By Jennifer Bevan; Jan Lovie-Kitchin; Brnwyn Hein; Eric Ting; Paul Brand; Monique Scott and Paul Fotkou
Reading is an important aspect of child development. Determining the appropriate method of magnifying text for children with low vision thus becomes an important issue, to ensure that difficulties in reading do not impede progress in educational, vocational and recreational activities.
The use of large print, known to researchers as relative size magnification (RSM) and the use of near spectacle correction - relative distance magnification (RDM) - are two ways to assist readers with low vision. Studies comparing these two approaches have tended to yield reading rates that were equivalent or better for subjects using optical correction with regular text, including closed circuit televisions (CCTVs), than for subjects reading large print. The variation between the two has tended to be small, whether the subjects have normal or low vision.
One study by Corn (1990), however, showed about 40% of the large-print readers have reading rates under 20 words per minute. It also indicated that a higher proportion of optical device users than large-print users achieved reading levels above eighth-grade standards. No definite conclusion could be drawn, however, as the study was based on questionnaires completed by teachers of students who are visually impaired, and the teachers may have decided that large print was better for slow learners. In addition, reading rates of subjects using large print were not compared with those of subjects using optical devices.
In the current study conducted by researchers based in Queensland, Australia, 46 children with low vision (27 male, 19 female), ranging in age from 6.9 to 18.7 years, were drawn from the database of the multi-disciplinary Pediatric Low Vision Clinic in Brisbane. The subjects' low vision resulted from disorders such as: oculocutaneous albinism, rod monochromatism, optic atrophy, retinitis pigmentosa and high myopia.
The children's reading skills were tested using a series of cards, based on the Minnesota Low Vision Reading Test, each one containing a sentence made up of 56 characters (9.3 standard words) over four lines - or 14 characters per line. The cards varied in content according to reading age, and the subjects were asked to read them at working distances of 160, 120. 100. 80, 63 and 50 mm. Illumination was maintained at a constant level. Binocular reading rates and visual acuities were measured for: (1) RSM at a test distance of 160 mm for six print sizes; (2) RDM for a fixed print size at the six set working distances.
Additional positive lenses were used as needed to correct for working distance. The two magnification methods were alternated for each successive subject, and the six print sizes or working distances were presented in random orders.
Subjects were instructed to read each sentence aloud at their normal rate, and to continue reading even if they made a mistake. Reading rates were calculated in standard words per minute (wpm). Maximum oral reading rates (MORRs) were determined for each subject using the computer program MNRead Analysis VO.3. The mean MORRs for RSM and RDM were 117.27 ± 47 wpm and 94.39 ± 404.04 wpm, respectively. This difference, while small in practical terms, proved to be statistically significant, and the results of the test ran contrary to the expectations of the researchers. Reading rates at high acuity reserves (0.3 to 0.5 log units is two to three times larger than threshold print size) for children with low vision in this study were significantly faster when magnification was provided by large print than by decreased working distances.
The study concluded that while large print gives faster reading rates, it is impractical for all reading tasks. It is therefore of long-term practical advantage for children to learn to use magnification devices to read normal-size print. Moreover, self-esteem may be enhanced if children are able to read the same books as their classmates. The researchers recommended that while children with low vision are learning to read, large print should be used. Once reading skills are acquired, training and practice in reading with optical devices becomes imperative.
Jennifer Bevan is at the Centre for Eye Research, School of Optometry, Queensland.
Jan Lovie- Kitchin is at the University of Technology, Queensland, Australia.
Bronwyn Hein is at the Low Incidence Support Centre-Vision Impairment Services, Queensland, Australia.
Paul Brand and Eric Ting, participated in the study as part of their undergraduate studies in optometry and are now involved in private practice throughout Australia.
Source: Lighthouse International's EnVision newsletter