[Standardized semiquantitative analysis of corneal neovascularization using projected corneal photographs--pilot study after perforating corneal keratoplasty before immune reaction].

BACKGROUND

A semiquantitative scheme for analysis of corneal neovascularization using projected corneal photographs is demonstrated and tested in a pilot study to analyze occurrence of corneal neovascularization in patients after perforating keratoplasty which subsequently developed transplant rejection.

METHODS

Corneal photographs on the slit lamp with diffuse frontal illumination were obtained in a standardized technique. Slides were projected with 100 x magnification and analyzed twice with a 2 months interval. Corneal vessels were graded by two independent observers in each of 12 corneal sectors in a standardized fashion (grade 0: no vessels beyond limbus, 1: vessels between limbus and outer end of a double-running diagonal suture; 2: vessels between outer suture end and graft-host junction; 3: vessels reaching graft-host junction; 4: vessels within donor cornea). All patients with endothelial graft rejection of the prospective Erlangen non-high-risk keratoplasty study were included in a pilot study (1/1997-6/2000: 13 of 325; 4%). One patient without photographs available was excluded. Corneal photographs taken prior to surgery (n = 10), at the last 3 monthly-routine control before (10), at rejection episode (12) and one year later (10) were evaluated for corneal neovascularization.

RESULTS

Interobserver correlation at the two assessments was 0.79 and 0.86 (Kendall's Tau B). Correlation between the assessments at the two analyses 2 months apart was 0.8. New vessels with diameter up to 6 microns can be detected. 8 of 12 analyzed patients (67%) with immune reaction after keratoplasty developed corneal neovascularization within 1 year after operation prior to transplant rejection in at least one corneal sector (2.1 +/- 1.9 sectors; 1-6). At time of rejection, new vessels reached the graft-host junction in 2 patients, in 1 patient vessels grew into the donor cornea, whereas in 8 the vessels were seen beyond the outer suture end without reaching host-graft junction (grade I: 1 patient). New vessels usually pointed to the outer suture ends of the double-running suture.

CONCLUSIONS

Development of corneal neovascularization e.g. after keratoplasty can be assessed reliably using projected slides of corneal photographs at 100 x magnification. This method has the advantage of being more objective, precise and available compared to simple evaluation at the slit lamp. Postkeratoplasty corneal neovascularization seems to be common in non-high-risk eyes later developing transplant rejection. However, new vessels usually do not reach the host-graft junction. Whether neovascularization after keratoplasty demonstrates a risk factor for subsequent transplant rejection remains to be analyzed in a greater study.