Shack-Hartmann Image Quality and Wavefront Correction in Normal and Diabetic Subjects

Abstract

Purpose: : Diabetes can affect the optical quality of the lens, resulting in increased aberrations and scatter. Degradation of the eyes optics may reduce the quality of Shack-Hartmann (SH) images, a critical component of wavefront sensing of adaptive optics (AO) systems. The purpose of this study was to compare SH image quality in diabetic and normal subjects and evaluate AO performance in these two groups.

Methods: : SH images were acquired from dilated right eyes of 10 normal and 15 diabetic subjects of similar age (P = 0.1) with the use of an AO imaging system before and after wavefront correction. To evaluate SH image quality, metrics consisting of area and circularity of SH spots were measured. To evaluate AO performance, the root mean square (RMS) of the wavefront error was calculated before and after AO correction. A statistical t-test was utilized to determine the significance of differences in SH spot metrics and RMS wavefront error between normal and diabetic subjects, before and after AO correction.

Results: : The mean SH spot area was found to be significantly lower in normal subjects (.023 ± .004 mm²) compared to measurements in diabetic subjects (.027 ± .005 mm²), both before and after AO correction (P <0.03). Before and after AO correction, the SH spots were more circular in normal subjects compared to diabetic subjects (P < 0.003). No significant difference in the total RMS wavefront error (2^nd - 7^th order) was found between normal and diabetic subjects, both before and after AO correction (P > 0.2). High-order RMS wavefront error (3^rd - 7^th order) in diabetic subjects (0.99 ± 0.23 µm) was significantly larger compared to normal subjects (0.72 ± 0.22 µm) before AO correction (P = 0.01). With AO correction, no significant differences in SH spot metrics were found (P > 0.3). A significant reduction in total and high-order RMS wavefront error was observed with AO correction, in both diabetic and normal subjects (P < 0.004).

Conclusions: : Diabetic subjects had larger and more irregular SH spots compared to normal subjects. AO performance in normal and diabetic subjects was comparable, despite the lower quality of SH images in diabetic subjects.

Keywords: imaging/image analysis: clinical • aberrations • diabetes