Influence of Bruch's Membrane Opening Area in Diagnosing Glaucoma With Neuroretinal Parameters From Optical Coherence Tomography.

PURPOSE: To determine whether the glaucoma diagnostic accuracy of age- and Bruch membrane opening area (BMOA)-adjusted normative classifications of minimum rim width (MRW) and retinal nerve fiber layer thickness (RNFLT) is dependent on BMOA, in a European descent population. DESIGN: Retrospective, cross-sectional study. METHODS: We included 182 glaucoma patients and 166 healthy controls for the primary study, and 105 glaucoma patients in a second sample used for a replication study. Optical coherence tomography (Spectralis) measurements of BMOA, global MRW, and RNFLT and normative classifications from the device software were exported for analysis. Sensitivity and specificity were calculated for a conservative criterion (abnormal = "outside normal limits" classification) and a liberal criterion (abnormal = "outside normal limits" or "borderline" classifications). The dependence of sensitivity and specificity on BMOA was analyzed with comparison among subgroups divided by tertiles of BMOA, and with logistic regression. RESULTS: For the conservative criterion, MRW sensitivity was independent of BMOA (P ≥ .76), while RNFLT sensitivity increased in the large BMOA subgroup (P = .04, odds ratio: 1.2 per mm2 [P = .02]). For the liberal criterion, MRW and RNFLT sensitivities were independent of BMOA (P ≥ .53). Specificities were independent of BMOA (P ≥ .07). For the replication sample, which included younger patients with larger BMOA and worse visual field damage than the primary sample, sensitivities were independent of BMOA for both criteria (P ≥ .10). CONCLUSIONS: RNFLT sensitivity was higher in eyes with larger BMOA; however, age and visual field damage may influence that association. MRW diagnostic accuracy was not dependent on BMOA.

Interobserver variability in confocal optic nerve analysis (HRT).

BACKGROUND/AIMS: To study the observer-related variability of optic nerve head (ONH) measurements using confocal laser scanning tomography (HRT I) in a screening setting. METHODS: Six experienced glaucoma specialists independently evaluated 50 ONH topographies from 25 adults using HRT software ver. 2.01 in a masked fashion. ONH topographies were obtained from a cohort study of 882 healthy adults and additionally included one patient with glaucomatous eyes. A glaucoma-screening-like setting was intended. The mean interobserver difference was defined as the mean percentual difference between an observer's analysis and the mean of all six observers for all eyes and all observers. The interobserver range was calculated for each eye as the percentual difference between the lowest and highest measurement, with the highest measurement as denominator. Additionally, Kendall's coefficient of rank concordance was assessed for the main HRT parameters. RESULTS: Mean disc area ranged from 1.83 +/- 0.49 to 2.21 +/- 0.40 mm(2) (mean interobserver difference: 8.3%; interobserver range: 5-50%; rank concordance: 0.86). The lowest mean interobserver differences were found for mean retinal nerve fibre layer thickness (RNFLT; 6.5%), maximum cup depth (2.9%) and cup shape (6.8%). An increased interobserver range was significantly correlated to a low cup to disc area ratio (r=0.64, P<0.0001). CONCLUSIONS: The observer-dependent diagnostic variability of HRT measurements can lead to divergent diagnostic evaluation of the ONH in a screening setting. Any HRT software relying on a reference database is exposed to relevant observer-related variability of the disc area. For screening purposes, HRT measurements should be completed by other diagnostic methods to compensate for possible diagnostic uncertainty.

Optic disc biomorphometry with the Heidelberg Retina Tomograph at different reference levels.

PURPOSE: The Heidelberg Retina Tomograph (HRT) is a confocal scanning laser tomograph that produces high resolution optical section images of the optic disc and central retina. Measurement accuracy and reproducibility is good. Several of the stereometric variables depend on the definition of a reference plane level. The purpose of the present study was to evaluate the four different reference levels in terms of their advantages and disadvantages in clinical work. METHODS: Sixty-seven randomly chosen eyes belonging to 67 subjects were included in this study. Forty of the eyes were healthy and 27 had glaucoma. The HRT with software versions 1.09 and 1.11 was used to acquire and evaluate topographic measurements of the optic disc. Image analysis was performed at four different reference levels: 320 microm fixed offset reference level (REFd) (version 1.09), an individually determined reference level (REFi), a papillo-macular reference level (REFm) and a flexible reference level (REFf) (version 1.11). ANOVA was used to determine differences in the topographic parameters between the reference levels. RESULTS: In terms of the healthy eyes, all the variables using different reference levels give rather similar results. However, with advanced glaucoma the measurement values provided with REFd are clearly different to those of the other reference levels. The measurement values using REFm and REFf provide fairly similar results in all clinical groups. REFf indicates the lowest point in the segment between 350 degrees and 356 degrees along the contour line and thus provides the most stable and clinically useful reference level at present. CONCLUSION: At present, the flexible reference level REFf gives the most reliable and adequate HRT measurement values, both in normal and in glaucomatous eyes.