DISEASES OF THE OPTICNERVEBY: SUMAYYA NASEEMINTERNEE OPTOMETRIST
Optic nerveThe optic nerve (also known as cranial nerve II) isa continuation of the axons of the ganglion cells inthe retina.There are approximately 1.1 million nerve cells ineach optic nerve.The optic nerve, which acts like a cable connectingthe eye with the brain, actually is more like braintissue than it is nerve tissue.
Optic Neuritis• “Optic neuritis” is an inflammation of the opticnerve.• It may affect the part of the nerve and disc withinthe eyeball (papillitis) or the portion behind theeyeball (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, Graves disease, bee stings,vaccinations, and injuries. However, the cause of optic neuritis is oftenunknown.
1. Papillitis• It is the inflammation of intraocular part ofoptic 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
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 FieldsTreatment:• 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• HaloesObserver will see:• Raised IOP• RAPD• Optic disc cupping• Hemorrhages on the disc margin.• V.F. defect• Optic atrophy (last stage)
Progressive cupping of the optic disc. Early progression of cupping can be seen bycomparing 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 hemorrhageof the optic nerve located at the arrow at 5 o’clock
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 orinflammation 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 isirreversible.
Tumors• Intrinsic - e.g. gliomas, melanocytomas andmeningiomas originating from nerve tissue.• Extrinsic e.g. meningiomas of sphenoidal ridge orolfactory groove, pituitary adenomas and somemetastatic tumors.
Optic nerve glioma• Optic nerve glioma (also known as optic pathway glioma) is themost common primary neoplasm of the optic nerve.Signs & symptoms:• Problem in ocular motility• Proptosis• Defective vision if they affect the ON conductive system• NystagmusDiagnosis:• CT• MRI
a) Axial orbit CT scan shows enhancing glioma involving the left intraorbital optic nerve (b) Fundusphotograph Image shows marked swelling of the left optic disc. (c) Patient was treated with an excision of theorbital optic glioma of the left eye. Photograph shows the excised specimen. (d) Fundus photograph 3months after the optic nerve excision. Image shows optic disc pallor and tractional retinal detachment.
Colobomas• Incomplete closure of fetal cleft thus appearing inferiorly. Maybe associated with choroidal /iris coloboma.• Optic nerve coloboma (medical condition): A hole in the eyestructure called the optic nerve which is responsible for sendingvisual information from the eye to the brain. Severity ofsymptoms is determined by the size of the defect.• Impaired vision• V.F. defect• Field defect corresponds to the area of projection of the missingfibers.