Image processing of retinal images. Identification of veins (angiography) or various other features. The two most prominent features are the optic disc (from where the veins stem) and the macula where the rods and cones lie.
More example photos can be found below. This is a good resource: http://retinagallery.com/
On retinal imaging: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3131209/
Crash course on retina diagnosis from imaging: https://darrellbaskin.wordpress.com/