Central vision loss affects reading speed

Loss of central vision affects reading speed, according to results of the Salisbury Eye Evaluation reported here at the annual meeting of the American Glaucoma Society by Pradeep Y. Ramulu, MD, PhD, assistant professor, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore.

Dr. Ramulu and colleagues studied reading speed in the study's 1,253 participants by assessing the rate at which patients read aloud non-scrolling, sixth-grade-level, newspaper-sized text flashed on a screen in each of four sizes for 16 seconds. They defined normal reading speed as 150 words per minutes and impairment as a reading speed of fewer than 90 words per minute.

A specialist divided patients into groups related to glaucoma diagnosis-no, possible, probable, or definite-based on the appearance of the optic disc and visual field testing. Seventy-four patients (5.9%) were classified as having unilateral glaucoma, and 74 patients were classified as having bilateral glaucoma.

Mean reading speed for all study participants was 137 words per minute; 17.8% were classified as reading-impaired. Univariate analysis found lower reading speeds associated with factors such as bilateral glaucoma, worse presenting visual acuity, lower visual field mean deviation, and more visual field points in the central 20 degrees of either eye with a sensitivity of less than 24 dB. Multivariate linear regression found no change in reading speed for patients with unilateral or bilateral glaucoma. Multivariate models that included age, race, score on the MiniMental State Exam, depression, and presenting acuity found decreased reading speed (-0.33 word/minute/point) and more frequent reading impairment with increased numbers of visual field points in the central 20 degrees with a sensitivity of less than 24 dB.

"Our conclusions are that normal reading speed is at least possible for short durations in most elderly subjects with glaucoma," Dr. Ramulu said. "Impairment is more common in patients with advanced bilateral glaucoma, and we think that most of this effect is because the glaucoma was advanced enough that either the treatment or the extent of the visual filed loss was actually causing a decease in the visual field."