A comparison of the TMS-1 and the corneal analysis system for the evaluation of abnormal corneas.

We used two computerized corneal topography instruments (EyeSys Laboratories' Corneal Analysis System and the Topographic Modeling System (TMS-1) from Computed Anatomy, Inc.] to evaluate 18 eyes (ten patients) with abnormal corneas. The diagnoses included keratoconus, corneal scars, and residual postoperative astigmatism following refractive surgery. The patients were randomly selected from a busy corneal practice to include those with significant corneal refractive error whose management, it was believed, would benefit from corneal topography imaging. Images were taken with both systems, and comparisons were made of the ease of operation, the accuracy of corneal readings, and the usefulness of generated data. Three millimeter zone (Corneal Analysis System) and Simulated Keratometry (TMS-1) values were also compared to each other and to standard keratometric readings. We found the two systems to be very similar in their application and results, although certain differences were apparent in terms of operation, patient acceptance, and the ability to obtain useful data from the more distorted corneas. Neither system worked ideally for severely irregular surfaces.

Clinical management of keratoconus. A multicenter analysis.

The clinical management of 746 eyes in 417 patients referred for keratoconus from January 1984 through January 1988 was retrospectively analyzed. In 357 patients, 554 eyes (74%) did not require surgery and were managed with contact lenses or spectacles, 156 eyes (21%) in 137 patients either underwent penetrating keratoplasty (PK) (140 eyes) or surgery was recommended (16 eyes), and 36 eyes (4%) in 34 patients underwent epikeratoplasty. Comparing baseline and final examination findings, the nonsurgical group showed a significant improvement in average best-corrected visual acuity from 20/30 to 20/25, the PK group from 20/70 to 20/25, and the epikeratoplasty group from 20/40 to 20/30. Average keratometry was unchanged in the nonsurgical group, but decreased by 10.7 diopters (D) for the PK group and 6.5 D for the epikeratoplasty group. Corneal cylinder was unchanged in the nonsurgical group, whereas there was a reduction of the percentage of eyes with indeterminant cylinder from 55 to 2% in the PK group and from 36 to 0% in the epikeratoplasty group. Previous contact lens history, best-corrected visual acuity of 20/50 or worse, and average keratometry of 55 D or greater at baseline were associated with a significant risk for PK. No baseline variables were associated with significant risk for epikeratoplasty, suggesting that this group was similar to the nonsurgical group, except for contact lens intolerance. The nonsurgical management of keratoconus continues to play a predominant role in the management of this disorder in a referral population.