ESCRS - FPS03.02 - Topographic, Elevation, And Keratoconus Indices For Diagnosis Of Keratoconus By A Combined Placido And Scheimpflug Topography System

Topographic, Elevation, And Keratoconus Indices For Diagnosis Of Keratoconus By A Combined Placido And Scheimpflug Topography System

Published 2022 - 40th Congress of the ESCRS

Reference: FPS03.02 | Type: Free paper | DOI: 10.82333/6s3w-xf47

Authors: Ahmed Hamdy Oreaba* 1

1Moorfields Eye Hospital,London,United Kingdom;Eye World Hospital,Dokki, Giza,Egypt

Purpose

To determine the accuracy of various corneal parameters in keratoconus diagnosis using Scheimpflug camera combined with Placido disk corneal topography (Sirius, CSO).

Setting

Eye World Hospital, Dokki, Giza, Egypt

Methods

One hundred and fifteen keratoconic eyes (group1) and a 111 normal eyes (group2) were assessed prospectively between March 2018 and July 2019 for: corneal keratometric indices at different corneal rings of both corneal surfaces, central corneal thickness, thinnest corneal thickness , corneal asphericity, elevation at thinnest point, root mean square, and root mean square per area in spherical, aspheric and aspherotoric reference for both corneal surfaces and keratoconus summary parameters; surface asymmetry index of front and back, elevation at keratoconus vertex front and back, Baiocchi Calossi Versaci front and back index (BCVf, BCVb) and its vector summation (BCV) and convergence radius and cutoff value for each was calculated.

Results

All studied indices were significantly different between the two groups. The highest predictive accuracy “Area under receiver operating characteristic curve (AUROC)” of 0.999 was observed for BCVf, KVb, RMS and RMS/A at 6 mm aspherotoric reference posterior surface. Keratoconus summary indices had high AUROC (0.986, 0.984, 0.948, 0.999, 0.999, 0.998 respectively). Curvature indices had lower AUROC than elevation indices, except for curvature of corneal apex at anterior (0.98) and posterior surface (0.99). Higher AUROC was noted with elevation at thinnest point especially at aspherotoric reference surface.

Conclusions

Sirius topography showed high predictive accuracy in detection of keratoconus. Elevation indices and keratoconus summary parameters have the highest diagnostic ability.