Astigmatism is a very common eye condition that causes blurry vision since the eye is not perfectly round on the front. This creates blur and distortion which can be corrected by wearing glasses or contact lenses. Determining whether glasses or contact lenses will be better for correcting astigmatism is an important step in an eye examination and your eye doctor will discuss which option is the best for you.
What Causes Astigmatism?
Astigmatism is caused by the shape of the cornea – which is the clear front part of the eye. In eyes without astigmatism, the cornea is perfectly round like a basketball.
However, in eyes with astigmatism, the cornea is not perfectly round and has a shape that is more like a football or can even be more irregular than the shape of a football.
This change in the curvature of the cornea causes light to focus at different points in the eyes. When this occurs, the brain merges these different points of light and forms a blurred image instead of a clear one.
The blurry vision that is caused by astigmatism is present at the distance and up close, rather than one or the other being clear.
How is Astigmatism Corrected?
In glasses, the lenses are made to match the different curves of the cornea and correct the different powers as needed. This causes light to focus on a single, clear point in the eye.
In contact lenses, there are two ways that astigmatism can be accounted for and corrected. First, similar to glasses, contact can be made with two powers corresponding to the powers of the front of the eyes.
However, in rigid contact lenses, another method can be used as well. These lenses allow tears to flow beneath the lens and smooth the cornea into a sphere like a basketball.
Then, only one power is needed on the contact lens.
When are Glasses the Best Option for Astigmatism?
Correcting astigmatism with glasses will provide better vision and more stable vision for anyone with regular astigmatism.
Regular astigmatism means that the two curves on the cornea are exactly 90 degrees apart and are symmetric across the cornea. This is the case for almost all astigmatism that is not caused by an eye disease or after surgery.
Glasses provide a steady, precise way to correct astigmatism and will routinely provide the best vision when compared to contact lenses in these cases.
When are Contact Lenses the Best Option for Astigmatism?
Contact lenses are the best option for correcting irregular astigmatism. Irregular astigmatism occurs when the cornea is not shaped perfectly symmetrically or evenly.
Most cases of irregular astigmatism are due to eye conditions like keratoconus or pellucid marginal degeneration or are a result of previous eye surgeries like radial keratotomy or a corneal transplant.
In these cases, a rigid contact lens is the best option to provide clear and comfortable vision and correct astigmatism.