Quantifying ocular microaberration using a high-resolution Shack-Hartmann wavefront sensor.

Abstract

To quantify high-spatial-frequency wavefront errors caused by microaberration, we developed a high-resolution (20 µm) Shack-Hartmann wavefront sensor (SHWFS). This system was designed using a small lenslet array (100 µm) and a large CMOS sensor (24.6 × 32.8 mm), incorporating 5× pupil magnification. Measurements were performed on 20 normal subjects aged 25 to 60 years, all without clinically evident corneal scars or cataracts. Examinations were performed under cycloplegia with a 4.5-mm pupil diameter. Ocular wavefronts were reconstructed using both modal and zonal methods, derived from the same local wavefront slopes measured by each lenslet. To isolate high-frequency wavefront errors due to microaberration, the modal wavefront was subtracted from the zonal wavefront, and the resulting root mean square (RMS) was calculated as a metric of microaberration-induced wavefront distortions. The mean RMS values increased with age: 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, showing a strong correlation with age (R² = 0.73; P < 0.001). This study demonstrates the feasibility of quantifying microaberration using a high-resolution SHWFS combined with zonal reconstruction, confirming an age-related increase in microaberration. This technique offers potential for enhancing optical quality assessment, considering both wavefront aberrations and microaberrations, and could aid in diagnosing age-related ocular disorders such as cataracts and dry eye.