the logarithm of the visual strehl ratio (logVSX) over a 5mm pupil. Change in predicted logMAR visual acuity (VA) was calculated from the change in logVSX using an existing model.
The mean ± SD translation (mm) required to shift the WGO from the patient-specific aligned positions to the average misaligned position was x: 0.11±0.10 and y: 0.19±0.13, and the increase in HORMS (um) associated with this shift was 0.08±0.07. The change in logVSX associated with this shift was -0.28±0.22, resulting in a predicted loss in VA of 0.06±0.06 (3 letters). When aligning the WFO to the geometric center of the lens, the increase in HORMS associated with this shift was 0.26 ± 0.18 um. The mean±SD change in logVSX associated with this shift was -0.78±0.42, resulting in a predicted loss in VA of 0.22±0.12 (11 letters). Nine out of 20 (45%) eyes at the mean location and 19 out of 20 (95%) eyes at geometric center had loss in VA of 0.06 (3 letters) or greater. The shift to the geometric center was statistically more deleterious than the shift to the average location for HORMS (p < 0.001) and VA (p <0.001).
Use of the average misalignment or the geometric center of a lens for placement of the WGO are both predicted to, on average, result in a reduction in acuity that is noticeable to an individual. To maximize performance of the WGSL, placement of the WGO should be customized for each eye of each individual.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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