Comparison Of Dynamic Random Dot E Stereo Test And Lang II Test: Testability And Reliability In Preschool Children

Abstract

Purpose: : None of the currently available stereo tests (i.e. Frisby-Titmus-Lang II-Randot-TNO) are suitable screening methods to detect anomalies resulting in amblyopia. Dynamic random dot stereogram Snellen E-s (DRDS-Es) seem to be a promising method for screening by untrained examiners. The purpose of our present study was to compare testability and reliability of a new anaglyphic DRDS-E and the Lang II test in Hungarian preschool population.

Methods: : In this study, 297 children at the age of 4.8±1.1years were screened in 8 nursery schools. Five age groups were created: 1. 1.5-2.5yrs, 2. 2.5-3.5yrs, 3. 3.5-4.5yrs, 4. 4.5-5.5yrs, 5. 5.5-6.5yrs. Children’s testability was determined by non-stereoscopic Snellen E optotypes in 4 different orientations. When at least 7 out of 8 orientations were identified correctly, the child was considered testable. DRDS-E-, Lang II-, Bruckner-, cover- and Snellen visual acuity tests were performed. Software generated anaglyphic red-green DRDS-E stimuli containing the cyclopean Snellen E optotype were presented on a notebook with 16.6-inch LCD screen and viewed with red-green goggles (frame rate:15 Hz; distance:1m). Eight levels of horizontal crossed disparity (from 1’ to 115’ in octave steps) were introduced in the images. To pass the DRDS-E test 7 out of 8 correct responses were required within 20s time limit for each figure.

Results: : Testability of Lang test for age groups were 35.3%, 68.0%, 87.3%, 95.2%, 99%, for DRDS-E test 17.6%, 80.0%, 90.5%, 95.2%, 99.0%, respectively. Testability increased with age in both DRDS-E and Lang test (p=0.001 and p=0.002). In total, 14 children failed the Lang test, while 27 could not pass DRDS-E test over 3 years of age. All Lang positive cases were found positive by DRDS-E method too. There were three children who passed all tests except DRDS-E test. All three were eventually proved to be hyperopic (mean +2.6D ±0.3D) and/or astigmatic on both eyes shown by skiascopy in cycloplegia.

Conclusions: : Our results are in agreement with Schmidt’s data about testability of static random dot E stereotest in 3- to 5-year-old children. It is also suggested that DRDS-E method is cognitively not more difficult than Lang test and at least as reliable but seems to be more sensitive to mild binocular anomalies caused by i.e. hyperopia or astigmatism in children over 3 years of age.

Keywords: binocular vision/stereopsis • screening for ambylopia and strabismus