Optic neuritis may be asymptomatic or may present with the following symptoms [6]:

• Visual loss. Sudden, progressive and profound visual loss. 
• Pain above or behind the eye that increases on ocular movements, especially when looking up and down. The pain may last for several weeks.
• Visual difficulty is exacerbated in bright light.
• Impairment of color vision leading to patients complain of reduced vividness of colors or things looking “washed out”.
• Movement phosphenes and sound induced phosphenes. Patient complains of flashes or flickering of light.
• Uhthoff’s phenomenon: Episodic transient aggravation of visual loss on exertion and on exposure to heat, which recovers on resting or moving away from the heat. 
• Pulfrich’s phenomenon: Depth perception may be impaired, especially for moving objects.
• Difficulty in vison in low light conditions.
• Some patients may have normal central vision with complaints of loss of peripheral vision to one side in the superior or inferior fields.

• Inflammation

  Optic nerve inflammation, demyelination, and axonal loss are prominent features of optic neuritis, an inflammatory optic neuropathy often associated with the central nervous system demyelinating disease multiple sclerosis. [ncbi.nlm.nih.gov]

  Optic neuritis: the inflammation, degeneration, or demyelination of the optic nerve. Why: optic neuritis may be present in patients with sarcoidosis or reiter's syndrome (rarely). [icd9data.com]

  Treatment for the optic nerve inflammation will depend on the underlying cause. If the inflammation is related to infection, diabetes or uveitis, then these underlying conditions will need to be treated accordingly. [vision-and-eye-health.com]

  Optic neuritis describes inflammation of the optic nerves, which carry signals from the eyes to the brain. [barrowneuro.org]

  Inflammation of the optic nerve. optic neuritis Etymology: Gk, optikos, sight, neuron, nerve, itis, inflammation inflammation, degeneration, or demyelinization of the optic nerve or optic disc caused by a wide variety of diseases. [medical-dictionary.thefreedictionary.com]

• Fever

  Familial Mediterranean fever (FMF) is an inherited periodic auto-inflammatory disease characterized by recurrent attacks of fever, synovitis and serositis. Ophthalmological manifestations of FMF are extremely rare. [ncbi.nlm.nih.gov]

  Optic neuritis (ReelDx + Lecture) Presentation Lecture Pearls Diagnosis Treatment Patient will present as → a 47-year-old school teacher with a cough, hemoptysis, fever, chills and weight loss that has persisted since he returned from a summer trip to [smartypance.com]

  This can occur with increases in body temperature due to exercise, hot baths or showers, or fevers. This can lead to abrupt worsening or loss of vision. However, when body temperature returns to normal then vision also returns. [swedish.org]

• Anemia

  […] following: Spread of a cancerous tumor to the optic nerve Chemicals or drugs such as lead, methyl alcohol, quinine, arsenic, and certain antibiotics Myelin oligodendrocyte glycoprotein autoantibody (MOG-IgG) disease Rare causes include diabetes, pernicious anemia [merckmanuals.com]

  Sarcoidosis: As well as pernicious anemia, Graves disease, bee stings, and vaccinations, mall all cause vision loss from swelling of the person's optic nerve. [disabled-world.com]

• Epilepsy

  We prospectively followed clinical and radiographic courses of 13 patients undergoing laser ablation for focal epilepsy by the senior author (N.T.). [ncbi.nlm.nih.gov]

  Author Erhan Ergene, MD Clinical Assistant Professor, Department of Neurology, University of Illinois College of Medicine at Peoria; Medical Director, Comprehensive Epilepsy Program and Clinical Neurophysiology, Illinois Neurological Institute at OSF [emedicine.medscape.com]

  The authors declared that EPO might show neurotrophin-like properties in models of ischemia, trauma, epilepsy and MS and might therefore be a modulator in neurodegeneration. [ 13, 69 ] In this view of ischemia, EPO activates signaling cascades that increase [journals.plos.org]

• Pseudotumor

  During the early stages of ON, in the setting of bilateral disc swelling and pain, patients may initially be suspected as pseudotumor cerebri (PTC). [ncbi.nlm.nih.gov]

  Pseudotumor Cerebri (or Idiopathic Intracranial Hypertension) Pseudotumor cerebri (PTC) or idiopathic intracranial hypertension (IIH) is a condition in which the pressure from the cerebral spinal fluid inside your head is elevated. [themedicaleyecenter.com]

• Pertussis

  Diphtheria, tetanus, pertussis, and inactivated poliovirus combined vaccine is widely used in young children as part of a series of immunizations before they start attending school. [ncbi.nlm.nih.gov]

  Herpes viruses, hepatitis A, enteroviruses and exanthemata have all been associated with this complication, as have bacterial infections involving such organisms as streptococcus, meningococcus, Brucella, Pertussis, Salmonella typhi, Treponema pallidum [doi.org]

• Macula

  The retinal thicknesses in all eyes with ON also decreased around the disc and at the macula compared with those of the fellow eyes (disc, P < 0.001; macula, P = 0.003). [ncbi.nlm.nih.gov]

  Six months later, the lipid exudates in the macula had been reabsorbed, and normal vision (20/20 in the right eye and 20/25 in the left eye) had returned. [nejm.org]

  There is concomitant swelling of the optic nerve and macula. Exudates that form around the macula give the appearance of a star. Perineuritis and neuroretinitis are not associated with MS, and if they are found they suggest another etiology. [mdedge.com]

• Alopecia

  Few days later, she developed bilateral panuveitis, shallow exudative detachments and alopecia. Clinical picture with normal magnetic resonance imaging (MRI) and laboratory tests helped us in reaching the diagnosis of Vogt-Koyanagi-Harada syndrome. [ncbi.nlm.nih.gov]

• Eruptions

  In ONMRG 1999, hyperglycemia was noted in four participants; constipation, diarrhea, acneiform eruption and hyperlipidemia were reported for two participants; headache and increasing fever were reported for one participant, and transient diarrhea was [doi.org]

• Eye Pain

  A 35-year-old woman with acute onset of left-eye pain and vision decline. Axial, fluid-attenuated inversion recovery (FLAIR) image demonstrates bilateral periventricular white matter lesions. [emedicine.com]

  A middle-aged woman who experienced recurrent episodes of unilateral vision loss and eye pain. [ncbi.nlm.nih.gov]

  Most patients have mild eye pain, which often feels worse with eye movement. If the optic disk is swollen, the condition is called papillitis. If the optic disk appears normal, the condition is called retrobulbar neuritis. [merckmanuals.com]

• Blurred Vision

  Two pregnant women developed one-eye blurring vision within three weeks after Tdap vaccination. Neurophtalmologic and MR examination confirmed an unilateral optic neuritis without evidence of underlying disease. [ncbi.nlm.nih.gov]

  Signs to look for include: Headache, fatigue, and fever Blurred vision Double vision Scalp tenderness Jaw pain Weight loss. [themedicaleyecenter.com]

• Photopsia

  Additionally, dyschromatopsia, photopsia and visual field defects may also occur 1. [radiopaedia.org]

  […] vision loss in one eye, which can vary from mild to severe and lasts for 7 to 10 days periocular pain, or pain around your eye that’s often worsened by eye movements dyschromatopsia, or the inability to see colors correctly Other symptoms can include: photopsia [healthline.com]

  Eye movements also may bring about photopsia (flickering or flashes of light), a symptom reported by 30% of the ONTT participants. Loss of color vision out of proportion to the loss of visual acuity is characteristic of optic neuropathies. [mdedge.com]

  Symptoms: Common symptoms of optic neuritis are: Vision loss in one eye – this is temporary and can last seven to 10 days Periocular pain – when pain worsens when the eye moves Dyschromatopsia – inability to see colors correctly Photopsias – seeing flashing [msunites.com]

  Eye movements also may bring about photopsia (flickering or flashes of light) to about 30% of those with optic neuritis. Loss of color vision out of proportion to the loss of visual acuity is characteristic of optic neuropathies. [my-ms.org]

• Progressive Loss of Vision

  We report the case of a 30-year-old Asian woman who presented a rapidly progressive loss of vision. [ncbi.nlm.nih.gov]

  Symptoms and Signs of Optic Neuritis Typical optic neuritis causes progressive loss of vision over hours to 10 days. Deviation from this time frame points to some other cause of the disease. [doctorstrizhak.com]

• Miosis

  […] in the involved eye in all patients with optic neuritis if the other eye is uninvolved and healthy. 12 The best way to elicit this sign is to perform the swinging light test in a dark room with the patient fixating at a distant target, which prevents miosis [mdedge.com]

• Papilledema

  At later stages the disk margins are blurred and may be slightly elevated simulating papilledema. Refs: vaugn, d and asbury, t: general ophthamology, 8th edition, 1977 ICD-9-CM Volume 2 Index entries containing back-references to 377.30 : [icd9data.com]

  At later stages the disk margins are blurred and may be slightly elevated simulating papilledema. Refs: vaugn, d and asbury, t: general ophthamology, 8th edition, 1977. [icd10data.com]

  […] tooth abscess in the upper jaw, syphilis, Lyme disease, herpes zoster), autoimmune disorders (e.g. lupus, neurosarcoidosis, neuromyelitis optica), methanol poisoning, Vitamin B12 deficiency, and diabetes, or an injury to the eye.Less common causes are: papilledema [en.wikipedia.org]

  A more thorough list includes: Papillitis (inflammation of the head of the optic nerve) Retrobulbar neuritis (inflammation of the optic nerve sparing the head) Compression of the optic nerve Papilledema (optic nerve disturbances due to increased intracranial [clinicaladvisor.com]

  September 2003 Accepted 04 September 2003 Published 08 November 2004 Issue Date 01 November 2004 DOI https://doi.org/10.1038/sj.eye.6701575 Keywords diagnosis optic nerve diseases signs and symptoms Further reading Decision Support System for Detection of Papilledema [doi.org]

• Seizure

  Limbic encephalitis is characterized by rapid onset of working memory deficit, mood changes, and often seizures. The condition has a strong paraneoplastic association, but not all cases are invariably due to tumors. [ncbi.nlm.nih.gov]

• Paresis

  Other reported ocular findings in the disease are cortical blindness, hemianopsia, nystagmus, extraocular muscle paresis and optic atrophy. [ncbi.nlm.nih.gov]

The diagnosis of acute demyelinating optic neuritis is based on the history, symptoms and clinical signs from the following eye tests:

• Visual acuity: Visual acuity worsens over several hours,days or even minutes and may range from 20/20 to no light perception on examination. 
• Visual fields: A central scotoma is common. Less frequently, an arcuate scotoma, a superior or inferior altitudinal scotoma, peripheral constriction, a cecocentral scotoma, and bitemporal or a left or right hemianopic defect may be seen. 
• Contrast sensitivity and color vision: Both reduced, sometimes more severely than the loss of visual acuity. Color vision testing is preferably done with the Farnsworth–Munsell 100-hue test. 
• Pupillary examination: The relative afferent pupillary defect is almost always present in anterior (swollen disc) or retrobulbar neuritis, unless there is a coexisting optic neuropathy in the fellow eye or other causes of visual loss unrelated to an optic neuropathy. 
• Fundus examination: Lesions that are adjacent to the optic nerve head cause papillitis (anterior optic neuritis) with minimal blood vessel enlargement and rarely peripapillary hemorrhages. Vitritis is present in anterior optic neuritis caused by infections or inflammations and intermediate uveitis with multiple sclerosis. Retrobulbar neuritis does not produce papillitis. The presence of peripheral retinal venous sheathing has been shown to be correlated with the development of multiple sclerosis [7]. 
• Other diagnostic tests are magnetic resonance imaging (MRI), cerebrospinal fluid analysis, and serological studies, done in order to determine the cause in atypical cases and the prognosis or risk for subsequent development of multiple sclerosis in cases presenting with only optic neuritis. Contrast MRI of the brain is done to detect lesions in the white matter [8] [9]. 

In a patient having the first attack of acute demyelinating optic neuritis, in the presence of two or more white matter lesions on MRI (3mm diameter or larger, at least one lesion periventricular or ovoid), the recommended treatments is one of these [10]:

• Intravenous methylprednisolone (1g per day, single or divided doses, for 3 days) followed by oral prednisone (1mg/kg per day for 11 days, then 4-day taper).
• Interferonβ-1a (Avonex 30μg intramuscularly once a week). 
• Interferonβ-1a (Rebif 22μg subcutaneously once a week). 
• Betaseron (250μg subcutaneously every other day). 

In a patient with optic neuritis having fewer than two MRI white matter lesions, and in patients with established diagnosis of multiple sclerosis, and in patients with unilateral and severe visual loss or bilateral visual loss, treatment is intravenous methylprednisolone treatment followed by oral prednisone (as described above). This will hasten visual recovery but not influence the final visual outcome.

Intravenous methylprednisolone 1000 mg/day for 5 consecutive days followed by oral prednisone taper for optic neuritis with neuromyelitis optica.
Based on findings from the Optic Neuritis Treatment Trial, oral prednisone alone (without prior treatment with intravenous methylprednisolone) may increase the risk of recurrent optic neuritis and should be avoided.

Nonsteroidal anti-inflammatory agents may be prescribed for disabling ocular pain.
Treatment of the specific cancer in paraneoplastic optic neuropathy patients with chemotherapy and/or radiation therapy.

Even with no treatment, most patients of optic neuritis start to recover their lost vision within 2-3 weeks of the onset of symptoms, achieving the maximal improvement within 1-2 months or at the most within a year. Final visual outcome has been correlated with the initial severity of visual loss. In spite of visual recovery, patients continue to experience subtle visual problems which can be objectively documented as persistent defects in visual acuity, contrast sensitivity, color vision, visual field, visual-evoked potential and stereopsis.

In about 20% of patients, multiple sclerosis is associated with optic neruritis at the onset itself. Around 40% of affected individuals will develop multiple sclerosis at later stages. Recurrent episodes of optic neuritis in the initially affected or fellow eye may occur and the risk of recurrence is twofold greater in patients who are diagnosed with multiple sclerosis in the next ten years than in patients who do not develop multiple sclerosis [5].

These are the etiological factors associated with optic neuritis.

• Acute demyelinating disorders: The most common form of optic neuritis is acute demyelinating optic neuritis, which is often associated with multiple sclerosis. Other demyelinating conditions include neuromyelitis optica and diffuse periaxial encephalitis of Schilder. 
• Leber’s hereditary optic neuropathy
• Parainfectious: It can occasionally result from a local infectious process involving the orbits or paranasal sinuses. It may occur in association with systemic infections like measles, Epstein–Barr virus (EBV), herpes zoster, cat scratch fever, primary or secondary syphilis, Lyme disease, tuberculosis, HIV and cryptococcal meningitis in patients with AIDS [2]. 
• Autoimmune disorders: Behcet’s disease and systemic lupus erythematosus. 
• Malignancies: Leukemia, intraocular lymphoma, malignant melanoma and metastatic lesions spreading to the optic nerve.
• Inflammatory disorders: Sarcoidosis.
• Post vaccination: It may also occur following immunization with rabies vaccine, Bacillus Calmette–Guerin (BCG) and tetanus toxoid. 
• Idiopathic 
• Paraneoplastic syndrome: Acute demyelinating optic neuritis, without malignant invasion of the nerve itself, has been seen in bronchial carcinoma, oat cell carcinoma and lymphomas [3].

The annual incidence of optic neuritis is approximately 3–5 per 100,000 per year, while the prevalence is 115 per 100,000. The majority of patients who develop optic neuritis are between the ages of 20 and 50 years. Women are affected more commonly than men (2:1). In most cases, the pathogenesis of optic neuritis is inflammatory demyelination, whether or not multiple sclerosis is diagnosed clinically. Many cases where optic neuritis is the only presenting feature later are diagnosed with multiple sclerosis [4].

Although the exact underlying cause is unknown, the pathophysiology of acute optic neuritis and multiple sclerosis is that of primary inflammatory demyelination, substantiated by presence of abnormal intrathecal immunoglobulin G (IgG) synthesis in 60-70% of patients with isolated optic neuritis.

Regular follow up for future recurrences of optic neuritis as well as for future development of multiple sclerosis is important for timely management. A combination of azathioprine and prednisone has been used for the prevention of relapses in neuromyelitis optica.

Optic neuritis is an inflammation of one or both optic nerves, often associated with multiple sclerosis and demyelinating diseases. Adults and women are more affected. It clinically presents with the triad of reduced vision, ocular or orbital pain and impaired colour vision. Nearly full visual recovery over time is common but residual visual defects may persist. Intravenous steroids are given in severe or bilateral cases to speed up recovery. Patients with an isolated incident of optic neuritis have better final visual outcome, whereas the prognosis is worse for patients with recurrent attacks or multiple sclerosis [1].

Definition: Optic neuritis is an inflammation of the optic nerve, which is the nerve responsible for transmitting visual information from the eye to the brain. 

Cause: Optic neuritis is often associated with multiple sclerosis. It is believed that optic neuritis may have an autoimmune cause, where the body mistakenly destroys the nerve sheath (known as myelin) leading to nerve damage. Optic neuritis can also be associated with infections, neuromyelitis optica and autoimmune diseases. 

Symptoms:

• Pain above or behind the eyes, it may increase on looking up or down. 
• Sudden decrease in vision that rapidly increases over hours or days. You may notice a loss of vividness of colors. 
• Sensation of flashes or flickering lights. 
• The vision loss may be aggravated when you are very tired or when you take a hot shower or in presence of very bright light. 

Diagnosis: The eye doctor will take a detailed history of your symptoms and medical conditions that you and your close relatives have. A detailed examination of your eyes will be done, including an examination of the inside and back of the eyes with an instrument called ophthalmoscope. Magnetic resonance scans of the brain and eyes are often required. Blood tests may be required to rule out other diseases and infections. 

Treatment and follow-up: Optic neuritis often improves spontaneously and a large number of people regain their vision almost completely in a year. The doctor may give you steroid medication through veins. Steroids reduce the inflammation in the optic nerve and speed up the visual recovery, but do not improve the extent of lost vision that you will recover. Steroids will also be given if multiple sclerosis is suspected. You may have repeat attacks of optic neuritis in future. Presence of multiple sclerosis or neuromyelitis optica leads to poor prognosis for long term visual recovery and preservation.

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2. Sanborn GE, Kivlin JD, Stevens M. Optic neuritis secondary to sinus disease. Arch Otolaryngol. Dec 1984; 110(12):816-9.
3. Calvert PC. A CR(I)MP in the Optic Nerve: Recognition and Implications of Paraneoplastic Optic Neuropathy. J Neuroophthalmol. 2006; 26:165-167.
4. Koch-Henriksen N, Hyllested K. Epidemiology of multiple sclerosis: incidence and prevalence rates in Denmark 1948-64 based on the Danish Multiple Sclerosis Registry. Acta Neurol Scand. Nov 1988; 78(5):369-80.
5. Sorensen TL, Frederiksen JL, Bronnum-Hansen H, Petersen HC. Optic neuritis as onset manifestation of multiple sclerosis: a nationwide, long-term survey. Neurology. Aug 11 1999; 53(3):473-8.
6. Cleary PA, Beck RW, Bourque LB, et al. Visual symptoms after optic neuritis. Results from the Optic Neuritis Treatment Trial. J Neuroophthalmol 1997; 17:18.
7. Lightman S, McDonald WI, Bird AC, et al. Retinal venous sheathing in optic neuritis. Its significance for the pathogenesis of multiple sclerosis. Brain 1987; 110 ( Pt 2):405.
8. Flanagan P, Zele AJ. Chromatic and luminance losses with multiple sclerosis and optic neuritis measured using dynamic random luminance contrast noise. Ophthalmic Physiol Opt. May 2004; 24(3):225-33.
9. Jackson A, Sheppard S, Laitt RD, et al. Optic neuritis: MR imaging with combined fat- and water-suppression techniques. Radiology 1998; 206:57
10. The clinical profile of optic neuritis. Experience of the Optic Neuritis Treatment Trial. Optic Neuritis Study Group. Arch Ophthalmol 1991; 109:1673.