Abstract
Purpose: :
To determine the number of false positive and false negative referrals made to a Hospital Eye Service from a Community Vision Screening service carried out by Health Visitors
Methods: :
A retrospective cross sectional study was carried out from January 2000- January 2002. Data was obtained from patient records of 126 children referred to the Princess Mary’s Hospital, MOD Cyprus, who were booked to see either the Ophthalmologist &/or the Orthoptist. Health visitors under went training in 2001 with the visiting orthoptist in order to carry out a pre-school visual screening service. Standards of testing and referral guidelines were issued for them to follow and further data was collected to determine the number and % of children referred that were true and false positives, source of referral, age of the child at referral, time lapse between referral and ophthalmic appointment, reason for referral, whether standards of testing were followed. A convenience sample was then taken from the children that had been previously tested by the health visitor during 2001 and re tested by the orthoptist to determine the number of false negative results. Factors that were also examined included, method of assessment, assessment outcome, general logistics for examination, equipment used and age of child at testing.
Results: :
Prior to the introduction of the new direct referral system to the ophthalmic service at The Princess Mary's Hospital, MOD, Cyprus 41% were false positive. This shows a high percentage of the total referrals made were unnecesssary.Following the training of health visitors in pre-school visual assessment, 54% of the direct referrals made by the health visitor proved to be false positive. In spite of this high false postive referral rate, 8 out of 34 children that had been classified as normal were found to be false negative on retest by the orthoptist. 4 children were found to have bilateral reduced vision, 2 had manifest squints, 1 child was found to have a significant esophoria and a further child failed the 20 dioptre prism test. All required referral to the ophthalmologist.
Conclusions: :
This study provides considerable support to the recommendations that orthoptists should carry out pre-school visual screening services.Despite training and a higher false positive referral rate, the number of false negatives is a concern and could be indicative of an even higher number prior to training.The effectiveness of orthoptists in the detection of visual defects remains to be the most acceptable method of assessment of pre-school children but further evaluation needs to carried out in order to provide a service when there is not a permanent orthoptist. Is some screening better than none?
Keywords: screening for ambylopia and strabismus • visual acuity • strabismus: diagnosis and detection