Intraocular Pressure and Trabecular Meshwork Outflow Facility After Descemet Stripping Endothelial Keratoplasty

Increased intraocular pressure (IOP) is a frequent complication after penetrating keratoplasty and can be due to reduced trabecular meshwork outflow facility. Descemet stripping endothelial keratoplasty (DSEK) is a lamellar technique for replacing pathologic corneal endothelium and may be associated with a lower risk of postoperative IOP rise. In a prospective clinical study we studied IOP and outflow facility before and after DSEK.

In 23 eyes of 23 patients before, 1 day, 6 weeks, and 3, 6, and 12 months after DSEK, IOP was measured using Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT). Trabecular meshwork outflow facility (C-value) was assessed by impression tonography with the Schioetz tonometer. Central corneal thickness was measured by Haag-Streit pachymetry. Best spectacle corrected visual acuity, ocular surface fluorescein staining, and corneal sensation were also recorded.

Mean IOP showed a trend toward increase from preoperatively to 1 year postoperatively, which was not statistically significant (GAT: 13.5±3.3 to 15.3±4.7 mm Hg; DCT: 13.7±2.9 to 16.7±4.8 mm Hg; Schioetz: 12.4±2.8 to 15.3±2.9 mm Hg). Outflow facility increased significantly from 0.19±0.03 before to 0.29±0.05 mm/Δmm Hg/min at 1 year after DSEK (P=0.002). Best spectacle corrected visual acuity increased significantly from 0.98±0.48 to 0.36±0.17 logMAR (P=0.0004). Corneal sensitivity was unchanged and corneal staining significantly decreased from the preoperative to 1 year postoperative period (P=0.01). Mean central corneal thickness changed significantly from 650±59 to 621±73 μm (P=0.002).

IOP as measured by GAT, DCT, and Schioetz tends to increase during the first year after DSEK in eyes without previous glaucoma, whereas trabecular meshwork outflow facility as measured by Schioetz tonography improves. These findings are likely to be due to a progressive increase of corneal rigidity affecting transcorneal pressure measurements of both IOP and trabecular meshwork outflow facility.