Nearsightedness

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

Symptoms of nearsightedness

Nearsightedness symptoms may include:

• Blurry vision when looking at distant objects
• The need to squint or partially close the eyelids to see clearly
• Headaches caused by eyestrain
• Difficulty seeing while driving a vehicle, especially at night (night myopia)

Nearsightedness is often first detected during childhood and is commonly diagnosed between the early school years through the teens.

A child with nearsightedness may:

• Persistently squint
• Need to sit closer to the television, movie screen or the front of the classroom
• Seem to be unaware of distant objects
• Blink excessively
• Rub his or her eyes frequently

Causes of nearsightedness

Nearsightedness usually occurs when your eye is too long or has a cornea that's curved too steeply. This causes the light rays entering each eye to focus in front of the retina, instead of on the retina, leading to blurry images. The exact reason for some people developing longer eyes is unknown, but it may be related to genetics or environmental conditions.

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 crystalline lens, a clear structure inside your eye that changes shape to help focus objects

In a normally shaped eye, each of these focusing elements has a perfectly smooth curvature like the surface of a smooth 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.

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. Instead of being focused precisely on your retina, light is focused in front of your retina, resulting in a blurry appearance of 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. In adults, both near and distant objects are blurred.
• Astigmatism
  This occurs when your cornea or lens is curved more steeply in one direction than in another. Uncorrected astigmatism blurs your vision.

Risk factors for nearsightedness

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

• Family history
  Nearsightedness tends to run in families. If one of your parents is nearsighted, your risk of developing the condition is increased. The risk is even higher if both parents are nearsighted.
• Reading
  People who do a lot of reading may be at increased risk of myopia.
• Environmental conditions
  Some studies support the idea that a lack of time spent outdoors may increase the chances of developing myopia.

Complications of nearsightedness

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
  Uncorrected nearsightedness may cause you to squint or strain your eyes to maintain focus. This can lead to eyestrain and headaches.
• Impaired safety
  Your own safety and that of others may be jeopardized if you have an uncorrected vision problem. This could be especially serious if you are driving a car or operating heavy equipment.
• Other eye problems
  Severe nearsightedness puts you at a slightly increased risk of retinal detachment, glaucoma and cataracts.