Optic neuropathy

# Overview
Optic neuropathy refers to damage to the optic nerve due to any cause.

# Pathophysiology
The primary change occurring in optic neuropathy is nerve cell damage. The optic nerve comprises axons that emerge from the retina of the eye and carry visual information to the primary visual nuclei, most of which is relayed to the occipital cortex of the brain to be processed into vision. Neurons from retina leave the eye at the optic disc, and go to the visual cortex via the optic nervce, optic chiasm, optic tract and optic radiations. Damage and death of these neurons leads to characteristic features of optic neuropathy.

# Causes

## Common Causes
- Acute disseminated encephalomyelitis
- Anterior ischemic optic neuropathy
- Anterior ischemic optic neuropathy
- Benign multiple sclerosis
- Central retinal artery occlusion
- Central retinal vein occlusion
- Chloroptic
- Conjunctival orbital cysts
- Cranial blood suppy disorders
- Demyelinating disorders
- Diffuse sclerosis of schilder
- Encephalomyelitis
- Guillain-barre syndrome
- Intraocular hypertension
- Leber's optic neuropathy
- Leber's optic neuropathy
- Low tension migrane
- Low-tension glaucoma
- Meningioma
- Meningitis
- Migraine
- Multiple sclerosis
- Nerve damage
- Neurofibromatosis
- Neuromyelitis optica
- Ophthochlor
- Optic nerve glioma
- Optic nerve glioma
- Optic nerve tumors
- Optic nerve vascular lesions
- Orbital abscess
- Papillitis
- Postcataract
- Posterior uveitis
- Schilders disease
- Sudanophilic cerebral sclerosis
- Thyroid opthalmopathy
- Vascular occlusions of the optic nerve
- Viral encephalitis
- Wagener syndrome

## Causes by Organ System

## Causes in Alphabetical Order
- Acute disseminated encephalomyelitis
- Acute hypotension
- Ak-chlor
- Allergic vasculitis
- Anterior ischemic optic neuropathy
- Arteriosclerosis
- Bee stings
- Benign multiple sclerosis
- Borrelia burgdorferi
- Brucellosis
- Buerger disease
- Carotid occlusive disease
- Cat scratch fever
- Cavernous hemangiomas
- Central retinal artery occlusion
- Central retinal vein occlusion
- Cetina
- Chloramphenicol
- Chloroptic
- Cholesterol granuloma
- Churg-strauss syndrome
- Clorafen
- Conjunctival orbital cysts
- Cranial blood suppy disorders
- Cytomegalovirus
- Demyelinating disorders
- Dermoid cysts
- Diabetes mellitus
- Diffuse sclerosis of schilder
- Diochloram
- Drugs
- Encephalomyelitis
- Ethambutol
- Gca
- Giant cell arteritis
- Glucose-6-phosphate dehydrogenase deficiency
- Guillain-barre syndrome
- Head trauma
- Herpes zoster
- Hiv-1 disease
- Hypertension
- Hyperthyroidism
- Infectious mononucleosis
- Influenza
- Intraocular hypertension
- Isoniazid
- Lead poisoning
- Leber's optic neuropathy
- Low tension migrane
- Low-tension glaucoma
- Lyme disease
- Measles
- Meningioma
- Meningitis
- Metastases
- Methanol
- Methyl alcohol consumption
- Migraine
- Mucoceles
- Multiple sclerosis
- Mumps
- Nerve damage
- Neurofibromatosis
- Neuromyelitis optica
- Onchocerciasis
- Ophthochlor
- Oprelvekin
- Optic nerve glioma
- Optic nerve tumors
- Optic nerve vascular lesions
- Orbital abscess
- Orbital cellulitis
- Papillitis
- Paraxin
- Pentamycetin
- Pernicious anaemia
- Polyarteritis nodosa
- Polycythemia vera
- Postcataract
- Posterior uveitis
- Postimmunization
- Postviral vasculitis
- Primary malignancies
- Quemicetina
- Quinine
- Radiation necrosis
- River blindness
- Sarcoidosis
- Schilders disease
- Sickle cell disease
- Sinusitis
- Solid orbital tumors
- Sopamycetin
- Streptomycin
- Sudanophilic cerebral sclerosis
- Syphillis
- Systemic lupus erythematosus
- Takayasu disease
- Temporal arteritis
- Thallium
- Thyroid opthalmopathy
- Tobacco
- Treponema pallidum
- Tuberculosis
- Varicella
- Vascular occlusions of the optic nerve
- Vasculitis
- Viral encephalitis
- Wagener syndrome

# Signs and symptoms
Major symptoms are sudden or gradual loss of vision (partial or complete). There may or may not be pain on movement of the affected eye. Patients may lose some of their color vision in the affected eye, with colours appearing subtly washed out compared to the other eye.
On medical examination the head of the optic nerve can easily be visualised by an ophthalmoscope. A pale disc is characteristic of optic neuropathy. Primary and secondary optic neuropathy may have different morphological presentation. The nerve head in optic neuritis may be swollen in some patients.  In many cases, only one eye is affected and patients may not be aware of the loss of color vision until the doctor asks them to close or cover the healthy eye.

# Differential Diagnosis
- Acute angle closure glaucoma
- Anterior ischemic optic neuropathy
- Branch retinal artery occlusion
- Central retinal artery occlusion
- Compressive optic neuropathy
- Meningioma
- Multiple Sclerosis
- Optic Neuritis
- Sarcoidosis
- Sudden visual loss
- Syphillis
- Thyroid opthalmopathy