What Is Amblyopia?
Amblyopia is defined primarily as a loss of acuity. In anisometropia, grating acuity, Snellen (optotype) acuity, and vernier acuity are degraded in proportion to each other. In strabismus, Snellen and vernier acuity are degraded more than grating acuity. The main problem in both cases is loss of binocular function, producing loss of stereoscopic vision. A number of other properties are also affected. There is uncertainty about the location of an object in space, a reduction in the ability to detect shapes, deficits in motion and direction perception, less ability to track several objects at once, reduced counting ability, and suppression of the image in one eye by the image in the other, to avoid the diplopia and confusion arising when the two eyes are looking in different directions. Some of these deficits are seen in the fellow as well as the amblyopic eye and in binocular viewing. There are also deficits in eye movements: poor fixation, a longer latency for saccades, inability to follow an object moving away from the nose smoothly, and slow inaccurate movements in visually guided reaches. These particularly affect reading so that an amblyope’s reading speed in both eyes is one-half to three-quarters of that of a normal person.
KeywordsContrast Sensitivity Binocular Rivalry Spatial Uncertainty Snellen Acuity Binocular Interaction
- Bradley A, Freeman RD (1981) Contrast sensitivity in anisometropic amblyopia. Invest Ophthalmol 21:467–476Google Scholar
- Gstalder RJ, Green DG (1971) Laser interferometric acuity in amblyopia. Journal Pediatr Ophthalmol Strabismus 8:251–256Google Scholar
- Hess RF, Daw NW (2009) Amblyopia. In: Levin LA, Albert DM (eds) Ocular Disease: Mechanisms and Management. Saunders Ltd., New YorkGoogle Scholar
- Hess RF, Field DJ, Watt RJ (1990) The puzzle of amblyopia. In: Blakemore C (ed) Vision: coding and efficiency. Cambridge University Press, Cambridge, UKGoogle Scholar
- Irvine SR (1948) Amblyopia ex anopsia. Observations on retinal inhibition, scotoma, projection, light difference discrimination and visual acuity. Trans Am Ophthalmol Soc 66:527–575Google Scholar
- Katz B, Sireteanu R (1990) The Teller acuity card test: a useful method for the clinical routine? Clin Vis Sci 5:307–323Google Scholar
- Levi DM, Klein SA (1990a) Visual acuity in strabismic and anisometropic amblyopia: a tale of two syndromes. Ophthalmol Clin North Am 3:289–301Google Scholar
- Levi DM, Song S, Pelli DG (2007) Amblyopic reading is crowded. J Vis 7(2):21–17Google Scholar
- Maurer D, Lewis TL (1993) Visual outcomes after infantile cataract. In: Simons K (ed) Early visual development, normal and abnormal. Oxford University Press, New York, pp 454–484Google Scholar
- Pelli DG, Robson JG, Wilkins AJ (1988) The design of a new letter chart for measuring contrast sensitivity. Clin Vis Sci 2:187–199Google Scholar