Abstract
Purpose :
It has been challenging to quantify high spatial frequency wavefront errors induced by intraocular scatter. The goal of the study is to develop an ultrahigh-resolution Shack-Hartmann wavefront sensor (SHWFS) to quantify the wavefront errors mainly attributed to the intraocular scatter.
Methods :
The ultrahigh-resolution SHWFS was designed by using a small lenslet array (100 µm) and a large CMOS sensor (24.6 by 32.8 mm). The pupil was magnified by a factor of 5, resulting in a 20 µm sampling resolution at the pupil plane. Twenty right eyes from 20 normal subjects with a wide range of ages (25 to 60 years) were cyclopleged and measured for a 4.5-mm pupil diameter. The subjects were instructed to blink and the sequential array images at 20 Hz were recorded after 1 second for 3 seconds. Ocular wavefronts were reconstructed by both the modal (Zernike polynomials up to the 10th order) and zonal methods from the same local wavefront slopes measured from each lenslet. To extract high-frequency wavefront errors by intraocular scatter, the modal wavefront was subtracted from the zonal wavefront. The root mean square error (RMSE) of the difference map was calculated to represent scatter-induced wavefront errors.
Results :
During 1 to 4 seconds after a blink, the standard deviation of the total Zernike RMS, representing the tear film stability was 4.77 nm. However, the standard deviation of the scatter-induced wavefront errors was 0.72 nm, showing remarkably smaller short-term temporal variation. The mean RMSE in each age subgroup showed an increasing trend: 13.5 ± 1.1 nm in the 20s, 14.1 ± 0.7 nm in the 30s, 15.9 ± 1.3 nm in the 40s, and 16.3 ± 1.5 nm in the 50s. The RMSE values showed a strong correlation with age (R = 0.85; P < 0.001).
Conclusions :
The feasibility of quantitatively evaluating intraocular scatter was demonstrated by using an ultrahigh-resolution SHWFS combined with the zonal reconstruction and confirmed an expected increasing trend in the magnitude of intraocular scatter with aging. This technique has the potential to advance our ability to quantify the overall optical quality of the eye and to diagnose age-related ocular pathologies such as cataracts and dry eye.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.