An unusual case of homocystinuria.

A boy aged 8i years presented with a 2-week history of an irritable bloodshot left eye after being injured by a snowball. The eye was injected and there was an area of corneal oedema where the lens was in contact with the posterior corneal surface. The lens was dislocated antero-inferiorly and the intraocular pressure appeared to be raised on digital examination. Externally the other eye appeared normal. The patient was admitted to hospital and treated with topical steroids and Diamox. A mydriatic trial was performed on the right eye to investigate zonular function, and the anterior chamber became appreciably shallow through anterior displacement of the lens. Mydriatics were discontinued and miotics were substituted; these were required for 2 days before the anterior chamber deepened to its pre-test state. The intraocular pressure was at no time raised in this eye. Following this test, a provisional diagnosis of homocystinuria or Marfan's syndrome was made. Examination of the urine (R.J.P.) revealed a strongly positive cyanide nitroprusside test. Aminoacid chromatography and electrophoresis confirmed the presence of homocystine in the urine.