Corneal endothelial cell density and pachymetry measured by contact and noncontact specular microscopy

Abstract

Purpose To determine the endothelial cell density and thickness of normal human and postkeratoplasty corneas with contact specular microscopy and to compare these measurements with those obtained by noncontact specular microscopy. Setting Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany. Methods The central corneal endothelial cell density and thickness were determined in 65 healthy eyes of 39 patients with a mean age of 71 years ± 12 (SD) and in 50 corneal grafts of 41 patients with a mean age 53 ± 17 years using noncontact (Topcon SP-2000P, Topcon Corp.) and contact (EM-1000, Tomey) specular microscopes. Appropriate conversion factors were used for accurate cell count comparison. Results The mean cell count of the normal corneas was 2445 ± 425 cells/mm 2 measured by noncontact specular microscopy and 2471 ± 393 cells/mm 2 measured by contact specular microscopy ( P = .70). After penetrating keratoplasty, the mean cell density was 1610 ± 499 cells/mm 2 and 1584 ± 469 cells/mm 2, respectively ( P = .88). Significantly lower thickness was measured with the noncontact specular microscope than by contact pachymetry in normal eyes (543 ± 46 μm and 642 ± 42 μm, respectively) and postkeratoplasty eyes (538 ± 61 μm and 627 ± 48 μm, respectively) ( P < .0001). Conclusions To determine endothelial cell density, contact and noncontact specular microscopy may be used interchangeably. However, for the combined measurement of endothelial cell density and pachymetry, the use of the same specular microscope is recommended for long-term patient follow-up.