Correction of Astigmatism in the Eye
What is Refractive Errors?
Refractive errors in the eye come in three forms: myopia or nearsightedness, hypermetropia or farsightedness, and astigmatism.
In myopia or nearsightedness, images form in front of the retina, resulting in objects appearing blurry. Myopia usually starts in childhood and gradually progresses into adulthood, typically from ages 18 to 21.
Hypermetropia or farsightedness occurs when images form behind the retina, causing objects to appear blurry.
In a normal eye without astigmatism, the curvature of the cornea at different axes (horizontal and vertical) is similar to a football shape. In this case, when light passes through the cornea, it converges at a single point. However, when astigmatism is present, the curvature of the cornea is not the same in different directions (horizontal and vertical), similar to an egg that is steeper on one side and flatter on the other. This causes the light passing through the cornea to converge at different points, resulting in a distorted and irregular image.
The causes of eye astigmatism
Astigmatism is a common type of refractive error that occurs when the corneal or lens surface of the eye becomes irregular in shape.
When this irregularity and abnormal curvature occur on the surface of the cornea and the lens, the eye is no longer able to properly focus light onto the retina, resulting in a lack of clear vision. Blurred vision and the inability to see objects and people sharply are common issues for individuals with astigmatism.
What factors can cause astigmatism?
According to research, it has been determined that most individuals with astigmatism have inherited this condition.
B- Corneal and lens shape
In individuals with astigmatism, the corneal surface is more like a basketball, which is to say, it is uneven. On the other hand, in people with normal vision, the cornea is smooth and shaped more like a football. Because of these irregularities, the eye’s lens and cornea are unable to focus light on a specific point on the retina, causing images to appear blurry.
C- Eye injuries or eye surgery
If an individual experiences an eye injury or undergoes eye surgery, it’s possible for them to develop astigmatism later on.
It is possible for astigmatism to coexist with keratoconus and myopia. In keratoconus, the cornea becomes thinner and takes on a conical shape. Fortunately, this condition is relatively rare.
Vision problems in individuals with these conditions cannot be fully corrected with glasses, and in such cases, the use of contact lenses is highly suitable. However, it should be considered that these individuals may require corneal transplant surgery in the future.
E- Nearsightedness and farsightedness
Individuals with astigmatism often experience nearsightedness or farsightedness as well. Nearsightedness and farsightedness are types of refractive errors in which the eye is unable to focus light from various objects properly. As a result, individuals with astigmatism and nearsightedness or farsightedness can use specialized glasses and contact lenses to correct these refractive errors by consulting with an eye doctor.
In general, the treatment methods for astigmatism are divided into two categories: medical and surgical:
A) Medical methods include eyeglasses, soft toric contact lenses, and hard contact lenses.
B) Surgical methods involve laser procedures (PRK, LASIK), implantation of toric intraocular lenses, and creating corneal incisions with a diamond knife or laser (AK). Temporary sutures, especially for astigmatism correction in corneal transplantation patients, are also used.