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A new objective digital computerized vision screening system.

PURPOSE: Fewer than 40% of children in the crucial younger-than-4 age group are evaluated for visual problems by pediatricians. This is due to impracticality from either a clinical or practice efficiency standpoint. Current photoscreening methods require trained readers and suffer from significant subjectivity and interobserver variability. We report a cross-sectional, double-masked study using new digital imaging with objective, automated, computerized image analysis. METHODS: Two-hundred six children aged 9 months to 16 years were prospectively studied in a University-based pediatric ophthalmology practice. Images were taken by volunteers with a modified digital camera which, when downloaded, were analyzed within 35 seconds by new image analysis software. The analysis was compared to a masked review of a complete pediatric ophthalmic exam. RESULTS: Overall agreement between physician and the objective computerized analysis was 86.9%. Positive predictive value was 91%, sensitivity was 89%, and specificity was 83%. CONCLUSIONS: This automated digital imaging screening system eliminates human bias and provides accurate and immediate results. The system requires no special expertise.

Adolescent↗

Preschool vision screening in Cornwall: performance indicators of community orthoptists.

The performance of community orthoptists was retrospectively assessed in a primary preschool screening programme that has been established in Cornwall since 1982. The outcome of screening was compared between random samples of two birth year cohorts corresponding to the second and fourth years of existence of the screening programme (1980, n = 298 and 1982, n = 300). The mean age at screening was significantly later for the second cohort (4.3 years compared with 4.4 years) but otherwise performance indicators improved in the second cohort. Community orthoptists achieved a sensitivity of about 90% and specificity of 99% during the study. It is unlikely that the more commonly used two tier system of health visitors referring to a community orthoptist could achieve this degree of accuracy.

Child, Preschool↗

A cost-benefit analysis of vision screening methods for preschoolers and school-age children.

INTRODUCTION: The purpose of this study was to determine costs and benefits of visual acuity screening (VAS) or photoscreening (PS) in children. METHODS: A societal-perspective, decision-analytic model compared VAS and PS conducted in three age groups: children 6 to 18 months, 3 to 4 years, and 7 to 8 years old. Literature estimates of sensitivity, specificity, and prevalence were used. Cost estimates and referral rates for surgical treatment were derived from a managed care database and the United States Social Security Administration. RESULTS: All the benefit-to-cost ratios exceeded 1.0, meaning that all screening programs studied had benefits that exceeded the cost of screening. The total net benefit was highest for PS in children of 3 to 4 years of age (19,412 US dollars) and the least for VAS in children 7 to 8 years of age (15,179 US dollars). The benefit-to-cost ratio was highest for the VAS in children 3 to 4 years of age (162 US dollars) and least for PS in infants 6 to 18 month old (140 US dollars). Sensitivity of the PS instrument and VAS charts were the most influential variables in determining the most cost-beneficial program. CONCLUSIONS: Based on the best available data, the net benefit of PS in 3 to 4 year old preschool children is greater than VAS in children 7 to 8 years of age, PS in toddlers, and VAS in children 3 to 4 years of age.

Age Factors↗

Is vision screening in 3-year-old children feasible? Comparison between the Lea Symbol chart and the HVOT (LM) chart.

PURPOSE: The aim of this prospective study was to compare visual screening at the age of 3 years with screening at 4 years using two different charts. METHODS: A total of 478 3-year-old children were tested at four child health care centres (CHCCs). Of these children, 440 were tested again at the age of 4 years. A third group, a control group, consisting of 229 children, was examined only at the age of 4 years. All children were tested with both the HVOT chart and the Lea Symbol chart. RESULTS: Testability rates for 3-year-olds were almost the same with the Lea Symbol chart and the HVOT chart (82.8% and 84.8%, respectively). The corresponding rates for the same children tested at 4 years of age were 96.5% and 97.0%, and for the 4-year-olds not previously tested 92.9% and 92.8%. The mean testing time was somewhat shorter for the Lea Symbol chart in all three groups, but the difference was not statistically significant. The difference in the assessment of visual acuity between the two charts was small and less than 1/10th of a line. The positive predictive value was lower at 3 years (58%) than has previously been found at 4 years (74.6%). CONCLUSION: Three-year-old children co-operate well in visual acuity testing. However, the examination time is a little longer and the testability rate is about 10% lower than at 4 years. Both 3-year-old and 4-year-old children can be tested equally well with the HVOT and the Lea Symbol charts.

Amblyopia↗

Simple pointspread retinoscope suitable for vision screening.

A simple pointspread retinoscope and method of retinoscopy are described which use optical principles similar to those of photoretinoscopy or static photographic skiascopy. In this instrument the degree of defocus of an eye is estimated from the disappearance of the bright fundal reflex or "crescent" in the eye of the subject when the distance between the light source and the eye of the observer is increased systematically. The instrument is particularly suitable for large scale screening efforts because it is easy to use and can be constructed from inexpensive materials. The pointspread retinoscope was calibrated against an artificial eye of known defocus. Additionally, results from pointspread retinoscopy were compared against meridional photorefractive data from a sample of infants and young children, and a significant correlation was found to exist between measurements made by the two methods.

Child↗

The effectiveness of the random dot E stereotest as a preschool vision screening instrument.

Sixty nursery-school children (ages 39--76 months) were screened with a modified-clinical method (visual acuity, retinoscopy, cover test, NPC) and with a relatively new vectographic test for stereopsis--the Random Dot E. Screening outcomes indicate that the RDE was as effective in identifying children for referral as was the modified clinical battery. Implications are discussed.

Amblyopia↗

Vision screening of 4-year-old children in Singapore.

AIM OF THE STUDY: To evaluate the feasibility of an improved visual acuity screening program for Singapore 4-year-old preschool children and to draw up an appropriate referral criteria as well as evaluating the rates and outcomes of these referrals. METHOD: A total of 450 children aged 4 to 4 1/2 years, who attended 3 polyclinics of the Family Health Service (FHS) for their 4-year-old Developmental Health Screening during the study period from 1/4/1997 to 30/6/1997 were recruited for the study. Children who were tested with Snellen (or Sloan) visual acuity chart resulting in visual acuity of 6/9 or worse, or failed to pass the 3 mm medium plate at 30 cm distance (300 seconds of arc) in the Frisby Stereotest, or were found to have strabismus, or were untestable in either visual acuity test or stereotest were offered referral to ophthalmologists in the hospitals for specialist assessment. RESULT: 82.7% of the 450 children were successfully screened with Snellen (or Sloan) chart while 91.6% were successfully screened with Frisby Stereotest. In all, 180 children were evaluated by ophthalmologists. Majority of the children were referred because of their abnormal visual acuity test while only 2 children were referred for failing stereotest alone. Among the 180 children referred, 63 (35.0%) were found to have refractive errors for which spectacles were prescribed. Eight children had amblyopia and 2 children had strabismus which were not detected at the polyclinic screening. The untestable children evaluated had significantly higher abnormality rate (37.5%) than that of children who had 6/9 vision (8.8%) therefore they should be offered referral for further evaluation. There was high "refused referral" rate of 39.0%. Parents of children who were untestable or had 6/9 vision were found to be more likely to refuse offer of referral. If these two groups of children were excluded, the "refused referral" rate dropped to 13.3%. When the referral criteria for visual acuity was reset at 6/12 instead of 6/9, the referral rate dropped from 39.6% to a more manageable 26.7% and the positive predictive value improved from 35.4% to 48.3% and none of the children with amblyopia were missed being screened-out. CONCLUSION: The study confirmed the feasibility of doing visual acuity screening at 4 to 41/2 year-old. The referral criteria for abnormal visual acuity should be set at 6/12. The efficacy of adding Frisby stereotest needs further evaluation.

Age Factors↗

Peripheral vision screening for driving in retinitis pigmentosa patients.

The authors evaluated the test protocols used most frequently to screen the peripheral visual field of driving applicants to determine whether they are suitable for detecting peripheral field loss in patients with retinitis pigmentosa (RP). The peripheral vision tests available on the Keystone View Tester and the Titmus Vision Tester were administered to 23 subjects with RP, 3 subjects with Type 2 Usher's syndrome, and 1 subject who was a partially affected carrier of X-linked recessive RP. The subjects had varying degrees and types of visual field loss. Tests were administered using the standard protocol of the State of Illinois, which is a standard procedure used by state licensing bureaus nationwide. Results demonstrate that the screening protocols use stimulus conditions that are primarily sensitive only to appreciable field losses and examine locations that typically lie within an RP patient's remaining visual field rather than at locations that characteristically are scotomatous. The authors suggest that the current test protocols could determine peripheral field impairment more accurately by assessing additional locations in the visual field, and by introducing a background field and/or by reducing the luminance of the test targets.

Adult↗