Scottish Pre-School Vision Screening - First 3 Years of National Data

Prevalence of presenting bilateral visual impairment associated with refractive error - findings from the See4School, pre-school vision screening programme in NHS Scotland

BACKGROUND/OBJECTIVES

The See4School programme in Scotland is a pre-school vision screening initiative delivered by orthoptists on a national scale. The primary objective of any vision screening programme is to identify amblyopia, given the common understanding that this condition is unlikely to be detected either at home or through conventional healthcare channels. The target condition is not bilateral visual impairment, as it is believed that most children will be identified within the first year of life either through observations at home or as part of the diagnosis of another related disorder. This belief persists even though bilateral visual impairment is likely to have a more detrimental impact on a child's day-to-day life, including their education. If this hypothesis were accurate, the occurrence of bilateral visual impairment detected through the Scottish vision screening programme would be minimal as children already under the hospital eye service are not invited for testing. The overarching aim of this study was therefore to determine the prevalence of presenting bilateral visual impairment associated with refractive error detected via the Scottish preschool screening programme.

SUBJECTS/METHODS

Retrospective anonymised data from vision screening referrals in Scotland from 2013-2016 were collected. Children underwent an assessment using a crowded logMAR vision test and a small number of orthoptic tests.

RESULTS

During the 3-year period, out of 165,489 eligible children, 141,237 (85.35%) received the vision screening assessment. Among them, 27,010 (19.12%) failed at least one part of the screening and were subsequently referred into the diagnostic pathway, where they received a full sight test. The prevalence of bilateral visual impairment associated with refractive error and detected via the vision screening programme (≥ 0.3LogMAR) was reported to range between 1.47% (1.37-1.59) and 2.42% (2.29-2.57).

CONCLUSIONS

It is estimated that up to 2.42% (2.29-2.57) of children living Scotland have poorer than driving standard of vision (6/12) in their pre-school year, primarily due to undetected refractive error. Reduced vision has the potential to impact a child's their day-to-day life including their future educational, health and social outcomes.

A population-level post-screening treatment cost framework to help inform vision screening choices for children under the age of seven

PURPOSE/BACKGROUND

Visual acuity (VA) screening in children primarily detects low VA and amblyopia between 3 and 6 years of age. Photoscreening is a low-cost, lower-expertise alternative which can be carried out on younger children and looks instead for refractive amblyopia risk factors so that early glasses may prevent or mitigate the conditions. The long-term benefits and costs of providing many children with glasses in an attempt to avoid development of amblyopia for some of them needs clarification. This paper presents a framework for modeling potential post-referral costs of different screening models once referred children reach specialist services.

METHODS

The EUSCREEN Screening Cost-Effectiveness Model was used together with published literature to estimate referral rates and case mix of referrals from different screening modalities (photoscreening and VA screening at 2, 3-4 years and 4-5 years). UK 2019-20 published National Health Service (NHS) costings were used across all scenarios to model the comparative post-referral costs to the point of discharge from specialist services. Potential costs were compared between a) orthoptist, b) state funded ophthalmologist and c) private ophthalmologist care.

RESULTS

Earlier VA screening and photoscreening yield higher numbers of referrals because of lower sensitivity and specificity for disease, and a different case mix, compared to later VA screening. Photoscreening referrals are a mixture of reduced VA caused by amblyopia and refractive error, and children with amblyopia risk factors, most of which are treated with glasses. Costs relate mainly to the secondary care providers and the number of visits per child. Treatment by an ophthalmologist of a referral at 2 years of age can be more than x10 more expensive than an orthoptist service receiving referrals at 5 years, but outcomes can still be good from referrals aged 5.

CONCLUSIONS

All children should be screened for amblyopia and low vision before the age of 6. Very early detection of amblyopia refractive risk factors may prevent or mitigate amblyopia for some affected children, but population-level outcomes from a single high-quality VA screening at 4-5 years can also be very good. Total patient-journey costs incurred by earlier detection and treatment are much higher than if screening is carried out later because younger children need more professional input before discharge, so early screening is less cost-effective in the long term. Population coverage, local healthcare models, local case-mix, public health awareness, training, data monitoring and audit are critical factors to consider when planning, evaluating, or changing any screening programme.

Costs and effectiveness of two models of school-entry visual acuity screening in the UK

Cost effectiveness of different visual screening modalities cannot be calculated without long-term outcome data. This paper reports detailed outcomes from a gold-standard UK recommended orthoptist-delivered screening (ODS) at 4-5 years in school, compared to a neighboring school-nurse delivered screening (SNDS), both feeding into the same treatment pathway. The target condition was reduced visual acuity (VA) of worse than logMAR 0.2 in either eye.Available records from screening databases and hospital records were analyzed, comparing the two services wherever possible.More screening data was available from the ODS. ODS: 5706 screened, 3.5% referred. False positives 6.5%, PPV 91.4%, sensitivity 97.9%, and specificity 99.8% for reduced VA. Cost per child with reduced vision detected £195.22, and per amblyope detected £683.28. The mean treatment cost per child with reduced VA was £331.68 and for amblyopia treatment was £458.65.SNDS: 5630 screened and 3.8% referred (plus some referrals to local optometrists lost to follow up). False positives 34%, PPV 53.2%, sensitivity and specificity estimated as 89.3% and 98.67%. Costs to secondary services of false positives were seven times greater. The cost per child with confirmed reduced vision seen at the hospital was 46% more; and per amblyope detected was 39% more.Outcomes for treatment post referral in both groups were similar and excellent. 86% of genuine referrals improved to within normal limits with glasses alone. Of 221 genuine referrals with final outcome data, all now have better than 0.2logMAR acuity in the better eye and only two (0.9%) have residual amblyopia in one eye worse than 0.4logMAR.About 14-18% of children with reduced VA would have passed AAPOS photoscreening referral criteria.An orthoptist-delivered single VA screen at 4-5 years is highly cost effective with good outcomes. The main contributing factors to success appear to be training and experience in accurate VA testing, the opportunity to rescreen equivocal results, and monitoring, audit, and feedback of outcomes.