The risk factors were placed into one of five groups for analysis: group 1 (32%), contact lens wear (daily wear soft, extended wear soft, or rigid gas permeable); group 2 (27%), corneal disease (edema, dystrophy, keratopathy, recurrent erosion, foreign body trauma, previous corneal surgery); group 3 (7%), systemic disease (autoimmunity, immunosuppression, diabetes, other); group 4 (23%), ocular surface disease (atopic keratoconjunctivitis, limbal stem cell dysfunction, chemical injury, blepharitis, trichiasis and topical steroids); and group 5 (11%), previous microbial keratitis (herpetic keratitis, bacterial keratitis).