Comparison of the diagnostic capability of the Heidelberg Retina Tomographs 2 and 3 for glaucoma in the Indian population.

PURPOSE: To compare the diagnostic capability of the Heidelberg Retina Tomograph (HRT) 2 and 3 (Heidelberg Engineering, GmBH, Dossenheim, Germany) for glaucoma in an Indian population. DESIGN: Evaluation of a diagnostic technology. PARTICIPANTS: Ninety-eight glaucoma subjects and 79 normal controls. METHODS: All participants underwent imaging with HRT2. Heidelberg Retina Tomograph 2 examinations were exported to HRT3 software. The stereometric parameters of HRT2 and HRT3 were compared. The diagnostic capability of Moorfields Regression Analysis (MRA) in the HRT2, HRT3 with and without ethnicity correction, and Glaucoma Probability Score (GPS) of HRT3 were compared. Analysis was done with the borderline results of MRA and GPS considered as normal to derive the most specific criteria and as abnormal to derive the least specific criteria. MAIN OUTCOME MEASURES: Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC). RESULTS: On standard automated perimetry (SAP), the mean deviation (mean+/-standard deviation) of the glaucoma and normal groups were -7.3+/-6.7 dB and -0.4+/-1.1 dB, respectively (P<0.001). The AUC for the individual stereometric parameters of HRT2 were similar to that of HRT3. The sensitivity and specificity (most specific criteria) were 56.1% and 96.2%, respectively, for MRA of HRT2 and 56.1% and 91.1%, respectively, for MRA of HRT3. The sensitivity and specificity (least specific criteria) were 88.8% and 88.6%, respectively, for MRA of HRT2 and 70.4% and 81%, respectively, for MRA of HRT3. By using the Indian specific normative database of HRT3, the sensitivity and specificity were 37.8% and 97.5%, respectively, for the most specific criteria, and 55.1% and 89.9%, respectively, for the least specific criteria. Sensitivity and specificity of GPS were 86.7% and 68.3%, respectively, for the most specific criteria, and 93.9% and 39.2%, respectively, for the least specific criteria. CONCLUSIONS: In this cohort, the diagnostic capability of HRT2 MRA was similar to that of HRT3 MRA; ethnicity correction did not improve results; GPS was more sensitive but less specific than MRA in diagnosing glaucoma.

Clinical measurement and categorization of optic disc in glaucoma patients.

BACKGROUND: Assessment of optic disc size is an important component of optic nerve head examination. Agreement between different methods of disc size measurements is not very good. PURPOSE: To assess the agreement between the disc size assessed by Heidelberg retina tomograph (HRT) and stereobiomicroscopy with a 90 diopter (D) lens. To report the clinical (measured by biomicroscopy) disc diameters of small, average and large optic discs categorized by HRT disc areas. SETTING AND DESIGN: Observational study of subjects examined in the glaucoma clinic of a tertiary eye institute. MATERIALS AND METHODS: Seventy-five eyes of 75 glaucoma subjects were studied. Disc diameter was measured using stereobiomicroscopy and HRT. The agreement between the two sets of measurements was assessed by intraclass correlation coefficient (ICC). Discs were classified into small (<1.6 mm(2)), average (1.6-2.6 mm(2)) and large (>2.6 mm(2)) depending on cutoffs provided by the manufacturers of HRT. The means (95% CI) of the corresponding vertical disc diameter in these groups were assessed. STATISTICAL ANALYSIS: ICC, Bland and Altman plots. RESULTS: ICC for measurements of clinical and HRT horizontal disc diameter was 0.518 and for vertical disc diameter measurement was 0.487. The mean difference between the clinical and HRT measurements as analyzed by the Bland and Altman plot was 0.17 (95% CI, 0.13- 0.47) for horizontal and 0.22 (95% CI, 0.11- 0.54) for vertical disc diameter. Of the 75 eyes, 3 eyes had small discs, 54 average and 18 large discs. The mean clinical vertical disc diameter for small discs was 1.55 mm (95% CI, 1.2-1.7), for average discs was 1.91 mm (95% CI, 1.87-1.96) and for large discs was 2.15 mm (95% CI, 2.03-2.27). CONCLUSION: The agreement between clinical and HRT disc diameter measurements is moderate. Disc diameter measurement on stereobiomicroscopy can be used to categorize discs into small, average and large discs.