SEP 10, 2013
This prospective study found that maximum reading speeds can be near normal in infantile nystagmus when optimal font sizes are provided, even in individuals with poor visual acuity or intense nystagmus. However, reading performance was acutely sensitive to font-size limitations.
The authors write that the optimal conditions required for reading in infantile nystagmus patients have not been defined clearly. However, standardized reading charts, such as the MNREAD (Minnesota Laboratory for Low-Vision Research, University of Minnesota) and Radner reading charts, have been used to determine the effect of changing font size in a range of visual disorders, such as age-related macular degeneration, amblyopia, uveitis and drusen maculopathy.
The authors investigated the optimal font sizes for reading performance in 71 individuals with infantile nystagmus compared with age-matched controls using the Radner reading test. Of those with infantile nystagmus, patients with no obvious afferent deficits (idiopathic infantile nystagmus) were compared with those with infantile nystagmus associated with albinism.
In optimal reading conditions, maximum reading speeds were 18.8 percent slower in albinism and 14.7 percent slower in idiopathic infantile nystagmus patients compared with controls. Reading acuities were significantly worse (P < 0.001) in infantile nystagmus patients compared with controls. Also, the range of font sizes over which reading speeds were less than optimum was much larger (as much as 6 logMAR lines) in some infantile nystagmus patients compared with controls (P < 0.001).
In infantile nystagmus patients, reading acuity was strongly correlated with near visual acuity but was better than near visual acuity in participants with poor visual acuity. Near visual acuity was a poor predictor of maximum reading speed. Nystagmus intensity and foveation were poor indicators of both reading acuity and maximum reading speed.
The authors conclude that these results provide evidence for the potential use of reading speed measurements in patients with idiopathic infantile nystagmus and albinism for assessing functional vision because they more accurately reflect visual function than near visual acuity alone. They can be used as a guide to develop schemes for providing patients with the optimal font sizes for reading. Alternatively, where limitations in font sizes are imposed, they can indicate the adjustments in the time allowed for tasks requiring significant reading activity in schools and work places.