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Astigmatism surgery

Operations to correct astigmatism

Astigmatism surgery is common in refractive surgery, because this defect is sometimes isolated, but most often associated with nearsightedness or farsightedness. Contrary to received, astigmatism occursthat it is isolated or associated with another optical flaw. The results of LASIK or the PKR in correction of astigmatism are excellent, otherwise it uses latest generation lasers and certain options such as the recognition of the iris (Iris recognition), which helps to align the treatment according to the desired axis.

Astigmatism correction is deemed more difficult than that of myopia, quite rightly, because it should be not only to perfectly Center the laser treatment, but also to align it with the axis of astigmatism to be corrected.

To understand the principles of surgical correction of astigmatism, need to know certain characteristics of this optical defect, affecting the means of correction, as well as some of the constraints they impose.

The astigmatic eye has the particularity of not having the same optical power according to the eye meridians (see explanations of astigmatism). Thus, in case of astigmatism, all light rays from a distant source do not converge on the retina as the meridians of the eye do not have the same optical power (astigmatism corresponds strictly to the)lack of stigma !). The variation of optical power according to the meridians is most of the time related to a change in the curvature of the meridians of the cornea (corneal astigmatism, caused by an excess of toricite of the cornea).

The regularization of the corneal curvature laser is a logical solution for astigmatism surgery. LASIK and the PKR to correct the astigmatism with the issuance of a profile of ablation adapted.

In case of cataract, the appearance of an astigmatism of origin "internal" (cristallinienne, because cataract changes the optical properties of the lens) is also possible, he accompanies particularly gladly nuclear forms. This astigmatism is often to 'reverse' direction (non-compliant said astigmatism). In case cataract surgery, this component from astigmatism disappears with the removal of the lens. On the other hand, if a corneal astigmatism is associated with this internal astigmatism, should be possibly fix it by choosing a particular artificial lens called «toric implant» implant

-The formulation of astigmatism (example:-1 x 90 °) has the value of excess (positive sign) or failure (negative sign) to the largest refractive power caused by astigmatism of the concerned eye (it is the number - 1 in the previous example), as well as the axis of the Meridian along which is present this defect (90 °, which is the axis of the vertical Meridian).  Astigmatism can be associated to myopia: in this case, we get for example a myopia of - 4 d associated with previous astigmatism a correction formula that is written:-4 (-1 x 90 °)

The 'research-training' section contains a more detailed information on astigmatism.

The correction of astigmatism can be done by various methods including corneal laser surgery, and by the lens implant surgery. The choice of method is a function of many parameters (age, degree of astigmatism, presence of myopia or an associated farsightedness, astigmatism origin - horny or lens-, regularity of astigmatism, the thickness of the cornea, presence of a cataract, etc.):

Equalization of the optical power of the cornea:

It is listed in case fororiginal corneal astigmatism(majority of the case). The excimer laser sculpts the front of the cornea in order to reduce or increase the curvature depending on the meridians (ex: the LASIK technique, the PKR: see)are profiles of ablation for the correction of astigmatism).

principles of surgery of astigmatism on the cornea with excimer laser

Astigmatism is usually caused by an excessive or too little of certain meridians of the cornea curvature. Light rays focus in different planes and the retinal image is blurred. The correction by photoablation corneal laser (LASIK or PKR) aims to regularize the corneal curvature, in such a way that the corneal meridians have equal power and that they focus light on the retina. According to the case, the laser will sculpt the cornea to add power along some meridians, or take along some others. The treatment of astigmatism can be compared to that of myopia or a farsightedness that the degree of correction depends on the considered position of the meridian (the "Cup" of the eye). It is therefore important to check the correct alignment between the eye and the treatment delivered. Correction of astigmatism may be combined with myopia and hyperopia when these defects are in addition to astigmatism.

Latest refractive laser platforms allow to achieve a cut of flap adapted to the geometry of the LASIK laser correction (ex: suite Wavelight refractive, see) video about the cutting of elliptical flaps).

In more specific case as after a cornea transplant, we can use a different approach and make incisions in the corneal graft to correct astigmatism, without removing corneal tissue as with photoablation techniques. The incisions (say arc because circulars) are carried out with the femtosecond laser.

Replacement of the lens with an artificial lens implant said "o-ring":

The power of the implant is calculated so that the operated eye is more astigmatism (technique used in patients with cataract and an original corneal astigmatism). L' ring implant should be aligned with the axis of astigmatism of the cornea, otherwise induce a under correction in case in malposition or rotation. Cataract surgery allows the correction of the corneal component from astigmatism (corneal astigmatism).

surgery for astigmatism with a toric implant principles and representation

Astigmatism is usually caused by an excessive or too little of certain meridians of the cornea curvature. Light rays focus in different planes and the retinal image is blurred. In some indications (beginner cataract, very pronounced astigmatism) correction of astigmatism can be done by replacing the lens by an "o-ring" implant, which neutralizes the corneal astigmatism. The calculation of the power of the implant is called 'biometrics '. It depends on the length of the eye (axial length) and the degree of astigmatism present in the cornea. It is important to align the implant with the cornea.

Adding a toric implant in the anterior chamber or the posterior Chamber keeping the lens;

Such an indication is rarer, it concerns patients with anterior Chamber is deep enough, the realization of a LASIK impossible (ex: Keratoconus), and an age too young for surgery of the lens.

In all case, astigmatism is a "oriented" optical defect (axis), the correction of astigmatism requires adequate guidance of treatment, and a correct alignment of the main axes of astigmatism with the corrective device. If the orientation of the treatment is imperfect, theaxis error induces a residual astigmatism.

 

7 responses to "astigmatism surgery"

  1. Mary says:

    Hello doctor,

    I am 27 years old and I am myopic since my earliest age as well as astigmatism. My myopia is very stable and my astigmatie moved two years ago. I'm wearing Bausch + Lomb Pure Vision 2 lenses:
    OD: SPH (-6.00) cyl (-1.25) AX 100
    OG: SPH (-5.00) cyl (-1.75) AX 70
    I would like to have an operation of my myopia and astigmatism but I ask myself several questions:
    – Is my astigmatism necessarily due to a keratoconus?
    – Has the lens worn for 15 years been able to trigger one?
    – would my ophthalmologist have had to report me a keratoconus if I had one?
    – Is that with the figures above I am according to you operable?

    Thanks in advance,

    Mary

  2. Dr. Damien Gatinel says:

    Your degree of correction is available for surgical treatment a priori. There is no sign of kératocone a priori, and before any surgery, a topography of the cornea is carried out to confirm the absence of this condition. The keratoconus is triggered by vigorous and repeated eye rubbing. Take a checkup at a specialized center!

  3. Denis says:

    Hello doctor,

    I have just undergone cataract surgery. OD April 2, 2019;
    The installation of an o-ring implant was planned.
    Seeing very badly after the operation, I watched my map implant and I saw that the implant was not the one intended.
    The surgeon I asked for the reason told me that the bag was fragile and that he feared having to replace the implant and prefer to put a normal one.
    I do not understand why the o-ring implant could not be installed.
    He tells me that only glasses can make an improvement.
    I am very disappointed and I do not support this blurred view.
    Are there any solutions to correct this bad result?

  4. Naw says:

    Hello Dr Damien Gatinel,

    I would write to you to learn more about operation laser (refractive surgery) of the eyes.

    I am 24 years old and I wear glasses from primary school (grades CE2, if my memories are good).

    I am Myope and strong Astigmate.

    Here are the data from my ophthalmologic prescription (which dates from 2016):
    – OD: 0 (-4 to 0 °)
    – OG: + 0.5 (-3.5 to 170 °)

    Over time, I am increasingly frustrated with my vision. I have always hoped (and dreamed) to have an excellent vision (or only be nearsighted)!
    My strong astigmatism is very restrictive.

    However, wearing glasses becomes binding (easily breakable, sporty...) and unsightly and then it cannot correct the angles. To this day, I have not worn my glasses for a few years (because I became complexed) except to work my classes, watch TV and drive at night.

    I would like to at least wear lenses but I'm thinking more and more about doing laser surgery to correct these Visual flaws.

    I am eager for curiosity, I have done hundreds and hundreds of research on astigmatism, myopia, rigid toric lenses and refractive surgery.

    But I would like to know please if:
    – Am I operable? By which method laser? Are there really risks? Will the laser succeed in reducing my astigmatism considerably? My astigmatism is not likely to evolve over time, is it?
    – Can I at least wear lenses (time to do the operation)?
    – Do rigid toric lenses correct high astigmatism?
    – Can you explain the number 0 and + 0.5 Please (for the rest of the data, I understood that it was to define astigmatism).
    Please

    I beg you to apologize for the length of my message.

    Waiting for a response from you
    Thank you in advance

    Well cordially

    N.

  5. Dr. Damien Gatinel says:

    You have a bilateral congenital myopic astigmatism, the origin of which is a particular cornea geometry (more vertically "arched", which induces myopia on the vertical axes). The best technique to consider is LASIK, if your corneas have the required thickness and regularity. The risks are low, and it is appropriate to benefit from the use of recent laser platforms (femtosecond and excimer). Toric or rigid lenses are also able to correct astigmatism. The number 0 and 0.5 is related to the "defocus" associated with your astigmatism, it is not very important in your situation.

  6. Dr. Damien Gatinel says:

    The installation of an o-ring or multifocal implant requires a perfect performance of the procedure, so that the implant can be positioned at its best. In case complications such as capsular rupture, it is preferable to opt for a monofocal implant, and correct a possible residual optical defect in glasses or in corneal refractive surgery (LASIK or PKR).

  7. Denis says:

    Hello doctor,

    I follow up on my question of 11 April 2019 concerning the non-installation of an o-ring implant.
    Thank you for your reply today.
    My surgeon has indicated to me since there had actually been rupture of the capsular SAC and that the monofocal implant posed ACRYSOF MA50BM 20.0 D, spherical implant, had been put in the sulcus and not in the bag.
    Temporary correction:-0.75 (-1.25 to 160 °) add not known.
    I see very cloudy, split with light distortions.
    Because of this location, is there any possibility of relocating or changing the implant?

    My surgeon told me that there was always cataract at the bottom of the bag;
    If I understand a YAG laser is to make a hole in the bag. So would I have 2 holes in the bag and if so, fragility?

    Thanking you,

    Distinguished greetings

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