User:CorwinBM/Astigmatism

Epidemiology
In 2019, the World Health Organization reported that 123.7 million people worldwide were affected by uncorrected refracting errors, including astigmatism. A compilation of many systematic reviews found that there was an 8-62% prevalence of astigmatism among adults, with an estimated prevalence of 40% worldwide. The country with the highest reported prevalence among the compilation of systematic reviews is China at 62%. The prevalence of astigmatism increases with age due to changes in refractive index gradients.

Studies have shown that infants in their first few months have a high prevalence of astigmatism due to a steep cornea. The steepest corneas are found in infants with low birth weights and post-conceptional age. By the age of four, the prevalence of astigmatism has reduced as the cornea flattens. The cornea remains mostly stable during adulthood, and then steepens again in older adulthood (40+ years).

Mild astigmatism has a higher prevalence than moderate and significant astigmatisms and increased until the age of 70, while moderate and significant astigmatisms showed an increase in prevalence after the age of 70. Of the levels of astigmatism, mild astigmatism is most prevalent, making up about 82% of the total reported astigmatisms.

With-the-rule astigmatism among the total population has a prevalence range of 4 to 98% globally. The prevalence range for against-the-rule astigmatism is from 1 to 58%. For oblique astigmatism, the prevalence range is from 2 to 61%. With-the-rule astigmatism is more prevalent in young adults, and over time, the prevalence shifts to be mostly against-the-rule astigmatism.

The main cause of astigmatism is changes in the curvature of the cornea. When left untreated, astigmatism causes people to have a lower vision-related quality of life. Some factors that lead to this are a decrease in vision quality and an increase in glare and haloes. People with astigmatism have more difficulty with night driving and can have a decreased productivity due to errors. However, there are many ways to help correct astigmatisms. The use of glasses, contacts, Toric intraocular lenses, Toric implantable Collamer lenses, corneal refractive surgery have been shown to correct astigmatisms.