Ever wonder what 20/20 eyesight actually stands for? 20/20 vision is a term to describe a normal level of clarity of eyesight also known as visual acuity assessed from 20 feet away from the object. In other words someone with such vision can see an object clearly from 20 feet away that most individuals are expected to be able to see from such a distance.
In cases of individuals that don’t have 20/20 visual acuity, the number is determined based on where they begin to see clearly in relation to the norm. As an example, if your acuity is 20/100 that means that at a distance of 20 feet you can only see what the baseline would see at 100 feet away.
A person whose vision is 20/200 or below is considered legally blind however, they can often achieve much improved eyesight with the use of glasses or contact lenses or by having LASIK if they are eligible.
Most optometrists use some version of the Snellen eye chart, which was designed by Dutch eye doctor, Herman Snellen in the mid-1800’s, to perform a vision test. While today there are quite a few versions, the chart usually shows 11 lines of uppercase letters which get smaller in size as they move toward the bottom. The top of the chart usually shows one capital letter – ”E” with the addition of more letters on the lines as they get smaller. During the eye exam, the eye doctor will look for the smallest line of letters you can see clearly. Your score is determined since each row is given a rating, with the 20/20 row typically being ascribed the eighth row. In cases in which the patient isn’t able to read, such as small children or disabled individuals, the ”Tumbling E” chart is used. At the same scale as the traditional Snellen chart, this variation portrays only the capital letter E in different rotations. The patient uses their hand to point to the right, left, top or bottom based on the direction the E is facing. Both charts must be placed 20 feet away from where the patient is viewing it.
Despite what many think, 20/20 visual acuity does not mean an individual has perfect vision but rather that they see well at a distance. Total eyesight includes many other important skills such as side or peripheral vision, depth perception, focus for near vision, color vision and coordination between the eyes to name a few.
While an eye exam with a Snellen chart can establish whether you need eyeglasses for better distance vision it will not provide the optometrist a complete understanding of your total eye and vision health. It’s recommended that you still book a yearly comprehensive eye exam to screen for potential diseases. Contact our office now to schedule an eye exam in Miami Beach, FL.
Originally posted 2017-05-10 20:32:25.