Astigmatism? A stigmatism? An astigmatism? Which is correct, and what exactly is this odd-sounding eye condition?
You might have heard your eye doctor tell you you have astigmatism in one or both eyes, and he or she may have prescribed a specific kind of contact lens to help. But what does that all mean for you and your vision? The cornea of your eye is shaped like a rounded dome on the surface of your eye. When the curve of the cornea is perfect, it focuses light on your retina, and crisp, clear vision results.
But when there are irregularities in the shape of the cornea or the lens, that eye has astigmatism. Instead of being rounded, like a basketball, the cornea’s surface is shaped more like an egg or football. This means the eye can’t focus light evenly on the retina. Because the retina is the part of our vision that is sensitive to light, when you have astigmatism, anything in your field of view appears out of focus, blurry or distorted.
“Vision without a point”
Astigmatism is an eye condition, and doesn’t need the article “an” before it. Just like saying, “I have nearsightedness,” we say an eye has astigmatism, rather than an astigmatism.
Where does this term come from? It’s Greek in origin. The prefix “a” means “without.” “Stigma” means “point” in Greek, so the term means “vision without a point,” since the shape of the eye doesn’t allow light to meet at a single point.
Causes and symptoms of astigmatism
Astigmatism is both common and hereditary, and most people who have it are born with it, although some might develop it after eye surgery or eye injury.
The amount of astigmatism can increase or decrease throughout your life, and depending on how severe it is, you might not even know you have it.
You can experience astigmatism as a number of vision problems, including blurred or distorted vision at any distance, poor night vision, double vision, or squinting.
Types of astigmatism
Not all astigmatism is the same. There are three common classifications: myopic, hyperopic and mixed, and to understand what each of those mean, we need to know about meridians of the eye.
Think about the center of the pupil as a pole, then imagine horizontal and vertical lines around the eyeball that intersect at either end of the pole (the posterior and anterior). Those are the meridians of the eye. The steepest and flattest meridians are called principal meridians, and the amount of astigmatism has to do with the refracting power (how well they focus light) of the two principal meridians.
- Myopic astigmatism means the principal meridians of the eye are nearsighted.
- Hyperopic astigmatism means the principal meridians are farsighted.
- Mixed astigmatism occurs when the principal meridians are both nearsighted and farsighted.
Vision correction options
Eyeglasses, contact lenses, and sometimes LASIK surgery or other types of refractive surgery are used to correct astigmatism.
Talk with your eye doctor about the best options for you. If you prefer contact lenses, soft contact lenses usually don’t do enough to correct astigmatism symptoms. Your doctor will prescribe what are called toric contact lenses or gas permeable contacts. Both can compensate for the cornea’s irregular shape and help you find visual comfort.
Do you have blurry, out-of-focus vision or other symptoms of astigmatism? We can help! Contact us to schedule your next eye exam today.