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Presbyopia

Presbyopia: definition

Presbyopia is a gene in near vision that appears a bit after the age of 40, and is caused by the gradual reduction of the ability of the eye to focus in close vision (mechanisms of the human eye for near vision are explained on the page dedicated to the)accommodation the lens).  Installation of presbyopia at midlife is inevitable, and translates into a growing difficulty to read small print in near vision, making it necessary to use an optical aid (glasses, magnifiersMultifocal lenses, etc). Presbyopia is changing over 15 years ago; the first glasses are prescribed to 45 years (see the page dedicated to the) prevalence of presbyopia, and the correction increases and stabilizes around 55/60 years old then.

Mechanism of presbyopia

Presbyopia translated the gradual reduction of the power of accommodation of the eye (amplitude of accommodation), which is directly related to the reduction of the elasticity of the lens and its capsule. The lens is a lens that is natural, located in the anterior segment of the eye, which allows to make the update to have a clear vision of close objects. It is the equivalent of a 'autofocus' for a camera. In a subject Emmetropic (net without correction in the distance seeing subject) become presbyopic, near vision as one used for playback is increasingly blurred, while distance vision remains normal.

Presbyopia

A far-sighted Emmetropic sees net by far, because the image of a distant object (here the umbrella) is formed in terms of the retina: the light rays from an object away, they are parallel (non divergent) when they meet the eye, and the crystalline + horny couple has the optical power (vergence) sufficient for the rays they refract "intersect" in terms of the retina and form a sharp image. When this same subject become presbyopic, wants to read, the lens don't bomb is enough to allow the object seen close (here a famous formula in Physics) to form a sharp image on the retina: the rays arrive with a certain divergence, and the lens must bomber (increase its vergence) so that the rays from this image "intersect" in terms of the retina. Presbyopia reduces the ability of the lens to bulge, and the image formed on the retina is blurred because the light rays do not converge fast enough.

The following image details the optical mechanisms that allow to understand the mechanism of presbyopia.

presbyopia

The eye perceives the world by capturing the light rays that come from the surrounding objects: these objects can be assimilated to a set of elementary points, and one prefers to simplify the problem by focusing on an elementary point: the reasoning can be applied to all adjacent points. This point emits rays that "radiate" in all directions of space: a portion of these rays is captured by the eye. In order to form a "faithful" image of the source point, it is necessary to converge the captured rays so that they "intersect" in the retinal plane. The role of the cornea and the Crystalline lens is to focus these rays in the retinal plane, thanks to the addition of their vergence (optical power, ability to focus light). The captured rays that have been emitted from a distant source are either or are not divergent (they are quasi-parallel). For a emmetropic eye (without optical defect for distant vision), these parallel incident rays are focused in the retinal plane. On the other hand, the more a source point is close to the eye, the more the incident rays are divergent. It is more "easy" to converge rays that are little or no divergent, than divergent rays: in the absence of accommodation, the rays that arrive in divergence will be focused behind the plane of the retina. It is for this reason that the net vision of close calls for an increase in the vergence of the ocular diopter. The non-longsighted human eye has a flexible Crystalline lens, and the vision of a close-up source seeks accommodation, which is a complex mechanism whose purpose is the induction of a bulge from the Crystalline lens. When the Crystalline lens bomb, its vergence increases. The gradual loss of the accommodatif power of the eye, linked to a reduction in the flexibility of the Crystalline lens, results in insufficient convergence of light rays that are not sufficiently focused to form a clear image in the plane of the Retina. The recoil of the source makes it possible to make the Rays less divergent; That's why the beginner longsighted instinctively stretches his arms to see sharper.

 

Functional consequence of presbyopia

Presbyopia results in the appearance of a growing gene closely reading or the identification of fine details within a pattern observed at close range (i.e. less than 1 meter). The status of distance vision, the absence or the presence of optical default (myopia or hyperopia) determine the type and extent of symptoms of presbyopia.

-At a Emmetropic (Good vision from afar), presbyopia results in the appearance of a near-vision discomfort, especially for small print, and when ambient light is low. Over the years, the vision of the near continues to deteriorate, and requires an optical correction towards 43 years, which will be renewed and increasingly strong as the accommodation decreases.

-In a subject short-sighted Having become longsighted, the removal of the correction from afar can allow a closer vision to be sharper. The comfortable reading distance without glasses depends on the degree of myopia (the higher the myopia, the closer the distance is). But the removal of the glasses is accompanied by a blurred vision from afar (remember that myopia corresponds to a net vision effortlessly close, but blurred by far without correction). To see net from afar, the myopic shoes his glasses and to see closely, he removes them (the adaptation of progressive lenses allows to keep the same pair of glasses for these different distances). To learn more about the relationship between myopia and presbyopia: see: myopia and presbyopia

-In a subject farsighted become presbyopic, installation of presbyopia is particularly "bad living."  At the hypermetropia moderate (less than + 3 D of correction for distance vision), the effect of the reduction in the accommodative power of presbyopia appears earlier: it makes more difficult the efforts that the farsighted had used to do to offset the effects of hyperopia, and improve distance vision. That is why that the far-sighted became farsighted subject feels so an overall reduction in the quality of his vision: not only the near vision decreases, but the vision from afar, which was good or even excellent, degrades too quickly to quarantine. The optical prescription for near vision is then accompanied by a prescription for distance vision (progressive glasses, or the addition is expressed in) diopters). For more information: see the page on the peculiarities of the association hyperopia and presbyopia

Signs of presbyopia

Presbyopia is probably the sign related to aging whose age of installation is the most consistent: it truly is around 43 years that the effects of the loss of the amplitude of accommodation are beginning to be felt, especially for the emmetropes.

Symptoms begin with an appearance of a difficulty to see net of the small print, in particular when the ambient light is low. It may be a new difficulty to read a label on bottle of wine at the restaurant: intrinsic difficulties like that labels have an often colorful background, and employed calligraphy and sometimes in addition to the generally Dim light, normal.

effect of presbyopia

The onset of presbyopia can be felt suddenly: difficulties or impossibility to read the label of a bottle of Bordeaux wine to the restaurant (right). The particular calligraphy, and the low contrast of the text with the background requires an accurate and efficient accommodation (left).  The installation of presbyopia can also be felt in the occaseion of a gene to playback or a need to light more intensely to read, especially the small characters like those of a medication instructions, etc.

In most of the case, the beginner presbyter feels the need to do a 'effort' to readwhereas previously the focus of almost was "unconscious" and easily.

Instinctively,. the presbyter back his reading plan (for example, 35 to 50 cm), extending the arms, less soliciting his accommodation.  Finally, after some time, this type of strategy fails and it becomes necessary to wear a correction for near vision at least for the reading of texts printed. Indeed, reading on tablet or smartphone can be accomplished without optical aid initially; Unlike the label of a bottle of digital screens contrast is high, and especially it is possible to increase the size of the characters to read them more easily.

Short-sighted becoming presbyopic often tend to remove their glasses from afar to see better close (the nearsighted eye blur by far because it is as "set" to see net, at a distance which is even lower than the myopia is strong). This strategy works poorly among wearers, because it is not practical to remove and replace the lenses over the day punctually. Presbyopic short-sighted have generally less difficult to read when they wear their glasses by far in correction by lenses; This is related to the fact that the objects seen through myopic glasses are certainly smaller, but especially appear as being located further away (so soliciting under the development closely and the convergence of the eyes).

As mentioned above, the hypermetropia experience symptoms of presbyopia of acutely, because the accommodation is often used to hone their distance vision (which can occaseionner a recurrent visual fatigue). The hyperopic eye is an eye too short; the incident rays from "Afar" converge at the back of the retina; the image that is formed in terms of the retina is blurred because insufficiently focused. The accommodation, which is the increase of the power (by bulge) of the lens, is used in the farsighted to improve distance vision. This works well in children and young adults because the amplitude of accommodation is important and allows to correct some diopters of farsightedness without too much effort. But at the age of presbyopia.  the vision from afar seems to deteriorate in parallel with near vision: this reflects the exhaustion of the accommodative mechanism of vision by far (see compensation hyperopia and presbyopia). Presbyopia is sometimes responsible for the return of the prescription of corrective lenses for vision far beyond those for vision closely ('progressive' lenses), including at low hypermetropes who wore glasses of 'rest' intermittently during childhood, for the school tasks including.

 

Can we delay presbyopia?

Presbyopia is not related to the reduction of the strength of the ciliary muscle (which is put in play with the accommodative effort to see up close), but to the loss of elasticity of the crystalline lens (understand the) mechanism of accommodation Allows to apprehend the one of the presbyopia). The ciliary muscle contracts, the zonule (the ligament of the Crystalline lens) relaxes, but the Crystalline lens itself does not bomb anymore enough (a Crystalline lens young bomb when releasing the tension of the Zonule) . If presbyopia was related to a reduction in the intensity of ciliary muscular contraction, treatments could be imagined to "restrengthen" the eye to maintain accommodation. Unfortunately, during the installation of the presbyopia, the ciliary muscle contracts well, but the Crystalline lens, which tends to increase in volume and lose its flexibility during existence, no longer bomb enough. Currently, no effective therapy is known to make its elasticity lost at Crystalline lens. Therapeutic tests were carried out using the femtosecond laser to make incisions directly in the Crystalline lens, in the hope of restoring any flexibility to it. The results of these techniques do not appear to be sufficient, and the risk of induced cataracts is real. The answer to the question of a possible prevention of presbyopia is therefore negative, and it is also remarkable to see how consistently the presbyopia settles in time in humans (between 42 and 44 years most often).

Principles of the correction of presbyopia

We can't stop the presbyopia, but fortunately, it is quite possible to correct.

Presbyopia can be corrected logically by the port (or adding to the correction by far) convex lens designed to compensate for the lack of focal power (originally from the defocus) to form a clear picture of the objects located at a distance of about 35 cm.

The value of this addition (expressed in) diopters (: ex: + 1 D) is a function of the degree of presbyopia, him even in relation to age. The first glasses prescribed early presbyopia have usually close power of ' addition + 0.75 D. This addition must be increased over time, and reaches + 2.75 D or + 3.00 D in the late fifties.

The importance of presbyopia is quantified by the number of diopters for near vision (between + 0.75 D and + 3 D by no + 0.25 D). In a subject Emmetropic and far-sighted, lenses + 3 D reflects the fact that presbyopia is "total": the vergence provided by glass of + 3D equipped eye vision is sharp at 1/3 = 0, 33 meters, approximately 33 cm. A myopic-3D sees net effortlessly to 33 cm, and it is for this that in by wearing its correction by far, this type of medium nearsighted (between-2 and-3.50 D about) can be read closely by removing his glasses. Yet it is far-sighted, because when he's wearing his correction by far (glasses or lenses), it is no more able to see net nearly a no myopic presbyter.

Optical correction adds close initially ametropic topic (nearsighted or farsighted, and/or astigmatism) so the lens correction which is necessary to correct distance vision. It is performed only on the lower part of the corrector glass lunette (half-moon, progressive lens or bifocals) because the drive tends to look down to the bottom to read his book.

glasses and presbyopia

The glasses to several homes or variable focal power (progressive lenses) allow you to adjust the correction required to see NET at a given distance (far vs close vs intermediate).

 

The correction by lenses (Special)so-called multifocals) is sometimes possible, but Visual compromise between vision far and vision up close can occaseionner a gene for certain activities (including driving at night, as halos around bright lights can be seen).

Refractive surgery and surgery of the lens (cataract) can enable the presbyter to read and see from a distance without glasses (see the page dedicated to the) presbyopia surgery). The corneal chiurgie uses the Excimer Laser)LASIK) to reshape the cornea realize a "static" pattern and can not truly correct presbyopia, in the proper sense which would mean the return of accommodation (which is a dynamic phenomenon; reversible deformation of crystalline). However, correction by multifocalite, taking into account certain anomalies in distance, vision can be part of a strategy of overall visual improvement and allow the far-sighted no longer (or much less have to) wear's glasses. Like what the correction of hyperopia by LASIK comes most often a profit important for near vision. This improvement is related to the induction of a multifocalite corneal. It is possible to optimise this benefit by making a slight correction on the non-dominant eye. Incomplete deliberately planned correction of nearsightedness on a non-dominant eye can preserve a vision closely in myopic subjects: this strategy is called «» Monovision "(or"switches"). These alternatives can be tested with contacts to test in a subject previously presbyter candidate for refractive surgery. More recently, the development of intra corneal implants for example intended to increase the depth of field by creating a "small pupil" (Implant KAMRA) offer a new alternative to presbyopes. the placement of the implant on an eye to give the possibility to read close without glasses, while maintaining good visual acuity by far.

Patients who have a beginner cataract presbyopia surgery will logically refer to a cataract surgery with installation ofMultifocal implants. In all case, prior consultation is necessary in order to accurately determine visual needs and the existence of a possible correction of vision from afar, in addition to measuring the level of presbyopia (in addition close). Video: presbyopia surgery consultation

Learn more on the presbyopia surgery See the page on presbyopia and multifocalite TV France 5-Hello doctor show "presbyopia".  Guest Dr. Gatinel

8 Responses to "Presbyopia"

  1. WECK says:

    Hello

    Is it possible to have surgery of a presbyopia at age 45? This has worsened since a year. The port of a correction is for me is not an option.
    Thanks for your reply.

  2. Dr. Damien Gatinel says:

    An operation is theoretically possible, but the choice of technique and of the correction depends on the pre-surgery, the correction you need (by far), etc. It is not possible to restore the accommodation, but some strategies to replace him, and at least partially reduce the port of an optical correction.

  3. Inijustix says:

    Congratulations once again for your pedagogical explanations without mathematical formulas for this page.
    But I'm going to ask you a school case: I'm going to be 66 in July, and I always read without glasses. Since Europe has allowed the letters of 0, 7mm instead of 1.2 before for the food ingredients, I have a little trouble in the shops, I just put the packet of cookies in the sun or pile under a lamppost and it becomes readable again. But for the common use, magazines, books, computer, no problem, and without stretching the arms.
    I give my recipe somewhere on my site, but rest assured, you do not risk any competition, it is an initiation recipe within the reach of a thousandth of the population about.....

  4. Dr. Damien Gatinel says:

    Thank you, and share your experience. The near-vision performance of some patients is indeed surprising. It is often explained by the conjunction of a certain degree of myopia or uncorrected astigmatism, at least on one eye. Patients without correction but whose pupil contracted strongly during the reflex accommodation convergence (pupil less than 2 mm) have the possibility to read relatively well without visual help (increase of the Depth of field).

  5. Tirel says:

    I have a friend who at 67 years old and sees from afar and ready without glasses.
    I thought to myself, it's bound to be myopic.
    I did the test with him. By far he sees very well, with one eye then with the other.
    The test makes a loan too, hiding one eye and the other.
    He did not have an operation.
    This is due to its pupil?

  6. Dr. Damien Gatinel says:

    There are actually case where the vision not corrected by far and near remains relatively satisfactory. This apparent increase in depth of field may be the result of the combination of various factors: small pupillary diameter (effect comparable to that of "diaphragm closure"), slight myopia (compatible with good acuity when the diameter Pupillary is weak), high degree aberrations (spherical aberration), slight astigmatism, etc.

  7. CORINNE says:

    Hello
    I was in myopia 10 years ago with the Lasik laser, now 48 years old I would like to have a presbyopia, is it possible to be operated twice?
    Thank you for your answer
    Kind regards

  8. Dr. Damien Gatinel says:

    This is quite possible and is one of the advantages of LASIK technology. Indeed, patients operated as you myopia in the past and become presbyopic can consider a possible retouching once the presbyopia installed. It is possible to raise the flap realized during the initial surgery, on the side of the non-dominant eye, to induce a correction intended to give a certain visual acuity to the eye in close vision. It is therefore a technique called "monovision". This recovery, however, would result in a reduction of the visual acuity of this eye in vision from afar. A simulation with the port of a Contact lens intended to mimic the result of surgery can be performed before the surgery.

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