Contrast Sensitivity In Amblyopia And Normal Adults

Amblyopia, sometimes referred to as "lazy eye", is poor vision in an eye (less frequently, both eyes) that did not develop normal function during childhood. Amblyopia is the most common cause of visual impairment in childhood. The condition affects approximately 2 to 3 out of every 100 children. Unless it is successfully treated in early childhood, amblyopia usually persists into adulthood, and is the most common cause of monocular (one eye) visual impairment among children, young and middle-aged adults.The neural correlates underlying amblyopia are still not entirely clear though it has been widely accepted that amblyopia develops as a result of abnormal visual experience during a so-called "sensitive period". To investigate the mechanisms of amblyopia will benefit not only early sreening, interference and treatment but also the understanding of several related visual functions in normal visual system.The present study focuses on contrast perception in amblyopia, a deficient function commonly found in amblyopia, which covers four related topics, ranging from the evaluation of spatial vision in treated amblyopes (Exp I), the potential of perceptual learning in treating amblyopia (Exp II) to the comparative study of perceptual learning between amblyopia and normal adults (Exp III) to the mechanisms of perceptual learning (Exp IV).Exp I) To evaluate spatial vision of treated amblyopes using contrast sensitivity function, in addition to visual acuity tests, five clinically treated amblyopes (mean age = 10.6 yrs) were recruited. Contrast sensitivity functions (CSF) in both previously amblyopic eyes (pAE) and fellow eyes (pFE) were measured using a standard psychophysical procedure for all the subjects. The results indicated that the treated amblyopes remained deficient in spatial vision, especially at high spatial frequencies, although their Snell visual acuity had become normal in the pAEs. To identify the mechanisms underlying spatial vision deficits of treated amblyopes, threshold versus external noise contrast (TvC) functions — the signal contrast necessary for the subject to maintain a threshold performance level in varying amounts of external noise ("TV...