Some ophthalmologists specialise in the treatment and management of posterior segment disorders and diseases.
The posterior segment is the back two-thirds of the eye that includes the anterior hyaloid membrane and all structures behind it: the vitreous humor, retina, choroid, and optic nerve. On the anterior side of the lens is the aqueous humour which is bounded on all sides by the lens, ciliary body, suspensory ligaments, and by the cornea. It lets light through without refraction, helps maintain the shape of the eye and suspends the delicate lens. In some animals, the retina contains a reflective layer (the tapetum lucidum) which increases the amount of light each photosensitive cell perceives, allowing the animal to see better under low light conditions.