KEY CONCEPTS
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Superficial corneal epithelium cells show an elongated shape in keratoconus patients.
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Stromal corneal nerves are thicker in keratoconus patients.
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After cross-linking treatment, stromal keratocytes become activated.
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Vogt striae can be seen as vertical and dark linear images.
Introduction
By using confocal microscopy systems, the study of in vivo tissues is possible, noninvasively and in real time, and with high-quality images.
In 1955 Minsky developed the first confocal microscope, a technique based on conjugation of the microscope objective lens and light in a small tissue portion to acquire high-quality images. , The cornea provides an excellent tissue for study by confocal microscopy because of its easy access and transparency. ,
The purpose of this chapter is to describe corneal confocal microscopic findings in keratoconus (KC) and corneal tissue changes after cross-linking treatment.
Corneal Epithelium and Subepithelial Nerve Plexus
In normal conditions, confocal microscopic images of superficial corneal epithelium cells show regular and symmetric shapes. In contrast, superficial epithelium cells in KC patients show regular elongated shapes ( Fig. 19.1A, B ). Basal epithelial cells are similar in both patients with normal eyes and KC patients ( Fig. 19.2 ). Bowman’s layer cannot be seen by confocal microscopy, but the subepithelial nerve plexus, which rests above it, can be observed, and those nerves do not show morphological differences between KC and normal eyes ( Fig. 19.3 ).
Corneal Stroma
With confocal microscopy, evaluating the stromal corneal nerves is possible. Stromal corneal nerves are more visible at slit lamp examination in KC patients compared with normal corneas, and several studies have shown this finding. With corneal confocal microscopy, it has been possible to verify these differences in corneal nerves, as these nerves appear as linear hyperreflective structures in corneal confocal microscopy, can be measured and compared between KC and normal eyes and are thicker in KC patients. By using confocal microscopy, corneal stromal nerve thickness has been measured. The mean stromal nerve thickness in KC patients is 7.2 ± 1.9 (range 3.5–12.0) microns, compared with 5.7 ± 1.7 (range 3.3–10.4) microns in normal eyes ( Fig. 19.4A,B ).
