Astigmatism

Astigmatism is a refractive error characterized by a variation in the dioptric power of the eye from one meridian to another.

The most common symptom is diminished visual acuity.

The etiology is still unknown, but it is probably influenced by both genetic and environmental factors.

Among the common risk factors are a family history of astigmatism; myopia; Native American, East Asian, Hispanic, or Brazilian ethnic origin; eye trauma or surgery; and certain genetic and eyelid pathologies.

In most cases, the diagnosis is clinical and further diagnostic tests are usually not necessary.

Screening in the pediatric population is essential, primarily to decrease the risk of amblyopia.

Astigmatism is a refractive error characterized by a variation in the dioptric power of the eye from one meridian to another, rendering the optical system incapable of generating a clear image.[1]Jacobs DS, Afshari NA, Bishop RJ, et al. Refractive errors preferred practice pattern®. Ophthalmology. 2023 Mar;130(3):P1-60. https://www.aaojournal.org/article/S0161-6420(22)00867-3/fulltext http://www.ncbi.nlm.nih.gov/pubmed/36543603?tool=bestpractice.com ​ Instead of having a spherical cross-section, the cornea and/or lens is cylindrical, with different focal power depending on the plane in which the light travels (the meridian). The meridians that have the greatest and the least dioptric power are known as the principal meridians.

Total refractive astigmatism can be divided into corneal (most cases), lenticular, and retinal.[1]Jacobs DS, Afshari NA, Bishop RJ, et al. Refractive errors preferred practice pattern®. Ophthalmology. 2023 Mar;130(3):P1-60. https://www.aaojournal.org/article/S0161-6420(22)00867-3/fulltext http://www.ncbi.nlm.nih.gov/pubmed/36543603?tool=bestpractice.com Regular corneal astigmatism occurs when the principal meridians are at 90° to each other; irregular corneal astigmatism refers to cases where the magnitude and the axis of astigmatism varies at different points of the cornea. Lenticular astigmatism is a result of uneven lens curvature, lens tilt, and differing refractive indices within the lens.