|
General Info
The eye is one of the
most important organs of the intelligent human being. The
features of this incredible organ are amazing. Approximately
80% of perception in human beings is through the eyes. 70%
of sensory receptors of the body are in the retina layer of
the eye. Sony's 2002 model most advanced digital camera has
4,200,000 receptors while the human eye operates with an
incredible sensitivity provided by its 120,000,000 black
& white and 6,500,000 color receptors.
How do we see?
The eye functions
like a camera or more like a video camera. Light rays coming
from the objects arrive on the cornea first. The cornea
provides 70% of the refractive power of the eye. After
refracting the light rays, it directs them to the lens
through an aperture called the pupil. The lens bends, in
turn, refracts the rays again. It makes a fine adjustment to
focus the light rays on the retina. This adjustment is
similar to the auto-focus function of cameras. This superb,
silent and continuous auto-focus function is due to the
lens' ability to change its refractive power by altering its
form and thickness. This function is called accommodation.
In a non-accommodating young eye the refractive power of the
lens is below 20 diopters but with maximum accommodation it
increases to more than 30 diopters, which is nearly equal to
an 8.5 diopters increase in the eye's total refractive power.
Because of this ability the young eye can see both near and
far objects well.
|
- Lasik
- The
Practice
- The Team
- The Procedure
- The Process
- The Candidate
- The Eye
- The Trip
- The Cost
- The City Istanbul
- Contact Us
|
|
After the light rays
are bent at the lens, they pass through the vitreous, the
jelly-like substance filling the back part of the eyeball,
and reach the retina. The retina, which makes up the inner
lining of the eyeball functions like a camera film, or a CCD
of a digital video camera. Then light rays are converted
into electrical impulses by the retina and carried to the
brain by the optic nerve. These impulses are processed and
perceived as images by the brain.
REFRACTIVE ERRORS
An eye that , which
does not have any refractive errors, and has the ability to
see the far and near and distant objects clearly, is called
an emmetropic (normal) eye. A refractive error means that
the shape of your eye does not bend (refract) the light
rayscorrectly. In other words, the eye can not focus images
properly, resulting in a blurred image. In an emmetropic eye
parallel rays of light from a distant object and divergent
rays of light from a near object focus on the retina after
being refracted by the cornea and the lens. The eyes, having
refractive errors have problems with focusing light rays on
the retina. Myopia (nearsightedness), hyperopia (farsightedness),
astigmatism and presbyopia are names given to different
refractive errors.
The refractive errors are quantified with the power of the
lens that corrects the refractive error. The unit of the
lens power is measured in diopters. 1 Diopter (D) is equal
to the optical power of the lens which has a focusing
distance of 1 meter. A lens with 1 diopter power focuses
parallel light rays at 1 meter while a lens with 2 diopters
power focuses parallel light rays at 0.5 (1/2) meter.
Total focusing power of the eye is between 58 and 71
diopters. Due to this amazing focusing ability the eye can
see images from 25 cm to infinity by focusing on a tiny
screen (retina), which is only 17 mm away from its lens.
|
