Diagnostic Accuracy of Anterior Segment Optical Coherence Tomography Pachymetry Mapping and Detection for Early Keratoconus using Corneal Topography as Gold Standard

Abstract

Background: Optical coherence tomography (OCT) derived pachymetry mapping has potential in diagnosis of early and advancing keratoconus. The OCT corneal pachymetry map–based logistic regression formula and the keratoconus risk scoring system has been proven to provide very accurate results in keratoconus identification. In keratoconus screening these techniques might be helpful. Objectives: To ascertain the diagnostic accuracy of anterior segment optical coherence tomographic corneal pachymetry to diagnose the cases the cases of early keratoconus by using corneal topography as a high standard with which other techniques of these kinds are compared. Study Design: Cross-sectional (validation) study. Duration: One year from July 01, 2019 to June 30, 2020. Settings: Department of Ophthalmology, Allied Hospital/DHQ Hospital, Faisalabad Pakistan. Methodology: A total of 195 patients having asymmetrical astigmatism (>1 diopter), 12-40 years of age of both genders were included. Patients with corneal ulcer and corneal opacity were excluded. After complete examination corneal topography and anterior segment optical coherence tomography was performed. Tomographic minimum central corneal thickness was recorded and assessed for cutoff value, if exceeding cutoff value patient was diagnosed with the early keratoconus. Results: In OCT pachymetry positive patients, 103 (True Positive) had early keratoconus and 05 (False Positive) had no early keratoconus on corneal topography. Among 87, OCT pachymetry negative patients, 04 (False Negative) had early keratoconus on corneal topography whereas 83 (True Negative) had no early keratoconus on corneal topography (p=0.0001). Overall sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of anterior segment optical coherence tomographic corneal pachymetry to diagnose the cases of early keratoconus in the suspected individuals by using corneal topography as gold standard was 96.26%, 94.32%, 95.37%, 95.40% and 95.38% respectively. Conclusion: This study concluded that diagnostic accuracy of anterior segment optical coherence tomographic corneal pachymetry to find out the cases of early keratoconus is very high. Keywords: Optical coherence tomographic corneal pachymetry, Keratoconus, Sensitivity