Eye surgery: which condition can it correct?

Here are the various eye-related conditions

Myopia 

Low myopia up to -4.00 diopters can be corrected by a simple laser procedure, achieving a perfect visual result in more than 95% of cases. For moderate myopia (-3.00 to -9.00 diopters), LASIK achieves an excellent result in 85% of cases. A touch-up may be necessary and remains possible in the remaining 15% of cases. LASIK or intraocular implants are recommended for myopia of -9 to -13 diopters. Finally, for myopia greater than -13 diopters, the myopic implant appears to be the most suitable option.

Hyperopia 

The preferred surgical technique is LASIK. For hyperopia below 4 diopters, the correction is technically straightforward and the results are reliable and reproducible. In the case of hyperopia greater than 4 diopters, improvement is certain but regression is possible, which may lead the patient to wear corrective lenses in certain circumstances.

Astigmatism 

Laser surgical techniques flatten one meridian more than the other. This allows correction of up to 6 diopters of astigmatism. However, total correction cannot be guaranteed for severe astigmatism. It is possible, however, to perform a repeat procedure in cases of insufficient correction. In all cases, LASEK provides more precise correction than LASIK because the flap is better centered and more regular. Results can be further improved with iris recognition.

Presbyopia 

This surgery is intended for patients over 45 who wish to stop wearing glasses for reading. Presbyopic patients often experience intolerance issues or complications related to contact lenses, which is why they turn to surgery — requests are becoming increasingly frequent.

In general, only one eye is operated on first, then the operation on the second eye allows vision to be adjusted according to the patient's wishes. It is therefore preferable to propose correcting the second eye after stabilization of the first eye's vision.

A precise surgical correction program for presbyopia is calculated for each patient by computer. Surgical techniques vary: laser, implants, etc. Laser treatment creates a progressive optical surface resulting in a "multifocal" cornea that corrects presbyopia. The center of the cornea becomes the zone dedicated to near vision.

The peripheral zone will provide distance vision, and the intermediate zone will provide near vision. A slight shift between the dominant eye, which is favored for distance vision, and the non-dominant eye, which is favored for reading, may be considered. The PRELEX technique (PREsbyopic Lens EXchange) applies cataract surgery techniques using multifocal implantation to correct presbyopia and any associated hyperopia or myopia. The presbyopic crystalline lens is replaced by a multifocal implant enabling correction of distance, intermediate, and near vision.

Correction is sometimes necessary during activities requiring significant visual precision (night driving, embroidery, etc.). 

However, according to clinical studies, 90% of people with this type of implant in both eyes perform daily tasks without glasses.

The power of the implant is carefully calculated by ultrasound. As the eye is living tissue, the precision of measurements is not always absolute (precision of approximately 0.75 diopters). The latest-generation implants cause fewer side effects (halos around light sources, glare, reduced contrast sensitivity, etc.) than previously used implants, but 12% of patients are still affected. They sometimes feature a UV filter. However, the patient must be motivated and have realistic expectations regarding visual outcomes. The implant can also be positioned in front of the iris (anterior chamber implant).

The scleral expansion procedure consists of increasing the work of the ciliary muscle in order to restore a certain degree of "accommodation" and compensate for presbyopia. It involves implanting 4 PMMA bands in the sclera, behind the limbus, at the top, bottom, right, and left.

These bands are designed to lift the sclera, thereby pulling on the zonule that supports the crystalline lens to move it away from the sclera and allow it to accommodate again. This technique is currently under study. The myopic patient over 40 who has not undergone surgery can, in most cases, read without corrective lenses. If they have undergone myopia surgery, they will need glasses for near vision.

Several options exist to compensate for both myopia and presbyopia:

monovision: one eye is left slightly myopic to allow near vision, while the other eye is perfectly corrected for distance. A cerebral adaptation is required since both eyes never see clearly at the same time. This technique does not always produce satisfactory results due to this imbalance.

A simulation is possible before the operation using contact lenses that will mimic the post-operative result. In the event of a poor outcome, it is possible to re-operate on the eye left myopic to correct it for distance vision. The corrective technique may be, depending on the degree of myopia, a PKR, LASIK, or LASEK laser, or an implant.

bifocality or progressive correction: the patient's cerebral flexibility is, in this case, very important, just as with bifocal or progressive lenses. Various techniques are still under evaluation. Laser is an option, as is the placement of a multifocal implant.

Unlike myopia, the correction of hyperopia partially addresses presbyopia. In 80% of patients, surgical correction of hyperopia sometimes eliminates the need for near-vision lenses. The technique used can be a laser or a unifocal or progressive implant.

Astigmatism and Presbyopia 

As with simple astigmatism, the combination of the two refractive disorders will be considered depending on the associated disorder, myopic or hyperopic. It is possible to perform implant placement combined with laser in order to correct presbyopia with an implant (there are no astigmatic implants) and astigmatism with laser.

Also discover our complete guide on the solutions available to correct visual impairments.

Risks common to all refractive surgery

The result depends on the healing process and is therefore highly variable from one individual to another. Additional correction using glasses, contact lenses, or reoperation is sometimes necessary. 

Refractive surgery procedures, like all surgeries, are not without risks, even if they are low. Complications are always possible. These include, in particular, the perception of halos, a tendency toward glare, a reduction in visual acuity (even when compensated), difficulty with night vision, double vision, and image distortion. These complications may sometimes require medical or surgical treatment. 

Intraoperative complications (during surgery) are estimated at between 0.3% and 1%, and post-operative complications of refractive surgery at between 1 and 2%. 

Widely popular, this surgery is currently on the rise, even though its long-term effects are not yet known. Several years will need to pass before that becomes clear.