phoropter

Why Is My Vision Different Between
my Contacts and Glasses?



 

For patients who wear glasses or contact lenses, they sometimes notice that their vision is different between the two modalities. This is especially true for people with higher prescription numbers. I often hear the following complaint: “I see fine with my contacts, but it gives me a headache when I wear my glasses,” or “I see fine when I wear my glasses, but the vision seems off, like I’m looking underwater or wearing beer goggles.” This phenomenon is known as aniseikonia.  Aniseikonia is a perception of different image size when either switching from contact lenses to glasses, or even between a person’s two eyes with glasses on if there is a big enough prescription difference between them. 

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The reason for this difference is that when someone wears glasses, image size is being introduced into the equation. When someone is wearing contact lenses there is no minimizing or maximizing of images. For someone who is near-sighted, the image is smaller or minimized due to a minus-powered lens being used to correct the vision. On the flip side of that, someone who is far-sighted has a plus-powered lens and therefore the image is larger or magnified (think of what is occurring when using a magnifying glass). If a patient’s brain is not well adapted to these quick vision changes (i.e. switching from contact lenses to glasses), then eyestrain, headaches, and an overall altered sense of awareness can occur.

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Usually when a patient complains about this, my first recommendation is to wear the glasses more often. The brain gets adapted to the vision, making switching between contacts and glasses a little easier. For patients with very high prescriptions, or for those who have a big difference between the eyes, I usually just recommend wearing contact lenses and saving glasses only for emergencies. In these rare cases, success of glasses adaptation declines dramatically. If you are a glasses wearer and are experiencing any of these symptoms, contact lenses might be the best option for you. 

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