Comparison of a videokeratoscope and an autokeratometer as predictors of the optimum back surface curves of rigid corneal contact lenses.
OBJECTIVE
To determine the differences in the corneal topography derived using a 16 mire videokerascope and a 2 mire autokeratometer and to examine whether the differences are clinically significant in the contact lens fitting context.


METHODS
The right corneas of 20 subjects were measured by an Eyesys videokeratoscope (windows workstation: version 2000 W) and a Topcon Autokeratometer (KR 3500). The corneal vertex radius and p-value were deduced and used to calculate the back surface specifications of a rigid corneal tricurve contact lens design required for an optimal fit on the corneal model. The study was aimed to evaluate the differences in contact lens specifications related to the current British Standards on contact lens tolerances.


RESULTS
In general there was good agreement in the lens specification derived from the two instruments. The differences that were present were small and, with the exception of the second back peripheral radius, were within tolerance limits.


CONCLUSIONS
The corneal topography was adequately described by the two mire keratometer for the purpose of fitting this particular lens design on the corneas of the 20 subjects examined.
Douthwaite
W
W
Department of Optometry, Bradford University, UK.
Pardhan
S
S
D000293:Adolescent; D000328:Adult; D003261:Contact Lenses; D003315:Cornea / Q000033:anatomy & histology*; D019781:Corneal Topography / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D014741:Video Recording