Single Vision: Most common. Features one prescription power throughout the entire lens, for correcting nearsightedness or farsightedness.
Progressive: Corrects multiple fields of vision (distance, immediate, near) in one lens. Typically prescribed for patients over 45 years old. Progressives offer all-in-one convenience with a seamless, invisible design where the power “progressively” changes throughout the lens – top to bottom.
Pupillary Distance #: Indicates the distance between the centers of your pupils. A required measurement that ensures your new lenses are correctly aligned over the center of your pupils. This number should be on your Rx information. If not, you can call your eye doctor’s office and they should have it on file. The average adult’s PD is between 54-74 mm; kids’ are between 43-58 mm.
Seg Height: For Progressive Lenses Only. The vertical measurement in millimeters from the bottom of the lens where it intersects into your frames, to the beginning of the progressive addition (center of your pupil). Will be specific to each frame and wearer. You can measure it yourself or if you have a progressive lenses in your frame already, we can take the measurement off of those lenses.
Use a ruler that has millimeter measurements.- Put the glasses on your face and adjust them so that they sit comfortably.
- Stand about 8 inches (20 cm) away from a well lit mirror with your face parallel and square to the mirror.
- Align the ruler’s zero (0) measurement to the lowest point at the bottom of your lens where it intersects into your frame, keeping it exactly vertical. Make sure you are measuring from the bottom of the lens, not the bottom of the frame.
- Stare straight ahead and read the millimeter line that lines with the center of your pupil. This is your segment height measurement for these specific frames.
- Repeat these steps at least 3 to 5 times to get an accurate and consistent measurement. Make sure your head and the ruler do not move after lining up the zero (0) measurement with the bottom of your lens until you note your measurement. Ask a friend to help if you are having trouble.
