Visual acuity tests using chart, line, and single optotype in healthy and amblyopic children

The purpose of this study was to evaluate the difference between full chart, single line, and single optotypes visual acuity (VA) test results in healthy and amblyopic children.

Thirty-five children with amblyopia (20 with strabismus and 15 with anisometropia) and 40 ophthalmologically normal age-matched children were examined. The mean age of the patients in the study and control groups did not differ significantly (P= .9). A commercial projector that projected tumbling-E randomly placed optotypes was used. The VA of the amblyopic eye of the patients in the study group and the right eye of the patients in the control group was examined first using a full chart of optotypes, then using a single line of optotypes, and finally with individual symbols. The procedure was repeated with the other eye.

LogMAR VA improved when the full chart was substituted with a single line, and improved by a similar increment further with single optotypes, in both the study and control groups. VA improved significantly more in eyes with amblyopia than in control subjects. Results were not influenced by age.

VA testing using a single line gives better, sometimes misleading results, than tests with a full chart because it reduces but does not eliminate the crowding effect. When using a device that can employ more than 1 mode, the exacttest mode should be specified and maintained throughout the follow-up.