Introduced in the 1980s, laser eye surgery is a surgical procedure designed to permanently correct visual defects such as myopia (blurred distance vision), hyperopia (blurred near vision), astigmatism (image distortion) and presbyopia (blurred near vision). This surgery involves reshaping the cornea, the transparent part at the front of the eye.
What is myopia?
Myopia is a visual defect characterized by light rays focusing in front of the retina. It can be explained either by an eye that is too long (increased axial length), or by a cornea with too much convergent power (overly curved cornea). Distance vision is therefore blurred.
Treatment to correct myopia
For myopes, the operation involves reshaping the center of the cornea to restore its optimal refractive capacity. The greater the myopia, the more extensive the remodelling.
For very severe myopia, the operation is performed not only on the cornea, but also on the lens, in front of which an implant is inserted. The surgeon calculates the power of the implant to be inserted according to the visual defect.
What is hyperopia?
Hyperopia is a visual defect characterized by light rays focusing behind the retina. It can be explained either by an eye that is too short (insufficient axial length), or by a cornea with too little convergent power (cornea too flat). In the case of mild hyperopia, vision is not impaired, thanks to the ability to accommodate. Compensation through accommodation can lead to visual fatigue. Accommodative ability declines around the age of 40. In the case of severe hyperopia, vision is impaired at both distance and near.
What is astigmatism?
Astigmatism is a visual defect that can be associated with myopia or hyperopia. Light rays converge at different focal lengths. Schematically, the cornea is not "round like a football" but "oval like a rugby ball". Visual blur varies in intensity, depending on the power (conventionally noted in brackets) and the axis of the astigmatism (noted in degrees).
Treatment to correct astigmatism
To correct astigmatism, the operation consists in making the cornea uniform if it is irregular and not perfectly spherical.
It gives good results, but it may not be possible to correct the entire visual defect. In this case, glasses are still needed to correct this small visual defect and achieve perfect visual acuity.
What is presbyopia?
Presbyopia is a visual defect that appears around the age of 45 and results in reduced near vision. It results from a reduction in accommodation capacity, due to rigidification of the crystalline lens, which can no longer focus when reading. Presbyopia progresses gradually until the age of 65.
Treatment to correct presbyopia
Monovision (or "tilt") is a technique used to correct presbyopia. It involves correcting one eye for distance vision and the other for near vision. In practice, after the operation, one eye is emmetropic (so you can see well at a distance without glasses), and the other slightly myopic (the slight myopia induced enables you to see well at close range without correction).
If you suffer from cataracts, it is possible to take advantage of the operation to replace your crystalline lens by inserting an implant to correct your optical defect:
Treatment for cataracts
Cataract surgery involves replacing the opaque crystalline lens with an implant placed behind the cornea. In the absence of a multifocal implant, reading usually requires near vision correction.
Surgery therefore brings good results and makes it possible to significantly reduce visual defects. However, perfect correction is not guaranteed and it is sometimes necessary to wear glasses with a low correction for distance or near vision.