What are the different types of astigmatism?
There are various types of astigmatism, based on which part of the eye it affects:
Corneal astigmatism
This form of astigmatism happens when the cornea, at the front of your eye, has an uneven curvature. It’s shaped more like a rugby ball, which causes light to bend differently and can make your sight appear blurred and/or distorted.
Lenticular astigmatism
This is caused by the lens inside the eye being slightly irregular in shape or tilted. Like corneal astigmatism, it makes it harder for light to focus properly on the retina, which can blur your vision at different distances.
Myopic astigmatism
This occurs when one or both principal meridians of the eye are myopic, meaning the eye bends light in front of the retina. If both meridians of the eyes are short‑sighted, but by different amounts, it’s called compound myopic astigmatism. If only one is, it’s simple myopic astigmatism.
Hyperopic astigmatism
Similar to myopic astigmatism. If both meridians of the eyes are long‑sighted, but by different amounts, it’s compound hyperopic astigmatism. Conversely, if only one meridian is hyperopic, it’s simple hyperopic astigmatism.
Mixed astigmatism
This occurs when one principal meridian is myopic, whilst the other is hyperopic. This type combines myopic and hyperopic astigmatism and causes blur at both near and far distances.
What causes astigmatism?
Most people with astigmatism are born with it. It’s often inherited and happens when the front of the eye (the cornea) or the lens inside has an uneven shape. That stops light from focusing properly and makes your vision look blurry or distorted. It’s more common in premature or low birth weight babies.