An optical prescription is an order that is written by either an ophthalmologist or an optometrist that specifies the formula that is needed to create corrective lenses that will correct a person’s vision problem. Optical prescriptions contain symbols (medical language codes). There are many codes that are on prescription. Each one represents a specific requirement for the optical prescription. If you’re experiencing vision problems, we recommend that you make an appointment with our Houston eye doctor at West U Vision to get an eye exam to determine if you need an optical prescription for corrective eyewear.
Many people don’t understand how to read their prescription. It’s a good idea for people to have a basic understanding of how to read it. When you come to our Houston eye doctor at West U Vision we will take the time to answer any questions you have. The basic symbols for an optical prescription include: The “sph box” (sphere)-amount of long or short sight that’s present (Plus signs indicate long sight, minus signs indicate short sight), The “Near VA” code- the smallest sized print that can be read with the prescription (usually written with the letter ”N” with a number after it), The “cl” box shows how much astigmatism is present, the “axis” tells the angle that the lens must be placed at when fit into the frame (ranges from 0-180 degrees), the “prism” is the correction that is needed to align the eyes in order for the eyes to work together and see straight, “Rdg add” is known as reading addition-it’s the additional positive power needed for the eyes to focus on close work (usually only needed for people with presbyopia, who need 2 prescriptions; one for reading and one for distance).
The “VA” symbol stands for visual acuity – it indicates the standard vision for each eye when corrected. In the United States, visual acuity is measured at 20 feet. It’s measured in a fraction (numerator is 20). The larger the denominator, the worse the vision is. A visual acuity test is done with a standard eye chart. The chart has several rows with letters (top row-largest letters, bottom row- smallest letters). 20/20 vision means that when a person stands 20 feet away they can read what people should be able to see from that distance. In the USA, usually the 20/20 line is 4th from the bottom on the chart. Since 20/20 vision is good (considered normal vision), people with 20/20 vision would not need an optical prescription. Want to learn more about your prescription, contact our Houston eye doctor today!