Keratoconus is a progressive, ectatic corneal disorder, characterized by protrusion of the cornea and thinning of the corneal stroma, causing astigmatism.
The etiology of keratoconus is still largely unknown, although many biochemical and pathological changes at the structural and cellular level of the corneal abnormalities have been suggested.
Patients with keratoconus often complain of decrease in visual acuity which can be mild or severe depending on the degree of corneal tissue affection. Keratoconus can be classified according to the severity of the clinical and topographic signs into mild, moderate and advanced.
The clinical manifestations of keratoconus include steepening of the cornea, especially inferiorly, thinning of the corneal apex, corneal scarring, Vogt’s striae and Fleischer's ring. In advanced keratoconus, two findings are associated with keratoconus diagnosis; Munson's sign and corneal hydrops.
Early in the disorder the astigmatism can be corrected by glasses. With the progression of the protrusion, the astigmatism needs hard contact lenses or even keratoplasty in advanced cases.
The keratometer aids in the diagnosis of keratoconus. The initial keratometric sign of keratoconus is absence of parallelism and inclination of the mires. The photokeratoscope or placido disc can provide an overview of the cornea and can show the relative steepness of any corneal area. The even separation of the
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rings in the spherical and the astigmatic cornea and the uneven spacing of the rings especially inferiorly in the keratoconic cornea should be noted.
Ultra-sonic Pachymetry is a technique for measuring corneal thickness that aids in diagnosis and evaluation of the stages of keratoconus.
Keratoconus is more accurately distinguished from the normal population by videokeratography. Videokeratoscopy is used clinically to demonstrate the topography changes in keratoconus distinguishing the different stages of keratoconus. Confocal microscopy and specular microscopy allow the visualization of more details in the corneal layers.
The aim of this work was to study the corneal endothelial integrity, count and morphology in keratoconus patients, and to correlate the endothelial changes to the stages of keratoconus.
The critically important functions of the endothelium appear to require its careful assessment in KC corneas. Apparently, as a consequence of problems with different methods of examination used for endothelial assessment, current evidence of changes that have been detected in KC corneas is contradictory. Observations cited in this review raise the possibility that guttae, polymegethism, and pleomorphism could be significant findings in KC, perhaps especially for the cone area and particularly in any location of episodes of acute or subacute hydrops. Any heterogeneity of the endothelium in a KC cornea may not be fully characterized unless observations are made from multiple areas including some in the cone region. Contact lens intolerance in KC may be associated with endothelial changes such as reduced cell density, guttae, polymegethism, and pleomorphism. |
