What Is It
In astigmatic eyes, the curvature of the cornea is greater in one direction than in the other. The images are focalized in a non-homogeneous way on the various meridians, which cause distortion. This visual defect is similar to myopia and hypermetropia. Traditionally, astigmatism is corrected with glasses or contact lenses. It is possible that the patient undergoes a safe and effective refractive surgery that can correct this visual defect, thus eliminating or reducing the need for glasses or contact lenses.
Astigmatism is not a disease but a common and widespread ametropia or refractive error. Depending on the involved anatomical elements, astigmatism is defined as:
- corneal, if it is due to an abnormal curvature of the cornea,
- internal or lenticular, if it is determined by an alteration of one of the internal sections of the eye, primarily the crystalline lens.
In both cases, the result is an inaccurate vision and indefinite objects that, both near and far are distorted, blurred or even split. This defect can be simple or compound if, as happens frequently, it is associated with myopia or hyperopia.
What Causes Astigmatism
As in nearsightedness, farsightedness, or other refractive defects, astigmatism is caused by the deformation of some internal structures of the eye. The astigmatic eye has a greater curvature in one direction that is relative to one another. Because of this, the light does not strike the retina in a uniform manner, thus the images are focused unevenly on the various meridians and vision is distorted.
Inheritance is an important factor. The defect is often acquired if it is present in other members of the family. One should understand that a high degree of astigmatism in both eyes can be a symptom of a serious ocular disease such as keratoconus in which the cornea thins and weakens.
How Is Astigmatism Treated
While some degree of corneal astigmatism is quite natural and the eye compensates for the defect spontaneously, beyond 0.75 diopters, degrees of external correction is necessary. This is done by:
- Glasses And Toric Contact Lenses
Most forms of astigmatism are easily manageable and traditionally, the defect is corrected with glasses or contact lenses. The lenses are toric as they have a particular form that is capable of accurately correcting vision in all meridians of the eye, thereby aligning the power of the lens at each meridian.
- Laser Refractive Surgery
Individuals whose special needs at work or sports activities that do not allow for wearing contact lenses or glasses, can opt for refractive surgery. Surgery with an excimer laser is safe, effective, and definite. It corrects astigmatism substantially, thus eliminating or greatly reducing the need for eyeglasses and contact lenses.
- Implant Of Intraocular Lenses
Finally, a further solution is an implant of intraocular toric lenses that are able to almost completely remove the astigmatic defect. The implant of a multifocal or toric lens, that is highly customized to the anatomical and functional characteristics of the patient’s eye, is able to reduce or completely eliminate the need for glasses.