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Roxana Tahirih Hemmati, Gareth D Hastings, Lan Chi Nguyen, Jason D Marsack, Raymond A Applegate; Performance of Spherical and Wavefront-Guided Scleral Lenses in Keratoconus. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1277.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of this study is to compare the measured optical performance of a spherical scleral lens (Sph) design and wavefront-guided scleral lens (WFG) design using the metrics of high order root mean square (HORMS) wavefront error and visual Strehl ratio (VSX) compared to age-matched normals over a 5mm pupil.
Wavefront error was measured 3 times using a COAS HD wavefront sensor, scaled to 5mm and averaged on each eye of 4 subjects (8 eyes) with keratoconus (KC) for 3 conditions: 1) with no correction, 2) with a Sph and 3) with a WFG. Average Zernike coefficients for each eye and each condition were then used to calculate both HORMS and logVSX and were compared to age-matched normals.
On average, the Sph reduced HORMS levels by 65% (range: 49% to 88%) compared to the uncorrected eye. Two of the 8 eyes achieved normal levels of HORMS during wear of the Sph. The addition of the WFG correction to the Sph further reduced HORMS allowing at least 1 eye of each subject to reach age-matched normal levels (6 of 8 eyes). When compared to the uncorrected eye, the WFG lens showed an average reduction of 77% in HORMS (range: 70% to 89%). When considering logVSX, only 1 eye in 1 subject reached age-matched normal levels with the Sph. When compared to an uncorrected eye, logVSX improved by an average of 41% (range: 25% to 57%). The addition of the WFG correction to the Sph showed an improvement in all 8 eyes. When compared to an uncorrected eye, logVSX improved by an average of 56% (range: 42% to 69%). Two eyes in 1 subject achieved age-matched optimized levels of logVSX with the WFG lens correction.
Although the Sph reduced levels of HORMS, the additional reduction with the WFG correction allowed typical levels of HORMS to be achieved in the majority of eyes and improved visual image quality as quantified by logVSX. Using a metric like VSX, that has been shown to be predictive of visual performance, may help explain the observation that some subjects with low HORMS continue to experience reduced perceived image quality while wearing either the Sph or WFG lenses.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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