Accuracy of Topometric Indices for Distinguishing between Keratoconic and Normal Corneas (original) (raw)
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Topometric and Tomographic Indices for the Diagnosis of Keratoconus
International Journal of Keratoconus and Ectatic Corneal Diseases, 2012
Purpose To compare topometric (front surface curvature) and tomographic (3D corneal shape) indices for diagnosing keratoconus. Methods Pentacam data from one eye randomly selected of 200 normals (N) and 177 keratoconus (KC) were analyzed. Tomographic and topometric indices were tested. Receiver operating characteristic (ROC) curves were calculated, along with pairwise comparisons. Results All tested variables had significant differences among N and KC (Mann-Whitney, p < 0.001). Most accurate tomographic indices had higher AUC than best topometric ones (DeLong, p < 0.05). Belin-Ambrosio D (BAD-D) had AUC of 1.00 (sensitivity 100.0%; specificity 98.5%). Conclusion Tomographic data was superior than topometric data to detect keratoconus. The BAD-D was an enhanced approach for detecting keratoconus. How to cite this article Correia FF, Ramos I, Lopes B, Salomão MQ, Luz A, Correa RO, Belin MW, Ambrósio R Jr. Topometric and Tomographic Indices for the Diagnosis of Keratoconus. Int J...
Pentacam top indices for diagnosing subclinical and definite keratoconus
Journal of Current Ophthalmology, 2016
Purpose: To determine pachymetric, aberrometric, and topometric indices in patients with definite and subclinical keratoconus and the validity of these indices in the diagnosis of keratoconus. Methods: We evaluated 262 keratoconic and 97 healthy eyes in this study. Pentacam HR examination was performed for all participants, and the data of all pachymetric, aberrometric, and topometric indices was extracted for the study population. Results: The average of all evaluated pachymetric and topometric indices and the 3rd and 5th order vertical coma aberrations showed a significant difference between the study groups (p < 0.001). Belin/Ambrosio Deviation Display (BAD_D), Index of Vertical Asymmetry (IVA), Index of Surface Variance (ISV), and 5th order vertical coma aberration were identified as the best diagnostic criteria for the diagnosis of subclinical keratoconus (R 2 ¼ 0.65, p <0.001), and BAD_D, mean keratometry and 3rd order vertical coma aberration were identified as the best diagnostic criteria for the diagnosis of definite keratoconus (R 2 ¼ 0.91, p <0.001). The sensitivity and specificity of the above-mentioned models were 83.6% and 96.9%, and 97.9% and 96.9%, respectively. Conclusion: Simultaneous evaluation of BAD_D, 5th order vertical coma aberration, IVA, and ISV, especially when the pattern of the corneal curvature is normal, can detect subclinical keratoconus with high sensitivity and specificity. As for definite keratoconus, each of the BAD_D, mean keratometry, and 3rd order vertical coma aberration indices has a desirable diagnostic validity. However, the aforementioned indices do not negate the importance of widely recognized and acceptable indices like keratometry and central corneal thickness.
Comparison of corneal indices between normal and keratoconus (kc) using pentacam hr for patients aged 6-21 years, 2024
Comparison of corneal indices between normal and keratoconus (kc) using pentacam hr for patients aged 6-21 years HAYA ALFARHAN Ph.D • OBJECTIVES: The aim is to compare normal and KC corneas using Pentacam keratometry, curvature indices, elevation indices, and pachymetry indices for patients aged between 6 to 21 years in the Riyadh area and analyze the indicators' sensitivity and specificity in differentiating between normal and KC corneas. • METHOD: The present study employed a prospective, cross-sectional, observational, multicenter design to gather data from patients aged 6 to 21 who were seen in several non-ophthalmic emergency departments in Riyadh, Kingdom of Saudi Arabia, in 2017. Scheimpflug corneal tomography system in rotation was used to measure the cornea. Following optometric exams, corneal imaging and KC index measurements were performed using the Pentacam. • RESULTS: Between the normal and KC groups, the majority of variables showed noteworthy statistical differences (p < 0.001). The most effective indicators for keratoconus discrimination were K Max, ISV, and IHD. K Max, ISV, and IHD each had an area under the curve of 0.94, 0.90, and 0.93. IHA, IHD, and in the paired study of the ROC curves, CKI indices performed significantly better than the other topometric variables. (p < 0.05). Nevertheless, when comparing the ROC curves with ISV, IVA, and KI pairwise, there are no statistically significant variations. Furthermore, the area under the curve (AUC) of the ROC for display TP in the pairwise comparison was smaller than that of Pachy apex (p 0.002). PPI max, ART average, and TP all had larger areas under the curves than TP (p<0.05). • CONCLUSION: Pentacam indices are vital to the diagnosis of KC. K Max, ISV, and IHD are the best diagnostic indices for KC. Yet, using a combination of indices is advised to improve the diagnosis and accuracy of Pentacam indices to differentiate KC from normal.
Topometric and Tomographic Evaluation of Subclinical Keratoconus
Ophthalmic Epidemiology, 2020
Purpose: To investigate the corneal topometric and tomographic findings that can be used in the diagnosis of subclinical keratoconus. Methods: A retrospective cohort study. The study group was selected from patients with clinically evident keratoconus in one eye and subclinical keratoconus without evident topographic findings in fellow eye. The age-matched control group was selected from patients who were candidates for laser in situ keratomileusis (LASIK) and did not develop ectasia after LASIK surgery at least 1-year follow-up. All subjects underwent topographic, topometric and tomographic (Belin-Ambrósio Enhanced Ectasia Display III) analyses via a Pentacam HR rotating Scheimpflug camera (Oculus, Germany, version 1.20r.98) before LASIK surgery. Results: The study group consisted of 151 patients (69 male and 82 female, mean age of 24.8 ± 7.2 years) and the control group also consisted of 150 patients (70 male and 80 female, mean age of 26.0 ± 6.3 years). There were statistically significant differences in all measured topometric (p˂.05) and tomographic (p˂.001) parameters between the eyes with subclinical keratoconus and those of the control group. In discriminating eyes with subclinical keratoconus from normal eyes, final D showed the highest area under curve value (0.858, sensitivity 85.2%, specificity 66.7%), followed by maximum pachymetric progression index (0.809, sensitivity 81.9%, specificity 69.4%) and average pachymetric progression index (0.796, sensitivity 81.9%, specificity 68.1%) in receiver operating characteristic analysis. Conclusion: Topometric and tomographic parameters might be useful for early detection of keratoconus, but the sensitivity and specificity of any parameter are not high enough to be used alone.
Elevation Matrix Data in the Evaluation of Keratoconus and Normal Corneas
Ophthalmology and Therapy, 2022
Introduction: To determine whether elevation matrix data of the anterior corneal surface could be useful for the diagnosis of keratoconus. Methods: In a cross-sectional study, subjects aged 10-40 years with keratoconus (n = 74) or age-matched controls (n = 36) underwent complete ophthalmological examination, including Scheimpflug corneal topography (Pentacam HR). Exclusion criteria comprised previous ocular surgery, other eye disease, or significant corneal scarring. A raw data matrix of distance measurements to the most anterior corneal point was used to compare each subject with the mean normal cornea. A central 6-mm zone (6.1 9 6.1 mm) and two inferior eccentric matrices (0.4 9 6.1 and 1.1 9 1.1 mm) were used. Outcome measures were sensitivity, specificity, positive and negative predictive value, likelihood ratio, accuracy, and odds ratio. Results: Sensitivity of central matrix for the diagnosis of keratoconus was low (6.7%) whereas specificity reached 94.4%. Sensitivity and specificity were respectively 93.2% and 94% for the 6.1 9 0.4 mm eccentric matrix and 97.2% and 97.2% for the 1.1 9 1.1 mm eccentric matrix. Positive predictive and negative predictive values were 71.4% and 33%, respectively, for the central matrix; 97.1% and 87.1%; 98.6% and 94.5%, for the two eccentric matrices, respectively. The likelihood ratio of a positive test was 1.1, 16.7, and 35, respectively. Sensitivity and specificity of the eccentric matrices were significantly better in the diagnosis of subclinical keratoconus (but not definite keratoconus) than other Pentacam indices. Conclusions: Using eccentric elevation matrix data analysis of the cornea is useful in the detection of keratoconus versus normal corneas.
Corneal Indices Determined with Pentacam in Possible Candidates for Corneal Refractive Surgery
The Open Ophthalmology Journal, 2020
Objective: To describe the level of correlation of clinical refractive variables with corneal indices in Pentacam Scheimpflug tomography, demonstrate the usefulness of the study of corneal indices in the diagnosis of keratoconus (KC), and identify the corneal indexes with the greatest influence on the diagnosis of KC. Methods: A descriptive, retrospective, and cross-sectional study was conducted in 69 patients (138 eyes) with refractive disorders, possible candidates for corneal refractive surgery, at the Exilaser Ophthalmological Center, Cuenca, Ecuador, from March to August 2019. Corneal indices were studied using Pentacam. Statistical correlation methods, Levene’s test, Fisher’s exact test, Cramérs’ V coefficient, and multiple correspondence analyses were used. Results: The variables refractive cylinder and central keratometry had a direct correlation with the corneal indices (p<0.001). An inverse correlation was obtained between central pachymetry and corneal indices (p<0....
Clinical Ophthalmology, 2013
To survey the standard keratoconus grading scale (Pentacam ® -derived Amsler-Krumeich stages) compared to corneal irregularity indices and best spectacle-corrected distance visual acuity (CDVA). Patients and methods: Two-hundred and twelve keratoconus cases were evaluated for keratoconus grading, anterior surface irregularity indices (measured by Pentacam imaging), and subjective refraction (measured by CDVA). The correlations between CDVA, keratometry, and the Scheimpflug keratoconus grading and the seven anterior surface Pentacam-derived topometric indices -index of surface variance, index of vertical asymmetry, keratoconus index, central keratoconus index, index of height asymmetry, index of height decentration, and index of minimum radius of curvature -were analyzed using paired two-tailed t-tests, coefficient of determination (r 2 ), and trendline linearity. Results: The average ± standard deviation CDVA (expressed decimally) was 0.626 ± 0.244 for all eyes (range 0.10-1.00). The average flat meridian keratometry was (K1) 46.7 ± 5.89 D; the average steep keratometry (K2) was 51.05 ± 6.59 D. The index of surface variance and the index of height decentration had the strongest correlation with topographic keratoconus grading (P , 0.001). CDVA and keratometry correlated poorly with keratoconus severity. Conclusion: It is reported here for the first time that the index of surface variance and the index of height decentration may be the most sensitive and specific criteria in the diagnosis, progression, and surgical follow-up of keratoconus. The classification proposed herein may present a novel benchmark in clinical work and future studies.