Q&A: i2Eye visual field analyser

i2Eye Diagnostics Limited plans to create a visual field analyser using the latest in Saccadic Vector Optokinetic Perimetry (SVOP) technology. The procedure has been developed to measure the visual fields of vulnerable adults, elderly people and young children who find it hard to remain stationary. We spoke to the inventor of the i2Eye visual field analyser, Professor Brian Fleck, to get the lowdown on the new device.

Why is it so hard to test visual fields in paediatric patients, vulnerable adult and elderly patients?Traditional visual field testing requires a high level of concentration and cooperation by the patient. Steady fixation on a central target, and responding by pressing a buzzer when a peripheral test stimulus is displayed can be extremely difficult, or impossible for young children, the very elderly and adults with learning difficulties. In addition, the need for steady positioning of the head is very difficult to achieve in young children

Could you please explain how the visual field analyser works?It works by simply asking the patient to look at a series of white dots or small pictures that are flashed up on a standard computer screen. There is no need for head restraint. An infrared eye tracker automatically calculates the position of the head and the direction of gaze of the eyes. The machine can therefore tell exactly where the eyes are looking, from moment to moment. The current machine updates 25 times every second. The patient looks at a target, and a second target is then flashed up in a new position. If that part of the visual field is working, the patient will look at the new point (fixation saccade) and the machine will record that this has been done accurately. Both accuracy and speed of the eye movement is measured. By repeated testing of new positions, a plot of the whole visual field is rapidly built up.

What is Saccadic Vector Optokinetic Perimetry (SVOP) technology and how will it benefit the visual field analyser?“Saccadic Vector” refers to the measurement of eye movement direction measured by the eye tracker during testing of a point in the visual field. “Optokinetic Perimetry” refers to the type of perimetry used – rather than maintaining constant viewing of a central target during testing, the eyes are allowed to jump around targets in a range of positions. This is a much more intuitive and physiological type of testing.

What will be the advantages of the visual field analyser?The test is extremely user friendly. No training is needed. The test is rapid – the test quickly moves from one point to the next without interruption, and without the need for any conscious action by the patient.

How will the launch of the instrument play an integral role in today's paediatric medical centres?There are likely to be a number of new applications of the technology, as no current technology exists that can rapidly and accurately plot the visual fields of young children. We anticipate the technology will be widely used in paediatric vision assessment. Ocular conditions include glaucoma, coloboma and retinal dystrophies. Neurological conditions include drug side effects (vigabatrin), neurosurgery for epilepsy, and a wide range of neurological diseases. In addition, young children with a range of developmental abnormalities may turn out to have visual field problems that have not previously been detected. It is likely that ophthalmologists and optometrists will incorporate the technology into their vision screening protocols.

How will the new visual field analyser affect the future of monitoring eye disease and brain tumours in children?The test has been developed in the Royal Hospital for Sick Children in Edinburgh. It has been used for some time to measure the visual fields of young children with brain tumours, before and after treatment. It is used to monitor the effect of surgery and of chemotherapy. It is also used to measure the visual fields of young children who have had strokes, who have visual field loss due to prematurity (periventricular leucomalacia), and who have had brain damage due to infection. We anticipate that the technology will revolutionise a number of areas of paediatric practice, and become widely used by paediatric ophthalmologists.

For more information on the i2Eye visual field analyser please contact:i2Eye Diagnostics LimitedEdinburgh BioQuarter47 Little France CrescentEdinburghEH16 4TJScotlandUnited KingdomOr email: Brian.Fleck@luht.scot.nhs.uk Or visit the website: www.i2eyediagnostics.com