Photographic screening for strabismus among mentally retarded children

The prevalence of squint among mentally retarded children is much higher than in the general population. A photographic screening method based on the positioning of the 1st and 4th Purkinje image was applied to 80 mentally retarded children. The method was validated against orthoptic examination of the children. Totally 320 exposures were taken. Fourth Purkinje image was visible on 73% of these. Five children were not evaluable from the 4th Purkinje image. The photographic technique was simple and easy to handle, but comparison between the clinical and photographic diagnoses were inconsistent in 12 out of 80 cases, which made the method unreliable. In some cases the clinical assessments also varied from time to time. A combination of clinical orthoptic assessment and the photographic method is suggested.