What is astigmatism? Astigmatism is a type of focusing or refractive error caused by the shape of your cornea and the eye’s internal crystalline lens. Your eyes don’t focus light on the retina, leading to out of focus images that leads to blurred or shadowed vision. Astigmatism can either be present at birth or develop (or resolve) over time, but it is treatable. Astigmatism is a common eye condition that can be diagnosed through an eye exam.
Symptoms of Astigmatism
Astigmatism can cause blurred or vision distortion of some kind, from all distances. Symptoms of untreated astigmatism include eyestrain, squinting and headaches. This is particularly present after reading or doing extended visual tasks like looking at a computer screen all day. If you experience any of these symptoms on a regular basis, contact your optometrist.
Causes of Astigmatism
This visual condition is typically caused when you have or develop a football shaped cornea. Instead of being symmetrically round, your cornea is shaped like a football, with the steepest and flattest meridians being both different in curvature (or steepness) and 90 degrees apart. In other cases, astigmatism can be caused by the shape of the eye’s internal, crystalline lens. Referred to as lenticular astigmatism, the amount caused by it is usually much less than can be caused by corneal astigmatism.
Types of Astigmatism
Three primary types include myopic astigmatism, hyperopic astigmatism and mixed astigmatism. Myopic astigmatism refers to one or both of the meridians, the curves perpendicular to one another, being nearsighted. If one or both of the meridians are farsighted, then it’s hyperopic astigmatism. Eyes that contains both nearsighted and farsighted aspects is defined as mixed astigmatism. Furthermore, there can be further classification of astigmatism, determined by the axis for which the steepest meridian exists. They are called with-the-rule, against-the-rule and finally, oblique astigmatism where the steepest meridian is closer to the 45- or 135-degree axes.
Astigmatism can also be categorized as regular and irregular, regular referring to the steep and flat meridians being perpendicular to each other or 90 degrees apart, while irregular refers to a shape that is warped, meaning it does not have a pattern of shape change that is defined regularly. Irregular astigmatism can result from an eye injury that leads to scarring of the cornea, have a growth such as a pterygium or the progressive corneal disease called keratoconus.
Astigmatism can be treated with prescription toric eyeglasses, toric contact lenses or refractive surgery. For proper correction, astigmatism requires cylindrical lenses. Refractive surgery, of which the most popular surgery is known as LASIK (less commonly: PRK, LASEK AND SMILE can be used), is effective in correcting most types of astigmatisms. In patients having both astigmatism and visually significant cataracts, a toric intra-ocular (IOL) can be implanted during cataract surgery to help both the blurriness caused by the presence of astigmatism and cataracts.
What is the best solution to correct your astigmatism?
To determine which treatment option is best for you, or all your options, a thorough eye health and vision exam is required. We would love to help.
Watch these animations to better understand your astigmatism. BEGIN