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Photoscreening for refractive errors in children and young adults with severe learning disabilities using the MTI
Purpose:
To test the potential ability of the MTI photoscreener to facilitate screening for significant refractive errors in children and young adults with severe learning disabilities.
Methods:
Thirty-eight patients with severe learning disabilities from a special school were examined with the photoscreener, and underwent cycloplegic refraction, an ophthalmological and an orthoptic examination. The age at examination, the cause of learning disability, the pupil size, the number of photographs required for accurate interpretation, the co-operation of the subject and the presence or absence of strabismus were recorded. An educational psychologist had performed a psychological assessment on all the children. The results of the cycloplegic retinoscopy were compared with the photorefraction results.
Results:
A photorefraction was possible in 37 patients and cycloplegic refraction in all the patients. The patients had severe learning difficulties with an intelligence quotient of less than 50. All the patients had behavioural problems, 9 patients had associated cerebral palsy, 8 had chronic epilepsy, 1 patient was brain damaged from a non-accidental injury and 1 from a road traffic accident. The mean age of the patients was 10.0 +/- 4.9 years (range 3-18 years), the average pupil diameter during photoscreening was 6.1 +/- 0.9 mm (range 4-8 mm) and the average number of photographs required for each subject was 2.1 +/- 0.9 (range 1-4). The photoscreener detected 10 patients with a manifest strabismus. There was one false positive and one false negative result giving a sensitivity of 92.8% and a specificity of 90%.
Conclusion:
The examination of children with severe learning disabilities for refractive errors can be extremely difficult. The MTI photoscreener is an effective means of screening such children and young adults for refractive errors and strabismus so that the children with these abnormalities may be targeted for a more detailed evaluation.