A 35-year-old man was referred with progressive impairment of vision. He was previously diagnosed with anisometropic amblyobia and registered partially sighted. He had lifelong problems of night vision and described a family pedigree suggestive of X-linked inheritance, with two generations of male members affected with nyctalopia and high myopia. No male-to-male transmission occurred and female relatives were unaffected. Family members could not be contacted.

Refraction showed distorted retinsocopy reflexes, with best corrected visual acuities of −18.00/+10.00 ×180 (6/60) OD and −10.00/+8.00 ×5 (6/36) OS. …