Paraformaldehyde-induced keratitis after photorefractive keratectomy

We examined three patients who developed keratitis after myopic photorefractive keratectomy. All patients were treated on the same day and in all three cases paraformaldehyde tablets were used for disinfection of the excimer laser iris cone. All patients developed an intense postoperative corneal inflammation that resulted in corneal opacities. In the first patient, the opacities were central and persisted for at least 4 1/2 months postoperatively. He became more myopic than before the operation. His best spectacle-corrected visual acuity worsened by four Snellen lines. In the other two patients, the corneal opacities were paracentral and of less density. Six months postoperatively, these opacities were barely seen. In these two patients the postoperative best spectacle-corrected visual acuity remained unchanged or improved one Snellen line compared to the preoperative level. In all three patients, astigmatism increased postoperatively. These observations suggest that paraformaldehyde tablets are not safe for the disinfection of the excimer laser iris cone.