Have you ever asked yourself why 20/20 is the benchmark for ''perfect'' eyesight and what it truly means? The term 20/20 eyesight represents a normal level of sharpness of vision (visual acuity) assessed from 20 feet away from the object. In other words someone with 20/20 vision can see an object clearly at a distance of 20 feet which is regarded as normal to see from that distance.
For those who cannot see an object clearly at 20/20, the number is determined according to the distance at which they are able to see sharply, in comparison to what is normally expected. For example, 20/100 vision means that at 20 feet you can only see an object that a person with normal vision can see at 100 feet distance.
Someone with 20/200 vision is considered legally blind however, they can often see normally by using eyeglasses or contact lenses or by having LASIK if they are eligible.
Most eye doctors employ some version of the Snellen eye chart, created by Dutch eye doctor, Herman Snellen in the mid-1800's, to conduct a vision test. While today there are a number of versions, the chart usually shows eleven rows of uppercase letters which get smaller in size as one looks toward the bottom. The top of the chart usually shows the uppercase letter - ''E'' with letters being added gradually as you move down the chart. During the eye exam, the optometrist will assess the smallest line of letters you can read. Every line is given a rating, with the 20/20 line usually being assigned forth from the bottom. For small children, illiterate or handicapped persons who are not able to read or vocalize letters, a different version of the chart is used called the ''Tumbling E''. Similar to the regular Snellen chart, the ''Tumbling E'' shows only the uppercase letter E in different rotations. The person being tested uses their hand to point to the right, left, top or bottom according to the direction the E is facing. Both charts should be placed 20 feet away from where the patient is viewing it.
Despite common perception, 20/20 vision doesn't show a person has perfect vision but rather that their distance vision is normal. Total vision includes a number of other important abilities such as side or peripheral sight, perception of depth, color vision, near vision and focusing and eye coordination to name a few.
It's important to remember that even though an eye exam with an eye chart will often establish if you require eyeglasses for better distance vision it will not provide the eye doctor a comprehensive understanding of the complete health of your eyes and vision. It's recommended that you still go in for a yearly comprehensive eye exam to screen for vision-threatening diseases. Contact us now to schedule a Old Bridge, NJ eye test.