Melbourne, July 22: Scientists have developed a new technique which can assess eye damage caused by diseases, like glaucoma, diabetic retinopathy and mascular degeneration, affecting millions of people globally, by examining the pupil.
An Australian team has developed the technique known as multifocal pupillography — the method involves monitoring minute responses of the eye’s pupils to light signals across different parts of the patient’s visual field.
According to the scientists, the technique relies on a feedback loop of nerve signals, which flow from each eye to the brain and back again to both pupils of the eyes by a secondary pathway.
“We’ve known for a century or so that the pupil reacts more to a stimulus on one side of the visual field than the other, though we did not know how or why until recently.
“In our research we have been trying to localise the responses of the pupil to particular places across the visual field and hence, the eye’s retina,” lead scientist Ted Maddess of ARC Vision Centre said.
By mapping places where the response of the retina is patchy and the pupil responds less strongly, the team is able to detect portions of the retina affected by disease and so improve the chances of early accurate diagnosis and treatment of a condition which, in many cases may result in vision loss.
The technique used is to video the pupils in infra-red light and record the tiny contractions they make in response to stimuli in different parts of the visual field, according to the scientists.
“This potentially offers a more accurate and earlier way to detect eye disease than techniques in use today, and a a way to monitor the success of treatment,” Dr. Maddess said.
By videoing the eyes, the team can also eliminate the problem of patient blinking or glancing away during diagnosis by editing these actions out, which improves accuracy.
“The pupil’s most important function is to guarantee the optical quality of what you see. Quite why it twitches in response to stimuli in different parts of the visual field we are unsure – but it provides a very useful form of feedback about what is happening in the eye itself and in the nervous system behind it,” he said.
Possible disease can be detected by measuring a single pupil, but measuring both gives even greater confidence in the results. This comes about because each pupil responds to stimuli presented to either eye: both the direct response from its own eye and the “consensual” response of the other eye.
“Mapping the consensual and direct responses at the same time gives us a clear impression of what is going on in the optical nervous system and brain. Differences in the ratio of responses can tell us about possible damage to a particular region of a single eye or particular parts of the brain,” Dr. Maddess said.
–Agencies