Low Luminance Reduces Facial Recognition in Central Vision Loss

Low luminance may result in a reduced ability to discriminate between faces and recognize facial expressions in individuals with central vision loss, according to a study published in Ophthalmic and Physiological Optics. While individuals with peripheral vision loss can also experienced a reduced ability to discriminate between faces, it does not significantly affect their ability to recognize facial expression in scotopic conditions, according to the report.

Researchers enrolled participants with central vision loss (n=33; mean age, 75.6 years; 55% women), peripheral vision loss (n=17; mean age, 70.0 years; 59% women) and age-matched control group individuals (n=20; mean age, 75.6 years; 45% women) in the investigation and evaluated facial identity discrimination and facial expression recognition abilities in both photopic and low luminance conditions.

Participants identified the odd-face-out after being presented with 12 sets of 3 faces with neutral expressions and identified facial expression (neutral, happy or angry) in 12 single faces. Study individuals underwent photopic and low luminance visual acuity measurements and contrast sensitivity assessment. Participants with peripheral vision loss also underwent 24-2 visual field testing.

Both individuals with central vision loss and participants with peripheral vision loss experienced a decline in their ability to recognize faces in low luminance compared with photopic luminance conditions (mean reduction, 20% vs 8%; P <.001), the report shows. 

Only individuals with central vision loss experienced a reduction in facial expression recognition accuracy (mean reduction, 25%; P <.001). Poorer visual acuity and contrast sensitivity were strongly associated with worse face recognition in low lighting conditions (ρ, 0.61-0.77; P <.05). In eyes with peripheral vision loss, 24-2 visual field mean deviation in the better-seeing eye was moderately correlated with low luminance (ρ, 0.54; P =.02).

“The reduced face recognition with [central vision loss] has been attributed not only to
reduced spatial resolution but also to the need to adopt an extrafoveal retinal location to maximize visual functioning, where [visual acuity] and [contrast sensitivity] are reduced, and crowding occurs (the inability to recognize objects in clutter), all of which worsen with increasing retinal eccentricity and under low luminance conditions,” the study authors explain.

A small sample size of participants with peripheral vision loss, the use of simulated unfamiliar faces in the facial recognition tasks, and the evaluation of only 1 luminance level, are acknowledged limitations to the research.