retinal (adj.)

late 14c., "membrane enclosing the eyeball;" c. 1400, "innermost coating of the back of the eyeball;" from Medieval Latin retina "the retina," probably from Vulgar Latin (tunica) *retina, literally "net-like tunic," on resemblance to the network of blood vessels at the back of the eye, and ultimately from Latin rete "net" (see rete).

The Vulgar Latin phrase might be Gerard of Cremona's 12c. translation of Arabic (tabaqa) shabakiyyah "netlike (layer)," itself probably a translation of Greek amphiblēstroeidēs (khiton).

suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).