The blood supply of the retina comes from two sources. The outer layers (photoreceptors) are avascular and depend on which nutritional source?

• A Choroidal circulation (via choriocapillaris, supplied by short posterior ciliary arteries) — diffusion through Bruch's membrane and RPE ✓
• B Central retinal artery — supplies all retinal layers uniformly
• C Vitreous humour — diffusion from the vitreous to outer retina
• D Aqueous humour — diffusion from the anterior chamber through the retina

Explanation

The retina has a dual blood supply: (1) inner 2/3 — supplied by the central retinal artery (branch of ophthalmic artery) via the retinal vessels, forming capillary beds visible on fundoscopy; (2) outer 1/3 (photoreceptors, outer nuclear layer, outer plexiform layer) — avascular, deriving nutrition by diffusion from the choriocapillaris of the choroid through Bruch's membrane (inner choroidal layer) and the retinal pigment epithelium (RPE). This anatomy explains: (a) why central retinal artery occlusion spares the fovea if a cilioretinal artery is present; (b) why RPE dysfunction (as in age-related macular degeneration) impairs photoreceptor nutrition; (c) why subretinal fluid in retinal detachment deprives photoreceptors of choroidal oxygen.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.