What is Astigmatism?

What is Astigmatism?

The common refractive error is not as scary as it sounds

Some of the most frequent questions we get from our patients have to do with a vision condition know as astigmatism. Like the more familiar myopia (nearsightedness) and hyperopia (farsightedness), astigmatism is what’s know as a refractive error. Refractive errors cause blurry vision because the light entering your eye is not being correctly focused on your retina. All three conditions are common and treatable problems, the effects of which can be corrected with the right prescription.


Refractive Errors


For those with natural 20/20 vision, rays of light from near or far pass through each eye’s perfectly round cornea and perfectly biconvex crystalline lens, which work together to perfectly focus them on the retina. This sends a crisp image through the optic nerve to the sight centers of the brain, resulting in clear sight. In cases of myopia or hyperopia, the shape of the eye correctly focuses the incoming light on a single point, but that point happens to be just in front of or just behind your retina. Adding a contrasting spherical lens to the equation (eyeglasses or contact lenses) compensates for the imperfect optics of your eye so the incoming rays of light properly converge on your retina.


Astigmatism Is More Complex


Astigmatism is a bit more complex, and usually presents itself in addition to one of conditions mentioned above. An astigmatic cornea is not round at all, but more irregularly shaped causing the light that passes through it to refract at different horizontal and vertical angles. This leads to two separate focus points in the eye and usually requires a corrective lens that does a bit more work than the more common spherical lens. The focus points need to not only be adjusted forward or back, but they also need to be brought together. While this may sound complicated, it’s a fairly straightforward process that involves a few extra measurements during your eye exam. Additionally, exciting advances in both contact lens and ophthalmic lens technology have greatly increased the treatment options available to patients with astigmatism, including digitally surfaced products and daily disposable contact lenses.