Q. What is Neuro-ophthalmology?

A. If the human eye works like a camera, we can imagine that the "processing of the film" into what we see as the visual image is transmitted by the optic nerves from the globe, to the visual pathways in the brain and finally to the visual processing centers in the back part of the brain. This is the realm of a Neuro-ophthalmologist, i.e., an eye specialist with special interest in the eye manifestations of diseases or injuries of the optic nerves and visual pathways (everything behind the globe involved in the visual process). Included in this field are brain pathways and processes involved in the control of eye muscles and movements. Several neuro-ophthalmic symptoms are also manifestations of systemic conditions like hypertension, diabetes, stroke, cardiovascular diseases, multiple sclerosis, and brain tumor.

Q. What are some specific conditions typically managed by a Neuro -ophthalmologist?

A. Some common neuro-ophthalmic conditions affecting vision include optic neuritis and toxic optic neuropathy from intake of anti-TB medications; while examples of those affecting eye movements are cranial nerve strokes and thyroid disease. Patients with eye problems secondary to brain tumors or strokes, as well as migraines are also commonly seen in the neuro-ophthalmologist's clinic.

 Optic Neuritis

 Optic neuritis is an inflammatory condition of one or both optic nerves causing decreased vision, accompanied by changes in color perception and contrast sensitivity. These symptoms are usually rapid and progress in days, ranging from mild to severe, and usually accompanied by eye pain or pain on eye movement. In temperate countries, optic neuritis is commonly associated with a neurologic condition called multiple sclerosis. In the Philippines, a vast majority of cases have no identifiable cause. On a case to case basis, intravenous steroid therapy may be beneficial in some patients.

 Toxic Optic Neuropathy from anti-TB medication intake

 Tuberculosis is still a major problem in a developing country like the Philippines. Especially in rural areas, triple or quadruple anti-tuberculosis medications are rampantly prescribed, with poor compliance in many cases leading to over or under-medication. Unfortunately, some of these drugs, most notably Ethambutol and Isoniazid have a propensity for causing toxicity to the optic nerves. As with many optic nerve conditions, some damage caused by these drugs may be irreversible and some permanent loss of vision or color perception persists despite discontinuation of medication intake. This does not suggest that patients stay away from these drugs at all. The systemic benefits of these drugs in patients with tuberculosis are foremost. Ideally however, patients who are about to start anti-TB medications should visit an ophthalmologist who will take baseline measurements of vision. These tests are repeated every 1-2 months to watch out for the earliest signs of toxicity so that adequate measures can be taken by the ophthalmologist when needed.

 Double vision from "muscle imbalance"

 (a) Cranial Nerve Stroke
One or more muscles controlling eye movements may occasionally be weakened by an infarction of the corresponding nerve. The resulting muscle imbalance may lead to symptoms like double vision and drooping of the eyelid. Most cases are benign and are caused by systemic conditions like diabetes and hypertension. They usually resolve spontaneously in 3-12 months without any treatment. Some may be caused by more innocuous conditions (see below).



 (b) Thyroid Disease
Thyroid disease can manifest in the eye with or without the clinical presence of hyperthyroidism. Some symptoms include proptosis ("eyeballs seem to pop out of sockets"), double vision, eyelid retraction ("frightened appearance"), red/congested eyes, and blurred vision. Depending on the severity of symptoms, a wide range of treatment options are available and can range from plain medical therapy to surgical procedures.

 Strokes and Brain Tumors

 As vast areas of the brain are involved in the overall function of the visual system, injuries from strokes or brain tumors affect vision and eye movements in various ways depending on the extent and location of the lesion. These include loss of vision (often described as loss of a particular field of vision, say, peripheral areas or one-half of field), and "muscle imbalance" with inability to move the eye to a particular position, causing double vision. Several post-stroke patients may also have visual perception difficulties, meaning the visual pathway may be intact, but the processing of the information is affected (the patient may not "understand' what he sees). Occasionally, patients with neuro-ophthalmic signs and symptoms from brain tumors are first seen by the ophthalmologist who makes the crucial initial detection and subsequent referral to a neurosurgeon. Ideally, the neuro-ophthalmologist, neurologist, and neurosurgeon should all be involved in the long term management and care of these patients (as well as in many other neuro-ophthalmic conditions).

 Migraine/Headache

 There are many misconceptions about migraine. First, migraine is NOT headache, as what many people perceive. We often hear people with headaches as saying "I have a migraine". In fact, around 90% of headaches are NOT migraine at all, and are just "stress headaches", often described as a vice- like grip or dullness around the forehead, nape, or neck area. True migraine on the other hand, is a distinct clinical entity with many symptoms, of which headache may or may not be one. (There are in fact migraine subtypes presenting with all other symptoms of the condition EXCEPT headache). Symptoms of classic migraine include headache, nausea, vomiting, light sensitivity (patients having an attack would prefer to stay quietly in a dark room) and blurred vision. Many patients present with an "aura" a few minutes before a migraine attack (impending) associated with lightheadedness, and visual hallucinations (so called visual aura, scintillating scotoma, or fortification spectra) described as zigzagged colored lights appearing and disappearing in a clockwise pattern. Attacks usually last 30minutes to an hour and are brought upon by certain "trigger" factors like food (caffeine, MSG, cheese, etc). Some types of migraines like "cluster headaches" typically present with severe one-sided headache lasting for hours, occurring successively in days or weeks, and recurring in clusters. They may also present with one-sided eye redness/tearing and sinus congestion.

 The ophthalmologist, often the first specialist a patient with headache/migraine sees (the patient assuming that the headache is caused by an eye problem), plays a very important role in the management of these conditions. Your ophthalmologist will examine you and perform tests to rule out the eyes as the source of the headache. Often, a Neurology and ENT consult may also be requested to rule out these areas as potential culprits causing the headache. In many patients, the simple avoidance of trigger factors and biofeedback techniques are enough to reduce or eliminate migraine attacks. Some patients do require medications, often starting out with over-the-counter analgesics like Mefenamic Acid and Paracetamol. Specific migraine medications are not over-the-counter drugs and can have potentially unwarranted side effects. Treatment options with these drugs are varied and complex, such that these should be discussed with your doctor.