<unk> (ophthalmic) is an ophthalmic agent that is FDA approved for the treatment of corneal cystine crystal accumulation in patients with cystinosis.   Common adverse reactions include headache, eye irritation, pain in eye, photophobia, red eye, and visual field defect.
Cysteamine 
Carnitine
Xanthine
Aminohippuric acid
Nicotinamide
Pyruvic acid
Ethionine
Citrulline