A Comprehensive Evaluation of Corneal Tomographic and Topographic Indices Using Pentacam and Sirius for the Diagnosis of Keratoconus and Subclinical Keratoconus
Zahra Heidari1 , Hassan Hashemi2 , Mehrdad Mohammadpour3 *, Akbar Fotouhi4
- Department of Rehabilitation Science, School of Allied Medical Sciences, Mazandaran University of Medical Sciences, Sari, Iran.
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
- Department of Ophthalmology, Farabi Eye Hospital and Eye Research Center, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Abstract: Assessment of the diagnostic ability of tomographic and topographic corneal indices using Pentacam (Oculus, Wetzlar, Germany) and Sirius (Costruzione Strumenti Oftalmici, Italy) for the detection of keratoconus (KCN) and subclinical keratoconus (SKCN).
Methods: In this prospective diagnostic test study, 70 Patients with clinical KCN, 79 patients with abnormal findings in topography and tomography maps with no evidence on clinical examination (subclinical KCN), and 68 normal control subjects were enrolled. The accuracy of tomographic and topographic parameters was evaluated using the area under the receiver operating characteristic curve (AUC), and the Delong method was used for comparing AUCs.
Results: In differentiating KCN from normal, all parameters showed statistically significant differences between the two groups (P<0.001). Indices with the excellent diagnostic ability (AUC?0.999) were Sirius KCN vertex of back (KVb), and Pentacam random forest index (PRFI), Pentacam index of height decentration (IHD). In differentiating SKCN from normal, Sirius Symmetry Index of back (SIb) (AUC =0.908), Pentacam inferior-superior difference (IS) value (AUC=0.862), and PRFI (AUC=0.847) performed best. There were no significant differences between the highest AUCs within keratoconic groups (DeLong, P>0.05).
Conclusion: In KCN, all tomographic and topographic indices have acceptable results in terms of sensitivity and specificity. However, in distinguishing subclinical KCN from normal corneas, curvature-based parameters (SIb and IS value) followed by integrated index (PRFI) are the most powerful indices for early detection of keratoconus.
