Understanding OC Height and Segment Height in Your Glasses
When ordering prescription glasses, accuracy goes far beyond just getting the correct prescription. Two key measurements—OC Height (Optical Center Height) and Segment Height—play a crucial role in ensuring optimal vision clarity, comfort, and overall performance of your lenses.
What Is OC Height?
The Optical Center Height is the vertical position where your line of sight passes through the lens. This is typically aligned with the optical center of the lens, the point where vision is clearest and free from distortion.
When the OC Height is correct, your eyes naturally align with the clearest point of the lens. If this measurement is too high or too low, you may experience:
Eye strain
Headaches
Blurry vision
Difficulty focusing, especially when looking straight ahead
What Is Segment Height?
Segment Height refers to the vertical position of the near-vision area in multifocal lenses such as progressive or bifocal lenses. It determines where the reading or intermediate portion begins.
If the Segment Height is not accurate, you may experience:
Difficulty reading or using digital devices
Needing to tilt your head to locate the correct focus point
Neck or shoulder discomfort due to forced head positioning
Why These Measurements Matter
Both OC and Segment Height are based on how the frames sit on your face. They depend on:
Frame shape and size
Your pupillary distance (PD)
Nose bridge fit
Natural posture and head positioning
Your unique visual needs
As these measurements are frame-dependent, they cannot be accurately determined at the moment the order is placed. Proper assessment requires trying on the frame to determine the exact lens placement.
How to Ensure Correct Measurements
To achieve the best lens performance and visual clarity, we recommend:
Professional Fitting: Visit an optician who can adjust the frame on your face and record the exact OC and Segment Heights.
Frame Positioning: Ensure the glasses sit properly—secure on the nose and comfortably aligned with the eyes.
Lifestyle & Posture Review: Mention your typical daily activities (e.g., reading, working at a computer) to tailor the measurements to your habits.
Progressives and Bifocals: These require precise segment positioning, so accurate frame fit and measurement are essential before lens installation.
Final Thoughts
Even with a perfect prescription, improperly positioned lenses can compromise visual clarity. Ensuring your OC Height and Segment Height are correctly measured after the frame is fitted is crucial to achieving maximum comfort and performance.
For best results, we recommend having these measurements professionally verified once the frame is selected and adjusted to your face.
If you have concerns about your current eyewear or need assistance with measurements, our team is here to help.