Delayed visual maturation: an update

The term ‘delayed visual maturation’ (DVM) can be applied either in a broad sense to all infants who appear to be blind yet subsequently develop some vision, or, more specifically, to a group with normal ocular and systemic clinical examination whose visual behaviour markedly improves by 4 to 6 months of age and whose visual acuity is subsequently normal. The term DVM is used both as a diagnostic label in this latter group (as there is no more specific diagnosis) or as a descriptive term of a behavioural phenomenon in its broad definition. Without a consensus on usage there is therefore some confusion in the literature. Those who favour the broad approach subclassify DVM into type 1, which corresponds to the latter specific group; type 2, in which there is neurological abnormality and/or learning disability and in which visual function is often, but not invariably, permanently impaired to some degree; and type 3, where there is an ocular abnormality and nystagmus develops with visual improvement (Uemera et al. 1981). Fielder and Mayer (1991) further expanded the classification by limiting type 3 to albinism and idiopathic congenital nystagmus, and separating severe ocular disorders into type 4.