The modified frisby stereotest

Effects of Target Size and Test Distance on Stereoacuity

Target size and test distance effects on stereoacuity were investigated in 24 subjects using a three-dimensional monitor. Examination 1: Target Size Effects. The test distance was 2.5 m for 0.1°, 0.2°, 0.5°, and 0.9° target sizes; crossed parallax was presented in 22-second units. Average stereoacuity values for 0.1°, 0.2°, 0.5°, and 0.9° target sizes were 59.58 ± 14.86, 47.66 ± 13.71, 41.25 ± 15.95, and 39.41 ± 15.52 seconds, respectively. Stereoacuity was significantly worse with a 0.1° target than with 0.2°, 0.5°, and 0.9° target sizes (P = 0.03, P < 0.0001, and P < 0.0001, resp.). Examination 2: Test Distance Effects. Test distances of 2.5, 5.0, and 7.5 m were investigated for a 0.5° target size; crossed parallax was presented in 22-second units. Average stereoacuity values at 2.5 m, 5.0 m, and 7.5 m test distances were 44.91 ± 16.16, 34.83 ± 10.84, and 24.75 ± 7.27 seconds, respectively. Stereoacuity at a 7.5 m distance was significantly better than at distances of 2.5 m and 5.0 m (P < 0.0001 and P = 0.02, resp.). Stereoacuity at a 5.0 m distance was significantly better than at 2.5 m (P = 0.04). Stereoacuity should be estimated by both parallax and other elements, including test distance and target size.

Stereoacuity norms for school-age children using the Frisby stereotest

BACKGROUND

The Frisby stereotest and the TNO test for stereoscopic vision are popular clinical tests for assessing stereoacuity: however, reference data for school-age children for the Frisby stereotest are limited. This study compared stereoacuity results of both tests in a large sample of typically developing school-age children.

METHODS

Primary (elementary school grades 1-6) and post-primary (high school grades 7-11) students aged 6-16 years were recruited and assessed in schools. Stereoacuity thresholds were measured using the Frisby and TNO stereotests. Children with ocular pathology, anisometropia of ≥1.00 D, interocular difference of visual acuity ≥0.2 logMAR, or strabismus were excluded.

RESULTS

A total of 212 children were recruited; data for 186 subjects were analyzed. Median Frisby stereoacuity scores were, for crossed disparity, 20 arcsec for primary and 10 arcsec for post-primary children and, for uncrossed disparity, 25 arcsec (primary) and 10 arcsec (post-primary). TNO stereoacuity was 60 arcsec for both age groups. For Frisby stereoacuity, scores of 85 arcsec (crossed) and 170 arcsec (uncrossed) or better were achieved by 95% of primary school children; scores of 85 arcsec (crossed and uncrossed) or better were achieved by 95% of post-primary subjects. A statistically significant difference in median stereoacuity scores was noted across age groups for the Frisby stereotest (crossed: z = 4.67, P < 0.0001; uncrossed: z = 4.67, P < 0.0001). No statistically significant difference in stereoacuity scores was noted with the TNO stereotest (z = 1.35, P = 0.18). A significant weak correlation was found between the Frisby and TNO stereotests (Frisby [crossed], r = 0.21 P < 0.005).

CONCLUSIONS

These data describe normative values for the Frisby stereotest for children aged 6-16 years. Participants recorded significantly better stereoacuity scores with the Frisby stereotest than the TNO stereotest. The Frisby stereotest values are weakly correlated with the TNO stereoacuity test.

Association between accommodative accuracy, hypermetropia, and strabismus in children with Down's syndrome

PURPOSE

A significant proportion of children with Down's syndrome have been shown to have reduced accommodation. The purpose of this study was to investigate any association between reduced accommodation and refractive error, strabismus, visual acuity, and other ocular parameters.

METHODS

Subjects were children with Down's syndrome enrolled in a longitudinal cohort to monitor visual development. Twenty-seven children with accurate accommodation were age-matched to children with reduced accommodation based on their most recent assessment for which a full, reliable data set was available. Each child was used only once for matching. Cross-sectional ocular and visual data were analyzed using chi or Fisher's exact test, or the Mann-Whitney U test for (non-normally distributed) quantitative data.

RESULTS

Children with under-accommodation were statistically more likely to have moderate/high hypermetropia (> or = +3.00 D) and to be strabismic (most with esotropia). No significant difference between the groups was found for any other ocular parameters.

CONCLUSIONS

This study demonstrates the marked association between under-accommodation, hypermetropia, and strabismus in children with Down's syndrome. No causal relation can be demonstrated with these data, but findings suggest that the link between under-accommodation and hypermetropia (and between accurate accommodation and emmetropia) is present in early infancy.

A study on the clinical usefulness of digitalized random-dot stereoacuity test

Existing methods of stereoacuity testing need specific glasses or optical device for use. We have designed a new stereoacuity test for the digitalized, random-dot stereogram and researched its clinical usefulness. A digitalized, random-dot, stereoacuity test card was created with a computer program that used a preferred symbol and the designed system was tested along with the Randot preschool stereoacuity, Titmus-fly and Lang tests to compare their sensitivity and specificity. The mean success rate of the digitalized, random-dot test was 98.2%, while the rates of the Randot preschool stereoacuity, Titmus-fly and Lang tests were 89.3%, 74.2% and 86.1%, respectively. Sensitivity and specificity of the new test were 100% and 95.3%, respectively, which were not that different from those of the Randot preschool stereoacuity, Titmus-fly and Lang tests. We found that the digitalized, random-dot, stereoacuity test has a high success rate and can be appropriately used in medical examinations and follow-up tests for strabismus patients.

Negative predictive value of a vision screening program aimed at children aged 3 to 4 years old

PURPOSE

Nova Scotia has a vision screening program which assesses children aged 4[1\2] to 5[1\2] years. However, its use in younger children proved impossible. This study will examine a modified screening protocol for the younger children (3 to 4 years old) and determine its negative predictive value and minimum age for reliable application.

MATERIALS AND METHODS

Public health nurses administered the study protocol to 3- to 4-year-old children. One hundred seventy-eight children were screened over two summers. Medical and family history, external inspection, as well as measures of visual acuity with the Lea Hyvarinen symbols chart and stereoacuity with Frisby plates were recorded. Results were compared with a gold standard examination that included full orthoptic and ophthalmologic evaluations. One hundred forty-one (79%) children underwent the gold standard examination. Agreement between screening and gold standard examinations was studied.

RESULTS

Data showed increased concordance between screening and gold standard examination results with increasing age up to 41 months. Negative predictive value (NPV) and specificity also improved when data were separated by this age. In children <41 months old, the screening test NPV was 90%, specificity, 68%, and sensitivity, 75%. In comparison, children >/=41 months old had screening test NPV of 96%, specificity, 95%, and sensitivity, 50%. Specificity was higher in the older age group ( P < 0.001). Sensitivity was lower ( P = 0.004).

CONCLUSION

This study's vision screening protocol appears better suited for children 41 months and older. They had better pass/fail reproducibility than children <41 months. The test's simplicity allows easy use by non-eye-care professionals. It could potentially lower the reliable screening age of children by 13 months, from 54 months of age (4[1\2] years old) to 41 months. This screening may miss some refractive errors and microtropia/monofixation syndrome, despite normal visual acuity, stereoacuity, and external inspection.

The moving Dynamic Random Dot Stereosize test: development, age norms, and comparison with the Frisby, Randot, and Stereo Smile tests

PURPOSE

To determine the response of infants and children to the Moving Dynamic Random Dot Stereosize (MDRS) test and to collect cross-sectional age-related data.

METHODS

Sixty visually normal individuals were divided into four age groups: 0.5-<2, 2-<5, 5-<8, and 8-<20 years. Stereopsis was measured with the MDRS test on two occasions, plus the Frisby, Randot, or Stereo Smile tests, as was age appropriate.

RESULTS

All children aged >2 years and 80% of the children between ages 6 months and 2 years were able to perform the MDRS test on at least one occasion. Sixty percent of the 6-month to 2-year-old children were able to perform the Stereo Smile test on both occasions. Performance on the MDRS test improved with age up to 9 years. Improvement on the Frisby and Randot tests was seen in children aged up to 7 years. Mean and 95% confidence interval ranges for each test are given.

CONCLUSION

This study gives evidence that aspects of the visual system are not fully mature until age 7-9 years. The MDRS test is a visually demanding but cognitively simple test that shows potential for detecting visual anomalies in young children.

Randot stereoacuity norms in a population of Saudi Arabian children

BACKGROUND: The onset and development of stereoacuity in children have been investigated by several authors. In addition to the study of those aspects of stereopsis, it is also important to collect normative data, which can be applied in the clinical setting. The purpose of this study was to establish Randot stereoacuity norms using a Saudi Arabian children population. METHOD: The Randot stereo test was used to measure stereoacuity for 791 male primary school children (aged six to 12 years) with normal vision. A battery of tests was used to establish that each child had normal eyes and vision prior to the stereoacuity measurement. RESULTS: The range of stereoacuities for all the age groups at 40 cm was 70 to 20 seconds of arc, except for the nine-year-old children in whom the range was 50 to 20 seconds of arc. More than one half (57.5 per cent) of the children achieved 29 seconds of arc. The mean stereoacuity for all of the children was 25.32 seconds of arc with a standard deviation of 9.93 seconds of arc. The mean stereoacuity for the children decreased from 29.11 seconds of arc at six years to 23.61 seconds of arc at 11 years. An inter-subject variation in stereoacuity development was observed. CONCLUSION: This paper provides normative data for Randot stereoacuity for children. The range and mean values presented here will be useful as reference data for clinical diagnosis of normalcy or otherwise of stereoacuity in children of similar ages when the Randot stereo test is used.