Most people are familiar with nearsighted vision, far sighted vision and the age related changes that typically occur over 40 years old affecting near vision. These are all called refractive errors. Patients with nearsightedness typically have the ability to see things up close rather well without glasses or contact lenses on their eyes. Their distance vision is quite blurry making it difficult to see the board in school, street signs while driving or a very common complaint, the guide on their television. Farsighted people tend to have an easier time looking at things far away when their eyes are most relaxed and blurred vision as an image gets closer to the face. The closer the object is to a farsighted person, the more difficult and more blurred out the image becomes. Presbyopia is an age related loss of focusing ability that affects everyone as they get older. A lens inside of the eye, the crystalline lens, does not have the overall ability to change shape in order to focus light and thus causes blurry vision. Just look at that person over 40 years old without glasses and see if they are starting to move their book or menu away from their face, they move it away because it puts less demand on the eyes to focus. Some patients call this age related change farsightedness because they can act quiet similar, but presbyopia is an age related change that affects everyone. A near sighted patient may be able to fend off reading glasses or bifocals because they can use the natural ability of their near sighted eye in order to read, but believe me, they have the age related changes too.
“Doctor Zaker, my last eye doctor told me I have the stigma”. Optometrists hear this all of the time. Patients seem to be frightened of astigmatism thinking of it as a disease. Just like nearsightedness, farsightedness and presbyopia, astigmatism is a refractive error causing blurred vision. Most people will have some astigmatism at some point in their lives. We typically associate astigmatism with an abnormal curvature of the cornea, the clear dome on the front of the eye. While that is the most common source, we also have that crystalline lens inside of the eye that causes some astigmatism as well. Let’s ignore the astigmatism caused from the inside of the eye and think about the cornea. Ideally the cornea is perfectly round sphere like a basketball. It would focus light inside of the eye to a very sharp point like a magnifying glass. Now take that same perfectly round cornea and/or basketball and stretch it out on one side. Now it looks like the side profile of a football. There are 2 curves that are distinctly different from each other and various curves at different angles between. That is astigmatism. You have light focusing in the eye at various different locations because of the different curvatures. An astigmatism affects distance, near and intermediate (computer) distances. A few of the more common complaints for patients with under or uncorrected astigmatism are blurred vision at night, glare with headlights and eye strain when working on the computer or while reading.
Just like the other refractive errors, we can correct for astigmatism with glasses or contact lenses. When we change the astigmatism prescription in eye glasses the light is being bent in a different way going into the eye. The eyes and the brain aren’t used to this new angle of vision and this causes some patients feel like the floor is tilted, a temporary fishbowl effect, or a feeling of their eyes are being pulled. After some adaption, most of the time less than a week, those feelings go away and you just have clear comfortable vision.
For patients who want contact lenses, we correct for astigmatism with toric contacts. These lenses are typically more difficult to fit as we need to closely monitor the alignment of the contact on the eye. All contact lenses need to move on the eye, but we need the alignment to be as stable for the toric lenses as the vision can become poor if the lens rotates. Different toric contacts have different stabilization designs allowing for maximum clarity throughout the day. Eye allergies, dry eyes or rubbing of the eyelids can cause the contact lens to rotate. This rotation will temporarily blur the vision. This may happen a few times throughout the day but it should not interfere regularly. If it is occurring regularly, we may need to treat the inflammation on the eye lids causing this problem or switch to a different type of toric contact lens.
A patient may be nearsightedness or farsightedness, but astigmatism affects all areas of vision. Some people only have astigmatism and no other refractive errors or any combination between both eyes. Once those age related changes occur, then we have presbyopia in the mix as well.
I hope this takes some of the stigma away from astigmatism.
If you have any other questions, come see one of our 3 family Optometrists at Zaker Family Vision.