Harwerth, Ronald S.2022-06-202022-06-2019735537731https://hdl.handle.net/10657/9481The site of the loss of visual acuity in amblyopia is unknown. Although amblyopes appear to have normal absolute thresholds, the contrast requirements of the amblyopic eye reportedly differ from those of normal eyes. An apparatus has been constructed for the investigation of brightness contrast functions using a haploscopic brightness matching technique. Ten subjects, 5 amblyopes with central fixation and 5 control subjects matched for age, were investigated. The psychophysical method of adjustment was used in brightness matching over a wide range of test and inducing field luminances. The results of this study indicate that both amblyopic and control subjects demonstrate brightness contrast function. Amblyopic subjects showed abnormal brightness contrast, most markedly at low and intermediate photopic luminances, but normal contrast function at high luminances. Except for one subject, the amblyopes demonstrated normal brightness matching in the absence of an inducing field; however, one individual showed differences of over 0.5 log units in brightness appreciation between the two eyes. It has been hypothesized that a shift in lateral interactions in the retina, as a result of enlarged retinal receptive fields, contributes to the reduction in visual acuity in amblyopia.application/pdfenThis item is protected by copyright but is made available here under a claim of fair use (17 U.S.C. Section 107) for non-profit research and educational purposes. Users of this work assume the responsibility for determining copyright status prior to reusing, publishing, or reproducing this item for purposes other than what is allowed by fair use or other copyright exemptions. Any reuse of this item in excess of fair use or other copyright exemptions requires express permission of the copyright holder.Thesisreformatted digital