Neuro-Ophthalmology...

What is Neuro-ophthAEC Neoralmology?

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.

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

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.