The motor, sensory and visual components of the eye are managed by 5 of the 12 cranial nerves. Damage to any one of these nerves can cause symptoms to manifest according to the specific function of that particular nerve. The nerves that are related to the eye are cranial nerves II, III, IV V and VI, which are also respectively known as optic, oculomotor, trochlear, trigeminal and abducens nerves.
Visual Defects
The retina, located in the back of the eye converts light into electrical impulses. The optic nerve conducts these impulses from the retina to the brain. Yale University explains that when the optic nerve is damaged, total or partial blindness can result.
The oculomotor nerve conducts impulses to the pupil and the ciliary muscles of the eye. The pupil controls how much light is allowed into the eye, and the ciliary muscles control the shape of the eye, which affects the ability of the lens to focus. Damage to the oculomotor nerve could result in a failure of the pupil to respond to light changes, and an inability to properly focus the lens.
Cranial mononeuropathy III is a condition where in the oculomotor nerve is damaged, either by diabetes, or compression of the nerve. It sometimes manifests as double vision. Visual disturbances caused by cranial mononeuropathy can sometimes be permanent.
Muscle Weakness
Yale lists 3 nerves, the oculomotor, trochlear and abducens, which conduct nerve impulses to the muscles that allow the eye to visually track moving objects. Cranial mononeuropathy III can cause the eyes to be misaligned due to an imbalance in the nerves that control eye movement. Oculomotor nerve damage can also cause the eyelids to droop, because the oculomotor nerve sends motor impulses to the levator palpebrae superioris muscle of the upper eyelid.
Nystagmus
Nystagmus is a condition in which the eye moves involuntarily, most often from one side to the other. It is sometimes observed in cases of damage to the oculomotor nerve. Septo-optic dysplasia is a congenital disorder mostly affecting the optic nerve, but it can be accompanied by oculomotor disturbances as well, notes Dr. Andrea Langmann of the Department of Ophthalmology at the Medical University of Graz, Austria.
Pain
Damage to the nerves that affect the eye can also cause pain, either within the eye itself, or manifesting as a headache, according to the National Institutes of Health .
