Abstract
Purpose: :
Assessment of keratocyte density in corneas with Fuchs’ endothelial dystrophy by confocal microscopy might be inaccurate because stromal haze could affect the visibility of cells. In this study, we estimated keratocyte populations by confocal microscopy in patients with Fuchs’ dystrophy and examined accuracy of this estimate in corneas that were also assessed by using histologic methods after penetrating keratoplasty (PK).
Methods: :
Eleven corneas with Fuchs’ endothelial dystrophy from 11 patients (age 62-89 years) were examined by confocal microscopy (Tandem Scanning confocal microscope). Keratocyte density was determined by using an automated cell counting program in 10 selected frames distributed through the stroma, and the number of cells was calculated in a full thickness column of stroma with frontal area of 1 mm2 (referred to as "column"). The column was subdivided into anterior 10% and 10-100% layers of stromal thickness. In two of these corneas, removed for PK, the central cornea was fixed, cut in 4 µm-thick sagittal sections and stained with DAPI. Keratocyte nuclei were counted manually from 14 sections and the mean number of cells in a column was calculated by using stereologic methods. The number of cells in a column in corneas with Fuchs’ dystrophy was compared to that in 44 normal corneas of 44 volunteers (age: 21-60 years) by using unpaired t-tests.
Results: :
In the two corneas with histology, the number of cells in the anterior 10% of the column was 1,529 ± 93 (mean ± sd) by confocal microscopy and 771 ± 215 by histology. Excluding this anterior layer, the number of cells from 10-100% of the column was 9,192 ± 1,288 by confocal microscopy and 10,537 ± 525 by histology. The number of cells from 10-100% of the column was 8,563 ± 1,779 in corneas with Fuchs’ dystrophy and 9,217 ± 1,628 in normal corneas (p=0.25); the minimum detectable difference was 1,594 cells (unpaired test, α=0.05, β=0.20).
Conclusions: :
The number of keratocytes distributed through the deeper central stroma (10-100%) in Fuchs’ dystrophy is similar to the number of cells in normal corneas, although volumetric density may be lower because of edema. Based on two histologic samples, the ability to identify keratocytes from confocal images of corneas with Fuchs’ dystrophy is good except in the anterior 10% of stroma, and this might be explained by increased haze in the anterior stroma.
Keywords: cornea: stroma and keratocytes • imaging/image analysis: clinical • microscopy: confocal/tunneling