Immunological graft reactions after penetrating keratoplasty - A prospective randomized trial comparing corneal excimer laser and motor trephination

Background and Purpose: Nonmechanical trephination has been established as an advantageous procedure in penetrating keratoplasty (PK) for avascular co rneal diseases and has been performed successfully in more than 1000 eyes a t our institution. The purpose of this study was to compare incidence, type and reversibility of immunological graft reactions after mechanical and no nmechanical trephination for PK. Patients and Methods: As part of a prospective randomized clinical trial 17 9 eyes of 76 females and 103 males were included, that had primary central PK without previous intraocular surgery between 10/1992 and 12/1997 for Fuc hs' dystrophy (diameter 7.5 mm, n = 73) or keratoconus (8.0 mm, n = 106). T he recipient and donor trephinations were performed from the epithelial sid e using either a motor trephine (Microkeratron, Geuder, n = 91) or an 193-n m excimer laser (MEL60, Aesculap-Meditec, 1.5 x 1.5 mm spot mode, 16-24 mJ/ pulse, repetition rate 25/s) along round metal masks with 8 "orientation te eth/notches" (n = 88). As a routine, donor oversize was 0.1 mm. 128 patient s (72%) had PK only, 51 patients had simultaneous cataract extraction and P C-IOL implantation (triple procedure). Wound closure was achieved using a 1 6-bite double running diagonal suture by one surgeon (G.O.H.N.). In 53% of procedures short-term-preserved donor tissue, in 47% organ-cultured tissue was used. The mean patient/donor age was 51 +/- 17/57 +/- 19 years with non mechanical trephination and 50 +/- 19/58 +/- 20 years with mechanical treph ination. Incidence, type and reversibility of endothelial immunologic graft reactions were recorded continuously by clinical follow-up in an outpatien t service with cornea specialization (after 6 weeks, then every 3 months un til after suture removal, then every half year). Results: During a mean follow-up of 40 +/- 15 months, 7.3% of eyes develope d an immunological endothelial graft reaction. Acute diffuse (5.6%) were mo re frequent than chronic focal reactions (1.7%). Only 1.7% of grafts became irreversibly cloudy. More than 80% of all graft recations occurred later t han one year (on average 23 +/- 13 months) after PK. Neither incidence (p = 0.82, Chi square test) nor cumulative 3-year-rate of immunological graft r eactions (p = 0.91, LogRank test) differed significantly comparing nonmecha nical (6.8% or 7.3%) and mechanical (7.7% or 5.6%) trephination. In eyes wi th keratoconus (6.6%, 16 +/- 8 months) graft reactions did not occur more f requently (p = 0.68) but earlier (p = 0.02) than in eyes with Fuchs' dystro phy (8.2%, 31 +/- 11 months). Donor age, post-mortem-time and preservation period did not significantly affect the rate of graft reactions in our stud y setting. Conclusions: Besides well-established optical advantages, non-mechanical tr ephination using the excimer laser seems to have no immunologic drawbacks i n contrast to conventional mechanical trephination. Donor parameters appear to have no major impact on the incidence of graft reactions after non-high -risk PK. Rather, an adequate postoperative therapy with topical steroids, an informed patients' compliance, a consequent long-term follow-up in a cli nical out-patient service with corneal specialization and a good education of and cooperation with the referring ophthalmologists are of utmost import ance for the clear corneal graft in the long run.