[Detection of amlyogenic risk factors with the vision screener S 04]

The Vision Screener® (Plusoptix) was developed for the recognition of amblyogenic refractive errors without cycloplegia. The aim of this study was to evaluate the sensitivity and specitifity for the detection of amblygenic refractive errors in preschool children. Furthermore it was investigated whether small angle strabismus as another cause for amblyopia could be detected by manual evaluation of corneal reflex images on printouts.

83 children aged between 0.5 and 6 years without strabismus had undergone 3 measurements without cycloplegia with the Vision Screener before cyclplegic retinoscopy was performed. In a second group of 72 children with orthotropia or a manifest strabismus < 10° the position of the eyes without correction was evaluated in a complete orthoptic and ophthalmological examination. Three measurements with the Vision Screener were performed in non-cycloplegic status. The centre of the "cloud of viewing directions" was determined on print-outs and the distance to the points of origin (middle of pupil) measured for each eye. The sum of distances of right and left eyes was taken for determination of total deviation and the assymetry was calculated by the difference of distances of the right and left eyes.

There was a total sensitivity of 75% (specifity 91%) for amblyogenic refractive error (prevalence: astigmatism 22%, hyperopia 6%, anisometropia 6%). A change of threshold criteria increased the total sensitivity to 86% and 93%, whereas specifity was lowered to 80% and 76%, respectively. Eight children showed a manifest strabismus. In 75% of these cases the determined deviation of corneal reflex images in the horizontal direction was outside of the normal range; analysis of asymmetry showed an abnormal result in 37.5% of the cases.

The examination using the Vision Screener may detect refractive errors and partially small angle strabismus as amblyogenic risk factors; however, additional tests should be added for screening examinations. An ophthalmological examination including cycloplegic retinoscopy cannot be replaced. Despite acceptable sensitivity and specifity the major portion of positively screened children will be without pathological findings at cycloplegic controls, because the amount of "false-positive" results exceeds the amount of "true-positive" results based on a prevalence of 5% for amblyopia.