Relationship of Low-luminance Visual Acuity with Ocular Aberrations in Older Participants

SIGNIFICANCE: This study highlights the importance of twilight adaptation for reliable assessment of low-luminance visual acuity and understanding the relationship between low-luminance visual acuity and ocular aberrations.PURPOSE: The human eye experiences reduced visual acuity as luminance decreases owing to reduced retinal and optical resolutions; however, the details are unclear. This study aimed to quantify the effects of refraction, pupil diameter, and ocular aberrations on visual acuity during the transition from high- to low-light environments, thereby contributing to the standardization of low-luminance visual acuity measurements.METHODS: In total, 27 older participants with a mean age of 70.0 +/- 4.1 years were included in this study. Visual acuity was measured according to the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol with three luminance conditions: high luminance (300 cd/m(2)), low luminance (10 cd/m(2)), and low luminance with short-term (15-minute) twilight adaptation (10 cd/m(2)).RESULTS: The mean logarithm of minimum angle of resolution values of visual acuity were -0.09 +/- 0.09, 0.10 +/- 0.13, and 0.03 +/- 0.09 at 300, 10, and 10 cd/m(2) with twilight adaptation, respectively. Multiple regression analysis determined that spherical aberration (P < .005) and tetrafoil (P < .005) were significant factors associated with low-luminance visual acuity after twilight adaptation, with an adjusted R-2 value of 0.35 for this model (P < .005).CONCLUSIONS: Although the influence of ocular aberrations on low-luminance visual acuity may be relatively modest compared with neural effects, it remains a crucial factor that should not be overlooked. The absence of twilight (or dark) adaptation can cause ocular aberrations and neural effects, potentially leading to inaccuracies in the measurement of low-luminance visual acuity.