Clinical use of the 193-nm excimer laser in the treatment of corneal scars
N. A. Sher, R. A. Bowers, R. W. Zabel, J. M. Frantz, R. A. Eiferman, D. C. Brown, J. J. Rowsey, P. Parker, V. Chen and R. L. Lindstrom
Phillips Eye Institute, Metropolitan Mt Sinai Hospital, Minneapolis, MN 55404.
Phototherapeutic keratectomy using a 193-nm excimer laser was performed at
four centers on 33 sighted patients with corneal opacity and/or irregular
astigmatism. Pathologic conditions included anterior stromal and
superficial scarring from postinfectious and posttraumatic causes,
including inactive herpes simplex virus, anterior corneal dystrophies,
recurrent erosions, granular dystrophy, and band keratopathy. Most patients
received peribulbar anesthesia and underwent removal of the epithelium
prior to laser ablation. A majority of patients had a reduction in the
amount of corneal scarring and approximately half had improved visual
acuity. No intraocular reaction or changes in endothelial counts were seen,
and some patients avoided the need for penetrating keratoplasty.
Reepithelialization usually occurred within 4 or 5 days and we noted no
significant scarring secondary to use of the laser. It was difficult to
eliminate preexisting irregular astigmatism despite the use of surface
modulators, such as methylcellulose. A hyperopic shift secondary to corneal
flattening was encountered in approximately 50% of the patients. A
combination of myopic ablation, followed immediately by a secondary
hyperopic steepening, may minimize this refractive change. The 193-nm
excimer laser is an effective new tool in the treatment of selected
patients with superficial corneal opacity from a variety of conditions.
