Emarah, S., Awad, E., Samra, W., Khalaf, M. (2022). Astigmatic Vector Analysis of Posterior Corneal Surface; Healthy versus Keratoconic Corneas. test, 2(1), 1-9. doi: 10.21608/ejomos.2022.94204.1031
Sally G. Emarah; Eman Awad; Waleed Ali Abou Samra; Mohamad Ahmad Khalaf. "Astigmatic Vector Analysis of Posterior Corneal Surface; Healthy versus Keratoconic Corneas". test, 2, 1, 2022, 1-9. doi: 10.21608/ejomos.2022.94204.1031
Emarah, S., Awad, E., Samra, W., Khalaf, M. (2022). 'Astigmatic Vector Analysis of Posterior Corneal Surface; Healthy versus Keratoconic Corneas', test, 2(1), pp. 1-9. doi: 10.21608/ejomos.2022.94204.1031
Emarah, S., Awad, E., Samra, W., Khalaf, M. Astigmatic Vector Analysis of Posterior Corneal Surface; Healthy versus Keratoconic Corneas. test, 2022; 2(1): 1-9. doi: 10.21608/ejomos.2022.94204.1031

Astigmatic Vector Analysis of Posterior Corneal Surface; Healthy versus Keratoconic Corneas

Egyptian Journal of Ophthalmology
Volume 2, Issue 1, March 2022, Pages 1-9    PDF (476.81 K)
Document Type: Original Articles
DOI: 10.21608/ejomos.2022.94204.1031
Authors
Sally G. Emarah* 1; Eman Awad2; Waleed Ali Abou Samra2; Mohamad Ahmad Khalaf2
1Ophthalmology Center Faculty of Medicine Mansoura University
2Mansoura Ophthalmic Center, Mansoura University
Abstract
Purpose: To define an unconventional diagnostic factor for keratoconus and to assess the correlation between anterior and posterior corneal surfaces based on vectorial astigmatic analyses.
Design: Observational descriptive comparative cross sectional study
Method: This study included two hundred and forty-four eyes of 244 patients divided into groups; normal corneas, or controls (C, n [100]), fruste (FFKc, n [28]) and manifest keratoconus (Kc, n [116]). Full Ophthalmic examination was performed. All candidates were examined using a rotating Scheimpflug corneal tomographer (Pentacam; Oculus Optikgeräte GmbH, Wetzlar, Germany) to obtain corneal measurements. Astigmatic vector analyses were carried out according to the method proposed by Thibos.
Results: The area under receiver operating characteristic curve (AUC) for posterior corneal APV between normal and manifest keratoconus was 0.73 (95% confidence interval): 0.66 - 0.80. By using ROC curve Sensitivity, Specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy at cutoff 0.30 were (65.0%, 80.0%, 78.9%, 66.1% and 73.1% respectively). As regard posterior corneal Blur; the AUC between normal and manifest keratoconus was 0.92 (95% confidence interval): 0.88 - 0.96. By using ROC curve Sensitivity, Specificity, PPV, NPV and accuracy at cutoff 6.65 were (85.3%, 89.0%, 90.0%, 84.0% and 86.1%) respectively.
Conclusion: Vector analysis of posterior corneal astigmatism; APV and Blur, is a simple, friendly, objective and supplementary approach in the differentiation of normal from manifest keratoconus. Astigmatisms of anterior and posterior corneal surfaces are correlated, particularly among keratoconic corneas.
Keywords
vector analysis; astigmatism; keratoconus; cornea
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