DISEASES OF THE OPTIC NERVE

BY: SUMAYYA NASEEMINTERNEE OPTOMETRIST

Optic nerveThe optic nerve (also known as cranial nerve II) is a continuation of the axons of the ganglion cells in the retina. 

There are approximately 1.1 million nerve cells in each optic nerve. 

The optic nerve, which acts like a cable connecting the eye with the brain, actually is more like brain tissue than it is nerve tissue.

Optic Neuritis

• “Optic neuritis” is an inflammation of the optic nerve. 

• It may affect the part of the nerve and disc within the eyeball (papillitis) or the portion behind the eyeball (retrobulbar optic neuritis) .

Causes• Malnutrition. E.g. vit B complex deficiency.

• Infections such as viruses (especially in children), measles, meningitis, syphilis, sinusitis, tuberculosis, and human immunodeficiency virus (HIV)

• Tumors

• Chemicals or drugs such as tobacco, lead, methyl alcohol, ethambutol, chloroquinine, arsenic, and certain antibiotics

• Certain autoimmune diseases such as multiple sclerosis

• Intraocular inflammation (uveitis)

• Rare causes include diabetes, hypertension, anemia, Grave's disease, bee stings, vaccinations, and injuries. However, the cause of optic neuritis is often unknown.

1. Papillitis• It is the inflammation of intraocular part

of optic nerve ( optic disc).

Symptoms• Loss of vision • Complete or partial blindness • Loss of some or all color vision (red green)• Pain behind the eye.• Painful eye movements

Blurred vision

Signs

Disc = hyperemic

Margins = blurred.

Oedematous

PAPILLITIS

2. Retrobulbar neuritis• It the inflammation of the posterior part

of the optic nerve, behind the globe.

• There is a common saying:

‘PATIENT SEES NOTHING & THE DOCTOR SEES NOTHING’

Signs & Symptoms

• Loss of vision• Pain behind the eye.• RAPD• Complete recovery may take place,

but usually optic atrophy.

Investigations:• Ophthlamoscopy• Pupillary reflex• Visual field• Color vision• CT Scan Brain• MRI Brain

Treatment:• Many cases improve without

treatment • Systemic I/V steroids—3 days.

Fundus photographs and visual fields of patient with ON. (a) Fundus photographs showing mild swelling of both optic discs (left,

right eye; right, left eye).(b) Visual fields showing bilateral central scotoma and blind spot

enlargement (left, left eye; right, right eye).

Papilloedema

• It is defined as swelling of the optic disc.Causes:• Increased ICP• Trauma / head injury• Tumor (brain, orbital)• Sub dural or sub arachnoid hemorrhage• Meningitis• Encephalitis

Signs & Symptoms• Headache• Nausea & vomiting• Mild decrease in vision• Paralysis of extra ocular muscles.

Observer will see:• APD or RAPD• Optic disc swelling• Hyperemia• Blurred margins• Loss of venous pulsations• Hemorrhages on the disc margin.

Investigations:• Ophthlamoscopy• Pupillary reflex• CT Brain• Visual Fields

Treatment:• Directed towards the

cause.

Glaucoma

• It is a syndrome in which there is :1. IOP is raised.2. Cupping of optic disc.3. Visual field constriction.

Signs & symptoms

• Decrease in vision• V.F. defect• Headache• Nausea & vomiting• Haloes

Observer will see:• Raised IOP• RAPD• Optic disc cupping• Hemorrhages on the disc

margin.• V.F. defect• Optic atrophy (last stage)

CDR (cup disc ratio)

Arcuate Scotoma

Progressive cupping of the optic disc. Early progression of cupping can be seen by comparing photographs of the optic nerve. The optic cup which was initially not visible (A) has enlarged over time (B).

Optic nerve hemorrhage. There is a flame-shaped hemorrhage of the optic nerve located at the arrow at 5 o’clock

Humphery visual field analyzer

Observed clinically as pallor of the disc:

•PRIMARY - disc pale & white, margins are distinct

•SECONDARY - disc pale & white, margins indistinct - such cases result from previous oedema or inflammation of the nerve head.

Optic atrophy

Causes:• Same as optic neuritis.

Signs & symptoms:• Loss of vision • Loss of brightness & color discrimination• Diminished or absent Pupillary reflex• V. F. defect• Blindness ( end result)

Treatment:• Optic nerve can’t regenerate, so visual loss

is irreversible.

Optic atrophy

Tumors

• Intrinsic - e.g. gliomas, melanocytomas and meningiomas originating from nerve tissue.

• Extrinsic e.g. meningiomas of sphenoidal ridge or olfactory groove, pituitary adenomas and some metastatic tumors.

Optic nerve glioma• Optic nerve glioma (also known as optic pathway glioma)

is the most common primary neoplasm of the optic nerve.

Signs & symptoms:• Problem in ocular motility • Proptosis • Defective vision if they affect the ON conductive system• Nystagmus

Diagnosis:• CT • MRI

a) Axial orbit CT scan shows enhancing glioma involving the left intraorbital optic nerve (b) Fundus photograph Image shows marked swelling of the left optic disc. (c) Patient was treated with an excision of the orbital optic glioma of the left eye. Photograph shows the excised specimen. (d) Fundus photograph 3 months after the optic nerve excision. Image shows optic disc pallor and tractional retinal detachment.

Proptosis due to Glioma

Congenital defects

• Optic nerve hypoplasia (small+ poorly developed disc)

• Optic nerve pit (small deep hole in centers of optic disc)

• Optic disc coloboma

Optic nerve hypoplasia

Optic nerve pit

Colobomas

• Incomplete closure of fetal cleft thus appearing inferiorly. May be associated with choroidal /iris coloboma.

• Optic nerve coloboma (medical condition): A hole in the eye structure called the optic nerve which is responsible for sending visual information from the eye to the brain. Severity of symptoms is determined by the size of the defect.

• Impaired vision• V.F. defect• Field defect corresponds to the area of projection of

the missing fibers.

Optic nerve coloboma