Measuring the Density of the Corneal Epithelium

A sufficiently high density of endothelial cells is very important for the transparency of the cornea (see Transparency). Gross estimation of the endothelial cell density is possible for a circumscribed area of the cornea using a slit lamp and indirect illumination. Both the viewing axis and illumination axis are offset from the visual axis. Precise quantification and morphologic evaluation of endothelial cells over large areas is only possible by means of specular microscopy, a technique designed especially for this purpose (Fig. 5.4). Exact

122 5 Cornea Computerized corneal topography (videokeratoscopy).

Corneal Topography Astigmatism
Fig. 5.3 a Regular corneal astigmatism in a normal cornea.

5.2 Examination Methods 123 Computerized corneal topography (videokeratoscopy). -

Placido Disc Keratoconus
Fig. 5.3 b Irregular corneal astigmatism in keratoconus. The Placido disk image is shown above; the respective color mapping of refractive values in diopters is shown below.

— Automatic measurement of endothelial cell density.

— Automatic measurement of endothelial cell density.

Specular Count

Fig. 5.4 Specular microscopy permits a precise endothelial cell count (CD = 2159 endothelial cells per mm2) while simultaneously measuring the thickness of the cornea (pachy-metry;

Fig. 5.4 Specular microscopy permits a precise endothelial cell count (CD = 2159 endothelial cells per mm2) while simultaneously measuring the thickness of the cornea (pachy-metry;

analysis is necessary when the number of cells appears extremely low under slit lamp examination and the patient is a candidate for cataract surgery. If exact analysis then verifies that the number of cells is extremely low (below 300-400 cells per mm2), cataract surgery is combined with a corneal transplant. This is done to ensure that the patient will be able to see even after cataract surgery, which sacrifices additional endothelial cells.

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