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A 39-year-old man was admitted to our hospital with acute bilateral RBN of unknown origin. His corrected vision was 0 4 OD and 0*01 OS. Ophthalmoscopic examination was normal except for a few small subretinal yellowish dots in the right macular area. There was a past history of CSR in the right eye. Corticosteroid treatment with betamethasone 10 mg per day in 500 ml of 5% glucose was started. This was a high initial dosage but was thereafter gradually reduced. On the sixth day of therapy, when the steroid dosage was 8 mg daily and the total dosage 52 mg, CSR with a detachment of about 2 disc diameters was noted in the right eye and rapidly increased to 5 disc diameters. Following termination of corticosteroid therapy the extent of the detachment reduced to about 2 disc diameters. Vision remained poor in each eye, and consequently a second course of betamethasone with Correspondence to Dr Masato Wakakura. a total dosage of 123 mg over 18 days was started. During this second course there was an increase in the CSR, but the detachment completely disappeared about 20 days after the termination of corticosteroid therapy. At that time the visual acuity was 1-0 OD and 0-05 OS. Because of continuing poor vision the patient requested a third course of corticosteroid therapy. Two months were allowed to elapse to allow adrenal function to recover.Neither a right central scotoma nor dye leakage on fluorescein angiography was detected before the start of the third course (Fig. 1A). Betamethasone 16 mg per day was given and the dosage gradually reduced. The total dosage was 141 mg over 15 days. On the third day. of treatment vision in the right eye deteriorated, to 0-6, and a central scotoma and CSR were noted. The same leakage site as before was confirmed by fluorescein angiography site (Fig. 1B).The leakage site was surrounded by a pigment epithelial detachment. On the eleventh day (Fig. 1C) the leakage changed to a mushroom or jet type with a retinal detachment of about 6 disc diameters. The CSR did not improve until the daily dosage of betamethasone was reduced to 2 mg. The detachment disappeared about 18 days after the termination of corticosteroid therapy with a vision of 1-0 OD and 0-1 OS. No dye leakage was seen at this stage (Fig. 1D).

Japanese patients with LHON exhibited a very high incidence (87%) of the 11,778 primary mutation. Most of the proposed secondary LHON mutations were rare in the Japanese population and they, except the 7444 mutation, may not influence the clinical features of LHON.

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