Ophthalmology is a medical science that is concerned with the maintenance of vision and the diagnosis and treatment of diseases of the eye. The eye is composed of several parts that work together to produce vision.

What are the parts of the eye and how do they work?

Next to the brain, the eye is perhaps the second most complex organ in the body. Its primary function is to convert light into images, much like a camera takes pictures. And just like a camera, the eye has several essential parts.

Lens system: the eye has a two-part lens system that focuses light into the eye in order to produce sharp images. This lens system consists of the cornea (60%) and the lens (40%).

Pupil: this is similar to the aperture of the camera-it limits the amount of light entering the eye so that we do not get too much light or glare.

Vitreous: a transparent gel.

Retina: a thin transparent tissue that functions as the "film" or "movie screen" of the eye. Light falling on the retina is converted to electrical energy and sent to the brain for form images.

Optic Nerve: a long cord of nervous tissue connecting the eye to the brain. It is like the cable that connects the VHS player to the television. When this is damaged, the image quality also suffers.

How does an ophthalmologist differ from an optometrist or an optician?

An ophthalmologist is a fully trained medical doctor who has undergone at least three years of special training in the recognition and treatment of eye diseases. The ophthalmologist performs eye surgery, laser treatment, and prescribes eye medicines and eyeglasses or contact lenses. An optometrist is a specialist trained to measure the grade of glasses and contact lenses that a patient needs to maximize his vision, while an optician is trained to manufacture and repair spectacles or glasses.

What kinds of diseases commonly afflict the eye?

A. Error of refraction

Error of refraction is a condition where a person needs eyeglasses or spectacle correction in order to see clearly. Normally, light entering the eye is focused on a sort of "movie screen" called the retina. When the light is not focused on this screen, there is an error of refraction causing blurred vision. Eyeglasses and contact lenses are used to focus it on the screen.

There are four kinds of error of refraction:

1) MYOPIA (near-sightedness): near things are clear while far things are blurred;

2) HYPEROPIA (far-sightedness): far things are clear while near things are blurred;

3) ASTIGMATISM: both near and far things are unclear because light is split into two planes;

4) PRESBYOPIA: inability to focus easily on near things without the aid of reading glasses as a result of stiffening of the natural lens of the eye; this usually begins at the age of 40.

B. Cataract

The natural lens of the eye is normally transparent to allow passage of the light into the eye. When a cataract develops, the lens become thicker and opaque, blocking entry of light into the eye. People with cataracts complain of cloudy or smoky vision, glare, poor vision, and whiteness in the center of the eye. The needle uses ultrasonic energy to dissolve the cataract and then sucks out the material. At the end of the procedure, an intraocular lens (IOL) is inserted into the eye in place of the natural lens. The IOL is made of a special hypoallergenic plastic and provides focusing power for the eye. Cataract surgery is the most successful surgery known to mankind with a 99% chance of improving vision.

C. Floaters and Flashes

Many people complain of flashes of light or floaters. These complaints result from movement of the gel inside the eye call the vitreous gel. Normally this gel is adherent to the "movie screen" inside the eye called the retina where images are formed. With aging or injury, this gel may separate from the retina causing pulling of the retina. This stimulates the retina resulting in the perception of light flashes. Occasionally, a small piece of retina may be pulled off leading to floaters. While neither of these two conditions are dangerous, sometimes, a large piece of retina is pulled off the retina or the retina is torn. This defect in the retina may allow fluid to get behind the retina causing detachment of the retina. Retinal detachment will manifest with blurred vision usually described as a "dark curtain" in the field of vision. It may lead to permanent loss of vision and requires immediate repair through surgery. Because of this potentially devastating complication, it is important to have the eye examined by the eye doctor for any holes or tears when a person experiences flashes or floaters. If any holes or tears are present, laser therapy may seal the hole and prevent detachment of the retina.

D. Dry Eye

Dry eye affects a large number of people especially over the age of 40. it is more common in dry or hot environments and is thought to be caused by decreased amount or quality of tears. Occasionally, dry eyes can cause damage to the cornea leading to deceased vision. The most common symptom is eye discomfort or stinging with eye redness, which is worse at the end of the day or with prolonged reading or watching television or computer work. The ophthalmologist can measure the amount of tears and check the cornea for damage. Treatment usually involves artificial tear eye drops, drinking more water and changing the environment. If this is not satisfactory, the eye doctor can plug the drainage system of the eye in order to increase the amount of tears remaining in the eye.

E. Allergy

Itchiness is the main symptom of allergy of the eye. Swelling of the eyelids, eye redness and discharge, and darkening of the skin under the eyes are other signs of eye allergy. Allergy results when the eye is sensitive to and comes in contact with substances in the environment (allergens). Common allergens include dust, smoke, pollen, bee stings and perfumes. The most important way of treating allergies is AVOIDANCE of the allergens. Depending on the severity of the allergy, the eye doctor may prescribe anti-histaminic eye drops or pills to prevent the allergic reaction of the eye. You may also use cold compress to obtain relief. DO NOT rub the eyes as this just makes the eye more irritable and itchy.

F. Glaucoma

Glaucoma is a most dreaded eye disease. In this condition, the pressure of the eye is high, much like an overinflated tire. This high pressure causes damage to the optic nerve. This nerve connects the eye to the brain and when it is damaged, vision deteriorates. In the beginning, there are only small patches of vision that are lost but later big areas or blind spots occur. The optic nerve may start to look damaged and excavated with loss of the normal tissue from glaucoma. For the most patients, glaucoma is symptomless until blurring of vision occurs however, for a few patients, there may be a sudden increase in pressure causing severe eye pain (acute glaucoma). This is an emergency. Glaucoma may be detected in a regular eye examination-the pressure of the eye is measured (just like the pressure of the tires in your car), the optic nerve is examined for damage. Sophisticated computers (perimetry) may also check the eye for patches of lost vision. Early detection and treatment can prevent loss of vision. Early detection and treatment can prevent loss of vision and preserve good vision. Treatment is usually by means of eye drops that lower the pressure of the eyes. These eye drops are usually used for life. Sometimes laser treatment or surgery may be necessary to improve the drainage of fluid from inside the eyes in order to lower the pressure. This is done in cases where eye drops do not work well. It is important to have regular eye exams to determine whether the pressure of the eyes is kept low.

Picture of glaucomatous disk and visual field

G. Macular Degeneration

This is the number one cause of permanently poor vision in elderly patients. In macular degeneration, the "movie screen" in the back of the eye, called the retina, starts to decay and deteriorate. This results in blurring of central vision. A person has a higher risk for this disease when he or she is above the age of 65 and when that person has a strong history of smoking. Some researchers have reported that certain vitamins and minerals may prevent macular generation.

There are two types of macular degeneration: the dry type that has no cure and the wet type that can be treated with laser. In the wet-type, there are abnormal blood vessels in the retina that cause leakage of blood or fluid under the retina leading to blurred vision. Laser treatment of these abnormal blood vessels may help limit the damage and preserve vision. Experimental eye surgeries are also being tried.

H. Diabetic Retinopathy

Patients with diabetes mellitus or high blood sugar may have damaged retinas. The high blood sugar affects the small blood vessels inside the eye that carry nutrients and oxygen to the eye tissues. When a person has been diabetic for more than 5-10 years, some of these blood vessels may become occluded or may leak or may bleed. The ensuing lack of oxygen, spillage of blood, and swelling of the retina leads to diminished vision. Good control of blood sugar may prevent or delay retinal damage.

When the retinopathy is early, laser treatment may be performed in order to decrease the oxygen lack of the eye and prevent blood vessels from leaking. Usually, a flourescein angiogram is done before laser treatment. In this test, a yellow dye is injected into a vein in the arm or hand. This dye travels to the blood vessels of the eye. A camera is used to take pictures of the dye in order to have a permanent record of the findings. These pictures show which areas of the retina are damaged and are in need of treatment.

When the retinopathy is advanced, a lot of bleeding may occur. A type of glaucoma called neovascular glaucoma may also develop and may lead to permanent blindness. Surgery may be done to remove the blood and other debris from the eye.

I. Obstruction of Retinal Blood Vessels

People with high blood pressure, diabetes, and large amounts of fat in their blood vessels are prone to developing blockage of blood flow. When this happens to the retinal blood vessels, there is a rapidly progressing blurring of vision. There are several types. In central arterial obstruction, the blood vessel carrying oxygen to the eye is blocked. This is an emergency that must be treated right away (minutes) in order to prevent permanent blindness. First aid measure includes breathing through a paper bag. The eye doctor will try to relieve obstruction to bring blood back into the eye.

In central venous occlusion or in branch venous occlusion, all or some of the blood vessels that bring blood out of the eye and back to the heart are occluded. As a result, a traffic jam occurs-these blood vessels then bleed and leak causing blurred vision. In most cases, there is a partial recovery of vision. However, some patients will develop neovascular glaucoma and laser treatment will have to be done. The best prevention for this condition is to control blood, blood sugar, watch the diet, and to stop smoking.

J. Strabismus or Squint

Children and adults may manifest a squint or misalignment of the eyes or what is commonly know as cross-eyed. Usually, the misalignment is horizontal; the eye may deviate inwards towards nose (duling) or outwards towards the ears (banlag). Occasionally, the eye may deviate upwards or downwards. There are many causes of this condition. A severe error of refraction may cause cross-eyedness. This is treated with eyeglasses and patching or occlusion of one eye to force the other eye to work.

The brain, acting through 6 muscles connected to the eye, controls the movement of the eyes. When there is an imbalance of muscle pull, the eyes may deviate. Sometimes, surgery on these muscles may be necessary in order to realign them.

What are lasers used for?

Lasers have many applications in ophthalmology. There are several types of lasers and each has a different role in the treatment of the eye disease:

A. Argon:

A photocoagulative laser used to burn tissues. It is useful in the treatment of many vascular disorders such as diabetes mellitus. Argon lasers are also used to seal holes or breaks as part of the prevention or treatment of retinal detachment.

B. YAG (Yttrium-Argon-Garnet):

A photodisruptive laser used to create a mini-explosive effect in tissues. It is used to create drainage holes in glaucoma patients or to make small holes in the treatment of after-cataracts (a membrane that forms after cataract surgery).

C. Excimer: Stands for Excited Dimer.

It is a photoablataive laser that vaporizes tissues. Its primary use is to reshape the cornea in order to change the refraction of the eye and reduce or eliminate the need of glasses and contact lenses.

Are there vitamins or food that are good for my eye?

Yes. For the eye to function well, it needs a regular supply of Vitamin A. Vitamin A rich foods include carrots, squash, and cod liver oil. Vitamin C and E are believed by some researchers to prevent or slow down the rate of cataract formation. Citrus foods are good sources for Vitamin C. Recently, scientists have become interested in carotenoids, particularly lutien and zeaxanthin. They believe that these two pigments may protect the eyes against macular degeneration. Spinach and kale are vegetables with high amounts of these substances.

How often should I see my ophthalmologist?

Since most eye manifest in the elderly, people over 50 years old should have their eye checked annually. Diabetics and glaucoma patients may need more frequent eye exams. Children with squint or leaning problems should have immediate eye exam. If a young child is wearing spectacles, this should be checked every 3-6 months. For young healthy individuals, an eye exam every 5 years is recommended. Otherwise an eye doctor should be seen when unusual symptoms arise.

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