When you undergo an eye exam , your optometrist or ophthalmologist will typically provide you with a prescription for either eyeglasses or contact lenses . These prescriptions contain numbers, abbreviations, and other technical terms that may be confusing at first. Understanding these terms will help you better manage and correct your vision.
Below are key terms you may encounter in your eye prescription and their explanations.
Interpreting Your Eye Prescription
An eye prescription contains critical information about your eye health and vision needs. Here are the main terms you are likely to encounter:
- O.D. (Oculus Dexter): Right eye.
- O.S. (Oculus Sinister): Left eye.
- O.U. (Oculus Uterque): Both eyes.
- CYL (Cylinder correction): Indicates the degree of astigmatism that needs correction.
- AXIS: Indicates the direction of astigmatism correction.
- DV (Distance Vision): Part of the prescription for correcting distance vision.
- NV (Near Vision): Part of the prescription for correcting near vision.
- ADD (Addition): Extra degree required for bifocal or multifocal lenses.
Understanding the Numbers
- Sphere (SPH): The first number in the prescription represents “sphere” and measures the degree of nearsightedness or farsightedness. A minus (-) sign indicates nearsightedness, while a plus (+) sign indicates farsightedness.
- Cylinder (CYL): If there is a CYL number in the prescription, it means you have astigmatism. Astigmatism is corrected with cylindrical lenses.
- Axis: This number, expressed in degrees, tells you the direction of the astigmatism correction.
The larger the numbers for Sphere (SPH) or Cylinder (CYL), the stronger the correction you need.
Difference Between Eyeglass and Contact Lens Prescriptions
Eyeglass Prescription: Eyeglasses are typically about 12mm away from the eyes. An eyeglass prescription usually includes corrections for nearsightedness, farsightedness, and astigmatism. Eyeglasses may also add an ADD power to meet the needs for bifocal or multifocal lenses.
Contact Lens Prescription: Contact lenses sit directly on the eye. In addition to the usual numbers, a contact lens prescription will include the following information:
- Base Curve: The curvature of the contact lens that matches the curvature of your eye, typically between 8 and 10.
- Diameter: The size of the contact lens, typically between 13 and 15 mm, depending on the size of your eye.
- Lens Brand: Specific brands or materials of contact lenses may be recommended.
- Validity: Contact lens prescriptions typically last 1 to 2 years, after which you need to undergo a new eye exam and obtain a new prescription.
How Astigmatism Affects Your Vision
Astigmatism is a common vision problem that causes blurred or distorted vision. It occurs when the shape of the cornea or lens is irregular, preventing light from being focused evenly on the retina. If there is a CYL number in the prescription, it indicates that you have astigmatism. If there is no CYL number, it means you either don’t have astigmatism or the condition is so mild it doesn’t require correction.
What is 20/20 Vision?
20/20 vision is considered normal vision, meaning you can see clearly at 20 feet what the average person can see at 20 feet. However, 20/20 vision does not mean perfect vision. You may still have issues such as poor peripheral vision or color blindness, and your eye coordination and focusing ability may also need improvement.
- Better than 20/20: A person with 20/15 vision can see objects at 20 feet that a person with 20/20 vision can only see at 15 feet.
- Worse than 20/20: A person with 20/40 vision can only see objects clearly at 40 feet that a person with 20/20 vision can see at 20 feet.
Does Vision Decline with Age?
As you age, your vision may change. However, aging does not directly cause vision deterioration; it is the increased risk of eye-related diseases and conditions that comes with age. For example, after the age of 50, the risk of developing the following diseases increases:
How to Protect Your Eyes
- Wear Sunglasses to Protect Your Eyes: UV rays not only cause skin cancer but also harm eye health. Long-term exposure to UV rays can increase the risk of cataracts and macular degeneration. Therefore, wearing UV-protective sunglasses is essential for eye protection.
- Prevent Eye Injuries: When engaging in sports, handling chemicals, or doing manual labor, it’s crucial to wear protective eyewear, especially in high-risk environments. Eye protection helps prevent external physical injuries and reduces the occurrence of infections and long-term health problems.
Regular Eye Exams
As mentioned earlier, regular eye exams are important to catch potential problems early and intervene in a timely manner. Even if you don’t have obvious vision problems, exams help track your eye health and prevent disease.
Vision and Quality of Life
Good vision greatly impacts daily life, directly affecting your work, social interactions, and activities. Many seniors experience falls, injuries, or anxiety due to vision issues. Therefore, maintaining eye health and correcting vision problems early is an essential step in improving quality of life.
Conclusion
Understanding your eye prescription, undergoing regular eye exams, and taking necessary preventive measures can help you maintain good vision and eye health. Whether it’s astigmatism, nearsightedness, farsightedness, or other eye diseases, timely correction and treatment can effectively manage vision problems and improve quality of life. If you experience any changes in vision or discomfort, consult a professional ophthalmologist promptly to avoid further deterioration.
