Normal Vision

The human eye gives us the sense of sight, allowing us to learn more about the surrounding world than any of the other five senses. The eye allows us to see and interpret the shapes, colors and dimensions of objects by processing the light they reflect or give off.

The cornea (the clear window on the front of the eye) and the lens of the eye (the transparent structure inside the eye) are both critical to normal vision. The goal of these two lenses is to focus light onto a layer on the back of the eye known as the retina. As light enters into the eye it is focused by the cornea and the lens so that images appear clearly on the retina. The retina then transmits these images to the brain where they are processed. If the images focus perfectly on the retina, this results in 20/20 vision; focusing in front or behind the retina results in nearsightedness or farsightedness. If the cornea is shaped like a football instead of a sphere, this is called astigmatism. When any of these conditions occurs, images are perceived by the brain as being blurry. This is due to "refractive error" which means the eyeball is not the right size or the cornea does not have the right curve. Presbyopia is a vision condition in which the lens loses its flexibility, making it difficult to focus on close objects.

Astigmatism

Astigmatism, unlike normal vision, occurs when the cornea is shaped like a football (more curved in one direction than the other) and often occurs in combination with myopia (nearsightedness) and hyperopia (farsightedness). This causes light to focus in more than one point on the retina, resulting in blurry and distorted vision.

Symptoms of astigmatism:

Blurry, distorted vision at all distances

Causes of astigmatism:

Heredity

Lid swellings such as chalazia

Corneal scars

Keratoconus

Diagnosing astigmatism:

Your eye doctor can conduct a refractive evaluation to determine whether your eyes focus light rays exactly on the retina at distance and near. A visual acuity test will determine your ability to see sharply and clearly at all distances. Your eye doctor will also check your eye coordination and muscle control, as well as your eyes' ability to change focus. All of these are important factors in how your eyes see.

Treatment of astigmatism:

Glasses and contact lenses are used by many for the temporary treatment of astigmatism. However, there are a number of vision correction procedures that can surgically reduce or eliminate astigmatism.

Nearsightedness (Myopia)

Myopia, unlike normal vision, occurs when the cornea is too curved or the eye is too long. This causes light to focus in front of the retina, resulting in blurry distance vision.

Myopia is a very common condition that affects nearly 30 percent of the U.S. population. It normally starts to appear between the ages of eight and 12 years old, and almost always before the age of 20. As the body grows, the condition often worsens. It typically stabilizes in adulthood.

Symptoms of myopia:

Blurry distance vision

Causes of myopia:

Heredity

Diagnosing myopia:

Many times, myopia is diagnosed during school screenings. Sometimes parents notice that their children are having difficulty seeing street signs or the television. Your eye doctor can conduct a refractive evaluation to determine whether your eyes focus light rays exactly on the retina at distance and near. A visual acuity test will determine your ability to see sharply and clearly at all distances. Your eye doctor will also check your eye coordination and muscle control, as well as your eyes' ability to change focus. All of these are important factors in how your eyes see.

Treatment of myopia:

Glasses and contact lenses are used by many for the temporary treatment of myopia. However, there are a number of vision correction procedures that can surgically reduce or eliminate myopia.

Farsightedness (Hyperopia)

Hyperopia, unlike normal vision, occurs when the cornea is too flat in relation to the length of the eye. This causes light to focus at a point beyond the retina, resulting in blurry close vision and occasionally blurry distance vision as well. Usually this condition is undetected until later in life because the young eye is able to compensate for the hyperopia by contracting the internal lens of the eye.

Symptoms of hyperopia:

Blurry close vision

Occasionally, blurry distance vision

Causes of hyperopia:

Heredity

Diagnosing hyperopia:

Many people are not diagnosed with hyperopia without a complete eye exam. School screenings typically do not detect this condition because they test only for distance vision. Your eye doctor can conduct a refractive evaluation to determine whether your eyes focus light rays exactly on the retina at distance and near. A visual acuity test will determine your ability to see sharply and clearly at all distances. Your eye doctor will also check your eye coordination and muscle control, as well as your eyes' ability to change focus. All of these are important factors in how your eyes see.

Treatment of hyperopia:

Glasses and contact lenses are used by many for the temporary treatment of hyperopia. However, there are a number of vision correction procedures that can surgically reduce or eliminate hyperopia.

Presbyopia

Presbyopia is a vision condition in which the lens loses its flexibility, making it difficult to focus on close objects. During the early and middle years of life, the crystalline lens of the eye has the ability to focus both near and distant images by getting thicker for near objects and thinner for distant objects. When this ability is lost, presbyopia results.

Symptoms of presbyopia:

Blurry close vision that starts after age 40

Difficulty adjusting focus when switching from near to distance vision

Eye fatigue along with headaches when doing close work

Causes of presbyopia:

Age: As we age, the lenses in the eyes lose some of their elasticity, and without elasticity they lose some of their ability to change focus for different distances. Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Long before an individual is aware that seeing close up is becoming more difficult, the lenses in the eyes have begun losing their ability to flatten and thicken. Only when the loss of elasticity impairs vision to a noticeable degree is the change recognized. Presbyopia usually becomes noticeable in the early to mid-forties.

Diagnosing presbyopia:

A comprehensive examination will include testing for presbyopia. Your eye doctor can conduct a refractive evaluation to determine whether your eyes focus light rays exactly on the retina at distance and near. A visual acuity test will determine your ability to see sharply and clearly at all distances. Your eye doctor will also check your eye coordination and muscle control, as well as your eyes' ability to change focus. All of these are important factors in how your eyes see.

Treatment of presbyopia:

Reading glasses and contact lenses are used by many for the temporary treatment of presbyopia. However, there are a number of vision correction procedures that can surgically reduce or eliminate the effects of presbyopia. Some presbyopic patients like monovision, which allows them to see distance clearly in one eye and close-up clearly with the other eye.