Severity of Vision Loss Interacts with Word-Specific Features to Impact Out-Loud Reading in Glaucoma.

Purpose: To assess the impact of glaucoma-related vision loss on measures of out-loud reading, including time to say individual words, interval time between consecutive words, lexical errors, skipped words, and repetitions. Methods: Glaucoma subjects (n=63) with bilateral visual field loss and glaucoma suspect controls (n=57) were recorded while reading a standardized passage out loud. A masked evaluator determined the start and end of each recorded word and identified reading errors. Results: Glaucoma subjects demonstrated longer durations to recite individual words (265 vs 243 milliseconds (ms), p<0.001), longer intervals between words (154 vs 124 ms, p<0.001), and longer word/post-word interval complexes (the time spanned by the word and the interval following the word) (419 vs. 367 ms, p<0.001) than controls. In multivariable analyses, each 0.1 decrement in log contrast sensitivity (logCS) was associated with a 15.0 ms longer word/post-interval complex (95% CI=9.6-20.4; p<0.001). Contrast sensitivity was found to significantly interact with word length, word frequency, and word location at the end of a line with regards to word/post-word interval complex duration (p<0.05 for all). Glaucoma severity was also associated with more lexical errors (Odds ratio=1.20 for every 0.1 logCS decrement; 95% CI=1.02-1.39, p<0.05), but not with more skipped or repeated words. Conclusions: Glaucoma patients with greater vision loss make more lexical errors, are slower in reciting longer and less frequently used words, and more slowly transition to new lines of text. These problem areas may require special attention when designing methods to rehabilitate reading in patients with glaucoma.