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Aim: To evaluate if functionally relevant deficits in reading performance exist in children with essential microstrabismic amblyopia by comparing the monocular and binocular reading performance with the reading performance of normal sighted children with full visual acuity in both eyes. Methods: The reading performance of 40 children (mean age 11.6 (SD 1.4) years) was evaluated monocularly and binocularly in randomised order, using standardised reading charts for the simultaneous determination of reading acuity and speed. 20 of the tested children were under treatment for unilateral microstrabismic amblyopia (visual acuity in the amblyopic eyes: logMAR 0.19 (0.15); fellow eyes −0.1 (0.07)); the others were normal sighted controls (visual acuity in the right eyes −0.04 (0.15); left eyes −0.08 (0.07)). Results: In respect of the binocular maximum reading speed (MRS), significant differences were found between the children with microstrabismic amblyopia and the normal controls (p = 0.03): whereas the controls achieved a binocular MRS of 200.4 (11) wpm (words per minute), the children with unilateral amblyopia achieved only a binocular MRS of 172.9 (43.9) wpm. No significant differences between the two groups were found in respect of the binocular logMAR visual acuity and reading acuity (p>0.05). For the monocular reading performance, significant impairment was found in the amblyopic eyes, whereas no significant differences were found between the sound fellow eyes of the amblyopic children and the control group. Conclusion: In binocular MRS, significant differences could be found between children with microstrabismic amblyopia and normal controls. This result indicates the presence of a functionally relevant reading impairment, even though the binocular visual acuity and reading acuity were both comparable with the control group.

Purpose To assess the performance of normal eyes in reading low-contrast texts. Methods We selected 14 subjects aged 20 to 31 years (mean, 23 ± 3 years) with corrected visual acuity of 1.0 or better. The subjects were asked to read texts when the contrast between the characters and background was adjusted to 100%, 40%, 20%, and 10%. Using a computer-generated reading chart, reading acuity (RA), critical character size (CCS), and maximum reading speed (MRS) were assessed. The reading performance was compared at various contrast levels. Results When the contrast between the characters and background was 100%, 40%, 20%, and 10%, the mean RA (logMAR) was −0.08 ± 0.07, 0.03 ± 0.09, 0.13 ± 0.09, and 0.26 ± 0.11, respectively; the mean CCS (logMAR) was respectively 0.10 ± 0.09, 0.18 ± 0.09, 0.29 ± 0.14, and 0.41 ± 0.10. The mean MRS (characters/min) was 379.2 ± 41.9, 369.7 ± 43.3, 369.2 ± 60.2, and 343.7 ± 67.0, respectively. In all subjects, a decrease in contrast was associated with an increase in RA and CCS, but the MRS was not affected. Conclusions In normal eyes, even when reading low-contrast texts, increasing the character size makes it possible to maintain the same MRS as when reading high-contrast texts.

In psychological measurement a distinction can be made between speed and power tests. Although most tests are partially speeded, the speed element is usually neglected. Here, the focus will be on latent trait models for pure speed tests. A particularly simple model has been developed by Rasch for the total response time on a (set of) pure speed test(s), based on the assumption that the test response times are approximately gamma distributed, with known index parameters and scale parameters depending on subject ability and test difficulty parameters. In the approach presented here the subject parameters are treated as random variables having a common gamma distribution. From this, maximum marginal likelihood estimators are derived for the test difficulties and the parameters of the latent subject distribution. This basic model can be extended in a number of ways. In a numerical example, an application of the Rasch model to reading data, which were incomplete by design, will be discussed.