The authors of this study aimed to: identify the differences in optic nerve sheath diameter (ONSD) as an indirect measure of intracranial pressure (ICP) in glaucoma patients and a healthy population; and identify variables that may correlate with ONSD in primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG) patients. They found that indirect measurements of ICP by ultrasound assessment of the ONSD may provide further insights into the retrolaminar pressure component in glaucoma.

Patients with NTG (n=46) and POAG (n=61), and healthy controls (n=42) underwent B-scan ultrasound measurement of ONSD by an observer masked to the patient diagnosis. Intraocular pressure (IOP) was measured in all groups, with additional central corneal thickness (CCT) and visual field defect measurements in glaucomatous patients. Only one eye per patient was selected and Kruskal-Wallis or Mann-Whitney was used to compare the different variables between the diagnostic groups. Additionally, Spearman correlations were used to explore relationships among these variables.

According to the study authors, ONSD was not significantly different between healthy, NTG and POAG patients (6.09 ± 0.78, 6.03 ± 0.69, and 5.71 ± 0.83 respectively; p=0.08). Visual field damage and CCT were not correlated with ONSD in either of the glaucoma groups (POAG, p=0.31 and 0.44; NTG, p=0.48 and 0.90 respectively). However, ONSD did correlate with IOP in NTG patients (r=0.53, p<0.001), while it did not in POAG patients and health controls (p=0.86, p=0.46 respectively). The authors noted that a patient’s age did not relate to ONSD in any of the groups (p>0.25 in all groups).

The correlation of ONSD with IOP solely in NTG patients suggests that the translaminar pressure gradient may be of particular importance in this type of glaucoma.

Danish investigators investigated the expression of the complement regulatory proteins CD46, CD55, and CD59 on peripheral leukocytes in neovascular age-related macular degeneration (AMD) in this prospective, case-control study.

They included 35 unrelated patients with neovascular AMD and 30 control individuals. All participants were subjected to a structured interview and the investigators performed detailed imaging (autofluorescence, digital funduscopy, spectral-domain optical coherence tomography, and fluorescein and indocyanine green angiography in patients suspected of having neovascular AMD). They obtained and stained fresh ethylenediaminetetraacetic acid blood with monoclonal antibodies. Using flow cytometry, they determined the percentage of CD14+ monocytes, CD45+ lymphocytes, and CD45+ granulocytes positive for CD46, CD55, and CD59 in patients with neovascular AMD and compared this with that of controls.

They found that the expression of CD46 and CD59 was significantly lower on CD14+ monocytes in patients with neovascular AMD compared with controls (p=.0070). The investigators also observed a significantly lower expression of CD46 on lymphocytes in patients with fibrosis compared with patients without fibrosis (p=.010).

This study suggests that neovascular AMD is associated with an inadequate regulation of the complement system, supporting current evidence on the role of complement dysregulation in the pathogenesis of AMD.

To describe and interpret the frequently observed spectral-domain optical coherence tomography (SD-OCT) finding of a marked hyporeflective wedge-shaped structure at the boundaries of the areas of atrophy, researchers in Spain conducted the following prospective, longitudinal follow-up study.

They examined consecutive patients (n=71) 50 years of age and older with geographic atrophy (GA) secondary to age-related macular degeneration (AMD) between January 2010 and June 2011. The researchers evaluated patients with the use of imaging techniques that included 35° fundus photography, infrared, fundus autofluorescence (FAF), and SD-OCT. They visualized the fundus simultaneously with FAF and OCT. They followed two acquisition protocols: a macular cube for coverage (19 horizontal B-scans centered on the fovea) and high-resolution horizontal B-scan for qualitative foveal detail. Estimation of the prevalence of a hyporeflective wedge-shaped band among patients with GA was the main outcome measure.

The study researchers observed a marked hyporeflective wedge-shaped structure, with its base on Bruch's membrane and its apex pointing toward the inner limit of the outer plexiform layer (OPL) adjacent to the margin between the atrophied area and the preserved retina in 72.9% of eyes (70/96; 95% confidence interval, 63.9–82.0). They noted that this hyporeflective band appeared to be within the OPL. Using eccentric SD-OCT acquisition, the boundaries between the outer nuclear layer (ONL) and Henle's fiber layer (HFL) were well defined, showing that the ONL ends before the margin of atrophy of the retinal pigment epithelium (RPE). A narrow hyperreflective band separated the margin of the ONL and RPE from the hyporeflective band, already within the atrophic area.

In conclusion, a hyporeflective wedge-shaped structure appears frequently within the boundaries of the OPL in patients with GA secondary to AMD, corresponding to an increase in the width of the HFL, presumably because of axonal swelling or interaxonal edema. This finding may improve the interpretation of SD-OCT images of the outer layers, may help in understanding better the interactions of between photoreceptor cells and the RPE, and may help in the development of monitoring techniques and therapies for GA secondary to AMD.