Why does preventive laser iridotomy sometimes cause vision loss?

Cataract?: A prophylactic laser peripheral iridotomy is performed when a person has narrow and occludable iridocorneal angles, which can cause acute angle closure glaucoma and profound to total vision loss. The hole in the iris is a "pressure release valve" to prevent angle closure, but the inflammation or treatment following the procedure can increase the pace of cataract formation. Check your glasses too.