Paulette P. Schmidt

Vision screening of preschool children: evaluating the past, looking toward the future.

Vision problems of preschool children are detectable with a comprehensive eye examination; however, it is estimated that only 14% of children below the age of 6 years receive an eye examination. Screening is advocated as a cost-effective alternative to identify children in need of further vision care. Thirty-four states recommend or require vision screening of preschool children. Although laws and guidelines exist, only 21 % of preschool children are actually screened for vision problems. There is little agreement concerning the best screening methods, and no validated, highly effective model for screening vision of preschool children. Newer screening tests have been designed specifically for preschool populations, and can be administered by lay screeners. Many have not been validated. Several are recommended by states or organizations without convincing scientific evidence of their effectiveness. This paper summarizes current laws and guidelines for preschool vision screening in the United States, reviews advantages and disadvantages of several test procedures, and provides recommendations for developing future preschool vision screening programs.

Effect of oculomotor and other visual skills on reading performance: a literature review.

The diagnosis and management of many oculomotor anomalies is within the domain of optometry. Thus, a thorough understanding of these systems and their relation to reading performance is vital. Efficient reading requires accurate eye movements and continuous integration of the information obtained from each fixation by the brain. A relation between oculomotor efficiency and reading skill has been shown in the literature. Frequently, these visual difficulties can be treated successfully with vision therapy.

Sensitivity of random dot stereoacuity and Snellen acuity to optical blur.

The purpose of this study is to investigate the usefulness of a random dot stereogram for the detection of refractive blur by determining the relative sensitivity of random dot stereoacuity (RDS) and Snellen visual acuity to the effects of optically induced blur. Measurements of Snellen and stereoacuity were completed on four young adult subjects under cycloplegia and through artificial pupils. Optical blur was varied binocularly and monocularly in 0.50 D steps up to −6.00 D while the subjects viewed targets composed of stimuli arranged in 0.1 log unit size increments. The results show the relation between RDS and Snellen acuity to be SA = 1.341 (VA) + 0.281 for equal amounts of binocularly induced optical blur. Moreover, the RDS appeared more highly sensitive when the blur in the 2 eyes was unequal [SA = 3.774 (VA) - 1.180], a condition approximating refractive anisometropic amblyopia. These results provide a rationale for the use of random element stereograms for the detection of refractive amblyopia and ametropia in the vision screening of children.

Vision screening with the RDE stereotest in pediatric populations.

The usefulness of the Random Dot E (RDE) stereotest in screening the vision of school-aged children for vision problems has been established. As a single screening procedure, the effectivity (ø) of the RDE (ø=+0.52) is greater than the widely used Snellen acuity technique (ø=+0.36) and faster to complete. Very-low-birthweight (VLBW) children have a higher incidence of vision problems including strabismus, amblyopia, and refractive error than children born with normal-birthweights (NBWs). My purpose was to determine: (1) whether a group of young children at high risk for vision problems could perform random dot stereotesting and (2) an age appropriate pass/fail criterion for stereoacuity screening. Furthermore, categorization as pass or fail by each screening method studied [stereoacuity (RDE), visual acuity [Teller Acuity Cards (TAC) and Broken Wheel (BWA)] and refractive error] was compared for independent agreement with vision examination results. The subjects were a cohort of NBW and VLBW) (<1500 g) children matched at birth for maternal age, ethnic origin, time of hospital birth, and parity. Results of a masked investigation of 30 children [VLBW (N=10) and NBW (N=20) children] tested at 3 years of age (mean age=3.0 years, range 2.11 to 3.1 years) showed that (1) 86.7% were able to complete the 168 sec arc random dot stereoacuity task when a two-alternative forced-choice preferentiallooking paradigm was used for testing, (2) the specificity and sensitivity were 88.2%, 76.9% (RDE); 81.2%, 64.3% (TAC); 52.9%, 92.3% (BWA); and 94.1%, 61.5% (refractive error), respectively, (3) the reliability the RDE stereoacuity screening was greater (k=+0.66) than any of the other procedures studied, and (4) there was 73.3% agreement on test-retest categorizations between observers. We conclude that a random dot stereotest shows excellent potential as a single vision screening method that effectively identifies children in need of further visual attention.

Relationship between visual skills and performance on saccadic eye movement testing

The effect of visual skills, such as binocularity, on saccadic eye movement test performance is currently unknown. Therefore, the relationship between performance on commonly used clinical saccadic eye movement tests and visual skill was studied in a masked investigation of 181 kindergartners and first graders (mean age 6.25 years) from a middle class, suburban, elementary school near Cleveland, Ohio. The New York State Optometric Association King-Devick saccade test (NYSOA K-D) and the Developmental Eye Movement test (DEM) were employed because they are two commonly used clinical saccadic eye movement tests. A Modified Clinical Technique (MCT) vision screening and Randot stereoacuity test were performed to evaluate other visual skills. Analysis revealed that for the whole study population, total errors on the NYSOA K-D were significantly related to referral on the MCT screening (p=0.015) and stereoacuity worse than 100 sec arc (p=0.011). A trend toward significance was also found between DEM ratio and stereoacuity worse than 50 sec arc for the whole study population. However, in the children who passed the MCT, stereoacuity was not found to be significantly related to performance on NYSOA K-D or DEM. Thus, our findings indicate that visual difficulties may affect performance on the NYSOA K-D in this population.

EFFECTIVENESS OF VISION-SCREENING IN PRE-SCHOOL POPULATIONS WITH PREFERENTIAL-LOOKING CARDS USED FOR ASSESSMENT OF VISUAL ACUITY

Screening the vision of pre-school populations has been suggested as a way to assure early identification of vision problems as well as early intervention, thereby enabling normal development of the visual system and learning process. In a masked investigation, 119 preschool children enrolled in Project Headstart with a mean age of 3.51 years (range 3 to 5 years) had their vision screened using the Modified Clinical Technique (MCT). Monocular visual acuities in this population were determined using preferential-looking (PL) cards. Visual acuity assessment of young children in screening settings is at best a challenge; yet, all 119 children were able to complete monocular acuity assessments on each eye. Acuities for nonreferrals (individuals who passed the screening) were significantly better than for referrals (individuals who failed the screening) at the 0.0167 level using a two-tailed Fishers Exact Test with the Bonferroni Method for multiple comparisons. The effectivity of the screening technique as determined by phi-coefficient remained highest ( ?=+0.94) with the visual acuity referral criterion set at 6/12 (20/40) or less either eye and/or ≥ a 2-octave difference between the eyes. The resultant referral rate (17.6%) was higher than that predicted by extrapolation from the Orinda Study for this age group (12.3%) but expected because of the different socioeconomic group. PL cards enabled monocular visual acuity measurement on 100% of the children tested and measurably increased the effectiveness of the screening procedure.