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Frank A. Proudlock, Niraj Barot, Rebecca J. McLean, Irene Gottlob; Optimising Reading In Infantile Nystagmus Syndrome: Effect Of Orientation, Contrast, Font And Line Spacing On Text And Number Reading. Invest. Ophthalmol. Vis. Sci. 2012;53(14):514.
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© ARVO (1962-2015); The Authors (2016-present)
Reading has been poorly investigated in infantile nystagmus syndrome (INS). The aim of this study was to compare text and number reading in INS investigating: (i) the effects of contrast, font and line spacing on text reading; and (ii) the effects of orientation, contrast and font spacing on number reading.
Nineteen individuals with INS associated with albinism, 14 with idiopathic INS and 13 healthy controls were recruited for the study. The volunteers were instructed to read paragraphs of text (iReST reading charts, mean 153.5 words, 831.3 characters) presented on a large monitor (Apple 27", 2560x1440 resolution). The text size was near the acuity limit (reading acuity + 0.1 logRAD) and was presented at two different contrasts (100% & 41%), and two different font and line spacing in random order. The same volunteers read a series of 11 digit numbers of the same font size presented at three different orientations (horizontal, rotated 90° and marquee), two contrasts and font spacing. Reading speed in words/numbers per minute (w/npm) and mistakes were calculated.
Mean text reading speeds were significantly lower in albinism (114.9wpm), compared to idiopaths (119.8wpm, p=0.039) and controls (155.5wpm, p>0.0001) although number of mistakenly read words was not significantly different (medians 1.9%, 1.3% and 0.8%, respectively). Number reading speeds were significantly lower in idiopaths (78.5npm), compared with albinism (95.0npm, p>0.0001) and controls (130.5npm, p>0.0001). Mistakes during number reading where much higher than during text reading, and were significantly higher in idiopaths (4.5%, p=0.023) and in albinism (2.8%, p=0.017) compared to controls (1.9%). Orientation of numbers had a significant effect on reading speeds although individuals with INS read quickest with the marquee orientation (p<0.0001) whereas controls read better with the horizontal orientation (p<0.006). Text reading speeds were most sensitive to contrast, whereas number reading was most sensitive to font spacing.
These findings highlight the difficulties that individuals with INS have with number reading where error rates are more than 5x that in controls and 3.5x that during word reading. Number reading in INS is particular sensitive to crowding effects along the horizontal axis which could be alleviated practically by increasing spacing between numbers or using marquee orientation.
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