The Human Eye

The eye functions very much like a camera. Light enters the eye through the cornea, passes through the pupil, and is focused by the lens onto the retina. For images to be perceived clearly, the light rays must be focused properly on the retina otherwise, a blurred or "fuzzy" image is seen. This condition wherein the images are not properly focused is called an Error of Refraction (EOR). In general, EORs may cause a person to be nearsighted, farsighted, or astigmatic
 

Myopia

Myopia is the medical term for "nearsightedness", a condition wherein the eyes can see close objects but are unable to see distant objects clearly. Compared to the normal eye, a myopic eye is longer from front to back. As a result, light is focused in front of the retina, rather than on the retina, resulting in the perception of a blurred image.

Astigmatism

In order to have normal, undistorted vision, the cornea should be smooth and spherical or equally curved in all meridians. Some eyes have some degree of astigmatism, or ovalness, to their cornea. Instead of being shaped like a basketball, the astigmatic eye is shaped more like an American football. Therefore, there is distortion or tilting of the images due to asymmetric bending of the light rays. This is sometimes perceived by the individual as a "shadow effect" or a doubling of the image.
 

Hyperopia

Hyperopia is the medical term for "far-sightedness." It is a misnomer, however, in that people do not necessarily see clearly only for far (distance). As opposed to myopia, a hyperopic eye is shorter when compared to a normal eye. This results in light being focused behind the retina causing the perception of a blurred image.

Presbyopia

Presbyopia is not an EOR, but rather, an age-related loss of the focusing power for near vision. It usually sets in as one approaches the age of 40 or thereabouts. Normal and farsighted individuals usually require reading glasses once they reach this age. A presbyopic person with a moderate amount of nearsightedness may need only to remove his corrective spectacles for near work or reading.
 

Retinal Tears and Detachments

The Retina

• The Retina is a thin layer of nerve  tissue which lines the inner back wall of the eye.
• The Retina is stimulated by light and acts like film in a camera.
• The light sensitive retinal fibers are responsible for taking "picture images" that are transmitted to the brain via the optic nerve.

The retina is subdivided here:
a) Macula is the center of the retina. It is responsible for sharp central vision, reading vision and most color vision.
b) Peripheral retina is the remaining 95% of the retina surrounding the macula. It is responsible for side vision (peripheral vision).

The Vitreous is a clear gel like substance that fills the inside of the eye. The vitreous is loosely attached to the retina. Aging and other conditions affecting the eye can cause the vitreous to shrink and the retina to thin.
If the shrinking vitreous pulls on a weak area of the retina, it may cause a hole or tear in the retina. Usually the vitreous separates from the retina without damaging it.
When a hole or tear does occur
The vitreous fluid may pass through a hole or a tear, lift the retina, and cause the retina to detach.

Warning Symptoms of Retinal Tears
- flashing lights.
- new floating spots known as (" Floaters")

Warning Symptoms of Retinal Detachment
- flashing lights
- many new floaters or "a shower of floaters"
- "a gray curtain or a black shadow " moving across your field of vision.
 

Treatment of Retinal Tears or Detachment
There are several ways to repair the retina.
It depends on:
- the severity of the tear.
- the location of the tear
The risk if the Retina is not treated is it can lead to visual loss or blindness.

Treatment of Small Holes and Small Tears
- is a outpatient procedure
- performed under local anesthetic.
 

The Retina may be repaired using:
- laser (heat or burning) treatment.
- cryotherapy (cold or freezing) treatment.

Both treatments create a scar. The scar formation that is caused,  joins the retina to the tissue layer under it (choroid).

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