THE EYE

Your eye is round like a ball. When babies are born their eye is small. During childhood, the eye grows until ten or twelve years of age when the diameter reaches about 22 mm. To simplify we shall consider what you can see of your eye when you look at yourself in a mirror and what you cannot see.

VISIBLE PARTS

sclera  white, external tissue. It gives strength to the eye structure

cornea   window in the sclera because it is transparent most talked about in laser vison correction

epithelium   transparent outer layer of the cornea. Highly sensitive, removed for PRK, grows back within a few days.

iris   colored circle around the pupil. Controls the opening of the pupil

pupil   black openingin the center of the iris, varies in diameter to control the light ray passing through


INVISIBLE PARTS

lens   soft and transparent, behind the iris and the pupil, varies in shape to allow fine focusing. progressively loses its flexibility around 45

vitreous   gel that fills up the eye, located behind the lens and in front of the retina

retina   nervous cells covering the internal surface at the back of the eye

optic nerve   transfers data collected by the retina to the brain


eye-map


VISION


Our eye is an optical system operating like a still camera:



sclera is the frame
iris and the pupil act as diaphragms
cornea and the lens compare to the lens
the retina is impressed like a film


When all goes well, light rays focus on the retina
- what you see is in focus

When something is not quite right, light rays will not focus on the retina
- what you see is out of focus
The problems you encounter because of this are called REFRACTIVE ERRORS by your ophthalmologist

 REFRACTION:   name of the phenomenon which bends light rays as they go through bodies of different densities in this case through the various parts of the eye.



REFRACTIVE ERRORS

Refractive errors are caused by the way the defects in the eye affect the path of light rays entering the eye.

Hyperopia or Farsightedness
Cause: the eye stopped growing too soon, it is too short.
Consequence: The image falls behind your retina.

In the early part of life, however, if you are hyperopic by +2 diopters you most likely make up for it. The lens will automatically adapt, "accomodate" and you may not even be aware of the problem. Everything seems normal because accomodation will make you focus in the right spot.
Trouble starts around 40-45 when your lens is less flexible so you start having difficulty reading small print or seeing small objects

Myopia or Nearsightedness
Cause : the eye keeps on growing.
Consequence : the image falls ahead of the retina.

With myopia there is no correcting system inside the eye.
The traditional way to make up for the error is to use a correction system outside the eye such as glasses or contacts.

Astigmatism
Cause : sometimes the cornea is not evenly round like a soccer ball but oval like a rugby or foot ball.
Consequence : the image is formed in two differents spots. Objects are either distorted or double.

This can cause some confusion especially with smaller objects. The traditional way to make up for the error is to use a correcting system outside the eye such as glasses or contacts.

REFRACTIVE ERROR CORRECTION

Assessment

 Proper assessment of your eyesight is the key to laser vision correction



requirements of customized surgery




To evaluate your personal degree of refractive error your eyecare specialist will do two things:
   measure your objective refraction with:
  • an automatic unit called an automatic refractometer
  • a corneal mapping system which gives the exact shape of your cornea
   measure your subjective refraction you are asked to try on thicker and thicker glasses till you see small     objects clearly.

Till recently the refractive power of your eye could not be modified so your eye care provider modified the refractive power of the glass or contact lens measured in diopters.

diopter: the measuring unit of your eye's refractive power

Hyperopia
is corrected with converging glasses made of biconvex glass, similar to a magnifying glass, is measured in positive diopters.



myopia
is corrected with diverging glasses made of biconcave glass, similar to the bottom of a glass bottle. is measured in negative diopters


visual acuity:    your eyecare specialist will also determine your ability to see small objects by checking the number of lines you are able to read on a standard chart.

So there is no misunderstanding, you must make the following distinction:
  • eyecare professionals talk about diopters:the closer to zero diopter, the happier your eye doctor.
  • patients talk about number of lines on a standard chart, the closer to 20/20 without glasses, the happier you are.


MEANS OF VISION CORRECTION
  • exchangeable: carved glass glasses and contact lenses
  • adjustable:




born to win


EXCIMER LASER
L.A.S.E.R. = L ight A mplification by S timulated E mission of R adiation. EXCIMER = EXCI/ted - Di/MER

The excimer laser emits ultra-violet light (193nm). It vaporizes a very thin layer of tissue less than 0.25 microns, without heat nor pain.

The first clinical tests go back to 1985 and took place in the United States and Germany.

 L.A.S.I.K

L.A.S.I.K = L aser A ssisted in S itu K eratomileusis.

Your opthalmologist combines an automated blade to the Excimer laser. The automated blade lifts a flap in the cornea.

We use the Krumeich Barraquer microkeratome manufactured in Germany and distributed by Summit Technology as well as the Supratome by Cariazzo Barraquer and manufactured by SCHWIND.

At Eurolasik®, our physicians choose what they feel is best in agreement with our protocole. Some centers use an APEX+ others the Schwind MULTISCAN with an online pachymeter. As we do not submit our patients to try outs, we choose reliable, extensively used, with excellent proven results Excimer laser systems.