Astigmatism: Update and Review

Abstract

Astigmatism is a common refractive error encountered in clinical practice. It nearly accounts for approximately 13 percent of refractive errors in the human eye. The first report of astigmatism came in early 1800 by Thomas Young, and George Airy used the first cylindrical lens in 1825. Recently, a great deal of research has been carried out on various aspects of astigmatism. Untreated astigmatism may result in loss of visual acuity and amblyopia. The association between myopia and astigmatism has also been reported. Astigmatism can be corneal, lenticular, or retinal. Based on the meridian, it can be with the rule, against the rule, oblique and bi-oblique astigmatism. Astigmatism can also be subdivided as simple, compound, and mixed. Various factors influence astigmatisms, such as eyelid pressure, the pressure of extraocular muscles, pupil size, and accommodation. Astigmatism usually causes asthenopic symptoms, and there can be different power in different meridians. Astigmatism is diagnosed by performing basic investigations like visual acuity, retinoscopy, slit lamp evaluation examination, keratometry, Schiempflug imaging, astigmatic fan test, and Jackson cross-cylinder. The management options available are spectacles, contact lenses, refractive surgery, toric IOL implantation, and astigmatic relaxing incisions. This activity is focused on the etiology, epidemiology, pathophysiology, clinical evaluation, treatment, differential diagnosis, prognosis, complications, postoperative care, and rehabilitation of patients with astigmatism.