A frequency analysis of cone characteristics for the different stages of keratoconus

Background: The stages of keratoconus can be classified according to the degree of corneal conicity as either early or advanced, or morphologically by the shape of the cone. Knowledge of the different cone characteristics for the different stages of keratoconus may assist practitioners in diagnosing and managing these patients. Aim: To describe the cone characteristics for the different stages of keratoconus. Methods: In this retrospective study, a sample of 190 eyes from 106 cases of previously diagnosed keratoconic patients was analysed. The stage of keratoconus and cone characteristics, namely: cone location, cone decentration, morphology, and topographical patterns were analysed using an Oculus 3M corneal topographer. Results: Our study revealed that for all stages of keratoconus centrally located cones were the most frequent, with corneal apical decentration between 0 mm and 2 mm. Frequency analysis revealed that nipple cones were most frequent in all stages. Topographical pattern frequencies revealed a wide distribution amongst the different corneal patterns in all stages of keratoconus. Conclusion: Cone analysis should be of consideration to the contact lens practitioner when deciding on management of the condition. It additionally serves to compliment the clinical signs such as nerve visibility, Fleischer’s ring, Vogt’s striae and corneal scarring