Astigmatism correction and treatment

We can correct astigmatism by cylindrical and toric corrective appliances which refract entering parallel rays of light in such a way that both of formed focal lines of astigmatic eye come so close to each other that they become identical. This eliminates the focal interval which is present in uncorrected astigmatic eye. People suffering from astigmatism have several options how they can again acquire sharp vision: eyeglasses, contact lenses or surgical procedures.

The correction of astigmatism by eyeglasses

It is important to realize that with the help of accommodation a person is capable of correcting only spherical but not cylindrical component of a refractive disorder. That is why it is necessary to correct this component completely that it does not cause any subjective problems.

All patients should be approached on individual basis because some people, mainly those with lower astigmatism, refuse cylindrical correction and some explicitly demand the correction of even low degrees of astigmatism. Even this can surprisingly improve visual sharpness.

Eyeglasses are often the first choice used to correct astigmatism. Nowadays there are many types of various corrective lenses which offer satisfactory vision for people of all ages.

For children cylindrical correction tends to be prescribed in maximal value. They are more adaptable and get accustomed to them more easily. However, we proceed more carefully with adults. It is not suitable to begin with full correction but it is advisable to increase it gradually and in this way adaptation will be smooth. When adaptation to cylindrical correction is problematic we try to move the lens as close to the eye as it is possible or it is necessary to decrease the value of cylinder. At the same time it is necessary to adjust also spherical correction or we do not use astigmatic part of the correction at all.

It is very important to begin with possibly the most tolerable correction. In this way a patient feels comfortable.

The correction of astigmatism brings also some specific problems mainly in the case of higher degree astigmatism. Then it can lead to formation of meridional aniseikonia (imbalanced sizes of images on the retina of both eyes) and distortion of images.

The correction of astigmatism by contact lenses

Contact lenses are a solution for clients who cannot stand wearing eyeglasses or they suffer from such type of astigmatism that cannot be corrected by eyeglasses or simply for those who do not want to wear eyeglasses due to various reasons. Contact lenses are more advantageous because wearing them achieves that image distortion and change in its size are minimal.

The correction of low degree astigmatism when spherical component dominates astigmatic component is usually achieved by spherical contact lenses with aspherical surface. Higher degrees are corrected by toric contact lenses. Sometimes soft contact lenses are not capable of correcting astigmatism completely. In such cases it is possible to use hard contact lenses. However, they are used only very sporadically.

Surgical procedures to correct astigmatism

Contemporary progress in technology influences also solutions for astigmatism as far as special methods of the correction are concerned. The most commonly used procedures can be divided to non-laser (astigmatic keratotomy) and laser (PRK, LASIK) procedures.

Astigmatic keratotomy

Astigmatic keratotomy is often connected with other surgical procedures, for example during cataract surgery. The substance lies in the change of incurvation of the cornea by tiny cuts. This makes the cornea flatter. These cuts are done at various distances from the middle of the cornea, have different profiles but they always have to be performed on the axis of the steepest meridian.

This procedure can be performed primarily or secondarily, for example after previous eye surgeries (cataract surgery, previous refractive surgeries). Astigmatic keratotomy eliminates only corneal astigmatism caused by irregular incurvation of the front surface of the cornea.

PRK - photorefractive keratotomy

During PRK - photorefractive keratotomy part of the corneal epithelium is removed by photoablation (volatilization by light), the cornea is corrected according to the type of disorder and desired refractive power. After the procedure a patient can feel moderate pain and it is necessary to wear special contact lenses which protect sensitive eye without the epithelium.

LASIK

LASIK procedure involves the separation of surface layer of the cornea which has the form of thin lamella. The part of the cornea beneath it, namely its incurvation, is adjusted by laser.

Then the separated lamella is returned to its original position. The advantage of LASIK procedure compared to PRK is that the healing process begins 2-3 hours after the surgery. Patients do not suffer from a lot of pain and sight is restored after only a couple of days.