Laser vision correction for high defects

Depending on the size of the defect, hyperopia is distinguished:

• small – up to +2.5D
• medium – +2.5D to +6.0D
• large – over +6.0D

Depending on the severity, myopia is divided into:

• small – also called school, up to -3 D,
• medium – between -3D and -6 D (according to some sources between -3D and -8D)
• large – above -6 D (according to some sources above – 8D)

Astigmatism is classified as:

• low – up to 1 cylindrical dioptres (usually does not require correction)
• high – up to 2 diopters cylindrical
• very high – more than 3 cylindrical diopters

Too high a visual defect – myopia above -10 diopters and farsightedness above +5 diopters – is a contraindication to laser correction. However, this does not mean that a farsighted or nearsighted person with a high visual defect must settle for glasses or contact lenses.

Similar problems with laser correction arise with irregular astigmatism, which is difficult to treat.

In the case of the most well-known method of laser vision correction – LASIK – to get to the corneal bed and remove refractive errors, the surgeon cuts an ultra-thin flap (called a flap), which is carefully deflected, and then the inside of the cornea is exposed to an excimer laser and reshaped so that the focus point is optimally on the retina.

Then the flap is resealed, and the cornea heals within a few days. The higher the refractive defect, the more tissue needs to be removed to correct it.

Therefore, the cornea must be thick enough to allow the procedure to be performed. Many patients simply do not have a cornea thick enough to undergo this method of laser vision correction.

But modern refractive surgery offers many other methods of laser vision correction. If you don’t qualify for LASIK treatment, your surgeon can choose from other deep methods – surface methods have a smaller range of defect removal than in the deep methods.

He can also opt for Carl Zeiss’ ReLEx® SMILE method (microlens laser vision correction), which is a recently developed generation of laser vision correction.

In this method, called the “keyhole” method, the corneal flap (flap) is not formed and cut – the procedure is performed through a small incision on the cornea, and is therefore minimally invasive.

This means that there is minimal interference with the cornea, so the healing process of the eye is very short. ReLex® SMILE is used only for patients with myopia from -0.5 to -10 diopters and astigmatism up to -5.0 diopters.

If neither spectacle lenses nor contact lenses produce the desired result, and the patient does not qualify for laser correction, one has to turn to traditional surgical methods, such as the implantation of intraocular toric single, bifocal or trifocal lenses, as a phakic lens doppler or refractive lens replacement.