The high axial resolution of OCT allows discrimination of the distinct retinal layers that are affected differentially in different diseases. More direct visualisation of the photoreceptor layer is afforded by use of an Adaptive Optics Scanning Light Ophthalmoscope (AOSLO), which provides excellent lateral resolution and allows direct visualisation of the cone and rod photoreceptor mosaics in vivo by correcting for ocular aberrations and resulting in a lateral comparable with histopathological sections.