Impact of increased intraocular pressure on long-term corneal endothelial cell density after penetrating keratoplasty

Abstract

Purpose: Besides immunological graft rejection, persistently increased intraocular pressure (IOP) is among the most important causes for graft failure after penetrating keratoplasty (PK). The purpose of this study was to assess the longitudinal development of IOP after PK and to investigate possible correlations with corneal endothelial cell density.

Methods: This longitudinal prospective study included 209 eyes after PK with a complete follow-up at 3 months, 6 months, before first suture removal (16 +/- 5 months) and after complete suture removal (21 +/- 5 months). At each examination, IOP was measured by Goldmann applanation tonometry. Endothelial cell density was assessed by specular microscopy (EM 1100, Tomey). The indications for PK were 48% keratoconus, 34% Fuchs' dystrophy, 5.4% stromal dystrophies, 8.6% secondary bullous keratopathy and 4% corneal scars. An iridotomy was performed routinely during PK. The postoperative treatment with topical steroids was standardized.

Results: Preoperatively, the mean IOP was 13.6 +/- 2.9 mm Hg with increased IOP (>21 mm Hg) in 2.0% of eyes. After 3 months, the incidence of increased IOP (24.5 +/- 4.6 mm Hg) was highest (6.7%) and decreased thereafter to 3.0% after complete suture removal. No patients showed IOP higher than 30 mm Hg. A persistently increased IOP for more than 3 months was seen in 2% of patients. At 3 months postoperatively, the mean endothelial cell density was 1,977 +/- 496/mm(2) and did not decrease significantly (p > 0.05) until 6 months (1,771 +/- 507 cells/mm(2)). At the end of the follow-up period, the mean endothelial cell density was significantly reduced (1,347 +/- 501 cells/mm(2)). There was no significant correlation between IOP and mean endothelial cell density at any postoperative examination stage (p > 0.24). Patients with persistently increased IOP for more than 3 months did not have significantly different endothelial cell densities in comparison with those without increased IOP.

Conclusion: From 6 months after PK, the incidence of increased IOP was not higher than the preoperative level. Mild to moderate temporary IOP elevations after PK do not seem to affect the endothelial cell density of the graft until complete suture removal. Further long-term studies are necessary to assess the clinical relevance of these observations.