A Devon scientist is developing a test to diagnose and monitor brain disorders in children using eye movements.
Electrodes monitor "flicks" of the eye affected by medical conditions
Professor Chris Harris, from the University of Plymouth, has been seeing youngsters with some of the country's rarest diseases.
Damage in various parts of the brain often leads to eye movement disorders.
He hopes to develop a standard test so that babies and the most seriously ill children - who are often the most uncooperative - can be diagnosed.
The earlier some conditions are treated, especially those with diseases that are only going to get worse, the better the possible outcome for the children involved.
A test would also mean new types of medication can be monitored for clinical trials.
Prof Harris' research has been funded by a charity called Cerebra, for brain-injured children.
He is particularly interested in diagnosing so-called neurometabolic diseases, which are very difficult to diagnose.
They are a group of 1,500 often terminal diseases that can be caused by chemical imbalances in the body which ultimately cause brain cells to die.
He uses a computer-controlled chair with electrodes attached to the patient's head to see how "flicks" of the eye are affected by various medical conditions.
He said: "The way we control our eye movements depends on brain function.
"Damage in various parts of the brain often leads to eye movement disorders. So by looking at abnormal eye movements we can pick up on problems before they become too severe.
"What we are trying to achieve here is a new way of measuring eye movements in particularly young children in order to diagnose them, as well to monitor how they respond to new treatments."
Prof Chris Harris is interested in neurometabolic diseases
One of those who has helped with the study to develop the test is Rachel Lewis, who has a rare neurometabolic condition called Niemann Pick Disease, type C. She is one of only a handful of children in the UK with it.
She was diagnosed as a baby, but has slowly lost brain function since she was a normal and playful four-year-old. Now she is barely able to walk, unable to reason, and is slowly deteriorating every year.
Her father Jon came from Ludlow in Shropshire to see Prof Harris.
He said: "If Rachel is able to progress the knowledge of the disease then some benefit can come out of the difficulties that she faces day after day."