Optic neuritis is common in MS, where people develop lesions on their optic nerves causing symptoms such as blurred or double vision. However, recent studies have shown that even people who do not have optic neuritis may still have thinning of the layer of retinal nerve cells, which could reflect damage deeper in the brain that is being passed along the visual pathway. In order to test this possibility, researchers are investigating whether lesions and neurodegeneration in the brain may be monitored through changes to the eyes.
Associate Professor Alexander Klistorner from the University of Sydney, has been working in this area for some time. This year he received an MS Research Australia Ian Ballard Travel Award to assist his international collaborations. He and his collaborators have recently published their latest findings in the prestigious journal Neurology.
They have shown that there is a relationship between retinal nerve layer thickness, and lesions in the areas of the brain involved in processing visual information (the visual pathway) in people with MS who do not have optic neuritis.
The work was done in collaboration with researchers at Macquarie University, four Australian hospitals, and the Hadassah Hebrew University Medical Centre in Israel.
The team used a number of techniques including magnetic resonance imaging to measure the integrity of nerve bundles in the brain (tracts), and optical coherence tomography (an echo technique similar to ultrasound) to measure retinal thickness in the eye.
Associate Professor Klistorner looked at the eyes of 53 people with relapsing-remitting MS who had not experienced optic neuritis, compared to 50 matched healthy control individuals. There are two key nerve bundles that carry information from the eyes to the brain, these are called the optic tract and the optic radiation.
The researchers found that the majority of MS participants had lesions within the optic radiation. They also found that there was a significant correlation with individuals showing a thinner retina also having more inflammatory lesions in the optic radiation. Retinal thinning was also associated with reduced visual acuity, especially when people were looking at low-contrast images. The findings build on Associate Professor Klistorner’s earlier MS Research Australia funded work, in which he showed that myelin loss in the optic nerve (detected by measuring the speed of electrical signals from the eye) also appeared to reflect damage deeper in the optic pathways in the brain.
This study has helped increase our understanding of how inflammatory demyelination, and the subsequent interrupted nerve transmission, affects the nerve cells that connect into a lesioned area, and helps to confirm the importance of the visual system as a potential marker for myelin and nerve damage occurring deeper in the brain in MS. Further work is underway to track these changes over time as a means of monitoring disease progression.