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Cornea Associates of Texas of Texas

Eyesight Trivia: Can you pass our “Vision” Test?

By Cornea Associates of Texas on February 26, 2015

For centuries, there have been many different beliefs about eyes and sight. We want to shed some light on what is fact and what is fiction.

 

The Cornea
 
True or False: The cornea is one of the few living tissues in the human body that does not contain blood vessels.  This is true.  This is what makes it possible to accept tissue from any donor if a cornea transplant becomes necessary. Because there aren’t any blood vessels in the cornea, there is no blood type to “match.”  You can accept anyone’s cornea. While there is always a slight possibility of rejection, it is not a result of a poor match, but your body responding to foreign tissue.
 

True or False: If you receive a cornea transplant you will need to match the color of your natural eye. This is false. The cornea is the topmost part of your eye that serves as a protective window. The color of your eye comes from the iris which is a tissue located under the surface of the cornea.
 

True or False: The first successful cornea transplant was performed on a pet gazelle in Egypt. This is true. In 1835 Irish surgeon Samuel Bigger was traveling near Cairo when war broke out and he was abducted for ransom by Bedouins. During his captivity, having his surgical instruments with him, he performed the first successful penetrating corneal transplant on a pet gazelle blinded by extensive corneal scarring. The first successful human cornea transplant was performed in 1906 by Dr. Edward Zirm in what is now known as the Czech Republic.
 
 
True or False: It is possible to transplant an entire eye.  This is false. Although you can transplant part of the eye such as the cornea, it is currently impossible to transplant an entire eye to restore vision due to the complicated and sensitive nature of the optic nerve, among other reasons.
 
 
Vision
 
 

True or False: If you see 20/20, that means you have perfect vision. This is false. 20/20 indicates the patient's vision relative to what is considered normal vision. Peripheral vision (the area of vision around you), eye coordination, depth perception, color perception, and focusing ability all contribute to your overall visual ability. 20/20 vision is a term used to express “normal” visual acuity, which is the clarity or how sharp your vision is, measured at a distance of 20 feet. The size of the letters on the standard eye chart is based on work done by the Dutch ophthalmologist, Herman Snellen, in the 1860’s. As a general guideline, if you have 20/20 vision, this means you can see clearly at 20 feet what the average person sees at 20 feet. If you have 20/80 vision, this means that you must be 20 feet away to see what the average person would see at 80 feet. Some people actually have better than 20/20 vision. For example, if someone has 20/15 vision, this means that that person could be at 20 feet to see an object clearly whereas the average person would have to be at 15 feet to see the same object clearly.
 

True or False: Eating carrots will give me perfect vision. This is false. Vitamin A is what is really essential for good eye sight. Carrots richly contain vitamin A (as well as beta-carotene, which has also been proven to help maintain good ocular health), but so do many other foods. Other examples of foods with vitamin A include milk, cheese, egg yolk, liver, asparagus, apricots, and nectarines. “A well-balanced diet can provide the vitamin A needed for good vision,” says The American Academy of Ophthalmology (AAO).
 
True or False: Looking straight at the sun will damage my sight. This is true. Not only can looking at the sun cause headaches and momentarily distort your vision, but it can permanently damage your eyes through UV exposure.  This type of overexposure is linked to eye disorders such as macular degeneration, solar retinitis, and certain corneal dystrophies. There is no exception to when you can’t look directly at the sun without it being dangerous. Even during a solar eclipse, the brightness of the sun is hidden, but the hazardous invisible rays that permanently damage your eyes are not reduced.
 
 
Stay tuned for more interesting True or False facts in the next coming blogs.

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