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Comparison between axial and tangential corneal topography maps in localisation of cone in keratoconus using Pentacam

Poster Details

First Author: A.El Sebaey Sarhan EGYPT

Co Author(s):    A. Elsebaey Sarhan   A. Ibrahim   R. Moustafa              

Abstract Details


To compare axial maps vs tangential maps in localisation of cone in Keratoconus using Pentacam and to describe the cone characteristics for the different stages of keratoconus.


This study was conducted at Tiba Eye Center and Ophthalmology Department of Menoufia University, Menoufia, Egypt during the period from October 2017 to October 2018


100 keratoconic eyes examined by Pentacam (WaveLight® Allegretto Oculyzer). Cone characteristics, including cone location, cone decentration, morphological patterns were analyzed. Cone location was labelled as central, paracentral or peripheral according to the extent of the cone area. Cone was labelled central or paracentral if more than half of the diameter fell within the central 3 or 5 mm respectively. Otherwise, it was labelled as peripheral. Cone location was determined for each case with both axial and tangential maps and compared for matching. Correlation between Kmax location and cone location according to axial and tangential maps was also established.


Our results revealed that the matching rate between axial and tangential maps in the total sample was 100%, 5%, and 9.6% for central, paracentral and peripheral groups respectively (p<0.001). Moreover, the paracentral group showed the greatest discrepancy where 38 out of 40 (95%) were labelled as central on tangential map although displayed as paracentral on the axial map. There was a positive correlation between Kmax location and cone location. The correlation between Kmax and tangential map was greater than correlation between Kmax location and axial map (p<0.001). For morphological pattern, the most frequent cone morphology in different stages was a nipple-shaped cone.


Analysis of axial and tangential corneal topography maps showed a significant discrepancy in cone location in a form of 'centralization tendency' on the tangential map. No correlation between stage, morphology or decentration was respectively revealed.

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