Evaluation of mild, moderate, and advanced keratoconus using ultrasound pachometry and the EyeSys videokeratoscope.
BACKGROUND
The absolute accuracy of videokeratoscope (VKS) mapping of keratoconus is still in question, with contact lens-induced corneal warpage and chalazion having been shown to resemble this condition closely. Corneal thinning is investigated as a further aid to the diagnosis and description of keratoconus.


METHODS
The diagnosis of keratoconus in 41 individuals was verified by measuring the corneal thickness difference (I-S difference) between two disparate corneal locations, one inferior to (I) and one superior to (S) the corneal apex, using a Humphrey model 870 Ultrasound pachometer. Corresponding measures of I-S radii were made using radius values obtained from the EyeSys VKS.


RESULTS
A comparison between I-S pachometry and I-S radius demonstrated a marginally increased sensitivity for the latter measurement. Using 95% confidence levels from normative pachometric data, classification of severity of keratoconus is proposed as follows: (1) keratoconus suspect/early keratoconus: I-S pachometry 75 to 100 microns; (2) moderate keratoconus: 100 to 125 microns; and (3) advanced keratoconus: > 125 microns.


CONCLUSIONS
I-S pachometry can be used as a descriptor of keratoconus.
Department of Optometry and Vision Science, University of Auckland, New Zealand.
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Watters
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Owens
D003315:Cornea / Q000000981:diagnostic imaging* / Q000473:pathology*; D019781:Corneal Topography / Q000379:methods*; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000145:classification / Q000175:diagnosis*; D008297:Male; D014463:Ultrasonography