IMMUNOLOGICAL GRAFT REACTIONS AFTER NONMECHANICAL CORNEAL TREPHINATION USING THE EXCIMER-LASER

Background: Nonmechanical trephination has been established as the sta ndard procedure in penetrating keratoplasty (PK) for avascular corneal diseases at our institution. The purpose of this study was to analyze the incidence and reversibility of immunologic graft reactions after nonmechanical trephination and to detect potentially causative factors . Patients and methods: Out of a total series of 400 nonmechanical PKs , 286 consecutive procedures with sufficient follow-up performed betwe en 07/1989 and 09/1997 were included in the study (104 x keratoconus, 78 x Fuchs' dystrophies, 31 xbullous keratopathies, 28 x ulcers, 25 x avascular scars, 12 x stromal dystrophies, 4 x buphthalmos, 4 x others ; 202 x PK only, 84 x combined procedures; 276 first PK). The age of t he 138 females and 148 males at the time of surgery ranged from 16 to 89 (mean 55 +/- 19) years. The recipient and donor trephinations were performed from the epithelial side using an 193-mm excimer laser (MEL5 0 or MEL60, Aesculap-Meditec, 1.5 x 1.5 mm spot mode, 16-24 mJ/pulse, repetition rate 30 or 25/s; metal masks). The shape of the recipient t rephination was either circular with four or eight ''orientation teeth '' (n = 251; 5.0-8.0 mm diameter) or elliptical (n = 35, 6.0 x 7.0 to 7.5 x 8.5 mm diameter). In 62 % of procedures fresh or short-term-pres erved donor tissue was used, and in 38 % of procedures the donor tissu e was organ-culture-preserved. Results: During a mean follow-up of 22 +/- 18 months (maximum 7.7 years), 10 acute diffuse (3 irreversible; 1 .0 %) and 3 ch ron ic focal endothelial graft reactions occurred (4.5 %) not earlier than 4 months and not later than 35 months after PK. El ective procedures (3.5 %) resulted in significantly (P = 0.01) less re actions than acute corneal ulcers (14.3 %). After 1, 2 and 3 years, th e cumulative reaction rates (Kaplan-Meier values) were 1.3 %, 6.3 % an d 13.9 % in elective procedures, none of which, however, occurred afte r 26 elliptical trephinations. With fresh or short-term-preserved dono r tissue (4.2 %), graft reactions did not happen more frequently but e arlier (12 +/- 6 months) than with organ-culture-preserved donor tissu e (2.2 %, 30 +/- 6 months). In patients with keratoconus (4.9 %), reac tions occurred more frequently (P = 0.05, LogRank) and earlier than in patients with Fuchs' dystrophy(1.3 %). Conclusions: In addition to we ll-established optical advantages, nonmechanical trephination seems to have no immunologic drawbacks.