Impact of short-term versus long-term topical steroids on corneal neovascularization after non-high-risk keratoplasty

Purpose: To analyze incidence and extent of corneal neovascularization (CN) after non-high-risk keratoplasty and to find out whether duration of posto perative topical steroid therapy (6 vs 12 months) affects CN, corneal endot helial cell count, pachymetry, aqueous flare values, and best-corrected vis ual acuity at 1 year after keratoplasty. Methods: Patients of the prospecti ve Erlangen non-highrisk keratoplasty study with available high-quality cor neal photographs taken preoperatively and 1 year later were analyzed (n=136 ). Corneal photographs were evaluated by two independent observers in a sta ndardized semiquantitative fashion. Slides were projected with 100x magnifi cation and corneal vessels classified into five grades with regard to the l imbus, sutures and host-graft junction in each of 12 corneal sectors. Incid ence and extent of CN after keratoplasty and relation to short-term (0-6 mo nths) versus long-term (0-12 months) postoperative topical steroid therapy were analyzed. The effect of duration of topical steroid therapy on corneal endothelial cell count, pachymetry, aqueous flare values, and best correct ed visual acuity was also analyzed. Of the 136 patients, 69 (51%) were rand omly assigned to short-term and 67 to long-term topical prednisolone acetat e 1%. Results: Fifty-eight percent of patients (n=79) developed a CN within 1 year after keratoplasty in at least one corneal sector (mean 3.1 +/-2.2, range 1-10). At 1 year after keratoplasty, only in 12% of these patients d id at least one vessel reach the host-graft junction or grow into the donor cornea, whereas in 51% vessels were seen beyond the outer suture ends of t he double running suture without reaching the host-graft junction. In 37%, capillaries were located between limbus and outer suture ends. New vessels usually pointed directly or indirectly to the outer suture ends and usually were located around the 12 o'clock and 6 o'clock positions. There was no s ignificant difference regarding incidence and extent of CN I year after ker atoplasty between the long-term and the shortterm group. Duration of topica l steroid therapy had no significant effect on corneal endothelial cell cou nt and thickness, aqueous flare values and best-corrected visual acuity at 6 and 12 months postoperatively (only at 12 months, corneas in the long-ter m treatment group were slightly thicker; P=0.03). Interobserver correlation of vessel assessment was 0.77 (Kendall's tau B). Conclusions: CN is a comm on phenomenon after non-high-risk keratoplasty. New vessels rarely reach th e host-graft junction, most commonly develop from the 6 o'clock and 12 o'cl ock positions and are usually located between epithelium and Bowman's layer (i.e., at the level of the superficial suture). The direction of vessel gr owth from the limbus towards the outer suture ends suggests release of angi ogenic factors in this area. Prolongation of topical steroid therapy after non-high-risk keratoplasty beyond 6 months in this study did not significan tly influence incidence and extent of CN, corneal endothelial cell count, a queous flare values and best-corrected visual acuity observed I year after keratoplasty.