Laser Mont-Blanc| Centre de chirurgie Réfractive

Optics aberrations

Webmaster — 2025-05-01T15:15:10Z

Until recently, the analysis of vision was expressed in terms of sphere (myopia or hyperopia), and cylinder (astigmatism) characterized by a power and an axis. In most cases the sphere and the cylinder combine to create sphero-cylindrical aberrations.

They are by definition called “LOW-DEGREE ABERRATIONS”.
These refractive errors are the basis of all corrections by corrective lenses which are always expressed (international name) in Sphere (cylinder and axis).

Example: -3.00 (-1.00 at 15°).

In recent years, research in optics and the availability of new devices (aberrometers) have made it possible to understand that vision is not only the association of low-degree errors, but the combination of multiple optical anomalies which integrate high-degree optical aberrations according to mathematical formulas called Zernike polynomials.

Defocus, symmetrical deformation, coma, trefoil

The best known are coma, spherical aberration, trefoil etc. these are the “HIGH DEGREE ABERRATIONS ”.
Thus, like a fingerprint, each individual presents a unique vision made up of the combination of multiple aberrations of low and high degrees.

In practice, the rate of high-degree aberrations does not exceed a very small percentage in most individuals, making it negligible to take these elements into account for laser treatment. Conversely, for some, the percentage of high-degree aberrations becomes sufficiently significant for personalized treatment to be necessary.

The Laser Mont-Blanc center is equipped with the entire system allowing personalized aberrometric processing: Analysis of all aberrations by the Wave Analyzer, the Topolyser Vario, the Pentacam and the use of specific processing software by the EX500 Alcon.

Long-Sightedness

Webmaster — 2025-05-01T15:10:23Z

Long-Sightedness corresponds to the loss of the accommodation which is the adjustment, between the vision by far and the vision of near, permitted by the muscles intraocular operating the crystalline lens.

Long-Sightedness appears as from approximately 40 years. Initially, it is necessary to move away the text to be read, and then the vision of the details becomes impossible without an adapted correction.

Long-Sightedness thus requires the port of a correction in vision of close different from the correction by far (glasses various, double hearths, progressive glasses or lenses of contact multifocales).

There is no treatment for the loss of accommodation of the crystalline. Current treatment of presbyopia involves two elements:

– Monovision: the principle is to set the dominant eye for distance vision and the eye directed (non-dominant) for near vision. This method is very efficient if the difference between the eyes is less than one diopter.:

– Changing the corneal asphericity.
The latest developments of Excimer Laser used to modify the corneal asphericity, enabling increased depth of field.

Both approaches, monovision and modified corneal asphericity to compensate effectively for presbyopia distance vision and near. It is often necessary, after 50 years, adding a correction (magnifier reading) very close to the vision.

Astigmatism

Webmaster — 2025-05-01T15:09:03Z

The cornea of the eye astigmate (short-sighted astigmate or hypermetrope astigmate) is deformed.

Instead of being spherical, it is bent in a direction (for example vertically) that in the other (for example horizontally).

TO INCLUDE/UNDERSTAND the ASTIGMATISM

In the astigmatism the eye sees more distinctly in a direction than in another. Thus the second image is stretched horizontally whereas the third is vertically.
It results from it that a confusion can join the fuzzy vision while making letters close not very different: confusion between N and m, O and C...

Hypermetropy

Webmaster — 2025-05-01T15:08:01Z

The image of an object seen by an eye hypermetrope is formed behind retina, the eye being "like" too small.

The hypermetropes see fuzzy especially near but also by far.

The correction of the hypermetropy is done by glass or a convergent lens. It is increasingly awkward while advancing in age.

One obtains a comparable optical effect by increasing by laser central convexity of the cornea. The postoperative visual fluctuation is longer than that of the short-sighted ones.

Short-Sightedness

Webmaster — 2025-05-01T15:06:28Z

The image of an object seen by a short-sighted eye is fuzzy because, this eye being longer than the normal, the image is formed in front of the retina.

On the other hand, the short-sighted ones see Net of near without correction when they bring the object closer to the eye.

The correction of Short-Sightedness is done by glass or a lens of divergent contact. One can obtain the same optical effect while flattening with the laser or by any other surgical means the center of the cornea.

Short-Sightedness is increasingly frequent for reasons related on heredity and the environment