Electrophysiologic alterations in patients with optic nerve hypoplasia

Abstract

The clinical and electrophysiologic data (electroretinograms and visual evoked potentials) were studied in 45 patients with optic nerve hypoplasia. The patients were divided into three fairly distinct groups on the basis of their electrophysiologic alterations. Group 1 consisted of 13 patients with almost extinguished visual evoked potentials and with mild electroretinographic alterations. These were the cases that are traditionally recognized as optic nerve hypoplasia. The serious visual impairment in these cases was accompanied by various developmental ophthalmologic and nonophthalmologic abnormalities. Group 2 included 26 patients without any significant visual evoked potential or electroretinographic alterations, but with overt funduscopic signs of optic nerve hypoplasia. These patients were consistently suffering from strabismus and/or amblyopia. The visual functions based on visual evoked potential and electroretinographic recordings could be fairly normal apart from a pathologic ophthalmoscopic picture characteristic of optic nerve hypoplasia. Group 3 included six patients with abnormal albeit well-recordable visual evoked potentials and subnormal or negative-type electroretinograms that suggested an accompanying retinal disease. This finding seems to prove that a subset of patients with optic nerve hypoplasia with nystagmus may have a primary retinal abnormality. Our study provides further evidence that optic nerve hypoplasia is not a uniform disease entity.

Retinal function in infants with optic nerve hypoplasia: electroretinograms to large patterns and photopic flash

“…4,5,[32][33][34] Although reports of ERGs in ONH are few, they agree that flash ERGs are normal in the majority of cases. [17][18][19][20][21]34,35 However, normal ERGs are not universal and a variety of ERG abnormalities have been reported in ONH. Subnormal b-wave amplitude is reported in up to one-third of eyes and, in a few cases, ONH has been associated with absent scotopic b-waves, suggesting retinal dysfunction similar to that in congenital stationary night blindness.…”

“…Subnormal b-wave amplitude is reported in up to one-third of eyes and, in a few cases, ONH has been associated with absent scotopic b-waves, suggesting retinal dysfunction similar to that in congenital stationary night blindness. 20,21 Severe ERG abnormalities have been reported occasionally in eyes with microphthalmos, colobomata, or other defects. 20,21,32 In contrast, a few cases of ONH with supranormal b-wave amplitudes have been reported for the scotopic ERG 19 or the photopic ERG.…”

“…20,21 Severe ERG abnormalities have been reported occasionally in eyes with microphthalmos, colobomata, or other defects. 20,21,32 In contrast, a few cases of ONH with supranormal b-wave amplitudes have been reported for the scotopic ERG 19 or the photopic ERG. 35 These could be explained by selective dysfunction involving the depolarizing bipolar cells, or by disinhibition of retinal function in the absence of ganglion cell-mediated feedback.…”

“…[16][17][18][19] The a-waves of flash ERGs are consistently reported as normal in ONH, but several authors have reported abnormalities in the b-wave. 20,21 Under photopic conditions, the b-wave is generated by the postreceptoral ON and OFF pathways mediated by the depolarizing and hyperpolarizing bipolar cells of the retina, with no significant contribution from ganglion cells. [22][23][24] Thus, abnormalities in the photopic b-wave are evidence for dysfunction distal to the ganglion cells.…”

Congenital disorders of the optic nerve: excavations and hypoplasia

“…58,59 In a small but significant proportion of patients with ONH (both with and without associated brain abnormalities), either subnormal or negative like electroretinograms have been recorded. It has been argued that these findings may indicate that in a subset of cases with ONH and nystagmus, the retinal pathology may have been primary 60 or that trans-synaptic degeneration beyond the ganglion cell layer may take place. 61 Septo-optic dysplasia (SOD) is now considered to comprise any combination of ONH, pituitary gland hypoplasia, and midline abnormalities of the brain.…”