Viewing the Inaccessible

Optical coherence tomography (OCT) has revolutionized imaging of the retina. The technique not only enables an ophthalmologist to view all the layers of the retina in high resolution, but it is also non-invasive. And by mapping structural changes in the retina, many retinal diseases can be diagnosed and tracked. But OCT of the retina also offers a door – or window – into a world beyond the eye; as an extension of the central nervous system, it offers insights into neurological health of both neural and vascular tissues.

To prove the point, ophthalmologists from the University Hospital Bonn in Germany have devised a way to use OCT to assess changes in the retina that can help detect and diagnose cerebral small vessel disease (CSVD) earlier than previously possible (1).

The main structural changes in CSVD patients appear to be a significant decrease in the ganglion cell layer and changes in retinal nerve fiber layer thickness, but other retinal areas also had disease related changes. These changes were independent of the participant’s age, and when grouped together can form a profile specific to CSVD or other neurodegenerative diseases. Notably, the team also correlated changes in retinal layers with MRI-measured white matter lesions that are indicative of the cerebral damage caused in CSVD.

The risk of CSVD in the elderly population is substantial – in a study of over 1000 people aged 60–90, only five percent were completely free of white matter lesions (2). Given the strong link between vascular problems and neurodegenerative diseases, coupled with the increasing global rise of vascular conditions, being able to track cerebral vascular changes more easily is becoming increasingly important. Shifting diagnosis and tracking of CSVD from the MRI machine to OCT examination would bring many advantages to patients and healthcare systems.

But there’s also a bigger picture: clinical trials of therapeutics for neurodegenerative diseases have long been blighted by patient pools that have been diagnosed far too late – when drugs have less chance of making a significant difference to patient pathology and lifestyle. With further work – and potentially the introduction of AI, could OCT unlock a new patient population for drug trials?