Nearsightedness

Nearsightedness (myopia)

 

Definition

Nearsightedness (myopia) is a common vision condition in which you can see objects near to you clearly, but objects farther away are blurry.

The degree of your nearsightedness determines your ability to focus on distant objects. People with severe nearsightedness can see clearly only objects just a few inches away, while those with mild nearsightedness may clearly see objects several yards away.

Nearsightedness may develop gradually or rapidly, often worsening during childhood and adolescence. Nearsightedness tends to run in families.

A basic eye exam can confirm nearsightedness. You can easily correct the condition with eyeglasses or contact lenses. Another treatment option for nearsightedness is surgery.

Causes

Nearsightedness is a type of refractive error. That means you can't see clearly because the light that enters your eye doesn't bend (refract) properly.

Normal vision

To focus the images it sees, your eye relies on two critical parts:

• the cornea, the clear front surface of your eye;
• the lens, a clear structure inside your eye that changes shape to help focus objects.

In a perfectly shaped eye, each of these focusing elements has a perfectly smooth curvature like the surface of a rubber ball. A cornea and lens with such curvature bend (refract) all incoming light in such a way as to make a sharply focused image on the retina, at the back of your eye.

A refractive error

However, if your cornea or lens isn't evenly and smoothly curved, light rays aren't refracted properly, and you have a refractive error. Nearsightedness is one type of refractive error. Nearsightedness can occur when your cornea is curved too much or when your eye is longer than normal. Instead of being focused precisely on your retina, light is focused in front of your retina, resulting in a blurry appearance for distant objects.

Other refractive errors

In addition to nearsightedness, other refractive errors include:

• farsightedness (hyperopia). This occurs when your cornea is curved too little or your eye is shorter from front to back than normal. The effect is the opposite of nearsightedness. Light is focused beyond the back of your eye, making nearby objects blurry. You're usually able to see faraway objects clearly.
• astigmatism. This occurs when your cornea is curved more steeply in one direction than in another. Uncorrected astigmatism blurs your vision. Typically, the images you see will be blurred more in one direction than another. For example, horizontal images may be more out of focus than are vertical or diagonal images.

Risk factors

Certain risk factors increase the risk of developing nearsightedness, such as:

Family history. Nearsightedness tends to run in families. If one of your parents is nearsighted, your risk of developing nearsightedness is increased. The risk is even higher if both parents are nearsighted.

Premature birth. Babies born prematurely are more likely to have eye conditions that can affect the shape of the eyes, increasing the risk of nearsightedness.

Close work. Some studies have shown that there is an increased incidence of nearsightedness among people who do a lot of reading or other close work.

Complications

Nearsightedness may be associated with several complications, such as:

- reduced quality of life. Uncorrected nearsightedness can affect your quality of life. You might not be able to perform a task as well as you wish, and your limited vision may detract from your enjoyment of day-to-day activities.

- eyestrain. Squinting to see in the distance can cause eyestrain and headaches.

- impaired safety. For your own safety and that of others, don't drive or operate heavy equipment if you have an uncorrected vision problem.

- glaucoma. Severe nearsightedness increases your risk of developing glaucoma, a potentially serious eye disease.

- retinal tear and detachment. If you're significantly nearsighted, it's possible that the retina of your eye is thin. The thinner your retina, the higher your risk of developing a retinal tear or retinal detachment. If you experience a sudden onset of flashes, floaters or a dark curtain or shadow across part of your eye, seek medical assistance immediately. Retinal detachment is a medical emergency, and time is critical. Unless the detached retina is promptly surgically reattached, this condition can cause permanent loss of vision in the affected eye.

Prevention

Although a number of scientific attempts have been made to halt or slow the progression of nearsightedness, there are no proven ways to prevent the condition from occurring or progressing.

Lifestyle and home remedies

Although you can't prevent nearsightedness, you can help protect your eyes and your vision. Follow these steps:

- have your eyes checked. Regardless of how well you see, have your eyes checked regularly for problems.

- control chronic health conditions. Certain conditions, such as diabetes and high blood pressure, can affect your vision if you don't receive proper treatment.

- recognize symptoms. Sudden loss of vision in one eye, sudden hazy or blurred vision, flashes of light, black spots, or halos or rainbows around lights may signal a serious eye problem, such as a retinal tear or detachment, requiring urgent medical attention. Similar symptoms can be caused by other serious medical problems, such as acute glaucoma or a stroke. Talk to your doctor immediately if you experience any of these symptoms.

- protect your eyes from the sun. Wear sunglasses that block both ultraviolet A (UVA) and ultraviolet B (UVB) radiation. This is especially important if you spend long hours in the sun or are taking a prescription medication that increases your sensitivity to UV radiation.

- eat healthy foods. Maintain a healthy diet that includes plenty of fruits and vegetables, which have shown to enhance eye health. Try foods that contain vitamin A and beta carotene, such as carrots. Dark leafy greens and fish also may be especially helpful for good eye health.

- don't smoke. Just as smoking isn't good for the rest of your body, it can affect your eye health as well.

- use the right glasses. The right glasses optimize your vision. Having regular exams will ensure that your eyeglass prescription is correct.

- use good lighting. Use adequate light for optimal vision.

 

By Mayo Clinic staff

 

 

Information from website: http://www.mayoclinic.com/health/nearsightedness/DS00528