Optic nerve is the nerve that carries visual messages from the back of the eye (retina) to the brain where visual information is processed. The front part of the optic nerve (optic disc) is visible on examination of the retina. This makes optic nerve a window to the inside of the brain. It is the only nerve in the body that can be seen without making a cut in the body.
Variety of diseases can affect the optic nerve - ischemic (affecting the blood supply), inflammatory, increased intracranial pressure (papilledema), demyelination, and infective. It can range from manifestations of major life threatening conditions like tumours or infections of the brain to mild non vision threatening conditions of the optic nerve. Glaucoma is a condition that causes optic nerve damage due to increased intraocular pressure. It can progress from being asymptomatic to loss of peripheral vision, leading to tunnel vision and eventually blindness. Routine ophthalmological evaluation can detect glaucoma.
Papilledema can be seen as swelling of the optic discs on examination of the retina. Thorough neurological and systemic examination is required in such cases.
Evaluation of optic nerve includes assessment of vision, eye pressures, visual fields, pupils and fundus examination. Depending on the clinical judgement, further investigations are required which include optical coherence tomography, visual evoked potential and fundus fluorescein angiogram. Optic nerve disorders like papilledema and optic neuritis require MRI and cerebrospinal fluid studies.
Dr. Rehna Rasheed
MS. DO. FRCO (London)
Amrita Institute of Medical Sciences & Research Centre, Kochi, Kerala.