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To the Editor.
—Research has clearly documented that a blurred retinal image (image distortion) occurring during the critical period of visual development causes functional and anatomical damage to the central visual pathways, resulting in impaired vision, ie, amblyopia. In humans, the critical period extends from birth to approximately 2 months of age. Bilateral, symmetrical image distortion during this time results in bilateral amblyopia, as is seen in patients with high hypermetropia and bilateral congenital cataracts. Unilateral image distortion is even more amblyogenic, as exemplified by the poor postoperative visual results in patients born with monocular opacities in the optical media. There has been controversy as to whether unilateral amblyopia occurs secondary to a lack of light stimulus or secondary to image distortion. Animal studies1 clarified the situation by showing that unilateral total light deprivation or unilateral image distortion resulted in amblyopia. In contrast to the detrimental effects of unilateral total
Wright KW, Wehrle MJ, Urrea PT. Bilateral Total Occlusion During the Critical Period of Visual Development. Arch Ophthalmol. 1987;105(3):321. doi:10.1001/archopht.1987.01060030035012