Aging Eyes Struggle More With Visual Crowding When Time Is Short

Millions of older adults complain of visual difficulties despite passing standard eye exams with 20/20 acuity. This study set out to explain why, focusing on foveal crowding — the impaired ability to recognize a target letter when flanked by nearby letters — a phenomenon previously considered rare in central vision and understudied across the full aging spectrum.

Researchers enrolled 33 participants aged 20–89 (mean 57.8 ± 24 years) who had best-corrected visual acuity of at least 20/40 and no ocular pathology. Participants completed a tumbling-E letter recognition task in two conditions: unlimited viewing (stimulus stays until response) and limited viewing (120 ms presentation). Within each condition, targets were shown either in isolation or flanked at one-letter or half-letter spacing. An adaptive staircase (3-down, 1-up) measured acuity thresholds, and reaction times were recorded throughout.

Under unlimited viewing, crowding effects were minimal and did not differ significantly between younger (≤49 years) and older (≥50 years) participants — both groups could identify flanked letters nearly as well as isolated ones when given unlimited time. However, under the 120 ms limited viewing condition, older participants showed dramatically increased crowding, with visual acuity thresholds declining substantially in the presence of flankers. The crowding effect correlated significantly with age as a continuous variable. Reaction times increased with age in both conditions, but the effect was especially notable in unlimited viewing, where older adults maintained high accuracy but took considerably longer to respond — indicating slowed processing even when accuracy is preserved.

The 120 ms presentation time was selected based on prior lab work showing it sits at the threshold where foveal crowding first emerges in younger adults at one-letter spacing. Older adults, by contrast, experienced robust crowding even at this relatively generous duration, suggesting their visual processing system requires more time to disentangle target from flanker signals. This aligns with well-established age-related declines in neural processing speed.

These findings have meaningful implications for everyday tasks. Reading in peripheral or cluttered environments, driving at speed, and recognizing faces in crowds all impose temporal constraints on visual processing. Standard clinical assessments, which test acuity under optimal, unlimited conditions, systematically miss these age-related vulnerabilities. The authors argue that incorporating time-limited viewing into routine visual assessments could better capture functional vision loss in older adults. Training-based interventions that reduce crowding — previously demonstrated in younger and presbyopic cohorts in this lab — may also be worth exploring in older populations.