Effect of light barrier and type of refractive error on the performance of a portable wavefront aberrometer-based...

Accurate and accessible autorefractors are essential for refractive error assessment, particularly in resource-limited settings. This study evaluates the accuracy and reliability of Instaref R20 with a light barrier (Instaref R20 LB) compared to a tabletop autorefractor (AR) and subjective refraction (SR) in an adult population. A light barrier (wearable polaroid filter) was used to reduce ambient illumination and stabilize pupil size, thereby improving measurement reliability under bright conditions.

A prospective study was conducted at a tertiary eye institute in Mumbai, enrolling 200 adults (mean age: 44.33 ± 13.97 years). All the participants underwent a comprehensive eye examination including objective refraction, subjective acceptance, and anterior and posterior segment evaluation. Non-cycloplegic refraction was assessed using Instaref R20, Instaref R20 LB, AR, and SR. Agreement between methods was analyzed using Bland-Altman plots, assessing power vector components (M, J0, J45). Statistical comparisons were performed using the Wilcoxon signed-rank test.

Instaref R20 LB demonstrated strong agreement with SR (M: 0.10D, P = 0.13; J0: -0.05D, P = 0.05; J45: 0.01D, P = 0.44), while Instaref R20 showed slight variance (M: 0.17D, P < 0.001). The agreement within ± 0.50D of SR was 64.64% (M), 85.35% (J0), and 89.39% (J45). Under bright illumination, Instaref R20 failed to capture readings in six cases, whereas Instaref R20 LB obtained stable measurements in all participants, demonstrating superior reliability in bright environments. Subgroup analysis showed higher accuracy in myopic eyes, while AR exhibited significant deviations in hyperopes.

The Instaref R20 LB improves measurement accuracy and reliability, particularly under bright illumination. Its strong agreement with SR and portable design make it a viable tool for refractive error assessment in resource-constrained settings.