Patients used cysteamine eye drops every 2 hours while awake to both eyes.

Patients were asked to use topical cysteamine 0.55% eye drops every 2 hours while awake to both eyes.

Patients had a baseline ophthalmic examination before initiation of topical cysteamine 0.55% eye drops and subsequent monthly follow up exams. The following parameters were recorded pretreatment, on each monthly visit and post treatment at last follow up visit: photophobia, slit lamp assessment of corneal cystine crystals and visual acuity. Photophobia was classified as grade 0 (none) for no photophobia, grade 1 (mild) for photophobia in bright light, grade 2 (moderate) for photophobia in room light and grade 3 (severe) for photophobia in dim light. Corneal cystine crystals were graded as Grade 0 = None, Grade 1 = 1-10 crystals/mm, Grade 2 = 11- 50 crystals/mm, Grade 3 = more than 50 crystals/mm. The level of cystine in the corneal layers was recorded and the location whether peripheral or central was also identified. Visual acuity was measured by Snellen chart at 20 feet with best distance correction.