Corneal thickness changes after high-risk penetrating keratoplasty. Collaborative Corneal Transplantation Study Group.

OBJECTIVE: To determine whether ultrasonic measurements of corneal thickness are of prognostic value after high-risk penetrating keratoplasty. DESIGN: A prospective, multicenter, randomized trial. PATIENTS: Four hundred fifty patients at high risk for graft failure because of previous immunologic graft failure or because of two or more quadrants of stromal vascularization. Patients underwent surgery and were treated according to a specific protocol and observed at frequent intervals. INTERVENTION: At each postoperative visit, ultrasonic measurement of central corneal thickness was performed and the corneal status was determined by biomicroscopic examination. MAIN OUTCOME MEASURE: Graft failure owing to immunologic or nonimmunologic causes. RESULTS: Corneal thickness stabilized by 3 months at a median thickness of 0.54 mm. The range of corneal thicknesses in patients with corneal grafts judged to be clear was large. In 49% of eyes, development of an allograft reaction episode was accompanied by an increase in corneal thickness of at least 10%; the greater the increase in thickness, the more likely the graft would fail. Clear grafts with central thicknesses of 0.59 mm or greater at 1, 3, or 6 months had a much greater risk of failure than those with thicknesses of less than 0.59 mm. CONCLUSION: Corneal thickness measurements after high-risk penetrating keratoplasty are of prognostic value.