Segment Height for Progressive Lenses Explained

If you’re new to progressive lenses or simply seeking clarity on how they’re customized for perfect vision, you’ve probably encountered the term “segment height“. Understanding and measuring segment height correctly is crucial for optimal vision comfort and effectiveness of your progressive lenses. In this guide, we’ll explore what segment height is, why it’s important, and how you can accurately measure it.

Note: In many labs and training materials the term ‘segment height’ is used. For modern progressive lenses we typically mean the fitting height or the position of the fitting cross; however, because ‘segment height’ remains widely used, we use both terms in this guide for clarity.

Segment Height vs Fitting Height: Clearing Up the Terminology

In many lab orders and optician workflows you’ll encounter the term segment height. But when it comes to modern progressive-addition lenses, the more precise term is fitting height. Here’s why it matters.

Terminology background

Segment height is rooted in bifocal/trifocal lens orders — you had a clearly defined near-vision “segment”, and the measurement was the distance from the bottom of the frame (or lens) to the top edge of that segment.
Fitting height (sometimes labelled “fitting cross height” or “height to pupil”) refers to the vertical measurement from the specified bottom of frame (or lens reference) up to the centre of the pupil (or fitting cross) when the patient is in primary gaze. That’s typically what the lab uses for progressive lenses.

Why this distinction matters for PALs

Progressive lenses do not have a discrete near “segment” the way a bifocal does—they have a continuous gradient from distance to near. So, strictly speaking, using “segment height” for PALs is a mis-nomer.
Practically though: many labs still accept/understand “seg height” and interpret it as fitting height. But if you use the term casually without clarifying, you risk mis-communication: e.g., the order-entry value might be mis-interpreted, the corridor/near-zone may not align, adaptation may suffer.

Practical advice for your workflow

When measuring and ordering for a progressive lens, use “Fitting Height (Vertical to pupil centre)”. Add a note like: “Often labelled ‘seg height’ in lab systems”.
In training or UI (for example your Optigrid interface), label the field clearly: Fitting Height (mm) and in smaller text “(may be referred to as Segment Height)”.
Always check with the lab what datum they use (bottom of frame vs lowest usable point of lens, and pupil centre vs fitting cross) so your measurement aligns with their process.
For junior staff or clients less familiar: you might initially explain “segment height” as the commonly used term—but immediately follow with “and yes, for modern progressives it means the fitting height where the near/transition zone begins”.

Bottom line

Yes – you can still call it “segment height” because it’s ingrained in many lab systems. But from a correctness and clarity viewpoint, when dealing with modern progressive lenses you should think and speak of fitting height. Clarify it upfront and you’ll avoid confusion.

Now back to the main subject 🙂

What is Segment Height in Progressive Lenses?

Segment height refers to the vertical measurement from the bottom of your eyeglass frame to the point where the progressive lens begins transitioning from distance vision to intermediate and near vision. It ensures your lenses provide clear vision at all distances: far, intermediate, and near through accurately positioned optical zones.

Progressive lenses, often called no-line bifocals, contain multiple optical strengths within a single lens. Unlike traditional bifocals or trifocals with visible lines, progressive lenses offer seamless vision correction at varying distances. Segment height is integral in tailoring these lenses specifically to your eyesight and the frame you choose.

Why Is Accurate Segment Height Measurement Essential?

An improperly measured segment height can lead to:

Blurred or distorted vision
Uncomfortable head and neck positioning
Eye strain or fatigue
Difficulty adjusting to your lenses

Ensuring an accurate segment height measurement is key to enjoying clear vision at every range without discomfort.

How to Measure Segment Height Correctly

While your optician or eyewear professional usually measures segment height accurately during fitting sessions, it’s useful to know the process. Here’s a simplified way to understand the procedure:

Step-by-Step Segment Height Measurement

Wear Your Chosen Frames
- Ensure frames are positioned comfortably on your face exactly how you’d typically wear them.
Keep a Natural Posture
- Maintain a natural, upright head and neck posture, looking straight ahead.
Mark the Reference
- Have an optician (or friend) mark a small dot directly over your pupil on the lens of your frames, keeping your gaze straight forward at eye level.
Measure the Height
- Using a millimeter ruler, measure vertically from the very bottom inner edge of your eyewear frame up to the marked dot.

These measurements typically range from 14 mm to 25 mm, depending on your frames and facial anatomy.

Quick Tip: Using digital measurement tools like Optogrid can help simplify this process by accurately analyzing images of your face and frames for precise measurements.

Common Mistakes and How to Avoid Them

When measuring segment height, avoid these frequent mistakes:

Incorrect Posture: Leaning forward or backward skews measurements. Always maintain a comfortable, natural position.
Improper Frame Placement: Ensure your frame sits correctly on your nose and ears before marking.
Ignoring Frame Shape: Segment height varies with frame designs; larger frames usually have higher segment height measurements.

Segment Height vs. Pupillary Distance (PD): What’s the Difference?

While related, segment height differs from Pupillary Distance (PD):

Segment Height: Vertical measurement from frame bottom to pupil (lens positioning vertically).
Pupillary Distance (PD): Horizontal measurement between the center of your pupils (lens positioning horizontally).

Both measurements ensure your progressive lenses align perfectly with your eyes. For a deeper dive, check out our comprehensive PD measurement guide.

Importance of the segment height for progressive lenses. Man holding his glasses

Choosing the Right Frames for Progressive Lenses

Some frames complement progressive lenses better. Ideal frames generally have:

Moderate lens height (at least 28mm vertically recommended for smooth progression zones)
Stability and comfortable fit
Minimal lens curvature or wrap-around style to avoid distortion

For helpful tips on choosing eyewear, see Consumer Reports’ Guide to Eyeglass Frames to ensure you select frames suitable for your vision needs. Also consider the face shape and size when selecting frames for progressive lenses. It’s essential to seek styles that allow for a wider field of vision and accommodate the lens design. Additionally, frames with adjustable nose pads can help achieve a more personalized fit, enhancing comfort and functionality.

Optimizing Vision Comfort with Segment Height Adjustment

Even perfect initial measurements might require fine-tuning. If you experience discomfort after receiving your glasses:

Visit your optician promptly to reassess and adjust segment height.
Allow sufficient adaptation time (typically 1-2 weeks) for new progressive wearers.
Avoid frequently switching between old and new glasses during the adaptation phase.

Final Thoughts

Accurate segment height measurement is crucial for optimal vision with progressive lenses. Understanding the basics of segment height can empower you to communicate effectively with your eyewear provider and enjoy comfortable, clear vision at every distance.

If you’re looking for precise segment height and PD measurement solutions for eyewear professionals or consumers, try our advanced and easy-to-use measurement platform Optogrid.

Segment Height for Progressive Lenses Explained: A Complete Guide