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  • Cup-to-Disc Ratio and Brain Changes

    By Mary Brophy Marcus
    Selected by Richard K. Parrish II, MD
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    Journal Highlights

    American Journal of Ophthalmology, May 2023

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    Loss of brain volume is linked with normal aging as well as neurodegener­ative disease. Because the optic nerve shares neuropathophysiology with the brain, Wang et al. sought to investigate the relationship between optic nerve cupping measurements and total and regional brain volumes. They found that in women 65 years of age and old­er, large cup-to-disc ratio (CDR)—defined as .6 or greater in either eye—was associated with lower relative total brain volume and decreased absolute regional volume in the frontal and occipital lobes.

    Previously, using measurements from the Women’s Health Initiative Sight Examination (WHISE) study, the authors found that women 65 years and older who did not have glaucoma but did have a large CDR had lower cognitive function than those who did not have a large CDR.

    To determine whether large CDR was associated with changes in brain volumes, the researchers performed a secondary analysis of data from two randomized clinical trials. The authors included measurements from 471 wom­en aged 65 to 79 without glaucoma who participated in WHISE and for whom MRI data on regional brain volumes were available from a second study, the WHI Memory Study (WHIMS).

    All told, 34 women (7.2%) had large CDR. When the researchers controlled for total brain volume and for demo­graphic and clinical characteristics, lateral ventricle volume was 3.01 cm3 larger for subjects with large CDR than for those without large CDR (95% CI, .02 to 5.99; p = .048). However, frontal lobe volume was 4.78 cm3 lower for subjects with large CDR compared to those without (95% CI, –8.71 to –.84; p = .02), and occipital lobe volume was 1.86 cm3 lower for those with large CDR compared to those without (95% CI, –3.39 to –.3; p = .02).

    According to the authors, this is the first epidemiologic analysis that demonstrates a relationship between large CDR and decreased brain vol­umes in individuals without glaucoma. They concluded that large CDR in women without glaucoma may be a sign of optic nerve and brain aging, but they noted that more longitudinal data are needed.

    In addition, in their conclusion, the authors pointed out that while they used “a large, well-characterized co­hort” of women from studies (WHISE and WHIMS) that enrolled people from a “variety of racial backgrounds,” most participants (93.8%) were White. Future investigations of CDR and brain volumes should represent multiple ra­cial groups and genders to expand the scope of this study, they wrote.

    The original article can be found here.