Naevi
Naevi occur in the choroid and are found in up to-6% of the general population. They are usually flat or minimally elevated measuring 1.5 -5.0mm in diameter. They often develop yellow drusen on their surface. Pigment clumping may also be seen.
Malignant Melanoma
Choroidal melanoma affects 1 in 6 million people in the USA. 30-50% of patients will die within 10 years of diagnosis. It usually presents in mid-adult life. They are often asymptomatic. Small tumours may produce overlying orange pigment and subretinal fluid. Larger tumours present as pigmented masses. If they rupture the basement membrane of the retinal pigment epithelium they may assume a “mushroom” shape.
Myelinated Nerve Fibres
Myelination of the visual sensory pathway normally occurs after the entire pathway has developed. It starts at 5 months gestation in the lateral geniculate bodies and gradually extends along the optic tracts, chiasm and optic nerves to reach the lamina cribrosa at birth (the opening in the sclera that allows the nerve fibres of the retina to leave the eye). Myelination of the retinal fibres affects up to 0.6% of the population. They do not affect visual acuity; however, they may cause a localised visual field defect.
Tigroid Fundus
If the retinal pigment epithelium is not well pigmented, as in people with blond or red hair, then the underlying choroidal vessels may become strikingly visible. This is sometimes termed a tigroid fundus.
Glaucoma
Primary open angle glaucoma is a chronic, progressive optic nerve disorder (neuropathy) of unknown aetiology that is associated with a characteristic form of optic nerve fibre loss.
This optic neuropathy is associated with cupping and atrophy of the optic disc in the presence of raised intra-ocular pressure but normal anterior chamber drainage. It is painless and because it affects peripheral vision first is often asymptomatic.