Foveal and eccentric acuity in one-eyed observers

The purpose of these two experiments was to examine the effects of enucleation on the foveal and near-periphery acuity of human observers. In Experiment 1, using high contrast illiterate-E optotypes, we measured foveal and 7-degree eccentric (nasal and temporal) acuity in the remaining eye of unilaterally enucleated children and adults. The data were compared to those of the fellow or 'good eye' of age-matched non-amblyopic and amblyopic strabismic observers-a different kind of monocular deprivation-and binocularly normal subjects. The main finding was that the 7-degree eccentric acuity of enucleated observers and normal controls was best, followed by that of the non-amblyopic and lastly, the amblyopic subjects. There were no naso-temporal asymmetries. In Experiment 2, foveal and 7-degree eccentric acuities of enucleated and binocularly normal subjects were tested at 96, 13.5 and 4.7% contrast levels using the same kind of stimuli. The foveal acuity of the enucleated observers was better than the monocular acuity of controls at all contrasts, and equivalent to their binocular acuity. The eccentric acuity of the enucleated observers was better at the two low contrast levels. No naso-temporal asymmetries were found in either group at any contrast level. These findings suggest that, in humans, visual deprivation from unilateral enucleation does not result in a naso-temporal asymmetry in the near periphery.