Astigmatism just simply bewilders patients. This post is to help you better understand what astigmatism is, why it is there and how we treat it.
Emmetropia is the condition where the eye is normal is non-astigmatic and sees clearly. When light contacts the eye it is bent by the cornea and the natural interocular lens of the eye and converges at a single focal point on the retina. If that point falls short or beyond the retina then you are either myopic (nearsighted) or hyperopic ( farsighted). I tell patients that astigmatism is simply a warpage of their eye either in the cornea or the crystalline lens.
This warpage causes light to fall at multiple different focal points which create blur at both distance and near. It appears worse at night due to the pupils dilating allowing more stray light to fall off the retina out of focus. People with astigmatism commonly have an oblong-shaped (oval-shaped) cornea rather than a perfect sphere shape. A ping-pong ball is a perfect sphere, while an American football.
Risk factors and causes:
Astigmatism can occur in children and develop in adults. The risk of astigmatism can be higher if:
- There is a family history of astigmatism or other eye disorders, such as keratoconus.
- You have had trauma, scarring or thinning of the cornea.
- Cataract formation can distort the interocular lens causing lenticular astigmatism.
- A history of certain types of eye surgery, such as cataract surgery or radial keratotomy exists.
- If your mother smoked when she was pregnant with you.
A variety of testing is done to determine the presence and scope of astigmatism as well as to determine the axis of astigmatism. Below is an example of a clock dial test.
Astigmatism can be corrected with glasses, contact lenses both soft or hard lenses or numerous refractive surgery options.
Dr. Matthew Ozment
Optometrist, Broken Arrow OK