The ERG is helpful in diagnosing several conditions, such as
generalized (eg, retinitis pigmentosa) and localized genetic retinal
degeneration (eg, macular dystrophies). It is also helpful in assessing
retinal function following retinal vascular occlusions and in determining
potential retinal function when the retina cannot be clearly viewed
due to opaque media (eg, cataract). Although the ERG does not test
visual acuity (which is a measure of foveal function, an area of retina
too small for the ERG to assess, as it is a mass retinal cone or
rod response), it is useful in assigning the anatomic location of
visual compromise in children with poor vision and nystagmus. We
recommend that all children with no other obvious cause for nystagmus
receive an ERG. Specific pediatric considerations include Leber
congenital amaurosis, rod monochromatism (achromatopsia), and congenital
stationary night blindness (CSNB), all of which can present with
nystagmus, decreased vision, and a normal retinal examination. Even
when the ERG is completely flat, the central vision can be 20/20 if
the tiny fovea is spared.