In vivoconfocal microscopy of the normal equine cornea and limbus

Abstract

Objective To describe morphologic features, pachymetry and endothelial cell density of the normal equine cornea and limbus by in vivo confocal microscopy. Animals studied Ten horses without ocular disease. Procedure The central and peripheral corneas were examined with a modified Heidelberg Retina Tomograph II and Rostock Cornea Module using a combination of automated and manual image acquisition modes. Thickness measurements of various corneal layers were performed and endothelial cell density determined. Results Images of the constituent cellular and noncellular elements of the corneal epithelium, stroma, endothelium, and limbus were acquired in all horses. Corneal stromal nerves, the subepithelial nerve plexus, and the sub-basal nerve plexus were visualized. Cells with an appearance characteristic of Langerhans cells and corneal stromal dendritic cells were consistently detected in the corneal basal epithelium and anterior stroma, respectively. Median central total corneal thickness was 835 lm (range 725-920 lm) and median central corneal epithelial thickness was 131 lm Conclusions In vivo corneal confocal microscopy provides a noninvasive method of assessing normal equine corneal structure at the cellular level and is a precise technique for corneal sublayer pachymetry and cell density measurements. A resident population of presumed Langerhans cells and corneal stromal dendritic cells was detected in the normal equine cornea. The described techniques can be applied to diagnostic evaluation of corneal alternations associated with disease and have broad clinical and research applications in the horse.

Morphology of endothelial cells from different regions of the equine cornea

“…Using images obtained by specular microscopy, it is possible to examine the corneal endothelium and obtain data related to endothelial cell density and morphology. This technique has been used to quantify endothelial parameters in humans and other animal species including pigs (TAMAYO-ARANGO et al, 2009), rabbits (SAILSTAD & PEIFFER, 1981;OJEDA et al, 2001), dogs (GWIN et al, 1982;PIGATTO et al, 2006;RODRIGUES et al, 2006), horses (ANDREW et al, 2001;LEDBETTER & SCARLETT, 2009), llamas and alpacas (ANDREW et al, 2002), chinchillas (BERCHT et al, 2015), and cats (FRANZEN et al, 2010), among others. The high cost of specular microscopes and the difficulty in obtaining good images in injured endothelial areas are common challenges or barriers to the use of this technique (ANDREW et al, 2001;PIGATTO et al, 2005a;SAAD et al, 2008).…”

“…Furthermore, the only way to treat horses with cataract is to surgically remove the opacified lens (MILLICHAMP & DZIEZC, 2000;HARDMAN et al, 2001;FIFE et al, 2006;HARRINGTON et al, 2013). Regarding equine corneal endothelium, there are only two published studies (ANDREW et al, 2001;LEDBETTER & SCARLETT, 2009). However, none of these previous studies analyzed the endothelial morphology with respect to different regions of the cornea of healthy horses.…”

Corneal Surface and Superficial Cells as Viewed by Scanning Electron Microscopy and Impression Cytology Sampling

“…In marked contrast, other coronal imaging techniques have revealed a contiguous mosaic of polygonal shapes (with a large range of sizes) but having lighter, medium, or darker appearances as viewed by specular microscopy, 11-15 by confocal microscopy, 8,[15][16][17][18][19][20][21][22][23] or by scanning electron microscopy (SEM). [24][25][26][27][28] It has been proposed that the larger dark reflex cells seen in SEM are those terminally differentiated "hypermature" cells in the final stages before desquamation.…”

The role of in vivo confocal microscopy in the diagnosis of hidden corneal foreign bodies

“…using the sequence scanning mode, which allowed images to be repeatedly acquired at different focus positions, enabling the construction of a three-dimensional image. [9][10][11] The scanned images were recorded for analysis.…”