Ask An Optometrist

Question:

I have astigmatism in both eyes and was told I would never be able to see perfectly through contacts (the way people without contacts are able to do) – is that true?

Answer:

The level of optimum visual clarity achievable with the contacts for patients with astigmatism depends on the amount of astigmatism one has in relation to other refractive errors, type of lens, and the success of fitting.

What is Astigmatism?

Astigmatism is a type of refractive error of the eye where the cornea, the front covering of the eye, or the lens inside the eye is irregularly shaped. It can also occur post-surgery or trauma as well as from a degenerative eye disorder called keratoconus, where the cornea progressively becomes thin and cone shaped instead of being round. Astigmatism is typically described as resembling a football where there are steep and flat curvatures.

How to correct astigmatism?

Patients with astigmatism can be corrected with a special type of soft contacts called toric lenses, which conform to the shape of the eye or with rigid gas permeable lenses which maintains their round shape on the cornea.  Most patients choose soft toric lenses instead of gas permeable lenses due to comfort of soft lenses.  In order to achieve the optimum vision with the soft toric contact lenses, which have two different powers in the lens, they must maintain in position and be oriented in a certain direction on the irregularly shaped cornea. The soft toric lenses are weighted, and the weight will orient the lens in that special direction on the cornea to provide visual correction. However, the lens rotates and moves out of its position with every eye blinking movement thereby causing temporary blurriness. The weight in the toric lens and gravity then rotates the lens back to its optimum position. Thus, it is normally expected that toric lenses will manifest some degree of fluctuating vision, unlike glasses.

Visual fluctuation with toric contact lenses

The degree of visual fluctuation with soft toric lenses depends on the amount of astigmatism the patient has and also on the ratio of patient’s other refractive errors, i.e., nearsightedness or farsightedness to astigmatism. If the amount of astigmatism is low to medium, the awareness of visual fluctuation gradually dissipate due to patient‘s eventual adaptation.  In addition, some soft toric lenses provide a better stability of vision than others depending on the design of the lens.  Thus, the visual correction with soft toric lenses may not be quite as ideal as with the glasses; however, there are many patients who are successfully fitted with soft toric lenses and they comprise major part of the contact lens wearer population.

-Dr. Kim

 

Grace M. Kim, O.D.

Optometrist Grace Kim

Dr. Grace Kim


Clinical Advisor Panel Chair for America’s Best Contacts & Eyeglasses.

Dr. Kim received her Doctorate from the Pennsylvania College of Optometry. Prior to entering optometry school, she worked as a research biologist at the Department of Microbiology and Immunology of the Uniformed Services University of the Health Sciences. She was involved in electron microscopy, ultramicrotomy and immunocytochemistry, in which fields she received acknowledgements and co-authored presentations, abstracts, and articles which were published in the Journal of Eukaryotic Microbiology. Following graduation, Dr. Kim joined National Vision’s America’s Best Contacts and Eyeglasses. Since 2007, Dr. Kim served as Chairperson on Clinical Advisory Panel. She is also a Doctor Mentor in which position she trains newly hired doctors and assist in conducting performance reviews on the Peer Review Committee.

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