Purpose Visual field testing uses high contrast stimuli in areas of severe visual field loss. However, retinal ganglion cells saturate with high contrast stimuli, suggesting that the probability of detecting perimetric stimuli may not increase indefinitely as contrast increases. Driven by this concept, this study examines the lower limit of perimetric sensitivity for reliable testing by standard automated perimetry. Design Evaluation of diagnostic test. Participants 34 participants with moderate to severe glaucoma (Mean Deviation (MD) on their last clinic visit averaged −10.90dB, range −20.94dB to −3.38dB). 75 of the 136 locations tested had perimetric sensitivity ≤19dB. Methods Frequency of seeing curves were constructed at four non-adjacent visual field locations by the method of constant stimuli (MOCS), using 35 stimulus presentations at each of 7 contrasts. Locations were chosen a priori, and included at least two with glaucomatous damage but sensitivity ≥6dB. Cumulative Gaussian curves were fit to the data, first assuming a 5% false negative rate, and subsequently allowing the asymptotic maximum response probability to be a free parameter. Main Outcome Measures The strength of the relation (R2) between perimetric sensitivity (mean of last two clinic visits) and MOCS sensitivity (from the experiment), for all locations with perimetric sensitivity within ±4dB of each selected value, at 0.5dB intervals. Results Bins centered at sensitivities ≥19dB always had R2>0.1. All bins centered at sensitivities ≤15dB had R2<0.1, an indication that sensitivities are unreliable. No consistent conclusions could be drawn between 15–19dB. At 57 of the 81 locations with perimetric sensitivity <19dB, including 49 of the 63 locations ≤15dB, the fitted asymptotic maximum response probability was <80%, consistent with the hypothesis of response saturation. At 29 of these locations the asymptotic maximum was below 50%, and so contrast sensitivity (50% response rate) is undefined. Conclusions Clinical visual field testing may be unreliable when visual field locations have sensitivity below approximately 15–19dB, due to a reduction in the asymptotic maximum response probability. Researchers and clinicians may have difficulty detecting worsening sensitivity in these visual field locations and this difficulty may occur commonly in glaucoma patients with moderate to severe glaucomatous visual field loss.

Objective Conventional optic disc margin-based neuroretinal rim measurements lack a solid anatomical and geometrical basis. An optical coherence tomography (OCT) index, Bruch’s 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 Multi-centred cross-sectional study. Participants Normal White subjects. Methods Approximately equal number of subjects in each decade group (20–90 years) was enrolled in 5 centers. Subjects had normal ocular and visual field examinations. 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), 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 of 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 (range, 19.8 to 87.3) years. The median FoBMO angle was −6.7° (range, 2.5° to −17.5°). BMO was predominantly vertically oval with a median area of 1.74 mm2 (range, 1.05 to 3.40 mm2). 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/y and −0.21 µm/y, equivalent to 4.0% and 2.1% loss per decade of life, respectively. Sectorally, 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), while sectorally the relationship ranged from moderate (r = 0.45, inferotemporal) to non-existent (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.

Purpose To test whether the minimum rim area assessed by spectral domain optical coherence tomography (SD-OCT), based on the shortest distance from Bruch's Membrane Opening (BMO) to the inner limiting membrane, corresponds more closely to retinal nerve fiber layer (RNFL) thickness and visual field mean deviation (MD) than current rim measures in early glaucoma. Design Prospective cross-sectional study. Methods 221 participants with non-endstage glaucoma or high-risk ocular hypertension performed standard automated perimetry, and received SD-OCT and confocal scanning laser ophthalmoscopy (CSLO) scans, on the same day. Rim area measured by CSLO was compared with three SD-OCT rim measures from radial B-scans: horizontal rim area between BMO and ILM within the BMO plane; mean minimum rim width (BMO-MRW); and minimum rim area (BMO-MRA) optimized within sectors and then summed. Correlations between these measures and either MD from perimetry or RNFL thickness from SD-OCT were compared using Steiger's test. Results RNFL thickness was better correlated with BMO-MRA (r=0.676) or BMO-MRW (r=0.680) than with either CSLO Rim Area (r=0.330, p<0.001) or Horizontal Rim Area (r=0.482, p<0.001). MD was better correlated with BMO-MRA (r=0.534) or BMO-MRW (r=0.546) than with either CSLO Rim Area (r=0.321, p<0.001) or Horizontal Rim Area (0.403, p<0.001). The correlation between MD and RNFL thickness was r=0.646. Conclusions Minimum rim measurements from SD-OCT are significantly better correlated to both RNFL thickness and MD than rim measurements within the BMO plane, or based on the clinical disc margin. They provide new structural parameters for both diagnostic and research purposes in glaucoma.

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The association between LCD and SCE varied greatly depending on the properties of the lamina and sclera, which shows that it is critical to consider the characteristics of the population when interpreting measurements of LCD and SCE. This work is the first systematic analysis of the relationship between LCD and SCE.