A Study of Amblyopia among Anisometropic Patients

DOS Times Vol. 11, No. 10 April, 2006 Amblyopia is defined as unilateral or bilateral decrease of visual acuity caused by vision deprivation or abnormal binocular interaction for which no organic causes can be detected by the physical examination of the eye and which in appropriate cases is reversible by therapeutic measures1,2,3. For detection purposes, on routine examination, amblyopia is defined as a minimum of two Snellen lines difference in visual acuity between either eyes, but amblyopia is truly a spectrum of visual loss ranging from missing a few letters on the 20/20 line to hand movement. Anisometropia is a very common cause of amblyopia. Refractive condition of the two eyes is usually not the same. Anisometropia is the condition in which the refractive status of the two eyes shows a considerable difference. The vision in anisometropia may be binocular, alternating or it may be entirely uniocular. Each 0.25 D difference between the refraction of the two eyes causes 0.5% difference in size between the two retinal images and a difference of 5% is probably the limit, which can be tolerated. If the defect in one eye is high and more especially if the visual acuity is not good, it may be excluded altogether from vision at an early stage in life ,the better eye is alone relied upon and if it is not so already, the more ametropic eye tends to become amblyopic, the image from it being suppressed.