Moorfields Eye Hospital Abu Dhabi has conducted a Vision Screening Initiative at two schools in Abu Dhabi that complemented and extended the testing work of the schools’ own medical teams.
We examined 140 pupils in years one and two at these schools and discovered visual problems in 17 of them. Of these, 15 were previously undiagnosed. These findings are in line with what has been found in many parts of the world.
Our experience is that the screening initiative has a minimal disruption to the business of the school. A team from Moorfields visits the school for one or two days to conduct the tests detailed in the appendix. Parents are invited to allow their children to be screened and pay AED100. A report is sent to the parents after the check (and a copy is retained by the school nurse).
Retinal (red) reflex
This is the red-orange spot (“red eye”) in the pupil made by the light that reflects out of the eye, it is more commonly noticed when one has taken a photograph using a camera with a built-in flash. Using a special instrument we can use this reflex to detect opacities in the visual axis, abnormalities of the back of the eye, and problems that may cause a lazy eye. The red reflex seen in each eye should be bright reddish-yellow (light grey in darkly pigmented, brown eyes) and identical in both eyes. Any asymmetry in colour, brightness, or size is indicative of a problem.
Vision screening is able to pick up many, but not all, eye problems – it is not a substitute for a full eye examination. Where problems are found we advise parents on the nature of the problem and will recommend a comprehensive examination in an eye centre.
Our eyes see two slightly different views of the world and because our visual system can fuse these two images into one this enables us to see in stereoscopic depth or 3-D. Having good stereopsis is dependent upon having two good eyes that work together, for this reason stereopsis testing provides an excellent way of detecting squints (strabismus), lazy eyes (amblyopia) and a variety of other conditions. Children are asked to identify the shapes, animals, or letters present on a random dot stereogram. The images will only be visible to those with normal stereopsis.
Eye Muscle Balance and Movement
Squint (strabismus) is a condition that occurs when one or both eyes are misaligned and the eyes do not point in the same direction. The eyes may turn inwards (crossed eyes), outwards (wall eyed), or up and down. This may be caused by a muscle imbalance or a need for glasses. More sensitive than the stereograms, cover testing or covering each eye and observing for any abnormal movement will reveal any manifest or latent tendency for the eyes to squint.
Convergence insufficiency, or CI, is an eye muscle disorder characterised by an inability to maintain convergence of the eyes while performing near related tasks such as reading. CI is the leading cause of eye-strain, blurry vision, and double vision in children. Treatment typically involves eye exercises that can be performed at home or as in-office therapy sessions.
Distance Visual Acuity
This is measured using an age-specific linear vision chart at a distance of 6 meters. Testing begins with large letters that should be easily visible to children; the size is then decreased at standard increments.