Nitin Negi¹, Benjamin Chin¹; ¹Rochester Institute of Technology

The human visual system uses a process known as accommodation to achieve clear images on the retina. Accommodation dynamically changes the shape of the crystalline lens, thus adjusting the eye’s refractive power. Notably, accommodation is not stable. Even under steady viewing conditions, the visual system exhibits temporal variations in accommodation known as microfluctuations. A longstanding hypothesis in vision science is that low-frequency components of microfluctuations generate odd-error feedback signals that assist with accommodation. We further hypothesize that the visual system may increase its microfluctuations under conditions when accommodation is more difficult, such as when light entering the eye is narrowband. We tested this hypothesis with an existing dataset (Chin et al., 2025) of continuous accommodation measurements in which participants viewed small (~1°), foveally presented words for 3 seconds. The light spectra of stimuli were varied by mixing pairs of narrowband display primaries with varying ratios of the red and blue primaries. The green primary was either absent or fixed to half the luminance of the other two primaries. Each subject completed 216 trials corresponding to 12 unique spectra, 3 target distances (1.5, 2.5 and 3.5 D), and 6 trials per combination of spectrum and distance. Accommodative state was quantified as defocus aberration in the eye’s wavefront, which was recorded at 30 Hz with a Shack-Hartmann wavefront sensor. We calculated total power in the low frequency components (0.1-0.6 Hz) on each trial via a power spectrum analysis of the time series, then averaged across all trials and participants for each combination of spectrum and accommodative distance. A two-factor repeated measures ANOVA indicated a significant effect of target distance on microfluctuations (F(2,180)=4.99, p<0.01), but not of color (F(9,180)=0.29, p=0.98). There was no interaction between the two factors (F(18,180)=0.2, p=1.0). Future work will explore the potential impact of other factors on microfluctuations.

Acknowledgements: Startup funds from the Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology