Optic neuritis symptoms
Optic neuritis symptoms
Optic neuritis is a condition that affects the nervous system. Sometimes optic neuritis is known as “papillitis”, “demyelinating optic neuropathy” and “retrobulbar optic neuritis”. Optic neuritis is caused by inflammation of the optic disc. It is called papillitis if the optic disc is affected while it is called retrobulbar optic neuritis if the optic disc is not affected. It is most commonly affect one eye only in adult (unilateral). However bilateral eyes involvements are more common in children. 25% of multiple sclerosis sufferers complain of having this problem. Generally, the patient with optic neuritis may complain of sudden/abrupt loss of vision, periorbital pain and defect in the colour vision or colour vision deficit/dyschromatopsia.
The aetiology of optic neuritis may include multiple sclerosis as the commonest cause. Other conditions may include any infection such as viral infection that includes herpes simplex virus 1, herpes simplex virus 2, HIV, cytomegalovirus, adenovirus Coxsackie virus, fungal infection, cryptococcosis, Lyme disease, meningococcus, tuberculosis, cystocerosis, bacterial causing sinusitis, streptococcus B and bacterial causing sinusitis. Systemic inflammatory disorder such as vasculitis, sarcoidosis and SLE as well as a localized inflammation of the orbit that spreads to the sinus or meninges may also cause optic neuritis. Exposure to toxic substances such as arsenic, methanol and radiation, lead as well as the chronic high level of chloramphenicol may also cause optic neuritis. Posterior uveitis and vascular lesion of the optic nerve are also the main contributor for the development of optic neuritis.
Optic neuritis is associated with other condition such as multiple sclerosis, multifocal demyelinating neuropathy, Charcot Marie Tooth , acute transverse myelitis, acute disseminated encephalomyelitis and Devic neuromyelitis optica.
The differential diagnosis of optic neuritis may include viral infection, toxoplasmosis, Bartonella which leads to neuroretinitis, acute papilloedema, nutritional or toxic optic neuropathy, systemic inflammatory disease, infection, multiple sclerosis, intracranial abscess/tumour, which compress the afferent visual pathway, orbital abscess/tumour , carotid opthalmo artery aneurysm and the orbital pseudo tumour. Other diagnosis may include non arteritic ischemic optic neuropathy, anterior ischemic optic neuropathy and Leber hereditary optic neuropathy. Other disorders may include trauma and radiation, Kjer type autosomal dominant optic atrophy and temporal arteritis.
Optic neuritis is common in female than male in 3: 1 ratio. It most commonly presents in the northern region and the typical age of presentation is 20 - 50 years old. The incidence of optic neuritis is 1- 5 / 100 000 /year and the prevalence is 115 /100 000/ year.
Patient with optic neuritis typically presents with decrease in visual acuity. The vision is deteriorating in hours and days and the vision will reach the lowest level in one week. The patient also complains of periorbital pain that precedes the loss of vision. In this case, the patient also complains of deep orbital pain, which is worst by eye movement, tender globe or brow ache. Impairment of the visual perception may also present especially towards the moving object. Desaturation of colour vision especially red tones that appear faded and dull is also common. The patient may also complain of dimness of light intensities. Uhthoff phenomenon is common where there is a transient increase in visual symptoms with exercise and fever due to increase in temperature.
Optic neuritis that present in the children is presented with bilateral disease and optic swelling and severe loss of visual acuity (20/200 or worse). In this case, optic neuritis is associated with infection and post infection causes of optic nerve impairment.
The physical examination is completed with neurological examination and Ophthalmological examination. The Ophthalmological examination will focus on visual acuity test and a visual field test. Visual field tests may involve automated Humphrey and Octopus and patients may present with central scotoma visual field loss. However it varies as it may be focal or diffuse. Besides that central, cecocentral and arcuate scotoma visual field defect is also common. The patient may also present with decrease in visual acuity. Fundoscopic examination may be normal in almost all cases. However some of them may present with peripheral haemorrhage or papillits . Later 4-6 weeks, temporal disc pallor is common. Marcus Gunn pupil or relative afferent pupillary defect is common. In this scenario, the pupil of the affected eye is dilated in the swinging light test.
Specific vision testing may also require which include colour vision testing or visual evoked potential to confirm afferent defect in unclear cases. Contrast sensitivity testing and contrast letter acuity testing may also be performed to identify any deficit.
The investigation requires may include laboratory investigation, imaging techniques and any surgical /diagnostic procedure.
The aim of the laboratory investigation is to rule out any underlying disorders. Besides that full blood count and urea and electrolytes as well as ESR remains the most important standard test in typical patient presented with optic neuritis. If a patient presented with swollen optic disc or retinal exudates for more than 1 month, without recovery, the following test such as full blood count, syphilis serology test, rapid plasma reagin test, antinuclear antibody test, fluorescent treponemal antibody absorption test is performed.
Imaging techniques may include MRI of the orbit, MRI of the brain and CT scan of the lung. In MRI of the orbit, any lesion is well presented in T2 weighted image as increase signal density which can be enhanced with IV Gd contrast. Dawson’s finger that present on multiple sclerosis is detected on the MRI scan of the brain. The MRI scan of the brain may reveal a perpendicular lesion in the white matter that is perpendicular to the ventricle. CT scan of the lung is useful to rule out sarcoidosis.
Any diagnostic procedure such as lumbar puncture is only performed in selected cases such as in the children, patient with bilateral deficit of infectious aetiology is suspected.
Treatment may include referral of the patient to the ophthalmologist and a neurologist. The first line of treatment may include parental corticosteroid treatment in case of significant visual loss. The decision of using parental corticosteroid is based on the consultation with the ophthalmologist or neurologist after weighing the risk and reviewing the evidence based medicine. Generally the treatment may begin with a period of observation and corticosteroid treatment.
The corticosteroid treatment is initially begun with high doses of intravenous methyl Prednisolone (250mg every 6 hours for 3 days). This is followed by 1mg/kg/d orally for 11 days oral corticosteroid that taper for 1 -2 weeks. IV Solumedrol infusion ( 1g in 250cc D5 1/2 normal saline infusion for over 1hour every day for 3- 5 days) is an alternative as it decreases the risk of developing multiple sclerosis for 2 years and decrease the recovery times but no evidence of long term benefit. Anti ulcer medication is given to the patient with steroids.
Other agents that are used in treating optic neuritis may include the use of disease modifying agent such as interferon-B 1alpha/beta and glatiramir acetate. These drugs are proposed based on the consultation with the neurologist and prescribed in patient with single episodes of optic neuritis with lesions on the brain is detected on the MRI scan and increase risk of developing multiple sclerosis. It may decrease the risk of developing multiple sclerosis . The use of oral Prednisolone should be avoided as it may lead to the recurrence of optic neuritis.
The visual acuity will rapidly and spontaneously improve in 2- 3 weeks. It will continue for several months. Within 1 year (95% of individuals) the vision will often return to normal or near normal level ( 20/40). This may also apply to patient with near blindness. Faster rate of improvement can be achieved with IV corticosteroid. Certain features of visual disturbance such as contrast sensitivity or steropsis will remain impaired after the visual acuity return to normal.
35% of cases will recur in 10 years where 12 % happen in contralateral eyes, 14% in the affected eyes and 9% in both eyes (bilateral). 48% rate of recurrence in multiple sclerosis patient.
The poor prognostic factors of optic neuritis may include the absence of peri orbital pain, low visual acuity initially and intracanalicular optic nerve involvement. However children who suffer from bilateral loss of vision will carry a better prognosis compare to adult.
Optic neuritis is associated with an increase risk of developing multiple sclerosis. 7 years old optic neuritis sufferer present with 35% risk of developing multiple sclerosis and 58% chances of multiple sclerosis at 15 years old. The risk of developing optic neuritis may also be detected by brain MRI scan. 16% risk of optic neuritis if no lesion on the brain, 1- 2 lesion carries a 37% risk of optic neuritis and more than 3 lesions carry a 51% risk.
The complication of optic neuritis may include permanent loss of vision. Patient follow up treatment may include monthly monitoring of the visual changes and observation of any steroid side effect.
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