Evaluation of Corneal Elevation in Eyes with Subclinical Keratoconus and Keratoconus using Galilei Double Scheimpflug Analyzer (original) (raw)
Related papers
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.
Journal of Ophthalmic and Vision Research, 2015
To determine the sensitivity and specificity of anterior and posterior corneal elevation parameters as determined by Orbscan II (Bausch and Lomb, Rochester, NY, USA) in discriminating between (sub) clinical keratoconus (KCN) and normal corneas. Methods: This prospective case-control study included 28 eyes with subclinical KCN, 65 with clinical KCN and 141 normal corneas. Anterior and posterior corneal elevation was measured and compared in the central 5-mm corneal zone using Orbscan II. Results: Receiver operating curves (ROC) curve analyses for posterior corneal elevation showed predictive accuracy in both KCN and subclinical KCN with an area under the curve (AUC) of 0.97 and 0.69, respectively while optimal cutoff points were 51 µm for KCN and 35 µm for subclinical KCN. These values were associated with sensitivity and specificity of 89.23% and 98.58%, respectively, for KCN; and 50.00% and 88.65% for subclinical KCN. ROC curve analyses for anterior corneal elevation showed predictive accuracy in both KCN and subclinical KCN with AUC of 0.97 and 0.69, respectively while optimal cutoff points were 19 µm for KCN and 16 µm for subclinical KCN. These values were associated with sensitivity and specificity of 93.85% and 97.16%, respectively, for KCN; and 60.71% and 87.94% for subclinical KCN. Conclusion: Anterior and posterior corneal elevation data obtained by Orbscan II can well discriminate between KCN and normal corneas, however the reliability of their indices is lower in differentiating subclinical KCN from normal cases.
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.
Corneal elevation and keratoconus indices in a 40- to 64-year-old population, Shahroud Eye Study
Journal of Current Ophthalmology, 2016
Purpose: To determine the corneal elevation values and keratoconus indices in the 40-to 64-year-old population and their changes with aging. Methods: The 6311 invitees of this study were selected through random cluster sampling, and 5190 of them participated in the study (response rate ¼ 82.2%). Here, we analyzed results of Pentacam acquisitions in 4148 respondents. Cases of keratoconus and forme fruste keratoconus (FFKC) were determined using topography and clinical data. Studied variables included keratoconus indices, central corneal thickness readings, maximum elevations on the anterior and posterior surfaces, and elevation values at the thinnest point, anterior steepest point, and posterior steepest point in healthy, FFKC, and keratoconus groups. Results: In all subjects, the mean maximum elevations were 6.80 ± 5.0 mm and 16.60 ± 7.7 mm on the anterior and posterior corneal surfaces, respectively. Maximum elevation values on the anterior and posterior corneal surfaces showed significant correlations in the keratoconus, FFKC, and healthy groups (P < 0.002). Maximum anterior elevation correlated with age (r ¼ 0.11, P < 0.001), but maximum posterior elevation showed no such correlation (P ¼ 0.476). Keratoconus indices demonstrated significant changes with age (P < 0.001). Conclusion: Anterior elevation values slightly increase with age, and keratoconus indices change as well. Elevation readings and keratoconus indices in the keratoconus group and FFKC cases are higher than the healthy corneas although their values could be compared with other studies on younger participants.
Türk Oftalmoloji Dergisi
Objectives: To evaluate tomographic and topographic parameters in subclinical and clinical keratoconus eyes by comparing them with normal eyes in a young Caucasian population. Materials and Methods: This cross-sectional study included 88 normal eyes (control group), bilateral data from the preclinical stage of 24 progressive keratoconus eyes (bilateral subclinical keratoconus group), 40 fellow eyes of patients with unilateral keratoconus (fellow eyes group) and 97 eyes with mild keratoconus (clinical keratoconus group). Topographic and tomographic data, data from enhanced elevation maps and keratoconus indices were measured in all study eyes using Scheimpflug tomography. Receiver operating characteristic (ROC) curve analysis was used to assess individual parameters to discriminate eyes of patients with subclinical and clinical keratoconus from control eyes. The sensitivity and specificity of the main effective parameters were evaluated and optimal cutoff points were identified to differentiate subclinical keratoconus and keratoconus from normal corneas. Results: Comparison of all subclinical and clinical keratoconus eyes from the normal group revealed significant differences in most diagnostic parameters. The ROC curve analysis showed high overall predictive accuracy of several Pentacam parameters (overall D value, anterior and posterior elevations and difference elevations, pachymetry progression index, index of surface variance, index of height decentration and keratoconus index) in discriminating ectatic corneas from normal ones. These outcomes were proportionally less pronounced in all subclinical keratoconus eyes than in the clinical keratoconus eyes. Pachymetric readings were progressively lower in the bilateral subclinical keratoconus eyes and sensitivity and specificity of the analyzed tomographic and topographic parameters were higher than the fellow eyes group when differentiating subclinical keratoconus from healthy corneas. Conclusion: Scheimpflug tomography parameters such as D value, elevation parameters, progression index and several surface indices can effectively differentiate keratoconus from normal corneas in a Caucasian population. Nevertheless, a combination of different data is required to distinguish subclinical keratoconus.