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Year : 2020  |  Volume : 33  |  Issue : 2  |  Page : 563-568

Comparison between axial and tangential corneal topography maps in localization of cone in keratoconus

1 Department of Ophthalmology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Ophthalmology, Menoufia University Student's Hospital, Menoufia, Egypt

Correspondence Address:
Rofaida M Serag EL-Deen
Shebin El-kom, Menoufia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/mmj.mmj_36_19

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Objectives The objectives of this study were to compare axial maps versus tangential maps in the localization of a keratoconus cone using pentacam and to describe the cone characteristics for the different stages of keratoconus. Background Cone location is an essential factor in the selection of intrastromal corneal ring segments' specification used in the treatment of keratoconus. Patients and methods This was a retrospective case series' study conducted between October 2017 and October 2018 on a sample of 100 eyes with keratoconus. Corneal topography with a rotating Scheimpflug device was carried out. Cone location, cone decentration, and morphological patterns were analyzed. Cone location was determined for each eye with both axial and tangential maps and compared for matching. A correlation between kmaxlocation and cone location according to axial and tangential maps was also carried out. Results 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, which was statistically significant (P < 0.001). For stages I, II, and III, the results were statistically significant (P < 0.001). Correlations between kmaxand tangential map were greater than correlations between kmaxlocation and axial map (P < 0.001). For cone apex decentration, the most frequent value of decentration was between 0.5 and 1 mm in the different stages. For morphological pattern, the most frequent cone morphology in different stages was a nipple-shaped cone. Conclusion Analysis of axial and tangential corneal topography maps showed a significant discrepancy in cone location in the form of 'centralization tendency' on the tangential map. No correlations between stage, morphology, or decentration were revealed.

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