Nutritional optic nerve degeneration. Illegal Non-pharmaceutical Drugs Amphetamines Amphetamines use can lead to a reduced focusing ability and dilation of the pupil. With this dilation comes a risk for acute angle-closure glaucoma. In this glaucoma, the eye pressure becomes suddenly extremely elevated, leading to eye pain, redness, blurred vision, loss of vision, seeing rainbows around lights, nausea, and vomiting. Angle closure glaucoma is a serious eye emergency.
Amphetamines otherwise can lead to hallucinations during usage.
Cocaine Cocaine has been reported to potentially lead to corneal ulceration. These ulcers are sometimes sterile, and sometimes infected with bacteria. It is not fully understood why this occurs, except that cocaine is a potent eye anesthetic. Thus, with the eye numb, damage can occur unknowingly leading to the ulceration. Once the anesthetic effect wears off, the eye can become very painful with blurred vision.