You might think that a prescription for glasses works just the same as one for contact lenses. However, prescriptions for glasses and prescriptions for contact lenses are not the same. To get the right correction for contacts, you need a dedicated contact lens exam.
Why Your Glasses Prescription & Contact Lens Prescription Are Different
The main reason for the differences between these two types of prescriptions comes down to where glasses and contact lenses sit relative to your eyes. Your glasses sit a short distance away from your eyes, usually about 12 millimeters.
Contact lenses, on the other hand, rest directly on the surface of your eyes. This small gap changes the power needed to focus light correctly for your vision.
Because of this, one prescription cannot simply be substituted for the other. You cannot accurately or safely convert a glasses prescription for contact lenses by yourself. Only a licensed optometrist can write a contact lens prescription.
Extra Measurements on a Contact Lens Prescription
A prescription for contact lenses includes details that you won’t find on a glasses prescription. This extra information helps ensure that your lenses fit correctly.
Base Curve & Diameter
The base curve (BC) of your contacts is designed to match the curve of your eye. The diameter (DIA) of your contacts refers to the size of the lens from edge to edge. A poor fit may lead to irritation, blurry sight, or reduced oxygen to the front of your eye, so getting these numbers right is crucial for clear and comfortable vision.
Lens Brand & Material
Your prescription also names a specific brand and type of contact lens. This is because different lenses use different materials and designs that affect factors like how much oxygen reaches your cornea. You shouldn’t switch to a different brand without first speaking with your eye care professional.
Learning to Read Your Vision Prescription
Vision prescriptions use several common abbreviations. You might see some of these common terms on your own prescription:
- OD & OS: These Latin abbreviations stand for your right eye (oculus dexter) and your left eye (oculus sinister).
- SPH (Sphere): This number indicates the lens power needed to correct your vision. A minus sign (-) means you are nearsighted, while a plus sign (+) means you are farsighted.
- CYL (Cylinder) & Axis: If you have astigmatism, these numbers show the additional power and orientation required to correct the irregular shape of your cornea.
- ADD: This is the added magnifying power for bifocal or multifocal lenses, which helps with your close-up vision.
Choose Between Glasses & Contact Lenses
Many people find that using both glasses and contact lenses offers flexibility. However, the right choice often comes down to your lifestyle, comfort, and what you prefer. Consider your daily activities, work setting, and personal style when you make a decision.
When Contact Lenses Are a Good Fit
- They provide a wider, unobstructed field of view.
- They can be a great option for sports and other active hobbies.
- They don’t fog up in changing temperatures or get splattered by rain.
When Eyeglasses Might Work Better
- They’re very easy to put on and take off as needed.
- They generally require less daily cleaning and maintenance.
- They can offer some protection from wind, dust, and debris.
Whether you lean toward glasses, contacts, or a combination of both, getting the right prescription is the first step. An annual eye exam allows your optometrist to check your vision and the overall health of your eyes. A current, accurate prescription helps you see your best and feel your best. Our team at River City Vision Center is ready to provide you with patient-focused eye care. Schedule an appointment to get the right prescription for your needs.
