Australian researchers have helped to identify a gene responsible for strabismus better known as turned eye – a vision problem which also has a major social impact for the sufferer.
Strabismus, the condition that causes “crossed” or a “lazy” eye, affects one in 50 Australians and previously for the majority of cases there was no known risk factor and its cause remained a mystery.
The condition was also known to occur at higher rates in some families, according to Dr. John Ruddle from the University of Melbourne’s Centre for Eye Research Australia (CERA).
The discovery of the gene could now lead to new treatments and methods of preventing the condition. The study also reveals a link between some complex forms of the condition and broader neurological disorders.
A 15-year study into one such Victorian family has revealed a faulty gene (TUBB3) at its root.
“There have been a couple of other small families around the world with genes causing strabismus, but this is the first from an Australian family,” Dr. Ruddle said.
“We looked at about 50 members of the family; about 25 of them were affected in different ways. Some of them had both eyes turning, for others it was one side.”
Dr. Ruddle said these families had “complex” strabismus, which was characterised by less uniform eye movements and where a hereditary link was particularly clear.
He said the hope is that finding the genes responsible for these cases would shed light on “simple” strabismus, which is much more common and even more of a mystery.
“We discovered that the TUBB3 gene drives the development of the nerves that control the eye muscles. Strabismus occurs when mutations in the TUBB3 gene cause the abnormal development of these nerves,” Dr. Ruddle said.
“We also found that the mutations can interfere with the brain’s ability to wire up properly which, in severe cases, can lead to intellectual, behavioral and social disabilities.”
Dr. Ruddle said the TUBB3 gene discovery debunked the common misconception that strabismus is a muscle disorder and not a nerve disorder. This discovery is exciting news for sufferers who often experience low vision and social difficulties.
“Childhood strabismus sufferers frequently develop amblyopia, or ‘lazy eye’. This occurs when the brain relies on the good eye and ignores the turned eye. Over their lifetime this leads to a greater risk of blindness as accidents or other disease can strike their one remaining good eye,” Dr. Ruddle said.
The study, recently published in the prestigious journal, Cell, is a joint undertaking by researchers at CERA and Harvard University’s Centre for Strabismus Research at the Boston Children’s Hospital.
To conduct the study, researchers recruited more than 100 families with a complex form of strabismus. Researchers performed brain scans and collected DNA samples from each family member to identify the genes and other features associated with the condition.
Four-year-old Jack Jasper was diagnosed with the common form of strabismus when he was just 18-months-old and according to Jack’s mum Kim, the condition appeared to develop overnight.
An ophthalmologist diagnosed Jack with the common form of strabismus in his right eye.
“Jack was fortunate in that his vision remained intact, so our main concern was the cosmetic effect and how it would affect his self esteem,” Kim said.
According to Dr. Jon Ruddle, Jack is fortunate that he only required one operation and the condition has no had no long term impact on his vision.
Kim said she is encouraged by the gene discovery and hopes the finding will lead to better treatments and preventative measurements.
Read more on strabismus in this issue of mivision. Ophthalmologist Dr. Frank Martin has written a very informative piece on Adult Strabismus Surgery commencing on page 36.