Optic Neuritis

Dr Ben Wild

Overview

Our vision comes from light waves stimulating retinal photoreceptors and these photoreceptors transferring their signals through a multitude of other cells to the ganglion nerve cells. These ganglion cells bunch together and form the optic nerve. The optic nerve then sends the signal to the occipital lobe in the brain where vision is interpreted and recognized.

An image of a healthy retina and optic nerve. This is also noticed in retrobulbar optic neuritis because the inflammation is contained behind the eye.

Optic neuritis refers to inflammation of the optic nerve thereby affecting the transfer of vision from the eye to the brain. It is extremely rare to see this bilaterally (in both eyes). The different presentations of optic neuritis include retrobulbar (inflammation of the optic nerve behind the eye), papillitis (inflammation of the optic nerve inside the eye), and neuroretinitis (inflammation of the brain extending into the optic nerve and the retina inside the eye).

The top image shows optic nerve swelling and retinal hemorrhages consistent with a papillitis, the bottom image shows the same inflammation plus swelling of the macula (darker area) in neuroretinitis.

Signs and Symptoms

Signs

Retrobulbar	Uneven pupil reflexes to light.
Papillitis	Red and swollen optic nerve, broken blood vessels around the nerve, inflammation inside the eye, uneven pupil reflexes to light.
Neuroretinitis	Same as papillitis but with additional swelling of the macula (central part of the retina).

Symptoms

Retrobulbar	Large blind spot in vision, intense pain on eye movement, light sensitivity, decreased vision, decreased colour vision, decreased contrast sensitivity.
Papillitis	Same as retrobulbar.
Neuroretinitis	Painless vision loss.

Causes and Risk Factors

Causes

Retrobulbar	Most common cause is demyelinating diseases like Multiple Sclerosis.
Papillitis	Most common cause is parainfection (a condition resembling an infection but not caused by an infectious agent such as post vaccine illness).
Neuroretinitis	Most common cause is infection by cat-scratch disease (65% of time), meningitis, shingles, Lyme, syphilis, tuberculosis, and more. Can be due to parainfections as well.

Risk Factors

Retrobulbar	Female gender.
Papillitis	Childhood age, measles, mumps, chickenpox, rubella, whooping cough.
Neuroretinitis	Scratched by cat or exposure to cat feces, tick bites.
Common	Autoimmune inflammation from sarcoidosis, lupus, and more.

Prevention and Treatment

Prevention

There are no known preventative measures other than reduce exposure to cats and ticks.

Treatments

Retrobulbar	· IV steroids if vision is worse than 20/40. · Immunotherapy to decrease frequency of attacks.
Papillitis	· IV steroids but usually none required.
Neuroretinitis	· Determine if infectious or not (IV steroids in non-infectious, antimicrobials if infectious). · Sometimes no treatment is required.

Prognosis

Retrobulbar	This is the presenting feature of Multiple Sclerosis in 30% of cases and occurs in half of patients with MS. Over 90% of patients regain vision better than 20/30 but colour vision will remain abnormal and there may be permanent effects on pupil reactivity. There is a fair possibility of this being recurrent.
Papillitis	Usually no treatment is needed and full recovery is likely. No re-occurrence expected. This means, even if this occurs after getting vaccinated, the benefit of the vaccine largely outweighs the effects of the temporary papillitis.
Neuroretinitis	Over 90% of patients regain vision better than 20/40. If the cause is found, and treated, neuroretinitis should not reoccur.