Familial Optic Atrophy with Negative ERG

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Earlier investigators reported that negative ERGs were rarely associated with optic nerve atrophy because patients with the inherited forms of optic atrophy had been reported to have normal ERG findings [2]. The optic atrophy was assumed to occur from transsy-naptic degeneration of the bipolar cells.

In 1992, in collaboration with Richard Weleber of Portland, Oregon, we found that the affected members of two families with presumably autosomal dominant optic atrophy also had negative-type ERGs (Fig. 2.126) [3]. They had poor central vision, and the decrease occurred during the second to third decade of life. Ophthalmological examinations showed that the affected members had visual acuities of 1.0-0.4, defective color vision, mild to moderate myopia, and pericentral or centrocecal sco-tomas. Optic atrophy was found in four of the five patients (Fig. 2.127). The age of the affected members ranged from 21 to 56 years (mean 42 years).

The amplitude of the a-wave of the full-field ERGs (Fig. 2.128) and the scotopic rod-cone ERGs were normal, but the amplitude of the b-wave was markedly reduced. The amplitudes of the rod responses were moderately reduced but with normal implicit times. The amplitudes of the b-wave of the photopic ERGs varied from normal to mildly reduced, and the implicit times were normal. The amplitudes of 30-Hz flicker ERGs were normal.

The moderately low visual acuity of these patients may be caused by optic atrophy or some macular problem. The essentially normal focal macular ERGs suggest that the low visual acuity is caused by optic nerve dysfunction. Because negative ERGs are not seen with other familial optic atrophies, we concluded that this disease, with an association of optic atrophy and abnormal negative ERGs, represented a new genetic disorder.

Fig. 2.126. Two pedigrees showing the family members with optic atrophy and negative ERGs.The black dot at the side of the symbols identifies individuals who were examined ophthalmoscopically. Males III-1 and III-2 of Family 2 were fraternal twins, one of whom died. Patients 4 and 6 of Family 2 also had McArdle's (Mc) disease, but this is an autosomal recessive trait unassociated with either optic atrophy or ERG abnormalities. (From Weleber and Miyake [2])

Fig. 2.126. Two pedigrees showing the family members with optic atrophy and negative ERGs.The black dot at the side of the symbols identifies individuals who were examined ophthalmoscopically. Males III-1 and III-2 of Family 2 were fraternal twins, one of whom died. Patients 4 and 6 of Family 2 also had McArdle's (Mc) disease, but this is an autosomal recessive trait unassociated with either optic atrophy or ERG abnormalities. (From Weleber and Miyake [2])

Fig. 2.127. Fundi of case 1 (top left), case 2 (top right), case 3 (center left), case 4 (center right), and case 5 (bottom). (From Weleber and Miyake [2])
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Fig. 2.128. Full-field ERGs recorded from a normal control and three patients (cases 1,2, and 3) examined in Nagoya, Japan (A); and two patients (cases 4 and 5), a patient with complete CSNB, and a normal control examined in Portland, Oregon, USA (B). A Rod ERGs are subnormal,and mixed rod-cone (bright white) ERGs have the shape of the negativetype ERG.The OPs are reduced.The cone and 30-Hz flicker ERGs are normal. B The blue light was sco-topically balanced with the red light for production of equal-amplitude rod responses. Note that the rod b-waves responses to dim white light and dim blue light were subnormal for both patients and nearly undetectable for the patient with complete CSNB.The cone-mediated ERGs were normal. (From Weleber and Miyake [2])

References 3. Weleber RG,Miyake Y (1992) Familial optic atrophy with negative electroretinograms. Arch Ophthal-

1. Miyake Y, Shiroyama N, Horiguchi M, Saito A, mol 110:640-645 Yagasaki K (1989) Bull's eye maculopathy and negative ERG. Retina 9:210-215

2. Yagasaki K, Miyake Y, Awaya S, Ichikawa H (1986) ERG (electroretinogram) in hereditary optic atrophy. Acta Soc Ophthalmol Jpn 90:124-130

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