Common Vision Problems

What is Myopia or Nearsightedness?

Nearsightedness, or myopia, is a vision condition in which close objects are seen clearly, but objects farther away appear blurred. Myopia occurs when the eyeball is too long or the cornea, the clear front cover of the eye, has too much curvature. As a result, light entering the eye isn’t focused correctly, causing distant objects to appear blurred.

Nearsightedness is a very common vision condition, affecting nearly 30 percent of the U.S. population. Some research supports the theory that myopia is hereditary, but there is also growing evidence that it can be influenced by visual stress from too much close work.

Typically, myopia first appears in school-age children. Since the eye continues to grow during childhood, myopia usually progresses until around age 20. However, it can also develop in adults due to visual stress or health conditions such as diabetes.

A common sign of myopia is difficulty seeing distant objects clearly, such as a movie or TV screen or the chalkboard in school. A comprehensive eye examination will include testing for myopia. An optometrist can prescribe eyeglasses or contact lenses that correct myopia by bending the visual images that enter the eyes, ensuring they are focused correctly at the back of the eye. Depending on the degree of myopia, you may only need to wear glasses or contact lenses for certain activities, like watching a movie or driving. However, if you are very nearsighted, they may need to be worn all the time.

What Causes Nearsightedness?

The exact cause of myopia is unknown, but two factors are primarily believed to contribute to its development:

Heredity: There is significant evidence that many people inherit myopia, or at least the tendency to develop it. If one or both parents are nearsighted, there is an increased chance their children will be nearsighted as well.
Visual Stress: Even though the tendency to develop myopia may be inherited, its actual development may be influenced by how a person uses their eyes. Individuals who spend considerable time reading, working at a computer, or doing other close visual work may be more likely to develop nearsightedness.

Myopia may also occur due to environmental factors or other health problems:

Some people may experience blurred distance vision only at night, a condition known as “night myopia.” This may be due to low light levels making it difficult for the eyes to focus properly, or the increased pupil size during dark conditions allowing more peripheral, unfocused light rays to enter the eye.
Individuals who engage in excessive near vision work may experience a false or “pseudo” myopia. Their blurred distance vision is caused by overuse of the eyes’ focusing mechanism. After long periods of near work, their eyes may struggle to refocus for clear distance vision. While the symptoms are usually temporary, continuous visual stress may lead to a permanent reduction in distance vision.
Symptoms of myopia can also be a sign of variations in blood sugar levels in people with diabetes or an early indication of a developing cataract.

What is Astigmatism?

Astigmatism is a vision condition that causes blurred vision due to either the irregular shape of the cornea, the clear front cover of the eye, or sometimes the curvature of the lens inside the eye. An irregularly shaped cornea or lens prevents light from focusing properly on the retina, the light-sensitive surface at the back of the eye. As a result, vision becomes blurred at any distance.

Astigmatism is a very common vision condition. Most people have some degree of astigmatism. Slight amounts of astigmatism usually don't affect vision and don't require treatment. However, larger amounts can cause distorted or blurred vision, eye discomfort, and headaches.

Astigmatism frequently occurs with other vision conditions like nearsightedness (myopia) and farsightedness (hyperopia). Together, these vision conditions are referred to as refractive errors because they affect how the eyes bend or "refract" light.

The specific cause of astigmatism is unknown. It can be hereditary and is usually present from birth. It can change as a child grows and may decrease or worsen over time.

A comprehensive optometric examination will include testing for astigmatism. Depending on the degree of astigmatism present, your optometrist can provide eyeglasses or contact lenses that correct the condition by altering the way light enters your eyes.

Another option for treating astigmatism involves a corneal modification procedure called orthokeratology (ortho-k). It is a painless, non-invasive procedure that involves wearing a series of specially designed rigid contact lenses to gradually reshape the curvature of the cornea.

Laser surgery is also a possible treatment option for some types of astigmatism. It changes the shape of the cornea by removing a small amount of eye tissue using a highly focused laser beam on the surface of the eye.

What Causes Astigmatism?

Astigmatism occurs due to the irregular shape of the cornea or the lens inside the eye. The cornea and lens are primarily responsible for properly focusing light entering your eyes, allowing you to see things clearly.

The curvature of the cornea and lens causes light entering the eye to be bent in order to focus it precisely on the retina at the back of the eye. In astigmatism, the surface of the cornea or lens has a somewhat different curvature in one direction than another. In the case of the cornea, instead of having a round shape like a basketball, the surface of the cornea is more like a football. As a result, the eye is unable to focus light rays to a single point, causing vision to be out of focus at any distance.

Sometimes astigmatism may develop following an eye injury or eye surgery. There is also a relatively rare condition called keratoconus, where the cornea becomes progressively thinner and cone-shaped. This results in a large amount of astigmatism, leading to poor vision that cannot be clearly corrected with glasses. Keratoconus usually requires contact lenses for clear vision, and it may eventually progress to a point where a corneal transplant is necessary.

What is Hyperopia or Farsightedness?

Farsightedness, or hyperopia, is a vision condition in which distant objects are usually seen clearly, but close ones do not come into proper focus. Hyperopia occurs when the eyeball is too short or the cornea has too little curvature, causing light entering the eye to be improperly focused. This condition affects about a quarter of the population.

Common signs of farsightedness include difficulty concentrating and maintaining a clear focus on near objects, eye strain, fatigue and/or headaches after close work, aching or burning eyes, and irritability or nervousness after sustained concentration.

Common vision screenings, such as those often conducted in schools, are generally ineffective in detecting farsightedness. A comprehensive optometric examination will include testing for hyperopia.

In mild cases of hyperopia, your eyes may be able to compensate without corrective lenses. However, in other cases, your optometrist can prescribe eyeglasses or contact lenses to optically correct farsightedness by altering the way light enters your eyes.

What Causes Hyperopia?

This vision problem occurs when light rays entering the eye focus behind the retina, rather than directly on it. The eyeball of a farsighted person is shorter than normal.

Many children are born with hyperopia, and some of them "outgrow" it as the eyeball lengthens with normal growth.

What is Presbyopia?

Presbyopia is a vision condition in which the crystalline lens of your eye loses its flexibility, making it difficult to focus on close objects. While presbyopia may seem to occur suddenly, the actual loss of flexibility takes place over a number of years. It usually becomes noticeable in the early to mid-40s. Presbyopia is a natural part of the aging process of the eye. It is not a disease, and it cannot be prevented.

Some signs of presbyopia include the tendency to hold reading materials at arm's length, blurred vision at a normal reading distance, and eye fatigue along with headaches when doing close work. A comprehensive optometric examination will include testing for presbyopia.

To help you compensate for presbyopia, your optometrist can prescribe reading glasses, bifocals, trifocals, or contact lenses. Because presbyopia can complicate other common vision conditions like nearsightedness, farsightedness, and astigmatism, your optometrist will determine the specific lenses that will allow you to see clearly and comfortably. You may only need to wear your glasses for close work like reading, but you may find that wearing them all the time is more convenient and beneficial for your vision needs.

As the effects of presbyopia continue to change the ability of the crystalline lens to focus properly, periodic changes in your eyewear may be necessary to maintain clear and comfortable vision.