OCT is a bit like an ultrasound scan, using light instead of sound waves. The retina is at the back of the eye, like a film in a camera. At the centre of the retina is the macula, which is responsible for clear central vision. The macula consists of layers. Very roughly speaking, these are like the layers in a cheesecake where you have a biscuit layer, a cheese layer, with a layer of icing on top. 

“The scan shows changes in the ‘biscuit’ layer with macular degeneration and in the ‘cheese’ layer with diabetes and a macular hole. An epiretinal membrane can be seen as ‘icing’ in the image.

Hirut von Lany Consultant Ophthalmologist, Royal Devon and Exeter Hospital