Will this frame take progressive lenses?

What is stacked inside a progressive lens

A single-vision lens has one power everywhere. A progressive has a different power at the top than at the bottom, and it gets from one to the other continuously, through a channel running down the middle of the lens.

That channel is the corridor, and it has a length: the vertical distance from the fitting cross — set at your pupil — down to the point where the full reading power has arrived. Above the cross is distance vision. Below the corridor is the reading zone. Either side of the corridor, in the lower outer corners of the lens, is a region of unwanted astigmatism that no design has ever eliminated, only moved around.

That last region is the price of the whole arrangement. A lens surface cannot change power down the middle without distorting either side of it — this is a geometric fact about surfaces, not a manufacturing shortcoming — and every progressive on the market is a different opinion about where to put the distortion.

Why the frame decides which lens you can have

All three zones have to fit between your pupil and the bottom rim. The distance zone sits above the pupil and costs nothing from the fitting height. The corridor and the reading zone sit below, and the frame either has room or it does not.

Manufacturers respond to shallow frames by shortening the corridor. An eighteen-millimetre corridor compressed to eleven still climbs the same number of dioptres, so it climbs nearly twice as fast — and the unwanted astigmatism in the corners rises with that gradient. The reading channel narrows from around eighteen millimetres of usable width to around eight.

Eight millimetres is about two words at reading distance. That is the difference between holding a book still and sweeping your head across the line.

Fitting height by frame depth

Estimated from the frame alone, assuming the pupil sits two millimetres above the vertical midpoint of the lens — where it usually falls on a frame sitting normally.

The jump between 30 and 34 mm is the one worth noticing. Four millimetres of frame depth moves you from a short corridor to a standard one, which is four millimetres of extra reading width and a noticeably gentler lens. If you are choosing between two frames you like equally, that is the tiebreaker.

Measuring it properly

The estimate above is an assumption dressed as a number, and it is worth being clear about which parts are which.

What is solid: the minimum fitting heights, which are published by every manufacturer and are the same across the industry within a millimetre; and the relationship between corridor length, reading width and distortion, which follows from the geometry.

What is assumed: where your pupil falls in that frame. Two millimetres above the midpoint is the usual case, but a frame that sits high on a low nose bridge, or low on a high one, can move it three or four millimetres either way — which is a whole design class. A real fitting height is measured with the frame adjusted on your face, by marking the pupil on a demonstration lens.

This matters most when the answer is close. If the estimate clears a standard corridor by five millimetres, a measurement will not change the conclusion. If it clears by one, it very well might.

What to ask for at the counter

Three questions, and the answers tell you most of what you need.

What is the minimum fitting height of the lens you are quoting? This is on the manufacturer's chart and any dispenser can produce it. If it is not volunteered alongside a shallow frame, that is worth noticing.

What is my measured fitting height in this frame? Not estimated from the frame, measured on you. If a retailer cannot do this — which is the structural problem with buying progressives online — you are relying on an assumption about your own face.

What is my monocular PD? Two numbers, one per eye, not a single binocular figure. A progressive needs the corridor in front of the pupil, and faces are not symmetrical.

If you do not have your monocular figures, you can measure them here — the tool reports both eyes separately for exactly this reason.

When a progressive is the wrong answer

It is worth saying, because the default recommendation is now so automatic.

If the frame you want is genuinely shallow and you will not change it, a lined bifocal gives you a reading area the full width of the lens and no distortion at all. The line is visible and the intermediate range is unserved; those are real costs, and for someone who reads books and rarely looks at a screen at arm's length they may be costs worth paying.

If most of your near work is at one distance — a monitor, a workbench, sheet music — a single-vision lens made for that distance beats any progressive at that distance, because it uses the entire lens for it rather than a channel. Occupational and computer lenses exist for this and are consistently underused.

And if you have tried progressives twice and could not adapt, the third pair is not obviously the answer. Non-adaptation is uncommon but real, and more often traced to a fitting error — wrong fitting height, wrong monocular PD, a frame that moved — than to the wearer.

This tool compares figures you supply against published design minimums. It is not a dispensing decision, and it cannot measure your fitting height, which must be taken on your face with the frame adjusted. A dispensing optician has the exact chart for the lens being quoted and should be asked for it.

Related: measure monocular PD, work out your reading addition, decode your frame's numbers, or estimate lens thickness.

Questions people ask

Can I get progressive lenses in any frame?

No, and this is a manufacturing limit rather than a matter of adapting. A progressive needs vertical room for three zones: distance at the top, a corridor where the power climbs, and reading at the bottom. Every design carries a published minimum fitting height — the distance from your pupil down to the lowest point of the lens — and below about eleven millimetres there is no design at all. Shallow rectangular frames and small round frames are the ones that fail.

What is fitting height and how is it measured?

The vertical distance from the centre of your pupil to the lowest point the lens reaches in that particular frame. It is measured on you, wearing the frame, adjusted as you will actually wear it: the dispenser marks your pupil on a demonstration lens and measures down. It cannot be worked out from the frame alone, because it depends on where the frame sits on your nose — which is why the estimate this tool makes is only a starting point.

Why does a short corridor make progressives harder to get used to?

Because the power has to climb the same amount over less distance, so it changes faster per millimetre of eye movement. The unwanted astigmatism that every progressive carries in its lower outer corners is a direct consequence of that gradient, and compressing the corridor concentrates it. The practical effect is a narrower usable channel and more of the swimming sensation when you move your head. A short design is not a bad lens, but it is a compromise made for the frame's benefit, not yours.

Is a bifocal better than a progressive in a small frame?

For some people, yes — and it is worth asking about rather than dismissing. A bifocal has no corridor and no peripheral distortion: the reading segment runs the full width of the lens, so the reading area in a small frame is far wider than any progressive could manage there. What you give up is intermediate vision, which lands between the two powers and is served by neither, and the visible line. If you mostly want to read and rarely use a screen at arm's length, that trade can favour the bifocal.

My frame only just clears the minimum. Is that fine?

It is riskier than it sounds. Frames settle — pads compress, temples relax, and a frame that sat one millimetre higher in the shop sits lower a month later. Since the fitting height is measured from your pupil to the bottom of the lens, a frame sliding down the nose reduces it by exactly the amount it slides, which can push a marginal fit below the design minimum and move your distance vision into the corridor. Adjustable nose pads matter more on a progressive than on any other lens.

Do I need monocular PDs for progressives?

Yes. A progressive is fitted to each eye individually, because the corridor has to sit in front of that eye's pupil. Faces are not symmetrical — a difference of two or three millimetres between the two sides is common — so a single binocular figure puts both corridors slightly out of position. The usual symptom is that one eye finds the reading zone before the other, which reads as the lens never quite settling.

How do I measure my frame's lens height?

Hold a ruler against the front of the frame and measure the vertical opening of one eye wire at its tallest point, inside edge to inside edge. That is the B measurement. Unlike lens width and bridge it is not stamped on the frame, because it varies across the lens shape and manufacturers quote it inconsistently. If you are buying online, the retailer usually lists it as lens height in the specifications.