Astigmatism

What do we mean by astigmatism?

The astigmatism represents a frequent visual condition, where the main symptom is blurry vision, both at distance and at near.

What is the cause of blurry vision of astigmatism?

In most of the cases, the astigmatism is caused by an irregular curvature of the cornea (the eye anterior lens). Normally, it is round, but in astigmatism it is oval (as a rugby ball); the light rays entering the eyes are distorted and are not focused appropriately on the retina. The irregular curvature of the cornea, where a half is more curved or flatter than the other, leads to the emergence of two different images on the retina (instead of a single one). This distorted projection leads to the blurry vision of astigmatism.

There is also the crystalline lens astigmatism, when the shape of the crystalline lens (the lens inside the eye) is irregular, having the same effects on the vision.

Astigmatism symptoms and how does it manifest itself

Blurry vision at all distances is the main symptom of astigmatism. Astigmatism patients see the world crooked, stress their eyes permanently, feel the need to squint, in the attempt to clarify images perception. They complain of eye fatigue, headache (pain) and/or light sensitivity.
Glasses sometimes give the feeling of dizziness, especially when they are changed, until your eyes get used to the new correction.

Is astigmatism a disease? Is it a dangerous diagnosis?

The astigmatism is a refractive error, being a condition consisting in the eye form abnormality. It can be associated to other refractive errors, myopia (when the axis of the eye is too long) or hyperopia (when the eye is too short). In all these cases, the light rays are not correctly projected in the back of the eye.

Therefore, we can talk about simple, myopic, hyperopic or mixed astigmatism.

When does astigmatism occur? Can it be inherited?

The astigmatism is usually congenital (we are born with it). Furthermore, it looks like we all have a certain degree of astigmatism at birth.

It occurs more often in children whose parents (one or both) have astigmatism. Also, it seems that astigmatism occurs more frequently in premature babies.

Astigmatism can occur during life, within a condition called keratoconus, following serious eye infections, a trauma or an ocular surgery, more precisely in situations resulting in scars or structural changes affecting the curvature of the cornea.

How is astigmatism diagnosis established?

Most of the children who are born with astigmatism do not realize that they have and eye problem (they think a distorted and unclear vision is normal). Reading and school concentration effort can be affected if the child is not diagnosed in due time. Therefore, it is important to conduct regular eye tests, the first should be at the age of 3.

Following visual acuity testing, corneal curvature is measured by keratometry and a corneal topography can be performed for further details on the corneal shape and surface.

The astigmatism can be regular, where one of the meridians is more curved, and the other one, the perpendicular one, is flatter. If there is not a 90 degree angle between the main meridians, the astigmatism is irregular (by corneal scars, in keratoconus).

Regular astigmatism can be according to the rule (vertical meridian is more curved), contrary to the rule (horizontal meridian is more curved) or oblique (main meridians are oblique).

Is it a dangerous disease? Can it lead to the loss of vision?

Generally, astigmatism can be developed during childhood or old age. With an appropriate optical correction, vision quality can be good, without long-term adverse effects.

There is a particular form of astigmatism, which is acquired, called keratoconus. It emerges in the teenage years and means the distortion of the cornea, which in time becomes conical and becomes progressively thiner.

In this case, the astigmatism is progressive, it worsens. Over time, the corneal thinning can become dangerous, with the risk of perforation. If the correction of the vision is performed by glasses or contact lenses (usually rigid) in the initial stages, in the advanced stages the corneal transplant (which removes corneal perforation risk) can be required.

How can astigmatism be treated?

Astigmatism optical correction can be performed by glasses or contact lenses (soft or rigid). Refractive surgery is used for permanent correction.

The prescribed glasses have cylindrical lenses. They have the role to correct the way the light rays are projected on the retina, thus providing a clear image. Firstly, the glasses create discomfort, an accommodation period being required. The same effect can be obtained by soft, toric contact lenses. However, they can move easily on the surface of the eye, and this instability can result in blurry images. The astigmatism contact lenses provide an instable vision due to unequal curvature radii.

Rigid, gas permeable contact lenses are an efficient alternative for high astigmatism correction or for keratoconus healing.

Which are astigmatism correction methods?

The astigmatism can be corrected by:

Lasek/PRK technique

PRK / Lasek are two similar methods of diopter correction by means of excimer laser. The technique is based on the property of the corneal epithelium (the first layer of the cornea) to regenerate naturally and consists in the partial removal of this layer. Subsequently, the cornea is reshaped by means of the laser, thus obtaining the correction of the diopters. The difference between these techniques consists of the fact that in case of LASEK, the removed epithelium is repositioned after the laser treatment, being gradually replaced by a new epithelium.
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FemtoLasik technique

FemtoLASIK is a diopter correction modern method which requires the use of two types of laser: Femto and Excimer. The diopters reduction surgeries are performed by means of a quick treatment, customized, with no sound, no odor, independent of the environment, with an accuracy of less than one micron, by fulfilling the corneal curvature.
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