Not everyone looks forward to an eye checkup schedule, but it need not be a source of dread. Knowledge is power, yes? Hence let the following facts make you feel more powerful on your next eye checkup appointment:
The Snellen Chart is not the only eye test chart.
The Snellen chart (figure A) is the classic eye test developed by Dutch doctor Hermann Snellen. It has 11 rows of capital letters, the first line showing a very large E. The rows that follow gradually decrease in size while the letters increase in number. There have been variations of the Snellen chart since its first use in the 1860s.
One example is the Tumbling E chart (figure B) which has the same features as the standard Snellen chart but uses only the capital letter “E” rotated in different increments of 90 degrees.
Another test used during eye checkups is the Jaeger eye chart. It is a small hand-held card consisting of short blocks of text in different font sizes.
20/20 does not mean perfect vision.
You have 20/20 vision if, like most human beings, you can identify the letters on an eye chart while standing 20 feet away. 20/20 vision is considered the “normal” vision, not the perfect one.
Your left and right eyes can have different visions.
Even people with normal vision may have up to a 5% difference in refractive power between their left and right eyes. For individuals with greater than 5% difference, developing anisometropia is more likely. Animestropia is a condition where eyes have different refractive powers, causing uneven focus.
[For further readings: 4 Basic Questions to Ask During Eye Check-up]
The stronger the lens, the more expensive the eyeglass is.
Apart from the quality of the lens, UV protective coatings, anti-glare, and other adjustments add to the cost of an eyeglass. Understanding your prescription after your eye checkup will help you see more how the cost was arrived at.
The eye chart cannot tell whether you have an eye disease.
Eye charts measure visual sharpness and do not include peripheral vision, depth perception, color vision, and eye pressure. Using eye charts during eye checkup then help in determining whether you need prescription eyeglasses or contact lenses, but cannot tell if you have glaucoma.
Hope your eyes were opened because of these facts — have a happy eye checkup!