Abstract Two studies of the perceptual effects of low‐power plus lenses were done on groups of young‐adult binocular emmetropic observers. The first study used visual masking to induce short‐term perceptual stress in two groups of 10 observers: one group wore piano lenses and the other wore +0.50 D lenses. No significant differences in visual perceptual performance were found between these groups. The second study used a more natural letter‐search task and rotated 18 observers through nine lens powers from piano to +1.0 D in + 0.12D steps, to form a test of the hypothesis that “critical” lens power benefits individual observers. Other conditions in the study were arranged to maximize the positive effect of short‐term wear of plus lenses, if one was found. Results showed neither an overall group benefit from a particular power of plus lens nor an individual lens power that benefited each individual observer. These data showed a strong practice effect over the nine experimental sessions, regardless of lens power, that could account for earlier reports in the literature of positive results from using these lenses.
Barry et al. (Thu,) studied this question.