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Editors Selection IGR 15-4
Quality of Life: Reading Speed in Glaucoma
Comment by Pradeep Ramulu on:
74764 Slow Reading in Glaucoma: Is it due to the Shrinking Visual Span in Central Vision?, Kwon M; Liu R; Patel BN et al., Investigative Ophthalmology and Visual Science, 2017; 58: 5810-5818
Kwon and colleagues compare reading speeds in a group of control and POAG patients, asking which vision measures are most relevant to reading speed. The Flash Card Reading test, in which patients read short 4-line sentences on a computer screen was used to evaluate reading. In regression analyses including multiple visual predictors (acuity, contrast, stereoacuity, visual field), size of the visual span was the only significant predictor of reading speed. Size of the visual span, measured by briefly flashing 13 letters spanning 10° of visual field to patients and asking them to identify as many letters as possible, was significantly smaller in glaucoma patients, who recognized two letters fewer than controls. This article recalls the fundamental findings of Gordon Legge in his Psychophysics of Reading series, which demonstrated that low vision patients have more trouble reading because they recognize fewer letters with each fixation because their contrast and acuity fall off more precipitously. Kwon's work suggests this same phenomenon obtains in persons with glaucoma and explains their difficulties reading. One study limitation is that models without reading span as a predictor were not presented, so the additional value of this measure is unclear. Also, the importance of visual span may have been artificially inflated as a result of the large number of regression covariates used in a sample of only 38 patients. Finally, the reading task presented short simple text which was read out loud, which may not relate to the more common scenario of silently reading more complex material over longer durations. Nonetheless, the article is a wonderful description of the importance of visual span with regards to reading in glaucoma, and furthers the concept that glaucoma Is not purely a disease of the peripheral visual field, but also has strong effects on tasks of central vision.
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