Corneal Topographic Diagnosis of Early Keratoconus and Observation of Corneal Change after Excimer Laser Photorefractive Keratectomy

ABSTRACT

We performed penetrating keratoplasty on the 40 eyes of 40 patients from Jan. 1991 through Dec. 1993, whose diagnosis was keratoconus. Among them, the opposite eyes of 5 patients had no keratoconus signs on the slit lamp biomicroscopic examination and keratometry reading. We performed computerassisted corneal topography on the 5 eyes and then they were classified as group I. We performed computer-assisted corneal topography on the 324 eyes of 324 patients. who visited our hospital to receive excimer laser photorefractive keratectomy(PRK). Among them, 7 eyes of 4 patients, which were suspected to be early keratoconus, were classified as group II. There were no signs of keratoconus by slit lamp examination and keratometry reading. Keratometry reading was 44.82D in the group I and 43.52D in the group II. Subtle mire distorsion of photokeratoscope was seen in the 1 eye of group I and 2 eyes of guoup II, but remaining 9 eyes were normal. We could not find keratoconus signs in the conventional examination such as above but on the corneal topography 12 eyes revealed cone-shaped corneal distorsion out of the corneal center. Two eyes in the group II were suspected to be early keratoconus in the corneal topographic examination, therefore we recommended them not to receive excimer laser PRK. But they received excimer laser PRK in the other hospital. They revisited our hospital due to progressively decreased visual acuity after excimer laser PRK. On the topography, 2nd and 12th months after PRK. corneal refractive power returned similarly to pre-PRK state. Therefore, computer-assisted corneal topography is a useful method in detecting corneal change in the early keratoconus stage. Performing PRK on the eye, suspected to be keratoconus, is unreasonable because corneal power is willing to return to pre-PRK state.