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Education – Refractive Errors

Types Of Refractive Errors

Myopia, Hyperopia and Astigmatism are different types of refractive error.  They are all reasons that someone may experience blurry vision — either far away, up close, or both.  These can be corrected with glasses, and in most cases, contact lenses as well.

Myopia, or nearsightedness, is when you have difficulty seeing things far away, but up close your vision is ok. Nearsightedness usually presents itself in pre-teen and teenage years, but can also be found in young children or adults in their 20’s. Glasses or contact lenses are a great way to correct this even for the youngest of people.

Hyperopia, or farsightedness, is when distance targets are clear but one may have blurry vision or strain when reading and doing near tasks. Severe farsightedness is something that can be diagnosed and screened for as early as during an infant vision screening. Our natural lens inside the eye can commonly compensate for the prescription to see clearly at all distances. High amounts of hyperopia are easily missed without a complete eye exam and may not have many symptoms. Some people can compensate so well that their hyperopia, and need for glasses, is not realized until someone’s 40’s or 50’s! However, sometimes because of overcompensation it is one of the most common reasons a child may have amblyopia or a “lazy” eye.

Astigmatism is a curvature imbalance usually from the front part or your eye, or cornea. The cornea of people without astigmatism is shaped like a basketball, with all the curves being the same and round. Corneas with astigmatism are more shaped like a football with one curve being steep and the other being flat. Having an astigmatism simply means that to focus the light to your retina correctly you need two different powers in your eyeglasses instead of one. Astigmatism is not something to be feared and can be corrected in glasses and contact lenses.

Presbyopia is a common refractive error as well. This is a vision condition in which the crystalline lens of your eye loses its flexibility, which makes it difficult for you to focus on close objects.

Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Presbyopia usually becomes noticeable in the early to mid-40s. Presbyopia is a natural part of the aging process of the eye, is not a disease, and it cannot be prevented.  Presbyopia progresses until the mid to late 50s when changes to your vision stop.

Some signs of presbyopia include the tendency to hold reading materials at arm’s length, blurred vision at normal reading distance and eye fatigue along with headaches when doing close work.

There are many ways to manage presbyopia including reading glasses, bifocals, progressives and in some cases contact lenses.

Now, there are even progressive lenses specifically for computer use.  These provide a wide area for comfortable intermediate and near vision.  Intended as a complimentary pair of eyeglasses to your everyday progressives these may relieve headaches and eye strain from computer use.

For more information on Refractive Errors, please visit the below websites:

www.aoa.org/presbyopia.xml 

www.allaboutvision.com/conditions/presbyopia.htm

www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002021 

www.aoa.org/Astigmatism.xml

www.aoa.org/hyperopia.xml

www.allaboutvision.com/conditions/myopia.htm

www.allaboutvision.com/conditions/hyperopia.htm

www.allaboutvision.com/conditions/astigmatism.htm

www.youtube.com/watch?v=0KPYMiEm5Nw