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Geunyoung Yoon, Ramkumar Sabesan, Lynette Johns, Olga Tomashevskaya, Hong-Gam Le, Deborah Jacobs, Perry Rosenthal; Custom Correction of Higher Order Aberration in Keratoconus with a Scleral Lens Prosthetic Device. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1394.
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© ARVO (1962-2015); The Authors (2016-present)
To improve optical and visual performance in keratoconic eyes after correcting the ocular higher order aberration with a scleral lens prosthetic device.
Six patients (11 eyes) with keratoconus who have clear media but advanced cones were recruited for this study. All had been previously fitted with a conventional scleral lens prosthetic device (SLPD) that leaves the considerable amount of the higher order aberration uncorrected. The customized SLPD correcting the residual higher order aberration was designed from decentration and rotation of a conventional SLPD with respect to the pupil center and the aberration measured through a conventional SLPD over a pharmacologically dilated pupil with a custom-developed Shack-Hartmann sensor. A submicron-precision lathe was used to fabricate the designed irregular surface profiles. Visual performance was evaluated for the natural pupil under mesopic light condition by measuring best corrected high contrast tumbling E visual acuity and contrast sensitivity at 4, 8 and 12 c/deg.
Mean ± standard deviation of higher order root-mean-square (HORMS) of the eyes in a SLPD with conventional optics was 1.17 ± 0.57 µm for a 6mm pupil. The most dominant higher order aberration was coma, accounting for 79% of the total higher order aberration. The average magnitude of x and y decentration and rotation of a customized SLPD was 63.4µm, 136.9µm and 6.9 degrees. Most of the higher order aberrations were effectively corrected in a customized SLPD; HORMS was reduced to 0.37 ± 0.19 µm for the same 6 mm pupils. Customized correction resulted in mean improvement of 1.9 Snellen lines. Contrast sensitivity was also improved by a factor of 2.4, 1.8 and 1.4 on average for 4, 8 and 12 c/deg, respectively. Although the magnitude of the residual aberration with a customized SLPD was comparable to that of a normal eye, average logMAR visual acuity of 0.21 (20/32 Snellen acuity) remained abnormal.
A customized scleral lens prosthetic device restored normal level of optical quality to eyes with keratoconus by effectively correcting the higher order aberration. However, visual performance with this correction remained abnormal. We conclude that long-term neural adaptation to poor image quality may limit improvement in vision when measured immediately upon introduction of customized correction.
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