[Influence of corneal thickness on intraocular pressure measurements following Descemet's stripping automated endothelial keratoplasty (DSAEK)]

Challenges in the complex management of post-keratoplasty glaucoma

Glaucoma is a serious complication after corneal transplantation and itself a common cause for graft failure and leading cause of vision loss post-keratoplasty due to corneal endothelial decompensation. Endothelial keratoplasty procedures like Descemet stripping automated endothelial keratoplasty (DSAEK) and Descemet membrane endothelial keratoplasty (DMEK) may be superior to penetrating keratoplasty (PK) regarding the incidence of elevated intraocular pressure (IOP) and development of glaucoma. There are indications that regardless of the method of keratoplasty, some corneal diseases like pseudophakic bullous keratopathy, corneal perforation, and graft rejection have a higher risk for developing post-keratoplasty glaucoma than keratoconus and corneal dystrophies and likewise respond less to IOP lowering therapy. In this review, the pathophysiology of post-keratoplasty glaucoma, the diagnostic tools with focus on different devices, and their limitations with regard to measuring IOP and the treatment modalities are presented.

Intraocular pressure measurement after DSAEK by iCare, Goldmann applanation and dynamic contour tonometry: A comparative study

PURPOSE

Corneal thickness inevitably increases following Descemet's stripping automated endothelial keratoplasty (DSAEK), owing to the addition of a donor graft. The current study compares different devices in assessing post-DSAEK intraocular pressure (IOP).

METHODS

We compared IOP values measured by the Goldmann tonometry (GAT), iCare rebound tonometry (iCare) and Pascal dynamic contour tonometry (PDCT) in eyes following DSAEK. Agreement between measurements was calculated with correlation analysis and Bland-Altman plots. Effects of keratometry, central, thickness (CCT), endothelial cell density (ECD) and axial length on IOP measurements were assessed with Pearson's correlation.

RESULTS

Twenty eyes of 20 patients (mean age 74.3±14.4, 14 females) post-DSAEK were included in this study. There was a high concordance between the IOP readings obtained by the three devices: a strong and significant correlation was found between GAT and PDCT (r=0.94, P<0.001) GAT and iCare (r=0.86, P<0.001) and iCare with PDCT (r=0.81, P<0.001). However, the iCare measurements were significantly and consistently lower than that obtained with GAT (ΔIOP=1.68±2.0, P=0.002, 95% CI: 0.7-2.6) and with PDCT (ΔIOP=1.61±2.5, P=0.01, 95% CI: 0.4-2.8). CCT, ECD, CCT, AXL, corneal curvature or astigmatism did not influence IOP measurement by any instrument.

CONCLUSIONS

IOP measurement with three different techniques (applanation, rebound and dynamic contour) showed good correlations, despite an increased corneal thickness following DSAEK. However, the iCare, which is based on a rebound tonometry showed significant lower IOP then the two other methods. This should be taken into account when evaluating patients post DSAEK.

Anterior segment analysis and intraocular pressure elevation after penetrating keratoplasty and posterior lamellar endothelial keratoplasty

BACKGROUND

Peripheral anterior synechiae (PAS) is a common problem after penetrating keratoplasty (PK) and leads to intraocular pressure (IOP) elevation. This study examines the risk factors for IOP elevation and post-keratoplasty glaucoma.

METHODS

A retrospective analysis was performed of 47 eyes following PK and of 65 eyes following Descemet's stripping endothelial keratoplasty (DSEK) between 2009 and 2011. The assessment included preoperative history of corneal disease and glaucoma, response to treatment, IOP, and visual acuity. Irido-trabecular contacts (ITC), the angle opening distance (AOD 500) and the anterior chamber angle (ACA 500) were calculated.

RESULTS

The incidences of IOP elevation and post-keratoplasty glaucoma were 27-36% and 10-29%, respectively. The incidence did not differ significantly between both procedures. Pre-existing glaucoma increased the risk for developing IOP elevation and post-DSEK glaucoma. Eyes with bullous keratopathy (BK) developed significantly more IOP elevation (p = 0.01, d.f. = 1, χ(2) = 6.11) and post-keratoplasty glaucoma (p = 0.01, d.f. = 1, χ(2) = 6.22) than eyes with Fuchs' endothelial dystrophy. Eyes with ITC developed post-keratoplasty glaucoma significantly more often than eyes without ITC (p = 0.01, d.f. = 1, χ(2) = 6.63).

CONCLUSION

IOP elevation and post-keratoplasty glaucoma showed a high incidence. Risk factors like pre-existing glaucoma, BK and PAS elevated the rate of IOP elevation and post-keratoplasty glaucoma for both procedures.