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Visual span significantly contributes to reading speed in glaucoma
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The size of the visual span was the only significant contributor to reading speed in glaucoma when binocular visual acuity, binocular contrast sensitivity, stereoacuity and visual field in the better eye were held constant, according to researchers.
Researchers examined the factors that may underlie slow reading in glaucoma and determined the best predictor of reading speed.
A total of 38 subjects took part, 17 with primary open-angle glaucoma and 21 age-similar normal controls.
Researchers measured binocular visual acuity (BVA), binocular contrast sensitivity (BCS), stereoacuity, visual field mean deviation and the visual span known to limit reading speed.
The glaucoma patients showed significantly slower reading speed and smaller visual span compared to normal controls, even after controlling for age.
While patients with glaucoma had relatively normal BVA, their BCS, stereoacuity and visual field mean deviation showed pronounced deficits, according to researchers.
The researchers concluded that reading speed in glaucoma was best predicted by the visual span.
This study further supports the view that reading difficulties are present even in relatively moderate stages of glaucoma and associated with noticeable defects in stereoacuity and BCS.
Even in early or moderate stages of glaucoma, stereopsis, convergence and binocular fusion are significantly more impaired in those with glaucoma, compared to glaucoma suspects or normal cohorts, they wrote. – by Abigail Sutton
Disclosures: The researchers report no relevant financial disclosures.
Perspective
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Carl H. Jacobsen, OD, FAAO
Historically, glaucoma was thought to spare central vision until late in the disease. A glaucoma-related reading deficit? Unlikely. Recently, we have come to understand that the macular area may be affected much earlier, hence the move to routine 10-degree visual field and macular scanning. Might diminished macular function affect reading ability? Probably.
Kwon and colleagues have noted that glaucoma patients often complain about reading and have set out to identify glaucoma-related factors that might be associated with poor reading ability. They found that slower reading speed in glaucoma was closely related to shrinking of the visual span (number of letters recognized in one glance). How might this new knowledge affect our clinical practice?
First, let’s remember to ask about patient problems. It’s possible that “glaucoma patients never complain” because we never ask. Second, consider referrals for symptomatic patients. A binocular vision specialist may help your patient maximize their reading ability, and a low vision colleague might assist in amplifying their visual span. In addition to disease management, we owe it to our patients to maintain an awareness of how this disease might affect their lives and what we can do to mitigate disease impact.
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