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Alaska Blind Child Discovery

A cooperative, charitable research project to vision screen every preschool Alaskan

BJO PlusoptiX Orthoptic


Br J Ophthalmol. 2008 Nov 10. [Epub ahead of print] Plusoptix Vision ScreenerTM: The accuracy and repeatability of refractive measurements using a new autorefractor. Dahlmann-Noor AH, Comyn O, Kostakis V, Misra A, Gupta N, Heath J, Brown J, Iron A, McGill S, Vrotsou K, Vivian AJ. United Kingdom. BACKGROUND: The Plusoptix Vision Screener(TM) (PVS) is a new non-cycloplegic videoretinoscopy autorefractor. Refractive accuracy may affect its performance as a screening tool. AIMS: Study 1: To determine intra- and interobserver variability of PVS measurements. Study 2: To compare PVS measurements with gold standard manual cycloplegic retinoscopy (MCR). METHODS: Study 1: PVS refraction of 103 children with mean (SD) age 5.5 (0.6) years by two observers. Study 2: PVS and MCR refraction of 126 children with mean (SD) age 5.5 (1.5) years, including 43 children with manifest strabismus >/= 5PD, comparing mean spherical equivalent (MSE) and Jackson cross cylinders J0 and J45. RESULTS: Study 1: Repeatability coefficients (observer 1): MSE: 0.63D, J0: 0.24D, J45: 0.18 D; those of observer 2 were nearly identical. Mean difference (95% limits of agreement) between the two observers for MSE, J0 and J45 were, respectively, 0.03 (-0.62 to 0.68D), -0.008 (-0.25 to 0.23 D), 0.013 (-0.18 to 0.20) D. Study 2: MSE tended to be lower on PVS than MCR, with differences of up to 8.00 D. Less than 20% of values were within +/-0.50D of each other. Agreement was better for J0 and J45. Strabismus was associated with an odds ratio of 3.7 (95% CI: 1.3 to 10.5) of the PVS failing to obtain a reading. CONCLUSIONS: The PVS may underestimate children's refractive error.

Br J Ophthalmol. 2008 Nov 19. [Epub ahead of print]) Vision screening in children by Plusoptix Vision ScreenerTM compared with gold standard orthoptic assessment. Dahlmann-Noor AH, Vrotsou K, Kostakis V, Brown J, Heath J, Iron A, McGill S, Vivian AJ. United Kingdom. BACKGROUND/AIMS: To evaluate a new autorefractor, the Plusoptix Vision Screener(TM) (PVS), as a screening tool to detect risk factors for amblyopia by comparing it with gold standard orthoptic vision screening in children. METHODS: Community-based screening study including 288 children age 4-7 years who were screened with the PVS and by orthoptic assessment (distance acuity, cover test, extraocular movements, 20PD prism test, Lang stereotest). Follow-up comprehensive eye examination of screening-positive children included manual cycloplegic retinoscopy. RESULTS: Testability was high for both methods. Orthoptic screening identified 36 children with reduced vision and/or factors associated with amblyopia (referral rate 12.5%). The PVS identified 16 children with potential vision problems (referral rate 5.6%), indicating only moderate sensitivity (44%; 95% CI: 27.9 to 61.9%), but high specificity (100%; 95% CI: 98.5 to 100%) to detect factors associated with amblyopia. The PVS underestimated visually significant refractive errors. CONCLUSIONS: Use of the PVS as single screening test in young children may miss a significant number of children with amblyopia or amblyogenic risk factors.

ABCD Commentary: A careful set of criteria against which investigators and manufacturers can calibrate and validate vision screening technology has been published[1]. Shortly thereafter, one of the largest preschool vision screening studies, VIPS[2], developed a different set of validation criteria for their studies- complicating validation and efforts at uniform referral set-point definitions for the few objective screener manufacturers on whom the world depends. The community prevalence for preschool amblyopia is probably between 2% and 3% in many communities[3]. One would hope the referral rate times the predictive value of a valid screener would come fairly close to the prevalence of target disease, if the criteria by which validation is performed is reasonable. This recent pair of publications by Dahlmann-Noor, et al, in BJO provides an entirely new set of “gold standard criteria” of conditions which may, or may not be risk factors for amblyopia. Some very good data reside within these studies, however they should not be used to conclude that the associated objective screener, the PlusoptiX S04, “may miss a significant number of children with amblyopia or amblyogenic risk factors” and that it “may underestimate children's refractive error.”

These two studies applied two screening methods on a group of preschool children; Plusoptix and a battery of orthoptic screening techniques. The proportion of these children previously screened and treated was not excluded, nor clarified. Instead of performing confirmatory cycloplegic exams on all children, only those referred by the orthoptic screening had cycloplegic refractions, however the “gold standard” against which the plusoptix was compared was the orthoptic screening. The orthoptic screening referred 12.5% of children whereas the Plusoptix, using poorly-described referral cut-offs, had a much more reasonable 5.6% referral rate. This study had [has] the potential to take those children failing acuity screening, and selecting those with true amblyopia. From that number, the actual validity of these methods for detecting amblyopia might be determined.

ABCD continues to implore any childrens’ vision screening investigator to simply report their findings using the original 2003 AAPOS criteria along with any other new option. We suspect that the primary risk factors for the majority of cases or treatable pre-school amblyopia aside from manifest, mainly esotropic strabismus and cataract, are insufficiently accommodated hyperopia in one or both eyes, in one or more meridia. The validation criteria suggested by Dahlstrom-Noor, et al, appear to have added risk factors not necessarily leading to amblyopia, and therefore increasing false positive referrals.

1. Donahue S, Arnold R, Ruben JB. Preschool vision screening: What should we be detecting and how should we report it? Uniform guidelines for reporting results from studies of preschool vision screening. J AAPOS. 2003;7(5):314-316.

2. VIPS. Comparison of preschool vision screening tests as administered by licensed eye care professionals in the vision in preschoolers study. Ophthalmology. 2004;111(4):637-650.

3. MEPEDS. Prevalence of amblyopia and strabismus in African American and Hispanic children ages 6 to 72 months the multi-ethnic pediatric eye disease study. Ophthalmology. 2008;115(7):1229-1236 e1221.

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