What Is Astigmatism?
Astigmatism is an imperfection in the curvature of your cornea — the clear, round dome covering the eye’s iris and pupil — or in the shape of the eye’s lens. Normally, the cornea and lens are smooth and curved equally in all directions, helping to focus light rays sharply onto the retina at the back of your eye. However, if your cornea or lens isn’t smooth and evenly curved, light rays aren’t refracted properly. This is called a refractive error.
When the cornea has an irregular shape, it is called corneal astigmatism. When the shape of the lens is distorted, you have lenticular astigmatism. As a result of either type of astigmatism, your vision for both near and far objects appears blurry or distorted. It’s almost like looking into a fun house mirror in which you appear too tall, too wide or too thin.
People can be born with astigmatism — in fact, most people probably are born with some degree of astigmatism — and they may have it along with other refractive errors: nearsightedness (myopia) or farsightedness (hyperopia).
While adults with a higher degree of astigmatism may realize their vision isn’t as good as it should be, children who have astigmatism symptoms may not be aware they have this condition, and are unlikely to complain about blurred or distorted vision. But uncorrected astigmatism can seriously impact a child’s ability to achieve in school and sports. And some forms of astigmatism can be a sign of keratoconus, a cone-like bulge of the cornea, which can distort vision. That’s why it is crucial that children have regular eye exams to detect astigmatism or other vision problems as early as possible.
Farsightedness: What Is Hyperopia?
Hyperopia (farsightedness), is a refractive error, which means that the eye does not bend or refract light properly to a single focus to see images clearly. In hyperopia, distant objects look somewhat clear, but close objects appear more blurred.
People experience hyperopia differently. Some people may not notice any problems with their vision, especially when they are young. For people with significant hyperopia, vision can be blurry for objects at any distance, near or far. It is an eye focusing disorder, not an eye disease.
Nearsightedness: What Is Myopia?
Myopia, or nearsightedness, is a refractive error, which means that the eye does not bend or refract light properly to a single focus to see images clearly. In myopia, close objects look clear but distant objects appear blurred. Myopia is a common condition that affects an estimated 25 percent of Americans. It is an eye focusing disorder, not an eye disease.
Myopia in children
Myopia is inherited and is often discovered in children when they are between ages eight and 12 years old. During the teenage years, when the body grows rapidly, myopia may become worse. Between the ages of 20 and 40, there is usually little change. Myopia can also occur in adults.
If the myopia is mild, it is called low myopia. Severe myopia is known as high myopia. High myopia will usually stabilize between the ages of 20-30 years old. With high myopia, you can usually correct vision easily with glasses, contact lenses or sometimes with refractive surgery.
Patients with myopia have a higher risk of developing a detached retina. Ask your ophthalmologist (Eye M.D.) to discuss the warning signs of retinal detachment with you if you are in this risk category. If the retina does detach and it is discovered early enough, a surgical procedure can usually repair it. It is important to have regular eye examinations by an ophthalmologist to watch for changes in the retina that might lead to retinal detachment.
People with high myopia may also have a higher than average risk of developing glaucoma and cataracts.
What Is Presbyopia?
Presbyopia (which literally means “aging eye”) is an age-related eye condition that makes it more difficult to see very close.
When you are young, the lens in your eye is soft and flexible. The lens of the eye changes its shape easily, allowing you to focus on objects both close and far away.
After the age of 40, the lens becomes more rigid. Because the lens can’t change shape as easily as it once did, it is more difficult to read at close range. This normal condition is called presbyopia.
Since nearly everyone develops presbyopia, if a person also has myopia (nearsightedness), hyperopia (farsightedness) or astigmatism, the conditions will combine. People with myopia may have fewer problems with presbyopia.
What Is Blepharitis?
Blepharitis is a common and ongoing condition where the eyelids become inflamed (swollen), with oily particles and bacteria coating the eyelid margin near the base of the eyelashes. This annoying condition causes irritation, itchiness, redness, and stinging or burning of the eyes. While the underlying causes of blepharitis aren’t completely understood, it can be associated with a bacterial eye infection, symptoms of dry eyes or certain types of skin conditions such as acne rosacea.
Anterior blepharitis affects the outside of the eyelid where your eyelashes are attached. This can be caused by bacterial (or sometimes viral) infection. If left untreated, anterior blepharitis can lead to thickened and inward-turned or outward-turned eyelids and even vision problems from in-turned eyelashes damaging the cornea.
Posterior blepharitis is a condition that results from a dysfunction of the eye’s tiny oil glands (meibomian glands) in the eyelids at the base of the eyelashes. When meibomian glands become clogged from posterior blepharitis, it can also can cause a stye or chalazion to form. Posterior blepharitis also leads to thickened eyelid margins and crusty eyelids. With this type of blepharitis, tears can even look foamy.
Many people have both anterior and posterior blepharitis at the same time in varying degrees.
Rosacea blepharitis is associated with ocular rosacea, a condition that causes eyelid swelling and redness due to malfunctioning oil glands. Acne rosacea is a common skin condition that leads to pimple-like bumps and facial redness.
What Is Dry Eye?
When you blink, a film of tears spreads over the eye, making the surface of the eye smooth and clear. Without this tear film, good vision would not be possible.
Sometimes people don’t produce enough tears or the right quality of tears to keep their eyes healthy and comfortable. This condition is known as dry eye.
The tear film consists of three layers:
- An oily layer;
- A watery layer;
- A layer of mucus.
Each layer has its own purpose. The oily layer, produced by the meibomian glands, forms the outermost surface of the tear film. Its main purpose is to smooth the tear surface and reduce evaporation of tears.
The middle watery layer makes up most of what we ordinarily think of as tears. This layer, produced by the lacrimal glands in the eyelids, cleanses the eye and washes away foreign particles or irritants.
The inner layer consists of mucus produced by the conjunctiva. Mucus allows the watery layer to spread evenly over the surface of the eye and helps the eye remain moist. Without mucus, tears would not stick to the eye.
Normally, the eye constantly bathes itself in tears. By producing tears at a slow and steady rate, the eye stays moist and comfortable.
The eye uses two different methods to produce tears. It can make tears at a slow, steady rate to maintain normal eye lubrication. It can also produce a lot of tears in response to eye irritation or emotion. When a foreign body or dryness irritates the eye, or when a person cries, excessive tearing occurs.
It may not sound logical that dry eye would cause excess tearing, but think of it as the eye’s response to discomfort. If the tears responsible for maintaining lubrication do not keep the eye wet enough, the eye becomes irritated. Eye irritation prompts the gland that makes tears (called the lacrimal gland) to release a large volume of tears, overwhelming the tear drainage system. These excess tears then overflow from your eye.
What Is a Pinguecula and a Pterygium (Surfer’s Eye)?
Pterygium (pronounced tur-IJ-ee-um) and pinguecula (pronounced pin- GWEK-yoo-la) are growths on the cornea (the clear front window of the eye) and the conjunctiva — the thin, filmy membrane that covers the white part of your eye (sclera). Both growths are noncancerous and are fairly common.
A pinguecula is a yellowish patch or bump on the conjunctiva, near the cornea. It most often appears on the side of the eye closest to the nose. It is a change in the normal tissue that results in a deposit of protein, fat and/or calcium. It is similar to a callus on the skin.
A pterygium (also known as surfer’s eye or farmer’s eye) is a triangular-shaped growth of fleshy tissue on the white of the eye that eventually extends over the cornea. This growth may remain small or grow large enough to interfere with vision. A pterygium can often develop from a pinguecula.
Some pterygia may become red and swollen on occasion, and some may become large or thick, making you feel like you have something in your eye. If a pterygium is large enough, it can actually affect the shape of the cornea’s surface, leading to astigmatism.
It is not entirely clear what causes pterygia and pingueculae to develop. Ultraviolet (UV) light from the sun is believed to be a factor in the development of these growths. Other factors believed to cause pterygia and pingueculae are dry eye and environmental elements such as wind and dust.