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Clinical Disc Margin and Bruch’s Membrane Opening in Normal and Glaucoma Subjects
Investigative Ophthalmology and Visual Science
2016;57(3):1468-1475
Amini et al. tested the hypothesis that a mismatch between the clinical disc margin (CDM) and Bruch’s membrane opening (BMO) is a function of BMO area (BMOA) and is affected by the presence of glaucoma.
The investigators studied 45 normal eyes (45 subjects) and 53 glaucomatous eyes (53 subjects) that underwent radial optic nerve head imaging with spectral-domain optical coherence tomography. The inner tip of Bruch’s membrane and the CDM were marked on radial scans and optic disc photographs, which were then coregistered by means of custom software.
The study’s main outcome measure was the difference between the clinical disc area (CDA) and BMOA (i.e., a CDA-BMOA mismatch) as a function of BMOA and glaucoma diagnosis. Multivariate regression analyses were used to explore and document the influence of glaucoma and BMOA on the mismatch.
The researchers found that global CDA was larger than BMOA in both the normal and glaucoma study groups; however, the difference was statistically significant only in the normal group (1.98 ± 0.37 vs. 1.85 ± 0.45 mm2, p = .02 in the normal group; 1.96 ± 0.38 vs. 1.89 ± 0.56 mm2, p = .08 in the glaucoma group). The sectoral CDA-BMOA mismatch was smaller in the superotemporal (p = .04) and superonasal (p = .05) sectors in the glaucoma group. The normalized CDA-BMOA difference decreased with increasing BMOA in both groups (p < .001), and the presence or severity of glaucoma did not affect the CDA-BMOA difference (p > .14).
The investigators concluded that the CDA was larger than BMOA in normal and glaucomatous eyes and that this finding was more pronounced in normal eyes than in eyes with glaucoma. The CDA-BMOA mismatch diminished with increasing BMOA, but it was not affected by the presence of glaucoma.
Modified Canaloplasty: A New Option for Patients With a Disrupted Schlemm Canal Wall
Journal of Glaucoma
Published online March 29, 2016
Xin et al. describe a modified canaloplasty technique and report its short-term efficacy in primary open-angle glaucoma (POAG) among patients who had a disruption of the Schlemm canal (SC) wall as a result of prior glaucoma surgery. They found that the technique was safe and effective in this setting.
In this single-surgeon, prospective cohort study, POAG patients who were scheduled for canaloplasty were divided into 2 groups. Group 1 included POAG patients who had not undergone glaucoma surgery; group 2 comprised patients who had failed glaucoma filtering surgery and had a disrupted SC wall.
The status of the SC wall was determined by gonioscopy and ultrasound biomicroscopy. Standard canaloplasty procedures were performed in group 1; group 2 received a modified canaloplasty technique. Primary outcome measures included intraocular pressure (IOP) and use of glaucoma medication at various follow-up points.
The modified technique was performed with a relay suture guided by an illuminated trocar. Unlike a standard 360-degree canaloplasty, the modified surgery avoided the site of the earlier trabeculectomy; the suture entered and exited on either side of the scleral flap, leaving a tissue bridge.
Seventeen patients were enrolled in group 1, and 9 in group 2. At the 12-month follow-up, no significant differences were noted between groups 1 and 2 in IOP (17.8 ± 2.7 mm Hg vs. 16.7 ± 2.4 mm Hg, respectively) or in the mean number of medications (0.9 ± 1.2 versus 0.3 ± 0.5).
In both groups and at all follow-up points, IOP and mean glaucoma medication usage had decreased significantly compared with baseline measurements (p < .001). The rate of successful circumferential catheterization was not significantly different between the 2 groups (88.2% vs. 77.8%, p = .063).
The researchers concluded that modified canaloplasty is a feasible, safe, and potentially effective option for patients with POAG who have regions of SC disruption as a result of previous glaucoma filtering surgery.
Retinal Thickness and Risk of Worsening Disability in MS
The Lancet Neurology
2016;15(6):574-578
Most patients with multiple sclerosis (MS) but no previous optic neuritis (ON) have thinner retinal layers than healthy controls. Martinez-Lapiscina et al. conducted a multicenter cohort study of eyes without ON or a history of ON in MS patients to assess the feasibility of using the peripapillary retinal nerve fiber layer (pRNFL) thickness and macular volume as a biomarker for worsening disability in MS.
Investigators in the multicenter cohort study collected data from 879 patients age 16 or older; 74 of them had clinically isolated syndrome, 664 had relapsing-remitting MS, and 141 had progressive MS.
The investigators assessed worsening disability with the Expanded Disability Status Scale (EDSS). In addition, pRNFL thickness and macular volume were measured once at baseline by optical coherence tomography (OCT). In patients without ON, the baseline OCT values were calculated as the mean value of both eyes without ON; and in those with unilateral ON, the baseline OCT values of the normal eye were recorded.
The investigators who performed OCT at baseline were masked to the EDSS results, and those who assessed disability with EDSS were masked to the OCT results. The risk of worsening disability was identified through proportional hazard models that included OCT metrics and age, disease duration, disability, presence of previous unilateral ON, and use of disease-modifying therapies as covariates.
The authors found that worsening of disability occurred in 252 (29%) of the 879 patients with MS after a median follow-up of 2 years (range, 0.5-5 years). Patients with a baseline pRNFL ≤87 μm or ≤88 μm (as measured by Spectralis or Cirrus OCT devices, respectively) had double the risk of worsening disability at any time after the first and up to the third years of follow-up (hazard ratio [HR], 2.06). The risk increased nearly 4-fold after the third and up to the fifth year of follow-up (HR, 3.81). The authors did not identify any meaningful associations for macular volume. They concluded that baseline pRNFL is a useful predictor of disability in patients with MS and could help in guiding treatment decisions.
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Other Journals summaries are written by Marianne Doran and edited by Deepak P. Edward, MD.
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