Visual Deprivation Amblyopia
The least common form of amblyopia, but the most severe and difficult to treat, is visual deprivation amblyopia (also known as stimulus deprivation amblyopia, deprivation amblyopia, visual stimulus deprivation amblyopia, and form-vision deprivation amblyopia), which is due to an eye abnormality that obstructs the visual axis or otherwise interferes with central vision. The most common cause is congenital or early-acquired cataract; other causes include blepharoptosis, periocular lesions obstructing the visual axis, corneal opacities, and vitreous hemorrhage. Visual deprivation amblyopia develops faster, and is deeper, than strabismic or anisometropic amblyopia. Unilateral visual deprivation tends to cause vision deficits in the affected eye that are more severe than the bilateral amblyopic deficits produced by bilateral deprivation of the same degree because interocular competition adds to the direct impact of image degradation (see Chapter 5). Even in bilateral cases, visual acuity can be 20/200 or worse if not treated early.
In children younger than 6 years, dense cataracts occupying the central 3 mm or more of the lens can cause severe visual deprivation amblyopia. Similar lens opacities acquired after age 6 years are generally less harmful. Small anterior polar cataracts, around which retinoscopy can be readily performed, and lamellar cataracts, through which a reasonably good view of the fundus can be obtained, may cause mild to moderate amblyopia or have no effect on visual development. Unilateral anterior polar cataracts, however, are associated with anisometropia and subtle optical distortion of the surrounding clear portion of the lens, which may cause anisometropic and/or mild visual deprivation amblyopia.
Reverse amblyopia (occlusion amblyopia) is a form of visual deprivation amblyopia that can develop in the initially dominant eye if it is patched excessively during treatment of amblyopia in the other eye. See the section “Reverse amblyopia and new strabismus” for further discussion.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.