organic amblyopia

Organic amblyopia is reduced vision caused by a pathological or anatomical abnormality, classically of the retina.¹ The organic group includes amblyopia from retinal disease such as receptor dystrophy or neonatal macular hemorrhage, nutritional amblyopia, toxic amblyopia from poisons such as arsenic, lead, or quinine, and idiopathic or congenital amblyopia of unknown cause.¹ Modern electrophysiology and imaging may reveal subtle causes in many idiopathic cases, and some of those causes may be cortical or subcortical.¹

Functional amblyopia is the contrasting group, in which no organic lesion exists. The functional group includes stimulus deprivation, strabismic, anisometropic, refractive, and psychogenic amblyopia.¹ Organic amblyopia has customarily been called the irreversible type and functional amblyopia the reversible type.² That split is less clean than it sounds. Recovery depends on the maturity of the visual connections at the onset of abnormal visual experience, the duration of deprivation, and the age at which treatment started.² Irreversibility may therefore mark only the most severe form of amblyopia.²

Organic amblyopia can exist without a visible lesion, because retinal damage may be too subtle to see with the ophthalmoscope.² Functional and organic amblyopia can also coexist. If treatment improves vision only to a certain level and cannot restore standard acuity, a reversible amblyopia is probably superimposed on an irreversible one.² Relative amblyopia of this kind also coexists with recognizable structural anomalies of the ocular media, retina, or optic nerve, and it responds to occlusion treatment.²