|
Glossary of Vision Terms
Types of Vision Prescriptions
Ablate
In surgery, it is to remove.
Astigmatism
A condition in which the curvature of the cornea is uneven, resulting in distant points in space being a blur on the retina.
Hyperopia
Or farsightedness; a condition which causes a point in space to focus behind the retina, making distant objects clear but near objects blurred.
Myopia
More commonly know as nearsightedness; a condition which causes a point in space to focus in front of the retina, resulting in distant objects appearing blurred or fuzzy.
Presbyopia
An age related (usually mid 40's) condition in which the eye is unable to focus on near and far objects, resulting in a need for bifocals.
Back to the top.
Anatomical Structures of the Eye
Optical Zone
The central part of the cornea through which vision occurs.
Cornea
The clear front part of the eye,
sometimes referred to as the 'window of the eye', provides most of the
focusing power when light enters your eye. The cornea is composed of three
basic layers: the endothelium, the epithelium, and the stroma.
Endothelium
The inner layer of the cornea.
Epithelium
The outer surface of the cornea and the
eyes protective layer. This layer is made up of highly regenerative cells
that have the ability to grow back within a few days, and therefore, allow
for fast healing.
Iris
This is the colored part you see in
people's eyes (i.e. blue/green/brown/hazel). The primary function of the
iris is to control the size of the pupil. This is achieved through
contraction or expansion of the muscles of the iris.
Lens
The lens is the clear structure
located behind the pupil. Its primary function is to provide fine-tuning
for focusing and reading. Between the ages of 40 and 50, the lens
becomes less flexible and presbyopia sets in. As people reach their 60's
or 70's, the lens sometimes becomes cloudy and hard (cataract
formation), preventing light from entering the eye.
Back to the top. Optic Nerve
The optic nerve carries images from
the retina to the brain.
Pupil
The pupil is the 'black circle' that
you see in people's eyes. The primary function of the pupil is to
control the amount of light entering the eye. When you are in a bright
environment, the pupil becomes smaller to allow less light through. When
it is dark, the pupil expands to allow more light to reach the back of
the eye.
Retina
The layer of light-sensitive cells in the back of the eye.
The retina consists of fine nerve tissue which lines the inside wall of the
eyes and acts like the film in a camera. Its primary function is to transmit
images to the brain. When your vision is perfect, the light rays coming into
your eye focus precisely on this part of the eye.
Sclera
This is the 'white part' that we see
in people's eyes. The sclera's purpose is to provide structure,
strength, and protection to the eye.
Stroma
The middle of the cornea composed of keratoytes and collagen tissue to which laser is applied in LASIK to give a predictable effect and fast unaided visual recovery time.
Vitreous Body
This is the clear 'gel like'
substance located inside the eye's cavity. Its purpose if to provide a
spherical shape to the eye. The vitreous may develop small clumps known
as "floaters," which are more common in nearsighted people than in the
rest of the population.
Back to the top.
Miscellaneous Terms
Diopter
A unit of measurement for eyeglass prescriptions indicating the severity of visual impairment. Moderate nearsightedness is three diopters.
Epi-Laser (AST or Surface Epi-Laser)
The process of treating the eye with
and excimer laser to the exposed surface of the cornea on top of
Bowman's membrane. This is also called flapless or capless surgery, made
with a non-cutting epithelial separator.
Excimer Laser
A 'cold' or 'non-thermal' laser used to reshape the cornea, and can remove cells and tissue without damaging or affecting surrounding cells or tissue.
Eye Chart Measure
Standard test to determine visual acuity. 20/40 means that at 20 feet (first number) a person can read the smallest letter on an eye chart that a person with normal vision can read at 40 feet (the second number). 20/40 vision is the legal unaided visual requirement for driving a car.
LASIK
Laser Assisted In-situ Keratomileusis, is a procedure for correcting prescriptions by reshaping the inner layers of the cornea with the Excimer laser.
The laser application is made by making a cap or flap in the cornea and then
placing the laser application inside the stroma or body of the cornea.
Structural weakening occurs which can be measured with cornea hysteresis.
Showing more weakening than with flapless or capless surgery.
Radial Keratotomy
A surgical procedure in which radial incisions are made on the surface of the cornea (epithelium) to flatten the central part (clear zone) so that light will focus closer to the retina than it did before surgery, reducing or eliminating the need for glasses. A permanent correction of myopia.
Back to the top.
Call for a
FREE consultation!
260-486-0065 or toll free 1-800-644-6393!
| 
