The optic nerve is the cable that transmits signals from the eye to the brain. Optic atrophy is a sign of remote damage to the optic nerve. The optic nerve will appear pale. The damage can be due to numerous causes such as lack of blood flow to the nerve, inflammation, infection, compression by a blood vessel, eye muscle or tumor, inherited conditions, toxic medication or substances, or poor nutrition with vitamin deficiencies. Optic atrophy can occur at any age. Treatment of the underlying condition is usually necessary to prevent further damage.
Ischemic optic neuropathy
Ischemia is a medical term for lack of blood flow and, in turn, lack of oxygen. This causes damage to the optic nerve. If the lack of blood flow is towards the front of the optic nerve, it will become swollen initially and this is called anterior ischemic optic neuropathy (AION). Signs of AION include sudden, painless loss of vision that can be central or affect the top or bottom half of the vision in one eye. This condition is most common in people over the age of 50 who also have vascular risk factors such as diabetes and high blood pressure (hypertension).
There is no effective treatment at this time, but there are clinical trials of possible new treatments being conducted.
Optic neuritis, inflammatory and infectious optic neuropathies
Optic neuritis is inflammation of the optic nerve that may result in damage if left untreated. Symptoms include pain with moving the eye, decreased vision, and decreased color vision or contrast sensitivity. Optic neuritis is most common in younger women. Typical optic neuritis can be associated with multiple sclerosis (MS), a neurologic condition that causes inflammation in the brain and spinal cord. An MRI is necessary to determine the risk of developing MS, as early treatment can decrease severity and delay progression. Other autoimmune conditions such as sarcoidosis and neuromyelitis optica can cause atypical optic neuritis and in these, prompt treatment with IV steroids or other treatments can prevent permanent visual loss. Some infections such as Lyme disease, syphilis and tuberculosis can involve the optic nerve and need to be treated with antibiotics often in conjunction with steroids to prevent damage.
Cranial nerve palsy
Third nerve palsy: Signs of a third nerve palsy include droppy eyelid (ptosis), a dilated pupil, vertical and horizontal double vision with inability to move the eye up, down, or in. Causes of third nerve palsy include head trauma, aneurysm, brain tumor, inflammation, or lack of blood flow to the nerve. If it occurs suddenly with pain, it can be a sign of a very serious condition (aneurysm) requiring emergency interventional neuroradiology treatment.
Fourth nerve palsy: The fourth nerve, also called the trochlear nerve, controls one eye muscle that turns the eye in and down and is responsible for inward rotation of the eye during head tilt. Symptoms of fourth nerve palsy include vertical double vision that can be worse looking in one direction or tilting the head. Causes of fourth nerve palsy can be congenital, due to head trauma or due to a tumor.
Trigeminal nerve abnormalities: The trigeminal nerve is the 5th cranial nerve and is responsible for sensation of the entire face. There are 3 divisions: one supplying the forehead, upper eyelid and eye, a second supplying the lower eyelid, cheek, side of the nose and upper lip, and a third division supplying the lower lip, jaw line and also the muscles responsible for chewing. Occasionally, injury, compression or infiltration of the trigeminal nerve can cause numbness or facial pain. This can sometimes be associated with serious underling conditions and therefore, a detailed examination and neuroimaging may be required.
Sixth nerve palsy: The sixth nerve controls the eye muscle that turns the eye outward. If that muscle is weak due to a sixth nerve palsy, the eyes will be crossed with horizontal double vision. The most common cause of sixth nerve palsy is lack of blood flow to the nerve, usually in patients over the age of 50 with vascular risk factors such as diabetes and hypertension. Sixth nerve palsy can also be from high intracranial pressure, inflammation, or compression from a blood vessel or tumor.
Facial nerve palsy: The facial nerve is the seventh cranial nerve and controls the muscles of facial expression that allow one to raise the brows, frown, close the eyes tightly, smile, puff the cheeks out or move the mouth. Part of the facial nerve is also responsible for controlling taste. Facial nerve palsy will result in weakness and drooping of the face with difficulty closing the eyelids. When a cause is not identified, facial palsy is called Bell’s palsy. Some causes of facial palsy include inflammation from autoimmune conditions, infections, stoke, compression from a tumor, or direct injury from trauma. A detailed MRI of the brain with contrast can often detect the cause. Treatment of Bell’s palsy can involve a short course of antiviral medication and corticosteroid, or if identified, treatment will be aimed at a more specific cause. Occasionally, facial palsy can be associated with spasm of one side of the face, or hemifacial spasm. This can be treated with onabotulinum toxin A (Botox) injections.
Myasthenia gravis and other eye muscle problems
Myasthenia gravis is an autoimmune condition that can cause muscle weakness, most commonly affecting the eyelids and eye muscles. Myasthenia gravis can occur in younger patients in their 20s and 30s, but is more typical in the 60s and 70s. Many will produce autoimmune antibodies called acetylcholine receptor antibodies that affect the transmission of signals between the nerves and skeletal muscles and in turn, cause muscle weakness. Signs of myasthenia gravis include droopy eyelids that fluctuate in position throughout the day, double vision, and occasionally difficulty swallowing, facial weakness, body muscle weakness, and shortness of breath. A blood test looking for the acetylcholine receptor antibodies can be done. Other tests include an ice pack test on the droopy eyelid, a Tensilon test looking for rapid improvement of muscle weakness, and electromyography to test the electrical activity of the muscles. Treatment is largely done with medications such as pyridostigmine and prednisone.
Tumors in the eye socket
The eye socket is referred to as the orbit. Within the orbit, there are several structures from which tumors can arise primarily, or from secondary spread from tumors in other locations in the body. The important structures include the eye muscles and their nerves, the fatty tissue that cushions the eye and other soft tissues, the optic nerve, the lacrimal gland and the bone that surrounds the orbit. Patients of any age or gender can develop an orbital tumor, but it tends to be more common in middle aged and older adults. Symptoms of orbital tumors include droopy eyelid (ptosis), swelling of the eyelids, a firm lump, protrusion or displacement of the eye, double vision, or decreased vision due to compression or infiltration of the tumor affecting the eye or optic nerve. Tumors will rarely cause pain or redness. Benign tumors can grow slowly over several years and more aggressive tumors can cause symptoms more rapidly over a few weeks. Diagnosis is achieved with a detailed eye exam including assessing the eye muscle and optic nerve function, and ultimately, with orbital CT/MRI and biopsy or excision of the tumor. Treatment usually depends on the type of tumor; some are completely removed by an orbital surgeon, while others can be observed closely, treated with chemotherapy and/or radiation. Occasionally, orbital tumors can spread from or to the sinuses and brain cavity, requiring collaboration with otolaryngology, neurosurgery and oncology for treatment.
Thyroid eye disease (Graves’ disease)
Patients with autoimmune thyroid disease (causing hyperthyroidism, hypothyroidism, or no changes in thyroid labs) can develop orbital (eye socket) involvement at any point in the course of their disease. The orbital fat and eye muscles can become inflamed, and scarred, causing swelling and decreased ability to move the eyelid and eyeball. Signs of thyroid eye disease (TED) include dry eyes, swelling or redness of the eye or eyelid, pressure or pain behind the eye (usually worse in the mornings), the eyelid being more open (or retracted), decreased blinking with difficulty closing the eyes all the way, double vision with crossing of the eyes or one eye appearing higher than the other, protrusion of the eye (proptosis), and rarely, decreased vision from optic nerve compression due to enlargement of the eye muscles. Fortunately, most patients will have mild to moderate eye involvement, which lasts between 1-3 years. Smokers tend to have a more prolonged and severe course, therefore, quitting smoking is advisable.
The most commonly affected age groups are the 40s and 60s, and women are more likely to have TED than men. TED is diagnosed by performing a detailed eye exam, blood tests to look for thyroid hormone abnormalities and autoimmune thyroid antibodies, and occasionally a CT or MRI scan of the orbit. Treatment of mild TED includes collaboration with the endocrinologist to maintain the thyroid hormone levels using medication or other treatments, and possibly selenium or non-steroidal anti-inflammatory medications. Moderate to severe TED may need more aggressive treatment. If significant double vision or visual loss is present, steroids or other medications to suppress the immune system may be used. In some patients unresponsive to medication, surgery (such as orbital decompression, eye muscle or eyelid surgery) or radiation may be required. Once in the inactive phase, many patients will have eyelid position, swelling and double vision spontaneously improve over time.
Giant cell arteritis
Giant cell arteritis (GCA), also known as temporal arteritis, is an autoimmune condition affecting women more commonly than men over the age of 50. It causes inflammation of the arterial blood vessels in the body (vasculitis), which narrows the blood vessel increasing the risk blockage leading to stroke in the area affected. The locations affected include the scalp, eye/optic nerve, neck, arms, and near the heart. Symptoms of GCA include headaches, pain and tenderness of the temple or scalp, soreness in the jaw while chewing, fever, fatigue, feeling ill (malaise), muscle aches, and weight loss due to poor appetite. It can commonly coincide with polymyalgia rheumatica. The most serious symptom is sudden temporary or persistent loss of vision or double vision due to lack of blood flow to the eye. This needs to be treated emergently. Diagnosis is usually made with assessing clinical symptoms, a detailed eye exam, blood tests looking for signs of inflammation, and possibly biopsy of the temporal artery (the small blood vessel under the skin of the scalp in the temple). Alternatives to temporal artery biopsy can include high resolution ultrasound of the temporal arteries or MRI to look for secondary signs of vasculitis. Treatment usually consists of corticosteroids (started right away) and possibly other medications to suppress the immune system, such as tocilizumab. This is usually done over several months with the collaboration of a rheumatologist.
Double vision can arise from one eye or can be present when both eyes are open. It can occur in men and women of any age group. Usually when present only in one eye, the issue is in the eye itself. When the double vision goes away with either eye closed but is persistent with both eyes open at the same time, the problem is due to misalignment of the eyes. The eye muscles that turn the eyes in different directions need to work together to maintain a single image. If one or more muscles are weak or not moving the way they should, there will be two images spread apart horizontally, vertically or diagonally. Causes of double vision can be cranial nerve palsy (3, 4, or 6), stroke, myasthenia gravis, thyroid eye disease, orbital tumors, orbital inflammation (orbital pseudotumor, myositis), or other problems in the brain disrupting the control of eye movements. Evaluation of double vision involves precise measurement of the pattern of misalignment, blood tests, and CT or MRI of the orbits and brain with and without contrast. Double vision can be managed with covering one eye with a patch or tape on glasses, prisms, or eye muscle surgery if the problem persists.
Papilledema is optic nerve swelling associated with high intracranial pressure. The surface covering of the brain and spinal cord also cover the optic nerve. When the pressure in the cerebrospinal fluid builds up, there is also increased pressure around the optic nerve, which causes it to swell inside the back of the eye. If the swelling continues for a while or if the swelling is severe, visual loss can occur. The main causes of raised intracranial pressure include idiopathic intracranial hypertension (or primary pseudotumor cerebri syndrome), meningitis, brain tumors, or blood clots in the veins that drain the cerebrospinal fluid (venous sinus thrombosis). Symptoms of increased intracranial pressure include headaches, neck stiffness, nausea and occasionally vomiting, hearing swooshing noises in the ear coinciding with the heart beat (pulsatile tinnitus), and episodes of temporary vision loss in both eyes (transient visual obscurations). Evaluation involves a detailed eye exam, visual fields, pictures of the optic nerve, OCT, and possibly fluorescein angiography. MRI of the brain and MR Venogram are usually performed followed by a spinal tap (or lumbar puncture) to check the cerebrospinal fluid pressure. The treatment to lower the cerebrospinal fluid pressure is directed at the underlying cause and usually involves medication, weight loss, and rarely requires urgent surgery. If not treated appropriately, the chronic swelling causes permanent damage to the optic nerve with loss of peripheral vision followed by central vision.
Idiopathic intracranial hypertension
Idiopathic intracranial hypertension (IIH), also called primary pseudotumor cerebri syndrome (PTCS), is a condition affecting mostly younger, overweight or obese women in their childbearing years. There is elevated intracranial pressure which causes papilledema (see above). Risk factors for IIH include recent moderate weight gain, oral contraceptive use, corticosteroids, retinoids or vitamin A-derivative supplements, acne medication, and antibiotics such as doxycycline and minocycline. Diagnosis is made with detecting papilledema on eye examination, a normal neuroimaging (brain MRI and MRV), and a lumbar puncture showing raised intracranial pressure (greater than 25 cmCSF opening pressure), with normal cerebrospinal fluid composition. For most patients, the recommended treatment is weight loss of about 6-10% of the body weight and acetazolamide (or other diuretics if not tolerated). Surgical treatments such as optic nerve sheath fenestration and cerebrospinal fluid-shunting procedures are usually recommended for more severe papilledema or if there is a greater degree of visual loss initially.
There is a complex network of blood vessels that supply the various parts of the brain and eye. Occasionally, the blood vessels can develop abnormal outpouchings called aneurysms, due to weakening of the wall of the vessel. The aneurysms can expand and press on important structures such as nerves, leading to double vision or loss of vision. A sudden rupture of an aneurysm can be fatal. Treatment of aneurysms is performed urgently/emergently by an interventional neuroradiologist or neurosurgeon and the neuro-ophthalmology team works closely with them to ensure timely care.
Another blood vessel abnormality that can present with vision disturbances is an arteriovenous malformation (AVM), which is an abnormal direct communication between an artery (higher flow vessel) and a vein (lower flow vessel). The AVM causes expansion and dilation of the veins and this can compress the adjacent area or cause a lack of blood flow leading to a stroke. When located in the area of the brain responsible for vision (the occipital lobe), AVMs can cause visual field abnormalities on one side of the vision and this can sometimes only be picked up on formal visual field testing. An MRA or CTA is performed for evaluation and the AVM is treated by interventional neuroradiology or neurosurgery.
Occasionally, blood vessels undergoing constant stress from high blood pressure or other vascular risk factors can become thickened and dilated and compress surrounding nerves. Usually the compression comes on very slowly and rarely requires treatment. However, some patients with more severe symptoms may elect to undergo treatment with neurosurgery to decompress the affected nerve.
The most common blood vessel abnormality is narrowing, or stenosis, causing an increased risk for stroke. This occurs in patients over the age of 50 with vascular risk factors such as diabetes mellitus, hypertension, high cholesterol/hyperlipidemia, smoking, sleep apnea, or a strong family history. Usually, there are no symptoms of arterial stenosis until it becomes more severe. One may experience transient ischemic attacks (TIAs), which are episodes of lack of blood flow to an area. Symptoms can include sudden painless loss of vision in one eye, drooping of the face, numbness or weakness on one side of the body. Work up entails CTA or MRA, as well as carotid Doppler ultrasound. Symptomatic arterial stenosis requires collaboration with internal medicine, neurology, cardiology and possibly vascular surgery to optimize treatment of underlying vascular risk factors.
Sudden vision loss
Sudden painless visual loss can occur in one eye or in both eyes simultaneously. If it occurs in one eye, it can be due to lack of blood flow to the eye itself, sometimes from an embolus, or piece of a nearby plaque in the carotid artery (the main artery in the neck supplying the brain and eye), or from a blood clot originating from the heart, carotid artery or other vessel leading to the eye. The affected eye can have a lack of blood flow to the optic nerve, retina, or both. Work up for this includes a detailed eye exam, visual testing, OCT, and fluorescein angiography. If a stroke of the eye is found (central retinal artery occlusion), work up for a cause includes MRI brain and MRA, EKG, echocardiogram, carotid Doppler, blood tests, and evaluation by neurology for other signs of stroke. (See neurovascular disease)
Sudden visual loss involving both eyes is due to a problem in the occipital lobe, the area in the brain responsible for processing vision. This most commonly affects older adults with vascular risk factors who may have narrowing or stenosis of the blood vessels supplying the back of the brain (posterior circulation). Other associated symptoms can include loss of balance and decreased visual field on one side of the vision. The amount of visual loss in an occipital stroke varies; some will only notice difficulty reading, which others may have more profound visual loss and not be able to navigate their environment. The work up is the same as that for neurovascular disease including MRI brain and MRA. If a stroke is detected very early within the first few hours, certain emergency treatments may reverse the visual loss. Treatment of stroke outside this window involves management of vascular risk factors and some patients may benefit from visual rehabilitation with low vision specialists to maximize the use of their vision.
Visual perception disorders
Occasionally after a stroke, one can have difficulty processing visual information, even if they can read the letters on the eye chart. Certain parts of the brain take the visual information obtained from the visual pathways and process them to make sense of the environment. Communication between different parts of the brain is required to be able to read and write what you see, or to be able to verbally describe a face, an object or a scene. Processing the right and left side of the vision also requires intact communication and processing of information on both sides of the brain. If there is a stroke in any of these pathways, a patient can lose the ability to recognize familiar faces or even a part of their own body. There can be neglect of one side of the vision, body or environment, making it hard to move around without bumping into things. Fortunately, many patients can improve with neurocognitive rehabilitation.