Abstract
Purpose::
In patients with AMD and an absolute central scotoma, eccentric viewing is a necessity for reading. We showed earlier that reading speed was significantly higher when using an area above or below the retinal lesion compared to an area to the left or to the right of the retinal lesion. It is our experience that patients subjectively prefer the upper retina (above the lesion, i.e. reading below the visual field scotoma) over the lower retina. Therefore, in the present study, we investigated whether there is an objective difference in reading performance between the upper and lower retina when using eccentric viewing.
Methods::
Thirteen volunteers with normal vision, aged 25 - 58 years, and able to maintain a stable eccentric viewing, were studied in a scanning laser ophthalmoscope (SLO) while reading a text 6 degrees above or below a fixation line (series A). The text, properly magnified, was scrolled at a speed of 60 words per minute. The number of missed or incorrectly read words was deducted as well as words read when occasionally fixating the text. Furthermore, in an other series of experiments (series B), a second line of a random letter text was added at the opposite side of the fixation line, also at a distance of 6 degrees from this line (i.e. at a distance of 12 degrees from the original text line), to see whether it would disturb reading. Finally, the random letter text was instead superimposed upon the fixation line (i.e. at a distance of 6 degrees from the original text line). The entire program was repeated in a reversed order, and the mean values of the two series were used for calculations (Student’s paired t-test).
Results::
In both series of experiments, the number of errors was significantly lower when using the upper retina compared to the lower retina (A: p=0.030; B: p=0.038). The additional random letter text line (at 12 degrees) did not influence reading performance when comparing either the upper retinas of series A and B (p=0.722) or the lower retinas of series A and B (p=0.404). When the random letter text was superimposed upon the fixation line, i.e. 6 degrees from the original text line, the number of errors was significantly higher (p=0.036) than when the random letter text line was placed at a distance of 12 degrees.
Conclusions::
Reading performance was significantly better when using the upper compared to the lower retina in eccentric viewing. A line of random letter text at a distance of 12 degrees from the original text line did not disturb reading significantly. A random letter text as close as 6 degrees from the original text line caused significantly more errors than a line at a distance of 12 degrees, however.
Keywords: low vision • reading