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J. Inoue, H.–M. Cheng, F.J. Van de Velde, T. Hirose; Reading Efficiency In Patients With Dense Central Scotoma . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5717.
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Patients with a dense central scotoma often develop preferred retinal loci (PRLs) for visual tasks, for example reading. The purpose of this study is to evaluate the patient’s reading efficiency using these PRLs with a scanning laser ophthalmoscope (SLO) based technique.
Patients (N=21) with a best correctable visual acuity of less than 20/100 in the better eye and with a dense central scotoma in this eye were enrolled in the study. Static SLO microperimetry, corrected for eye movements, with a low photopic background of 100 trolands was performed to identify the extent of dense scotomas and the PRLs. The reading speed was measured by timing the patients’ reading of MNRead charts of various sizes (logMAR 1.2–0.5) projected onto the PRLs through the SLO using a high background illumination of approximately 3000 trolands. The reading speeds were then correlated with the PRL and scotoma characteristics.
Different anatomical locations of the PRL lead to significantly different reading speed. Patients with dense central scotoma could not read letters smaller than 20/80. And they also need a minimal visual field of at least 10 degrees to read larger letters. The reading speed of patients with a PRL located inferior to the dense central scotoma was 54.0±9.3 wpm. If the PRL was located to the right or left of the dense central scotoma, but not adjacent to the optic disk, the reading speeds were respectively 36.3±14.3 wpm and 51.7±14.7 wpm. The reading speed of patients with a PRL located between the optic disc and the dense central scotoma in either eye, or patients with PRLs for reading that are located on both sides of the dense central scotoma had a significantly lower value of 18.7±2.6 wpm. As a comparison, patients with ring scotomas can read small letters albeit very slowly. They, however, cannot read large letters because of the restricted central visual fields. Those patients can read large letters only by using eccentric visual fields.
PRLs for reading can be readily identified using the SLO. The reading efficiency of patients with a dense central scotoma depends on the location and the available horizontal size of the PRLs. This information is useful for training the patients to develop or reinforce PRLs for reading outside the dense central scotoma.
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