An evaluation of the keratoconic cornea using computerised corneal mapping and ultrasonic measurements of corneal thickness.

Reports indicate the presence of up to three independent cone shapes in keratoconus (round/oval/global) but the preponderance of one cone over another is unclear. This work evaluates keratoconic corneal topography and corneal thickness using videokeratoscopy and ultrasound pachometry, respectively. An EyeSys videokeratoscope (VKS) (EyeSys Laboratories, Houston, TX, USA) was used to assess the topography of 54 keratoconic eyes (27 subjects) and 27 age-matched normals. In addition, ultrasonic pachometry measurements were made over 14 known areas in normal and keratoconic eyes. Corneal thinning was significant for all keratoconic areas measured except for the far temporal cornea. A correlation between corneal radius and thickness was evident. Analysis of cone shape revealed a potential fourth variety: the asymmetric bow-tie cone. Further topographic evaluation of this cone entity using the VKS revealed its dependence on gaze direction which may account for apparent differences in progression patterns between round and bow-tie cones.