Reading training with threshold stimuli in people with central vision loss: a feasibility study

To evaluate the effectiveness of a perceptual learning technique for improving reading performance of patients with central vision loss and to explore whether this learning generalizes to other visual functions.

Ten patients with central vision loss were trained binocularly, in four consecutive sessions, with serially presented words printed at each patient's reading acuity limit. Patients read 10 blocks of 100 words in each session. They were encouraged to read the whole word and were discouraged to read letter by letter. Assessment sessions before and after training measured fixation stability, monocular and binocular visual acuity, as well as reading acuity, critical print size, and maximum reading speed with continuous text. Another six patients with central vision loss were included in a test-retest control group and were tested twice, 1 week apart, with no intervention.

The average time required to read a block of trials decreased significantly with each training session. After training, continuous text reading improved in terms of reading acuity (p = 0.017) and maximum reading speed (p = 0.01), but critical print size did not change. Binocular acuity improved significantly from an average of 0.54 logMAR before training to 0.44 logMAR after training. Binocular ratio (better eye acuity/binocular acuity) increased from an average of 1.0 before training to 1.17 after training. There was a 62% improvement in fixation stability in the better eye and 58% in the worse eye. There were no changes in the outcome measures for the test-retest control group.

The technique described in this article can be used for vision rehabilitation of patients with central vision loss. When training is done with size threshold stimuli, learning generalizes to visual acuity, continuous text reading, and fixation stability.