Abstract
Purpose: :
Macular degeneration often causes severe impairment of reading function due to central vision loss. It has been shown that peripheral reading speed can be improved through perceptual training in people with normal vision. However, applying a similar training protocol to people with low vision faces several practical issues. Previously, we have described an internet based home training protocol to facilitate subject participation. Here, we report on a pilot project in which we customized the training stimuli to address individual differences in the characteristics of the central scotoma and preferred retinal locus (PRL). Stimuli were chosen with the goal of maximizing the size of the visual span for reading.
Methods: :
Four subjects with juvenile onset forms of macular degeneration participated in home-based training (age from 45 to 57 yrs old, acuity from 0.48 to 1 logMAR). MP1 microperimetry was conducted in the lab before and after all other tests. Pre and post tests at the subject’s home included flashcard reading speed, Rapid Serial Visual Presentation (RSVP) reading speed and visual span measurements. Training (one hour per day for four days, also at the subject’s home) consisted of either repeated RSVP reading, or a word recognition task. The retinal location and orientation (horizontal or vertical) of letter strings were selected to provide a suitable visual span for reading, centered on the subject’s PRL, and not obstructed by the scotoma.
Results: :
Two subjects had PRLs on the left side of the scotoma, and were trained with vertical RSVP reading, where letters were rotated clockwise and arranged in the vertical direction. They both showed a gain due to training for vertical RSVP reading (49 word/min and 52 word/min, respectively), with partial transfer to vertical flashcard reading, and also to horizontal RSVP and flashcard reading. One subject had the PRL below the scotoma and was trained with the horizontal word recognition task. He gained 39 word/min for RSVP reading and 18 word/min for flashcard reading. One subject had a central island of vision and a large ring scotoma. He fixated with his residual functioning fovea while RSVP training stimuli were presented in his lower visual field outside the scotoma. He demonstrated a training gain of 106 word/min for eccentric RSVP reading.
Conclusions: :
It may be useful to take into account the variability in the nature of central-field loss and the location of the PRL when designing a perceptual training procedure for enhancing reading performance in macular degeneration.
Keywords: low vision • macula/fovea