The corneal endothelium reflected: Studies on surgical damage tot the corneal endothelium and on endothelial specular microscopy

The endothelium is the innermost layer of the cornea. It is a mosaic of hexagonal cells that is only one cell thick. These endothelial cells actively maintain the corneal hydration equilibrium, and hence are very important for its transparency. However, they are vulnerable to trauma, disease, and intra-ocular surgery, because they have a very restricted capacity for cell division. In part II, studies are presented on the reliability of in-vivo examinations of the endothelium with a specific type of specular microscope. We found that after correct calibration and with adequate assessment methods, valid and reproducible measurements of the endothelial cell density (ECD) could be obtained. However, there is a systematic difference between specular microscopic ECDs and donor cornea ECDs that are measured with a different technique. This difference can only in part be explained by optical factors. In part III, in a clinical and an experimental study, no toxic effects on the endothelium of current common applications of the dye trypan blue, in cataract surgery and in eye banks on donor corneas, could be observed. However, caution is warranted, as higher concentrations or longer exposures were found to cause substantial toxicity. In part IV, endothelial cell loss patterns were investigated after selective transplantation of different parts of the cornea (deep anterior and posterior lamellar keratoplasty, DALK and PLK). After DALK, ECD-loss approached normal levels after an initial drop. When however in PLK a posterior lamella including the endothelium was transplanted, ECD-loss continued at an increased level for up to 7 years. The possible consequences of this result for graft survival were discussed

Toric intraocular lenses for correction of astigmatism in keratoconus and after corneal surgery

Purpose: To describe the results of cataract extraction with toric intraocular lens (IOL) implantation in patients with preexisting astigmatism from three corneal conditions (keratoconus, postkeratoplasty, and postpterygium surgery). Methods: Cataract patients with topographically stable, fairly regular (although sometimes very high) corneal astigmatism underwent phacoemulsification with implantation of a toric IOL (Zeiss AT TORBI 709, Alcon Acrysof IQ toric SN6AT, AMO Tecnis ZCT). Postoperative astigmatism and refractive outcomes, as well as visual acuities, vector reduction, and complications were recorded for all eyes. Results: This study evaluated 17 eyes of 16 patients with a mean age of 60 years at the time of surgery. Mean follow-up in this study was 12 months. The corrected distance Snellen visual acuity (with spectacles or contact lenses) 12 months postoperatively was 20/32 or better in 82% of eyes. The mean corneal astigmatism was 6.7 diopters (D) preoperatively, and 1.5 D of refractive cylinder at 1-year follow-up. No vision-compromising intra- or postoperative complications occurred and decentration or off-axis alignment of toric IOLs were not observed. Conclusion: Phacoemulsification with toric IOL implantation was a safe and effective procedure in the three mentioned corneal conditions. Patient selection, counseling, and IOL placement with optimal astigmatism correction are crucial

Improved interchangeability with different corneal specular microscopes for quantitative endothelial cell analysis

Introduction: During our clinical practice and research, we encountered an interchangeability problem when using the SP-2000P and SP-3000P TopCon corneal specular microscopes (CSMs) (TopCon Medical Systems, Tokyo, Japan) regarding the endothelial cell count (ECC). We describe a method to improve interchangeability between these CSMs. Methods: Five consecutive good-quality endothelial cell photographs were obtained in 22 eyes of 11 subjects. An ECC comparison between the two CSMs was performed after (I) gauging and calibration by the manufacturer, (II) adjustment of the magnification, (III) correction after external horizontal and vertical calibration. Results: There was a statistically significant difference between the ECC of the SP-2000P and SP-3000P at the start. The SP-2000P counted an average of 500 cells/mm2 more than the SP-3000P (p=0.00). After correction for magnification and determining a correction factor based on external calibration, the difference between the ECC of the SP-2000P and the SP-3000P was then found to be 0.4 cells/mm2 and was not statistically significant (p=0.98). Discussion: We propose a method for improving interchangeability, which involves checking magnification settings, re-checking magnification calibration with external calibration devices, and then calculating correction factors. This method can be applied to various specular or confocal microscopes and their associated endothelial cell analysis software packages to be able to keep performing precise endothelial cell counts and to enable comparison of ECCs when a CSM needs to be replaced or when results from different microscopes need to be compared

Endothelial cell decay after Descemet's stripping automated endothelial keratoplasty and top hat penetrating keratoplasty

Purpose. To analyze endothelial cell density (ECD) decay after Descemet's stripping automated endothelial keratoplasty (DSAEK) and top hat keratoplasty (THPK) in patients with Fuchs' endothelial dystrophy (FED) and/or pseudophakic bullous keratopathy (PPBK). Methods. Patients underwent either THPK (n = 33) or DSAEK (n = 39) at the Erasmus Medical Center, Rotterdam. For each nonrandomized cohort, a biexponential regression model for ECD decay was fitted. Factors associated with higher ECD decay were evaluated. Results. Median follow-up was 31.2 months (range, 11-91) in the THPK cohort, and 23.4 months (range, 6-61) in the DSAEK group. The early ECD decay was much higher after DSAEK (half time, 2.2 months) than after THPK (half time, 12.8 months). The late ECD decay after DSAEK was less steep (half time, 75.5 months) than after THPK (half time, 62 months). The 1-, 3- and 5-year endothelial cell losses derived from the models after DSAEK were 56%, 66%, and 73%, respectively, and after THPK were 24%, 50%, and 64%, respectively. For the DSAEK cohort, PPBK as an indication for surgery was associated with significantly higher late-phase decay rates. For the top-hat cohort, a significantly lower late-phase decay rate was found in PPBK. FED and same-session cataract surgery were confounding variables in the DSAEK cohort. Regarding DSAEK, postoperative re-bubbling was not found to have significant effects on early or late ECD decay rates. However, the small sample size and other limitations related to the method of evaluation may have influenced these findings. Conclusions. After DSAEK, early ECD decay was stronger than after THPK, as opposed to late decay. Late decay was faster for PPBK than for FED after DSAEK