Provide a valuable resource to your clients or customers by linking to this resource page. Just place the following link on your website.
A reading segment is the small near zone built into a bifocal or trifocal lens. It adds plus power so close text looks clearer. You look through the segment for reading and through the upper part for distance. The segment comes in different shapes and sizes.
read more about reading segment ...The reading segment sits in the lower part of the lens so it lines up with your eyes when you look down. Opticians set its height based on how the frame fits your face. A segment set too high sometimes feels distracting while walking. A segment set too low sometimes forces you to dip your chin to find the near zone.
Common shapes include a flat top segment, a round segment, and an executive style that runs across the lens. A larger segment feels nicer for long reading sessions, while a smaller segment looks less noticeable. Segment size is listed in millimeters. Your daily habits and frame size guide the choice.
For near work, drop your eyes into the segment instead of tilting your whole head forward. Keep reading material at a steady distance and use good lighting. If text still looks blurry, the add power could be wrong. Give yourself a few days to learn where the near zone sits.
A new segment sometimes causes image jump or a brief blur when you switch from distance to near. If it feels extreme, the segment height or the add power is a common reason. Slipping frames also move the segment out of place, so a frame adjustment helps. If symptoms continue, ask an optician to recheck the measurements.
Segment height is the vertical placement of the reading segment in the lens. It is measured from a reference point on the frame to where the segment should sit. Small errors feel big in daily use.
Progressives do not have a hard segment line, but they still have a near zone at the bottom of the lens. Some people call it a segment even though the design is different. The idea is similar, look down for near.
If the segment is too high, you could feel off balance when walking or see blur when looking straight ahead. You could also notice the line sitting in your normal line of sight. An optician checks the fitting height and adjusts the frame.
Some people use multifocal contacts instead of a reading segment in glasses. Another option is distance contacts with reading glasses over the top. Your eye doctor helps pick the safest option for your eyes.
Bifocals and trifocals: Solutions for “short arms”. All About Vision. https://www.allaboutvision.com/eyewear/eyeglasses/lenses/multifocal-glasses/. Date Accessed February 16, 2026.
Guide to Bifocals and Multifocals. Dr. Russel Lazarus. https://www.optometrists.org/general-practice-optometry/optical/guide-to-optical-lenses/guide-to-bifocals-and-multifocals/. Date Accessed February 16, 2026.
Multifocal Lens Designs and Image Jump. Brianna Cuenca. https://opticaltraining.com/blog/multifocal-lens-designs-and-image-jump/. Date Accessed February 16, 2026.
Bifocals explained. Glasses Direct. https://www.glassesdirect.co.uk/buying-guides/lens-options/bifocal-lenses-explained. Date Accessed February 16, 2026.
How to Measure Segment Height for Multifocal Glasses. Clearly. https://www.clearly.ca/thelook/how-to-measure-segment-height. Date Accessed February 16, 2026.