OPTIC NEURITIS

Steroid therapy

Ans. is ‘a’ i.e., Ethambutol

Optic neuritis :
Its of three types:

• Papillitis
• Neuroretinitis
• Retrobulbar neuritis

Most common cause:
o Demyelinating disorders

• Multiple sclerosis
• Neuromyelitis optica—Devic’s disease

 Symptoms
o Visual loss
 Sudden, progressive, profound
 Painful
o Pain on ocular movements—retrobulbar neuritis
o Painless in papillitis and neuroretinitis.
 Movement phosphenes and sound-induced phosphenes
o Phosphenes refer to glowing sensations produced by non-photic stimuli.
 Impairment of color vision
 Signs:

• Marcus Gunn pupil: Relative afferent pupillary defect (RAPD)
•  Hyperemia of the disc
• Blurring of the margins
•  Visual field changes: The most common field defect in optic neuritis is a relative
• central or centrocecal scotoma.

Other option:

Myasthenia gravis is the autoimmune destruction of the acetylcholine receptors at the neuromuscular junction.

C i.e. Abnormal electroretinogram 

Electroretinogram indicates the activity of retinal (esp. rods & cones) function and has no role in assessing the functional integrity of the optic nerve Q. So it can’t be abnormal in optic neuritis.

A i.e. Rifampicin

Ethambutol, streptomycin & isoniazid are anti-tubercular agents that cause optic neuritis.Q Rifampicin does not cause optic neuritis.

Ans. Goldman perimetery

Ans. B: Hypertension

Optic neuritis

• It is the inflammation of the optic nerve that may cause a complete or partial loss of vision.

Causes

• 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.
• Inflammation of the optic nerve causes loss of vision usually because of the swelling and destruction of the myelin sheath covering the optic nerve.
• The most common etiology is multiple sclerosis.
• The presence of demyelinating white matter lesions on brain MRI at the time of presentation of optic neuritis is the strongest predictor for developing clinically definite MS.
• Some other causes of optic neuritis include infection (e.g. Syphilis, Lyme disease, herpes zoster), autoimmune disorders (e.g. lupus), Inflammatory Bowel Disease, drug induced (e.g. chloramphenicol, Ethambutol) vasculitis and diabetes Symptoms
• Major symptoms are sudden loss of vision (partial or complete), or sudden blurred or “foggy” vision, and pain on movement of the affected eye.
• The vision might also look “disturbed/blackened” rather than blurry, like when feeling dizzy.
• Many patients with optic neuritis may lose some of their color vision in the affected eye (especially red), with colors 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; however frequently there is no abnormal appearance of the nerve head in optic neuritis (in cases of retrobulbar optic neuritis), though it may be swollen in some patients (anterior papillitis or more extensive optic neuritis).

• 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.

Epidemiology

• Optic neuritis typically affects young adults ranging from 18-45 years of age, with a mean age of 30-35 years.
• There is a strong female predominance.

Treatment and prognosis

• In most cases, visual functions return to near normal within eight to ten weeks, but they may also advance to a complete and permanent state of visual loss.
• Therefore, systemic intravenous treatment with corticosteroids, which may quicken the healing of the optic nerve, is often recommended
• Very occasionally, if there is concomitant increased intracranial pressure, the sheath around the optic nerve may be cut to decrease the pressure.
• When optic neuritis is associated with MRI lesions suggestive of multiple sclerosis (MS) then general immunosuppressive therapy for MS is most often prescribed (IV methylprednisolone may shorten attacks; initial only oral prednisone may increase relapse rate).