The technique uses fluorescent markers which attach to dying cells which can be seen in the retina and give an early indication of brain cell death.
This new technique enables scientists to track the progress of brain disease by looking at dying cells in the retina.
The cells show up as green dots because they absorb the fluorescent dye.
The research has so far been carried out on mice, but the team is optimistic that the technique can be translated to humans.
Professor Francesca Coredeiro, lead author from University College London Institute of Ophthalmology said: "Few people realise that the retina is a direct, albeit thin, extension of the brain."