Surgery presbyopia: possible discover the principles and techniques used for the presbyopic eye surgery!
There is not a single operation of presbyopia, but a range of techniques that allow most of presbyopes to reduce their dependence on glasses or lenses. The preoperative, indispensable, toll has aimed to choose the most suitable technique considered an eye and Visual ambitions of presbyopia surgery candidate.
Presbyopia is defined by the loss of the accommodative function of the eye (see the pages dedicated to accommodation and to the) lens). the focus for playback or clear vision of objects near the eye (ex: 40 cm) is no longer sufficient from the quarantine.
A well corrected not presbyopic patient far accommodates to see up close: the lens 'bomb' and the increase in the optical power of the eye form a sharp image on the retina of a nearby object. This is analogous to the function of autofocus cameras, making the update according to the distance of the plan which must be net on the cliché.
The presbyter, the amplitude of accommodation is reduced progressively: the autofocus of the eye (through the lens) is becoming less and less effective, because the lens and its envelope lose their flexibility. Despite the contraction of the ciliary muscle to make bomber the lens, it does not deform enough.
See article on presbyopia surgery: http://www.Medscape.fr/voirarticle/3600763
Show "Hello doctor", devoted to presbyopia (16 October 2012) - guest Dr. Damien Gatinel
Which can be operated of presbyopia?
Presbyopia can be a surgical operation, regardless of the default Visual partner by far. Schematically:
At the presbyopic myopesmonovision (an eye for distance vision and the other for near vision) is definitely the best alternative to consider.
At thepresbyopic farsightedthe use of a multifocal technique (combined with a slight monovision) is often a good option.
In all case, astigmatism to be corrected, since it affects both distance vision and near vision.
Finally, at the presbyopic Emmetropic, various options can be envisaged depending on the patient's Visual ambitions.
How to determine the best indication?
Each request for correction of presbyopia must be studied carefully, in order to choose the best strategy for correction.
The collection of parameters is essential:
-age (degree of residual accommodation), sex (male / female)
-motivation and ambition Visual / profession vs. leisure / activities rather than distance vision or near vision
-degree of correction bezel by far and close (addition)
-presence of a debutante same cataract
-presence of eye diseases associated
The presence of a cataract directs priori to a technique of cristallinienne surgery with placement of an implant multifocal in each eye, or monofocal implant intended to induce a monovision (one eye sees net from a distance without glasses, the other closely)
The principles used for the surgical correction of presbyopia:
Contrary to what may suggest various media campaigns or "publi - reports ' recurring, it there is no proven method that allows to fix the accommodation, l and so a true correction of presbyopia: Ideally, there should be flexibility to crystalline, but this is not yet in the domain of the possible with current techniques.
On the other hand, various methods can be used to offset presbyopia :
-the Monovision : she is to use the fact that we have two eyes: one can be dedicated to the vision, the other to distance vision (this difference can be induced during corneal surgery or implant). The dominant eye is usually operated before his vision by far is optimal, and the eye non-dominant to allow her near vision reading, all of course without having need to wear glasses or lenses. A page is devoted to the remediation strategy by Monovision.
-the multifocalite : she is to increase the depth of field of the eye by the induction of a multifocal profile. This profile allows the operated eye to see several remotely in a sufficiently clear way. The multifocalite can be introduced by a surgical technique interesting the cornea or the lens.
The correction on the cornea is to carry out a "multifocal" profile, most often by varying the corneal Asphericity to increase depth of field: the technique is essentially that of LASIK (who took the name of "presbyLASIK").
Presby LASIK brings together a wide range of operations, whose names vary: Supracor, Laser Blended Vision, Q-factor F - CAT, etc. They are all based on a common principle; the increase of aberrations, including spherical, of the eye surgery to increase its depth of field. These "LASIK for presbyopia" techniques differ more by their marketing positioning and some tricks of language, that of their common mechanism: increase the depth of field of the eye without reducing the quality of distance vision playing on the rate of eye spherical aberration.
The spherical aberration is indeed an aberration that is characterized by the fact that the rays refracted by the central area of the pupil converge faster (spherical aberration of negative sign) or slower (spherical aberration of the positive sign) that the rays refracted through the peripheral area of the pupil. We can dedicate the refraction of the pupillary Center to near vision, and refraction of the pupillary periphery vision from afar, and vice versa. To increase the negative spherical aberration rate, can reshape the profile horny to make more aspherical prolate ("playing" with the 'Q factor' of asphericity). Laser manufacturers are less prolific in terms of numbers, and it is difficult to know what rate of spherical aberration is covered with patterns specifically dedicated to the correction of presbyopia. It must be said that this area is relatively complex, because spherical aberration rate also depends on the far possible correction of the pupillary diameter, spherical aberration rate initial, etc,.. .and that a rule of marketing is instead to simplify some explanatory messages, so that they are better understood and received. This actually helps some confusion that surrounds the presbyopia laser correction techniques and their correction mechanism - yet universally based on the modulation of spherical aberrations.
A slightly more technical page is devoted to the principles and explanations of the traitements laser aspherical "custom Q F - CAT.
Multifocal contact lenses are produced according to a principle quite similar to laser corrections. Some are central addition (vision in the centre), other peripheral addition. In the language aberrometrique, Multifocal lenses modulate the rate of spherical aberration of the eye (while correcting any defect by far as farsightedness or nearsightedness).
The hypermetropic presbyopia is generally a good candidate for LASIK surgery: correction of vision far tends to increase the rate of negative spherical aberration, and naturally brings some improvement of near vision.
The multifocal implant
A multifocal implant placement requires the lens, comparable to that of cataract surgery: we replace the lens with a multifocal implant. Indications of implant placement concern especially for beginner cataract patients, or who have reached 60. Both eyes are usually operated. Several useful for vision homes, are created by the Diffractive implants (home for distance vision and close for bifocal implants, home for the intermediate vision and more for trifocals implants).
The implant intra corneal (inlay)
The increase in depth of field by reduction of the diameter of the pupil consists of the insertion of an implant in the cornea of an eye (usually the non-dominant eye). The intervention lasts only a few minutes and is performed under local anesthesia. The corneal implant is called implant KAMRA. This technique can be combined with LASIK to correct distance vision. The advantage of this technique is its reversibility, (it does not have lens or cornea), and the fact that it can be associated with virtually any type of correction laser for a far vision defect associated with presbyopia (myopia, hyperopia, astigmatism).