Astigmatism is one of those conditions that used to be a major problem for contact lens wearers.
Thankfully that is no longer the case, and recent advancements in soft contact lens technology have made soft lenses the choice for most astigmatism patients.
What is an Astigmatism?
Astigmatism is a condition associated with the cornea (link to our astigmatism page). With astigmatism, one area of the cornea is steeper and in another place it is flatter. Another way to think of it, is instead of being round like a basketball, the astigmatic cornea is more oblongly shaped like a football or an egg.
Why does a difference in curvature matter?
Because there are different curves in the cornea, there are also different prescription powers in different places. Now with glasses, that is not a problem because the glasses are always sitting in the same place. In contacts however, the contact lens has a tendency to spin and turn as you blink. This lens rotation causes the astigmatism prescription to change, making the vision blurry as the lens moves and turns.
Therefore, an astigmatism lens has to sit at the exact same place on the eye throughout the entire day in order to work properly.
How do we do this?
There are several ways of stabilizing a lens on the eye.
The main way to overcome the lens wanting to rotate on the eye is to “weight” the lens. As seen in the picture above, the bottom of the lens is slightly thicker than the top.
As you blink, the lid catches on the thicker bottom part of the lens pushing it downward and into position. Each astigmatism lens also has small markings on each lens, this tell the doctor how the lens is sitting on the eye and if any changes need to be made based on how the lens works with an individual’s blinking.
These weighted designs have been quite sophisticated recently and allow clear and consistent vision throughout the day.