Summary

• Astigmatism is a refractive error characterised by a variation in the dioptric power of the eye from one meridian to another.
• The most common symptom is diminished visual acuity.
• The aetiology 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 paediatric population is essential, primarily to decrease the risk of amblyopia.