Ophthalmology: causes, symptoms and treatment of astigmatism

By Cristiano Antonino On Dec 8, 2022

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Astigmatism is a visual defect in which – due to an oblong or oval shape of the cornea – there is a different refraction along the different meridians that causes light rays to focus at two points of the eye, instead of just one: in practice, the image forms simultaneously in front of and behind the retina and vision appears more or less blurred

Types of astigmatism

Astigmatism can be classified according to the position of the two foci in relation to the retina:

simple astigmatism
simple myopic astigmatism
simple hypermetropic astigmatism;
compound astigmatism.

The corneal form is due to an abnormal curvature of the cornea.

Internal or lenticular astigmatism, on the other hand, is caused by alterations in the dioptric media inside the eye.

Causes of astigmatism

A certain degree of corneal astigmatism is physiological (average 0.75) and is due to eyelid pressure.

However, this astigmatism is compensated by the dioptric means inside the eye.

High-grade astigmatism is generally congenital and may undergo slight variations throughout life.

Irregular astigmatism, on the other hand, arises due to changes in the cornea as a result of trauma, injury and infection.

Symptoms and diagnosis of astigmatism

Mild astigmatisms can be asymptomatic or present symptoms resulting from the continuous change of focus (accommodation) in an attempt to obtain as sharp an image as possible: pain in the eyeballs and on the ciliary arch, headache, burning eyes, excessive tearing.

Medium to high astigmatism usually presents blurred vision, both in distance and near vision.

There are numerous ophthalmic tests to diagnose astigmatism: the Snellen chart (used to quantify visual acuity), the keratometer (measures corneal curvature), corneal topography (provides a point-by-point mapping of the corneal curvature) and the subjective refraction test (allows the correct measurement of astigmatism).

Treatment of astigmatism

Astigmatism can be corrected with the use of astigmatic ophthalmic lenses, with contact lenses or through refractive surgery.

The coexistence of other ametropias, the degree of astigmatism, ocular health, lifestyle and other individual factors help determine the most suitable solution.