The Eye
The Normal Eye
-In order to see clearly, objects need to be brought to a focus point precisely on the retina of the eye.
The retina can be compared to the film in a camera. The light is brought to a focus point by the cornea and lens of the eye. The cornea's curvature is ideally matched to its length in the normal eye. As the normal eye ages, the lens loses the ability to focus for reading and will require the help of reading glasses. This usually begins to affect most people after the age of 40. |
The Nearsighted Eye
Myopia, also known as near-sightedness and short-sightedness, is a condition of the eye where the light that comes in does not directly focus on the retina but in front of it, causing the image that one sees when looking at a distant object to be out of focus, but in focus when looking at a close object. -If you are nearsighted, the cornea of your eye is overly curved or your eyeball is too long. This combination brings images of distant objects (street signs) to a focus point in front of the retina. When the light reaches the retina, a blurred image is seen since the light rays spread apart after the focus point.
The Farsighted Eye
Hyperopia, also known as farsightedness, is a common type of refractive error where distant objects may be seen more clearly than objects that are near. However, people experience hyperopia differently. Some people may not notice any problems with their vision, especially when they are young. For people with significant hyperopia, vision can be blurry for objects at any distance, near or far. -If you are farsighted, the cornea of your eye is not curved enough or your eyeball is too short.
This combination of factors causes the focus point of the eye to be located behind the retina. When light reaches the retina, a blurred image is seen since the light rays have not been brought to focus prior to reaching the retina.
The Astigmatic Eye
-If you have astigmatism, the cornea of your eye has a non-spherical shape (like a football) and
does not bring light to focus at a single point. Instead, it focuses images over a range of points producing a blurred image. Both nearsighted and farsighted eyes can also have astigmatism.
This combination of factors causes the focus point of the eye to be located behind the retina. When light reaches the retina, a blurred image is seen since the light rays have not been brought to focus prior to reaching the retina.
The Astigmatic Eye
-If you have astigmatism, the cornea of your eye has a non-spherical shape (like a football) and
does not bring light to focus at a single point. Instead, it focuses images over a range of points producing a blurred image. Both nearsighted and farsighted eyes can also have astigmatism.
Cornea
-The cornea is a transparent tissue in the front part of the eye. It is a curved spherical structure that is responsible for focusing the light onto the inside of the eye. Contact lenses sit on top of the cornea to change its curvature and eliminate the need for glasses. The Vision Correction Procedures discussed in this website attempts to improve vision by changing the shape of the cornea.
Iris
-The iris is the colored part of the eye. It opens up in dark rooms and at night to let more light into the eye. Conversely, in bright lights the iris constricts to decrease the amount of light that enters the back of the eye.
Pupil
-The pupil is the black spot in the center of the iris. Actually, the pupil is the name given to the opening in the iris through which light passes.
Lens
-The lens is responsible for helping to fine adjust the focus of the eye. The lens changes shape to allow clear vision both in the distance and for reading.
Vitreous
-The vitreous is a clear jelly-like material which fills the inside of the eyeball. Light passes through the vitreous on its way to focusing on the retina.
Retina
-The retina is a thin film of tissue (like film in a camera) where images are brought into focus. The retina lines the inside surface of the eyeball. The retina is connected to the brain where the visual signals are processed.
Anterior Chamber
-Between the cornea and the iris is a space called the anterior chamber. This space is filled with a clear water-like solution.
Pupil
-The pupil is the black spot in the center of the iris. Actually, the pupil is the name given to the opening in the iris through which light passes.
Lens
-The lens is responsible for helping to fine adjust the focus of the eye. The lens changes shape to allow clear vision both in the distance and for reading.
Vitreous
-The vitreous is a clear jelly-like material which fills the inside of the eyeball. Light passes through the vitreous on its way to focusing on the retina.
Retina
-The retina is a thin film of tissue (like film in a camera) where images are brought into focus. The retina lines the inside surface of the eyeball. The retina is connected to the brain where the visual signals are processed.
Anterior Chamber
-Between the cornea and the iris is a space called the anterior chamber. This space is filled with a clear water-like solution.