Astigmatism is a refractive vision problem, which can be treated with laser eye surgery. This condition can be corrected with LASEK, LASIK, and photorefractive keratectomy, which are discussed in this article.
Astigmatism is a refractive problem that is caused by the structural abnormalities of the cornea or the lens. This condition is characterized by blurred vision. The light entering the eye does not refract correctly on the cornea, because of the uneven or irregular curvature of the cornea or the lens. This in turn causes blurred vision.
This condition can be corrected with contact lenses and refractive eye surgery. The refractive eye surgeries used for correcting astigmatism can be of three types – LASIK (laser in situ keratectomy), LASEK (laser epithelial keratomileusis), and photorefractive keratectomy. These surgeries are used for other refractive vision problems as well.
What is Astigmatism?
Generally, the eye is sphere-shaped with a smooth and even curve. But the cornea of the individuals with astigmatism is usually oval-shaped, or their lens do not have an even and perfect curvature. If there is a defect in the curvature of the cornea, light do not get refracted properly to create a clear image of the object. Similarly, when there is a problem with the curvature of the lens, clear images of the objects do not form in the retina. In both the cases, the affected individual experiences distorted or blurred vision.
In astigmatism, the cornea or the lens can have irregular curvature, i.e., some areas can be flatter or steeper than other areas, instead of being even and smooth in all directions. The defect in the cornea can be caused by factors like scarring, eye injuries, infections, and certain types of surgery. Astigmatism can also be congenital, as some people can be born with a cornea with irregular curvature. Other possible causes include, premature birth, and having a low body weight at birth. On the other hand, a problem with the curvature of the lens can be associated with conditions like high blood pressure.
Astigmatism can be corrected with the help of contact lenses. Rigid contact lenses, gas or oxygen permeable contact lenses, and soft toric contact lenses are commonly used for correcting this refractive error. If contact lenses fail to correct this refractive problem, then surgery can be required. There are basically three types of laser eye surgery that are employed for correcting this vision problem.
LASIK surgery involves the use of a precision blade, known as microkeratome, to make a thin and small incision in the outer layer or epithelium of the cornea. This epithelial flap is then lifted to gain access to the middle layer of the cornea. An excimer laser is used to smoothen the cornea, so that it can refract light properly. Once reshaping is done, the epithelial flap is replaced, and then covered with a contact lens. The healing time for LASIK eye surgery is much shorter than LASEK surgery. However, some antibiotic eye drops may need to be applied to prevent infections, until the epithelium of the cornea heals completely.
Laser-assisted subepithelial keratomileusis or LASEK is the surgery ideal for people with a thin or steep cornea, as they are not considered eligible for LASIK surgery. In LASEK surgery, the thin epithelial layer of the cornea is preserved. The surgeon cuts the epithelium of the cornea with a fine blade, after which diluted alcohol solution is applied on that area. This solution helps loosen the edges of the epithelium or the outer layer of the cornea.
Once the edges of the epithelium are loosened, the alcohol solution is removed. A tiny hoe is used to lift and fold back this epithelial layer from the surface of the eye, after which the surgeon applies laser beams with an excimer laser to reshape the surface of the cornea. Once reshaping is done, the epithelial flap is placed back on the surface of the eye. In this way, LASEK eye surgery can preserve the epithelial layer of the cornea, and thus reduce the chances of any kind of injuries. However, the healing time can be much longer, as compared to LASIK surgery.
Photorefractive Keratectomy (PRK)
Photorefractive keratectomy involves the removal of the outer or surface layer of the cornea in order to change its curvature. After the outer layer or the epithelium of the cornea is removed, it is reshaped with the help of an excimer laser. This procedure is also known as surface ablation. This surgery often involves a longer healing time, which is its main disadvantage. People with thin cornea are generally considered eligible for this surgery.
So, LASIK, LASEK, and photorefractive keratectomy are the refractive laser eye surgeries used for correcting astigmatism. For high astigmatism, many surgeons recommend wavefront laser surgery. This surgery is comparatively more expensive than the usual laser eye surgery. But high astigmatism can require greater accuracy, which wavefront laser surgery can ensure. However, your ophthalmologist or surgeon will be the best person to recommend which one of these procedures would be suitable for you.
Disclaimer: This article is for informative purposes only, and should not be treated as a substitute for professional medical advice.