Correlation of average RNFL thickness using the STRATUS OCT with the perimetric staging of glaucoma

Objective@#To determine the correlation between average peripapillary retinal nerve fiber layer (RNFL) thickness measured with time domain optical coherence tomography (TD-OCT) in normal and glaucoma eyes. @*Methods@#This was a cross-sectional study of 281 eyes randomly selected from a previous study. Assessment of glaucomatous damage was done by glaucoma specialists who based their diagnosis on the visual field tests and optic disc photos, independent of OCT results. Eyes were classified into the following groups: normal, mild, moderate, or severe glaucoma. Severity of glaucoma was based on visual field abnormalities following a modified HodappAnderson-Parish criteria for staging. Average RNFL thickness of normal and glaucoma subgroups, as measured with STRATUS–OCT, were analyzed using single ANOVA test. Association between average RNFL thickness and severity of glaucomatous visual field loss was evaluated using the Pearson’s correlation coefficient analysis. @*Results@#183 eyes had no glaucoma; 27 had mild, 32 had moderate, and 39 had severe glaucoma. Mean average peripapillary RNFL thickness (μm) in the normal, mild, moderate, and severe glaucoma groups were 98.05(±13.46), 76.27(±11.79), 76.42(±16.01), and 56.17(±14.92) respectively. Significant differences were seen in the average RNFL thickness among the groups (P<0.05), except in eyes with mild to moderate glaucoma. A moderately strong correlation of -0.57 (P<0.05) was observed between average RNFL thickness and the stage of glaucoma. @*Conclusion@#TD-OCT showed moderately strong correlation between the average RNFL thickness and perimetric stages of glaucoma. Average RNFL thickness is a good parameter to discriminate normal from glaucoma eyes.

Diagnostic accuracy of the optical coherence tomography in assessing glaucoma among Filipinos. Part 2: Optic nerve head and retinal nerve fiber layer parameters

Objective@#To determine the accuracy of the optic nerve head (ONH) and retinal nerve fiber layer (RNFL) parameters using the Stratus OCT in the diagnosis of glaucoma and to determine the validity of these measurements. @*Methods@#Glaucoma suspects undergoing glaucoma diagnostic tests were recruited consecutively. The numerical results of the Stratus OCT fast optic disc and fast RNFL protocols were analyzed against an independent assessment by glaucoma experts who were blinded as to the results of the OCT. An ROC curve analysis was applied to derive estimates of diagnostic accuracy and multi-level likelihood ratios.@*Results@#A total of 119 subjects assessed as glaucoma and 397 subjects assessed as normal were included. All ONH and RNFL OCT parameters showed statistically significant differences in mean values between the 2 groups. The ROC curve identified the vertical integrated rim area (AUC: 0.822), the cup-disc area ratio (AUC: 0.816), and the horizontal integrated rim width (AUC: 0.794) as the best optic disc parameters; and the RNFL average thickness (AUC: 0.827), the superior quadrant (AUC: 0.807), and the inferior quadrant (AUC: 0.804) as the best RNFL parameters. Multi-level likelihood ratios for ONH and RNFL parameters were calibrated using a projected posttest probability of 70% for a positive test result (therapeutic threshold) and a 10% posttest probability for a negative result (diagnostic threshold). @*Conclusion@#The results showed that statistically significant mean differences in ONH and RNFL parameters did not translate into a high predictive ability for each individual parameter. Single cut-off value for each OCT parameter based on the best sensitivity and specificity combination did not result in high predictive values for any single parameter. Multi-level likelihood ratios for the best ONH and RNFL parameters were derived to increase the diagnostic capability of the Stratus OCT.

Diagnostic accuracy of the optical coherence tomography in assessing glaucoma among Filipinos. Part 1: Categorical outcomes­ based on a normative database

Objective@#To determine the accuracy of the optic nerve head (ONH) and retinal nerve fiber layer (RNFL) parameters using the Stratus OCT in diagnosing glaucoma among Filipino patients and to determine the validity of the OCT measurements compared with a reference standard. @*Methods@#Glaucoma suspects were recruited consecutively from patients undergoing diagnostic tests. The results of the Stratus OCT fast RNFL protocol were analyzed against the independent assessment by glaucoma experts who were blinded. Outcomes included RNFL thickness values of ≤5 percentile and ≤1 percentile of the normative database for each RNFL sector, quadrant, and for the average RNFL thickness. Estimates of diagnostic accuracy with 95% confidence intervals were calculated.@*Results@#A total of 119 subjects assessed as glaucoma and 397 subjects assessed as normal were included in the analysis. Using the best categorical criterion for abnormality (average RNFL thickness of ≤1 percentile of the normative database), the OCT had a specificity of 98% (95% CI 96 - 99) and a sensitivity of 37% (95% CI 28 - 46). The criterion with the highest sensitivity was the presence of at least one sector with thickness at ≤5 percentile. @*Conclusion@#The Stratus OCT demonstrated a specificity of 98% and a sensitivity of 37% for the diagnosis of glaucoma using as a criterion an average RNFL thickness of ≤1 percentile of the normative database. It was a poor screening test for glaucoma suspects, although it showed some promise as a confirmatory test.