Astigmatism means your cornea is shaped less like a football and more like a rugby ball
A healthy cornea curves evenly, like part of a sphere. In astigmatism it bulges more in one direction than another, so light focuses unevenly and vision blurs at every distance. Somewhere between 30 and 60 percent of adults in Europe and Asia have it, and Thomas Young first described it in 1801.
Astigmatism is a refractive error caused by uneven focusing power around the eye's axis. Either the cornea or the lens is slightly egg-shaped, so correcting it needs lenses with different strengths at different angles, unlike the simple spherical glasses that fix plain short or long sight. Mild cases may cause no trouble; stronger ones bring blur, double vision, squinting, eye strain, fatigue and headaches, and some studies link it to migraine. Night driving can be especially hard. Left untreated in early childhood, it can lead to amblyopia, often called lazy eye.
Opticians describe the shape by its principal meridians, the steepest and flattest curves. When they sit at right angles the astigmatism is regular. If the vertical curve is steeper, the cornea resembles a rugby ball lying on its side, called with-the-rule; if the horizontal is steeper, the ball stands on its end, against-the-rule. Oblique forms fall between, and when the meridians are not perpendicular the condition is irregular, as happens in keratoconus, where the cornea thins and steepens over time.
Many people are born with it, yet it can appear or change at any age. Scarring after cataract surgery or a corneal injury can flatten the cornea along one direction. Its cause is only partly understood. Twin studies around 2007 suggested genes play a small role, and genome-wide studies have produced mixed results: a 2011 study in Asian populations flagged variants near the PDGFRA gene, a 2013 European study did not confirm it, and a 2018 analysis spanning both ancestries replicated the signal and added three new candidate genes.
Diagnosis combines an automated measurement of corneal and lens curvature with a traditional refraction test. Treatment options are glasses, the simplest route; contact lenses, which give a wider field of view with fewer optical artefacts; and refractive surgery, which reshapes the eye to correct the error permanently.
Source: Astigmatism
