How to Tell if Your Dental Loupes Fit Properly

I run UK direct sales for Bryant Dental and hold equity in the business. I've fitted clinicians for custom loupes across several brands for about ten years, and diagnosing fit problems on delivery is most of what that job is. Where my affiliation colours a view below, I've said so.

The short answer

Close one eye and look through the other telescope. You should see one full, clean circle with an even ring of black around the edge. Swap eyes; same again. If either eye sees a circle with the black thicker on one side, the loupes are not sitting where they were built to sit, and the shape of the cut-off tells you exactly what's wrong.

Most fit problems on new loupes come down to the telescopes sitting slightly too high, too low, or off to one side relative to your pupils. Roughly nine in ten of those are fixed at the chair by adjusting the nose pads. The rest need to go back to the manufacturer. Working distance, which is what most people blame first, is almost never the problem in the first month.

This applies to every brand. If you're stuck with any pair, message me on Instagram (@theloupesguy) and I'll try to help.

First, know which type of loupe you have

The test looks different on the two main designs.

Straight Telescopes. Each eye alone sees one full circle. Both eyes together still see one full circle, because the two views sit on top of each other.

Refractive Telescopes. Each eye alone sees one full circle. Both eyes together see a figure of eight: the middle section comes from both eyes and the outer sections come from one eye each. That's deliberate. It works the way your eyes do without loupes, where each eye covers ground the other can't, and it's how Refractive loupes get a wider field of view at higher magnifications than the telescope alone would give.

Either way, the diagnosis is done one eye at a time. Two eyes together confuse things, because your brain merges the two views and hides the problem.

The one-eye test

Put the loupes on. Sit in your working position and focus on something at your working distance. Close your left eye and look through the right telescope. Ask yourself one question: where is the black?

• Even ring all the way round: that eye is correct.
• More black at the top: the telescope is sitting too low for that eye.
• More black at the bottom: the telescope is sitting too high.
• More black on the outside: the telescope is too close to your nose.
• More black on the inside: the telescope is too far from your nose.

Swap eyes and repeat. Write down what each eye sees as a rough percentage ("about a quarter cut off at the top on the left"). That's the language a fitter needs, and it's how a factory adjustment gets specified.

To confirm what you're seeing, use your hands. If the vision is cut off at the top, lift the frame slightly on your nose. If it improves, that confirms the telescope was too low. If the cut-off is at the bottom, push the frame slightly down; if that improves it, the telescope was too high.

Cut off at the top or bottom: adjust the nose pads

This is the most common fit issue I see, and the easiest to fix. The nose pads control how high the whole frame sits on your face, and therefore how high the telescopes sit relative to your pupils.

• Vision cut off at the top (telescopes too low): bring the nose pads closer together. Less gap between them lifts the frame.
• Vision cut off at the bottom (telescopes too high): move the nose pads further apart. More gap drops the frame.

Small movements. Adjust, re-test one eye at a time, adjust again.

If the nose pads are fully in and the vision is still cut off at the top, or fully out and still cut off at the bottom, the pupil height was built wrong and the loupes need to go back.

Don't fix it by sliding the loupes down your nose

Clinicians with Galilean loupes and a cut-off at the bottom often "fix" it by wearing the frame lower on the nose. It works, in the sense that the circle looks right. It also moves the eyepiece further from your eye, which shrinks the field of view through the telescope. Every millimetre of extra distance between eye and eyepiece costs you image. Adjust the nose pads instead and keep the frame where it was designed to sit.

Cut off at the sides: an IPD problem

If the top and bottom are even but one side is dark, the telescopes are not centred on your pupils horizontally. There are three patterns, and they need different fixes.

Cut off on the outside of both eyes. The telescopes are set closer together than your pupils. The IPD (interpupillary distance) built into the loupes is too narrow and needs widening. This is a factory adjustment.

Cut off on the inside of both eyes. Usually described as "too much black in the middle of the figure of eight". The telescopes are wider than your pupils; the IPD is too wide and needs narrowing. Also a factory adjustment.

Cut off on the same side of both eyes (both left, or both right). Both telescopes are shifted the same way, which usually means the frame is sitting slightly off-centre on your nose rather than a measurement error. You can often fix this yourself by nudging both nose pads sideways in the same direction, so the frame moves across your face. As the wearer, if both views are cut off on your left, the telescopes need to move left, which means shifting the nose pads to your right. It's counter-intuitive, so test one small move and check.

Do the top-and-bottom correction first, then the sides. If you fix pupil height with the nose pads and then start shifting them sideways, you'll undo the first fix.

A trap: your eyes move when you focus close

When you look at something in the distance your pupils are further apart than when you focus at working distance. That's convergence, and it's normal. So if you look in a mirror wearing your loupes and your eyes appear wider than the telescopes, that's expected: you're looking at the mirror, not at your working distance.

The telescopes should only line up with your pupils when you're actually looking through them. Any fit photos you send a manufacturer should be taken with you looking through the loupes at your working distance, not at the camera.

Loupes that slip down your nose

The temple tips (the black silicone ends that hook behind your ears) are adjustable on most loupes, and almost nobody adjusts them. A gap between the tip and the back of your ear is why loupes creep down your nose during a procedure and why you end up pushing them back with the back of a gloved hand.

Warm the tips in warm water for a minute to soften them, then bend them with your fingers so they follow the curve down behind your ear. Snug, not tight. That fixes most slippage. Check with the manufacturer if the tips are a material that shouldn't be heated.

Working distance: give it three or four weeks

This is where new wearers go first, and it's almost always wrong to change it early.

If your loupes were measured properly, the working distance was set to improve your posture over the position you were working in before. That means the patient will feel further away than you're used to, and your instinct will be to call it a measuring error. It isn't. You're paying for the loupes to change how you sit; the adjustment period is the point.

Two things to keep in mind:

• Every loupe has a depth of field. The working distance is the middle of that range, not a single point, so "it feels a centimetre or two off" is usually noise.
• Working distance controls how far the patient is from you. It does not change your head angle. If your neck hurts, that's declination angle, not working distance.

After three or four weeks, if the chair genuinely won't go low enough, or your arms are shorter than average, or you're convinced it was mismeasured, then talk to the manufacturer about adjusting it. Going shorter is a posture compromise; do it knowingly.

Related: if the new loupes feel "less magnified" than your old pair at the same nominal power, working distance is usually why. A shorter working distance makes the same telescope feel stronger. Your old 3.5x set at 38 cm will feel more powerful than a new 3.5x set at 50 cm. That's not a fault; it's the trade you made for posture.

The posture checks

Two things to look at from the side, with someone holding a phone:

• Elbows at roughly 90 to 95 degrees when your hands are at working distance. A little less if you stand, a little more if you sit low.
• Head angle: for prismatic loupes, your head should be tilted forward no more than about 10 degrees from vertical. For Prismatic loupes there's no target, because the fixed angle of the telescopes decides your head position for you.

When to send them back

Send the loupes back for adjustment if:

• The nose pads run out of travel before the top or bottom cut-off clears.
• Both eyes are cut off on the outside, or both on the inside.
• The angle only works with the temple arms above or below your ears.
• Working distance is still wrong after a month of proper use.

Tell the fitter exactly what each eye sees, as a percentage, and which direction. A vague "they don't feel right" gets a guess; "left eye 25% cut off at the top, right eye clean" gets a fix.