An evaluation of a school based vision screening programme.
The effectiveness of a vision screening programme in government schools in the Durban Functional Region under the jurisdiction of the House of Representatives was evaluated. For the purpose of the study a Comprehensive Vision Screening Programme (CVSP) was developed based on the Modified Clinical Technique (MCT) used in the Orinda Study. Of the represetative sample of 419 children assessed, the CVSP classified 85 (20.3%) as referrals. In comparison, the school health nurses referred 35 (9.6%) of the children for a complete ocular examination, 40 per cent of which were unwarranted. Analysis of the usable records showed that the school vision screening programme (SVSP) correctly categorised 307 (83.9%) of the children and incorrectly categorised 59 (16.1%) of them. The latter consisted of 3.8% over-referrals and 12.3% under-referrals. The school vision screening programme did not detect with a reasonable degree of accuracy those children with visual disorders. The effectiveness of the SVSP, as determined by the phi coefficient, was 0.35. Approximately two thirds of the children with visual disorders were not detected by the SVSP. One in every eight children classified as having no visual problem by the SVSP was an under-referral and two in every five children referred by the SVSP were over-referred. The high incorrect referral rates was attributed to the use of inappropriate screening techniques. The prevalence of visual disorders in the children was 20.3%; in boys 18.7% and 21.9% in girls. The relative risk of visual disorders in girls compared to boys was 1.2 (95% CI = 0.8 - 1.7). The prevalence of eye co-ordination disorders was 11.2%, refractive error problems 10.3%, visual acuity 4.5%, perceptual status (colour vision and stereopsis) 4.0% and organic disorders 1.2%. The binocular disorders were characterised as convergence insufficiencies and the disorders of accommodation were described as accommodative insufficiencies. Referable myopia (6.7%) was more prevalent than referable hyperopia (2.1%). Myopia was more prevalent in girls and hyperopia was more prevalent in boys. The clinical findings of the refractive error was compared to that measured by an autorefractor. The findings were remarkably similar and the study concluded that the difference between the two measures was not clinically significant. The study recommended that the MCT be used as the method of choice in school vision screening protocols.