Abstract
Purpose :
Even with magnified text, reading is slow and difficult for many patients with central vision loss who must use their peripheral vision. Similarly, reading in normal peripheral vision is also slow and requires larger print. The purpose of this study was to examine whether the properties of reading with central vision loss are similar to those of reading in normal peripheral vision for matched retinal eccentricities.
Methods :
Twenty-eight observers with bilateral central vision loss read aloud single sentences presented on a monitor. Words were presented as high-contrast text, one at a time, using rapid serial visual presentation (RSVP) at a range of word exposure durations. For each observer, reading speeds (based on RSVP exposure durations yielding 80% of words read correctly) were measured for five or six print sizes. Each set of reading speed vs. print size data was fit with a bilinear function. The slope of the first line represented how reading speed improved with print sizes smaller than the critical print size (CPS) and was free to vary. The slope of the second line was constrained to be zero, representing the maximum reading speed (MRS). The eccentricity of the preferred retinal locus (PRL) of the better eye of each observer was determined using a scanning laser ophthalmoscope. Values of CPS and MRS in normal peripheral vision at PRL-matched eccentricities were derived from Chung, Mansfield & Legge (1998).
Results :
Compared with reading in normal peripheral vision, observers with central vision loss as a group showed a shallower change in reading speed with print sizes smaller than the CPS (log-log slope: 1.77 vs. 2.32, p=0.03), representing poorer responses to magnification. On average, their CPS was 2.2× larger than, and their MRS was 48% of the corresponding values at PRL-matched eccentricities in normal peripheral vision.
Conclusions :
Despite the qualitatively similar dependency of reading speed on print size for observers with central vision loss and in normal peripheral vision, most observers with central vision loss responded to magnification poorly, and required larger CPS to read at their MRS, which were lower than those predicted based simply on the PRL eccentricities. These results imply a deficit in peripheral pattern recognition in the presence of central vision loss, limiting the suitability of normal peripheral vision as a model for reading with central vision loss.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.