Effects of Magnifier Training: Evidence from a Camera Built in the Magnifier

Abstract

Purpose: This study evaluated the effect of an evidence-based magnifier training on viewing behavior in visually impaired children aged 3 to 6½ years.

Methods: Effects of a training with a stand magnifier were evaluated by analyzing recordings of 21 visually impaired children, obtained from a miniature camera mounted in the magnifier. In a pre-test, post-test design, 11 of the children trained without magnifier and 10 children trained with magnifier. Three measures were compared from pre- to post-test assessment: 1) observation time in seconds through the magnifier during task performance; 2) the eye that was used during task performance with the magnifier (right eye/left eye as recorded by the camera); and 3) the self-chosen eye-to-chart distance (in cm) in near visual acuity measurement.

Results: Three important changes were found by analyzing the eye-camera recordings:

(1)	There was a significant shift in average observation time (i.e., the duration of looking through the magnifier in a single glance), before and after training. In the pre-test children used less than 10 s for a glance through the magnifier, whereas in the post-test this was 10–30 s.
(2)	In 5 children there was no preference with respect to the number of glances through the magnifier with right or left eye during pre-test measurement. However, such a task-specific dominance was clearly observed in this subgroup after training (post-test measurement).
(3)	The eye-to-chart distance, as measured during near-vision testing with LH-single and LH-line test, decreased significantly over the training period (from 9.5 cm to 7.9 cm, pre- to post-test).

There were no differences in the outcome measures between the with-magnifier and without-magnifier training groups. We can conclude that (1) the magnifier training had a positive effect on viewing behavior and the development of dominance, and (2) camera observations provide valuable data on children’s viewing behavior.

KEYWORDS::

• Visual impairment
• children
• magnifier training
• viewing behavior
• dominance

ACKNOWLEDGMENTS

The authors wish to express their appreciation to the following people for their participation in this research: Judy Chau, Tinie Bierman, Loukie de Vaere, Froukje Zuidema, Frank Jorritsma, and Michael Buckley. We also thank all of the students, trainers and of course the children and their parents who participated in this project for their considerable efforts.

This research was funded by the Dutch Organisation for health and Research Development (ZonMw) – Program InSight, project number 94303020, the Vereniging Bartiméus, and the Oogfonds.

Declaration of interest: The authors declare no conflicts of interest.