Prediction of the small aperture intraocular lens on visual acuity in patients with keratoconus

Abstract

Purpose: To investigate the impact of corneal higher-order aberrations (HOAs) on predicted corrected distance visual acuity (CDVA) in patients with keratoconus at varying simulated pupil apertures. Setting: Ophthalmology Clinics, Medical University of South Carolina, Charleston, South Carolina. Design: Retrospective chart review study. Methods: 56 eyes with keratoconus were examined using Scheimpflug tomography during routine examinations before medical intervention. The severity of keratoconus was graded using the Amsler-Krumeich classification. Zernike analysis was used to obtain corneal aberrations using simulated pupil diameters of 6 mm, 4 mm, and 2 mm. These data were extrapolated to obtain the total root mean square HOAs for a 1.6 mm simulated pupil to evaluate the potential effect of a small aperture intraocular lens (IOL). Correlation analysis was used to study the impact and relative contributions of HOAs on CDVA. Convolution of HOAs from OPD-Scan III provided a clinical method to predict CDVA with different simulated pupil sizes in corneas with irregular astigmatism. Results: There were statistically significant positive correlations between photopic CDVA and the magnitude of total and individual (coma, spherical aberration, and trefoil) HOAs in this cohort of keratoconus participants. A keratoconus case with the small aperture IOL confirms the improvement in vision due to the pinhole effect. Conclusions: The small aperture IOL is expected to markedly reduce aberrations in patients with keratoconus up to Amsler-Krumeich class 4 severity to levels consistent with the levels seen in healthy patients. Convolution of corneal HOAs with the Early Treatment Diabetic Retinopathy Study chart provides a useful simulation of the impact of pinhole optics in aberrated eyes.