Evaluation of City University computer-based vision screener for use on children of school entry age
Kiki Soteri
This study is based on the hypothesis that the use of a computer based screening program, involving an acuity test and a stereopsis test, on children of school entry age (4-5 years old) for the detection of any visual deficit with amblyogenic properties, is at least as effective as carrying out an orthoptic or optometric screening. The benefit of the existence of such a computerized screening program would be its consistency and accessibility, in that it could be carried out in schools across the country, by a non-clinical individual, with simple formal training.
The aim is to assess approximately 300 children aged 4-5 years old. Parents will be asked to sign an informed consent and to answer a few simple questions to form the basis of a visual, ‘symptoms and history’ for their child. This data will be entered onto the computer program by a third party in order to ensure that the optometrist and orthoptist remain ‘blind’ to the symptoms and history of the child before the screenings.
a) Orthoptist screening using the City University Vision Screener
A local community orthoptist will carry out the vision screening using the City Vision Screener program that has been developed specifically for this purpose and includes the following simple assessments:
- simple, high contrast, large shapes.
- stereo-acuity and therefore binocularity.
- For acuity assessment the target would be Lear symbols which are 4 single letters on a screen with crowding bars forming a rectangular arrangement around all the letters.
b) Optometric assessment
An optometrist will carry out a series of screening tests to determine whether the child would require further assessment, by conventional methods, according to predetermined pass/fail criteria.
- Acuity assessment would be carried out with Lear symbols at 3 metres on a computer screen as per the assessment with the City University Vision Screener to ensure consistency and uniformity of comparison.
- Cover test
- Retinoscopy
- Randot stereo test
Comparison of the two assessments
The order in which the children are assessed will be randomised to ensure that there is no learning effect biased towards one type of assessment. Ideally 150 children will be assessed by the orthoptist first and 150 children would have an optometrist assessment first.
A binary pass/fail criterion system would be used with the aim of using the screening to search for likelihood of the child having a squint or amblyopia, which are both difficult to detect by conventional methods of monocular Snellen acuity screening alone.
Any child that fails either of the two screenings will have a report sent to their parents with an explanation. Depending on the nature of their failure, i.e. refractive or orthoptic they would either be referred to an orthoptic clinic or advised to see an optometrist.