Vishva M. Danthurebandara

Enhanced Structure–Function Relationship in Glaucoma With an Anatomically and Geometrically Accurate Neuroretinal Rim Measurement

PURPOSE To evaluate the structure-function relationship between disc margin-based rim area (DM-RA) obtained with confocal scanning laser tomography (CSLT), Bruchs membrane opening-based horizontal rim width (BMO-HRW), minimum rim width (BMO-MRW), peripapillary retinal nerve fiber layer thickness (RNFLT) obtained with spectral-domain optical coherence tomography (SD-OCT), and visual field sensitivity. METHODS We examined 151 glaucoma patients with CSLT, SD-OCT, and standard automated perimetry on the same day. Optic nerve head (ONH) and RNFL with SD-OCT were acquired relative to a fixed coordinate system (acquired image frame [AIF]) and to the eye-specific fovea-BMO center (FoBMO) axis. Visual field locations were mapped to ONH and RNFL sectors with fixed Garway-Heath (VF(GH)) and patient-specific (VF(PS)) maps customized for various biometric parameters. RESULTS Globally and sectorally, the structure-function relationships between DM-RA and VF(GH), BMO-HRW(AIF) and VF(GH), and BMO-HRW(FoBMO) and VF(PS) were equally weak. The R(2) for the relationship between DM-RA and VF(GH) ranged from 0.1% (inferonasal) to 11% (superotemporal) whereas that between BMO-HRW(AIF) and VF(GH) ranged from 0.1% (nasal) to 10% (superotemporal). Relatively stronger global and sectoral structure-function relationships with BMO-MRW(AIF) and with BMO-MRW(FoBMO) were obtained. The R(2) between BMO-MRW(AIF) and VF(GH) ranged from 5% (nasal) to 30% (superotemporal), whereas that between BMO-MRW(FoBMO) and VF(PS) ranged from 5% (nasal) to 25% (inferotemporal). The structure-function relationship with RNFLT was not significantly different from that with BMO-MRW, regardless of image acquisition method. CONCLUSIONS The structure-function relationship was enhanced with BMO-MRW compared with the other neuroretinal rim measurements, due mainly to its geometrically accurate properties.

Bruch's Membrane Opening Minimum Rim Width and Retinal Nerve Fiber Layer Thickness in a Normal White Population: A Multicenter Study

PURPOSE Conventional optic disc margin-based neuroretinal rim measurements lack a solid anatomic and geometrical basis. An optical coherence tomography (OCT) index, Bruchs membrane opening minimum rim width (BMO-MRW), addresses these deficiencies and has higher diagnostic accuracy for glaucoma. We characterized BMO-MRW and peripapillary retinal nerve fiber layer thickness (RNFLT) in a normal population. DESIGN Multicenter cross-sectional study. PARTICIPANTS Normal white subjects. METHODS An approximately equal number of subjects in each decade group (20-90 years of age) was enrolled in 5 centers. Subjects had normal ocular and visual field examination results. We obtained OCT images of the optic nerve head (24 radial scans) and peripapillary retina (1 circular scan). The angle between the fovea and BMO center (FoBMO angle), relative to the horizontal axis of the image frame, was first determined and all scans were acquired and analyzed relative to this eye-specific FoBMO axis. Variation in BMO-MRW and RNFLT was analyzed with respect to age, sector, and BMO shape. MAIN OUTCOME MEASURES Age-related decline and between-subject variability in BMO-MRW and RNFLT. RESULTS There were 246 eyes of 246 subjects with a median age of 52.9 years (range, 19.8-87.3 years). The median FoBMO angle was -6.7° (range, 2.5° to -17.5°). The BMO was predominantly vertically oval with a median area of 1.74 mm(2) (range, 1.05-3.40 mm(2)). Neither FoBMO angle nor BMO area was associated with age or axial length. Both global mean BMO-MRW and RNFLT declined with age at a rate of -1.34 μm/year and -0.21 μm/year, equivalent to 4.0% and 2.1% loss per decade of life, respectively. Sectorially, the most rapid decrease occurred inferiorly and the least temporally; however, the age association was always stronger with BMO-MRW than with RNFLT. There was a modest relationship between mean global BMO-MRW and RNFLT (r = 0.35), whereas sectorially the relationship ranged from moderate (r = 0.45, inferotemporal) to nonexistent (r = 0.01, temporal). CONCLUSIONS There was significant age-related loss of BMO-MRW in healthy subjects and notable differences between BMO-MRW and RNFLT in their relationship with age and between each other. Adjusting BMO-MRW and RNFLT for age and sector is important in ensuring optimal diagnostics for glaucoma.

Importance of Normal Aging in Estimating the Rate of Glaucomatous Neuroretinal Rim and Retinal Nerve Fiber Layer Loss

PURPOSE To describe longitudinal rates of change of neuroretinal parameters in patients with glaucoma and healthy controls, and to evaluate the influence of covariates. DESIGN Prospective longitudinal study. PARTICIPANTS Treated patients with glaucoma (n = 192) and healthy controls (n = 37). METHODS Global disc margin-based neuroretinal rim area (DMRA) was measured with confocal scanning laser tomography, while Bruchs membrane opening-minimum rim width (BMO-MRW), BMO area (BMOA), and peripapillary retinal nerve fiber layer thickness (RNFLT) were measured with optical coherence tomography at 6-month intervals. Individual rates of change were estimated with ordinary least-squares regression, and linear mixed effects modeling was used to estimate the average rate of change and differences between the groups, and to evaluate the effects of baseline measurement and baseline age on rates of change. MAIN OUTCOME MEASURES Rates of change for each parameter. RESULTS Subjects were followed for a median (range) of 4 (2-6) years. The proportion of controls who had significant reduction of neuroretinal parameters was 35% for BMO-MRW, 31% for RNFLT, and 11% for DMRA. The corresponding figures for patients with glaucoma were not statistically different (42%, P = 0.45; 31%, P = 0.99; 14%, P = 0.99, respectively). Controls had a significant reduction of BMO-MRW (mean: -1.92 μm/year, P < 0.01) and RNFLT (mean: -0.44 μm/year, P = 0.01), but not DMRA (mean: -0.22×10(-2) mm(2)/year, P = 0.41). After adjusting for covariates, patients with glaucoma had faster, but not statistically different, rates of deterioration compared with controls, by -1.26 μm/year (P = 0.07) for BMO-MRW, -0.40 μm/year (P = 0.11) for RNFLT, and -0.38×10(-2) mm(2)/year (P = 0.23) for DMRA. Baseline BMO-MRW and RNFLT significantly influenced the respective rates of change, with higher baseline values relating to faster reductions. Older age at baseline was associated with a slower reduction in rates of BMO-MRW. Reductions in intraocular pressure were related to increases in BMO-MRW and DMRA. There was a tendency for BMOA to decrease over time (-0.38×10(-2) mm(2)/year; P = 0.04). CONCLUSIONS Age-related loss of neuroretinal parameters may explain a large proportion of the deterioration observed in treated patients with glaucoma and should be carefully considered in estimating rates of change.

Beta and Gamma Peripapillary Atrophy in Myopic Eyes With and Without Glaucoma

PURPOSE To determine whether beta and gamma peripapillary atrophy (PPA) areas measured with optical coherence tomography (OCT) enhances glaucoma diagnosis in myopic subjects. METHODS We included 55 myopic glaucoma patients and 74 myopic nonglaucomatous controls. Beta-PPA comprised the area external to the clinical disc margin, with absence of retinal pigment epithelium and presence of Bruchs membrane. Gamma-PPA comprised the area external to the disc margin, with absence of both RPE and Bruchs membrane. OCT scans colocalized to fundus photographs were used to measure PPA, choroidal thickness, border tissue of Elschnig configuration, optic disc area, and optic disc ovality. RESULTS Beta-PPA area was larger in glaucoma patients compared with controls (median [interquartile range], 1.0 [0.66-1.53] mm2 and 0.74 [0.50-1.38] mm2, respectively), whereas gamma-PPA was smaller in glaucoma patients compared with controls (0.28 [0.14-0.50] mm2 and 0.42 [0.17-0.74] mm2, respectively). However, the distributions of both beta- and gamma-PPA in the two groups overlapped widely. The areas under the receiver operating characteristic curve of beta- and gamma-PPA areas were 0.60 and 0.59, respectively. Larger beta-PPA area was associated with larger disc area, thinner choroidal thickness, longer axial length, less oblique border tissue configuration, older age, and greater disc ovality. Larger gamma-PPA area was associated with greater disc ovality, more oblique border tissue configuration, and longer axial length. CONCLUSIONS Subclassifying PPA with OCT into beta and gamma zones reveals association with different covariates, but does not enhance the diagnostic performance for glaucoma in a population of predominantly Caucasians myopic subjects.

Visibility of Optic Nerve Head Structures With Spectral-domain and Swept-source Optical Coherence Tomography

Purpose: To compare the visibility of deep optic nerve head (ONH) structures and the visible area of the anterior surface of the lamina cribrosa (ASLC) with spectral-domain optical coherence tomography (SD-OCT) and swept-source OCT (SS-OCT). Materials and Methods: In total, 33 glaucoma patients were imaged with SD-OCT (Spectralis, 24 radial B-scans centered on the ONH) and SS-OCT (Atlantis, 12 radial and a horizontal and vertical raster scan pattern containing 5 lines each, centered on the ONH). One of the SS-OCT horizontal and vertical scans that was best matching with the horizontal and vertical scan lines with those of SD-OCT was selected. All B-scans were then exported and deidentified. An independent observer determined whether the posterior choroid, border tissue, anterior scleral canal opening, and LC insertion into the sclera were detectable in the matched scan lines. Bruch membrane opening (BMO) and ASLC were segmented manually in radial scans. The segmented points were combined into a single plane and a linear interpolation was used to define BMO and ASLC areas. Results: The posterior choroid, border tissue, and anterior scleral canal opening were detectable in most patients (94% to 100%, 88% to 100%, and 76% to 100%, respectively) and were not different between SD-OCT and SS-OCT. The LC insertion detection rate was nonstatistically higher for SS-OCT compared with SD-OCT (58% to 85% vs. 42% to 73%; P>0.10). The mean (SD) ASLC visible area (percentage of the respective BMO area) was 124 (30%) with SD-OCT and 135 (32%) with SS-OCT (P<0.01). Conclusion: SD-OCT and SS-OCT had comparable detection rates of deep ONH structures; however, a larger area of ASLC was visible with SS-OCT.