Jameson Caliper Graduated Scale Marking | Ophthalmic Measuring Caliper

What a Jameson caliper is

Strabismus surgery is arithmetic performed on muscle. A recession moves a muscle back by a stated amount, a resection shortens it by one, and the amount is the operation. There is no eyeballing a figure on a muscle that is a few millimeters wide, and there is no room in an eye socket for a long instrument to take the measurement.

The Jameson caliper exists for that corner. It is an instrument that carries the measurement, so the surgeon brings the judgement and the steel holds the number: a short two point caliper with the graduations cut into the instrument, so the figure is read where it is set. The reach is the reason it is the right tool rather than a general purpose caliper with better numbers on it. As a strabismus caliper it is the one most ophthalmic trays carry for muscle work, and as an oculoplastic measuring caliper it does lid and canthal distances on the same short reach.

A muscle recession caliper has to hold its figure through the moment of doubt, and a Jameson caliper graduated scale holds it where you can see it. That is the difference between this and anything you have to carry a setting away from.

It is also one of the four products in this category that nobody searches for by name. The seed returned three ideas and no volume worth recording, which is not a problem to solve. It means the surgeon who wants this instrument already knows what it is called and is here to check a price and a specification, so the page is written for him rather than for a stranger who needs persuading.

Key design features

The scale is on the instrument

A Jameson caliper graduated scale is cut into the frame, so the figure is read while the points are still where they were set. On a muscle under a hook, with an assistant holding retraction, the step that gets dropped is the one where a setting is carried to a ruler. This instrument does not have that step.

Short reach

An eye socket is not a field you reach into with a long frame. The whole instrument is small, which is the single most important thing about it and the reason an ophthalmic tray carries one of these rather than borrowing a caliper from the plastics set.

Two points, set and held

The points are placed, the setting holds, and the surgeon reads and marks off the Jameson caliper graduated scale. What matters is that nothing drifts between setting and reading, because a caliper that relaxes by half a millimeter has changed the operation.

A marking instrument as much as a measuring one

The name on the product says graduated scale marking, and that is the honest description. The surgeon is usually not just taking a figure, he is putting a mark at a figure. Those are the same action with this instrument in the hand, which is why it is in a marking category rather than a measuring one.

What to order it with

One version of the instrument, so the decision is about the rest of the tray.

Where it is used

Eye work, and the parts of eye work where a stated figure is the operation rather than a note about it.

What it measures, and what it must not do

Three of these rows are about not asking a small instrument to do a large instrument’s job.

How it compares with the rest of the family

Four measuring instruments in this category, and the difference between them is reach and range rather than accuracy.

Materials and finish

Every Jameson caliper we make is cut from high quality medical grade stainless steel. The steel itself is made to a German specification. We do not publish a grade number. The number on a certificate tells a surgeon nothing about whether the two points still meet cleanly after two hundred autoclave cycles, and the answer to that is in the making rather than in the alloy.

The graduations are cut into the steel rather than printed onto it, which is the only way a scale on a reusable instrument survives. On an instrument this small the graduations also have to be cut cleanly enough to read without magnification, which is harder than it sounds at this size.

The points are finished last, after the frame is formed, so they meet each other rather than crossing. On a short caliper a crossing pair of points is a reading that is short by the amount they overlap.

No finish option is offered on this one. A small ophthalmic instrument is handled under a microscope or close to it, and a plated surface under that much light is a reflection in the surgeon’s eye.

Caring for it

Dry the joint. A small joint holds water in a way a large one does not, and a small joint that stiffens is a caliper that no longer holds a setting smoothly.

Clean the graduations, because dried fluid in a cut graduation on an instrument this size makes the figure unreadable long before anything wears out. Autoclave with the rest of the tray, and store it in a slot rather than loose, because a short instrument with fine points in a general tray is an instrument with blunted points.

Ordering and wholesale

The Jameson caliper is made in our own workshop and sold direct, which is why the price sits where it does against the catalogue houses. Order one for a single tray, or in quantity for a hospital list or a distributor line. We do OEM work under your own brand and your own item numbers. Send us a sample and we will hold a run to your pattern rather than ours. Stock items ship from our own workshop. Backorder items take 10 to 12 working days to make. Every instrument carries a three year replacement warranty against manufacturing defects. Production is controlled under an ISO 13485 quality management system.

Frequently asked questions

What is a Jameson caliper used for?

Marking and checking set distances in eye surgery, most often the recession or resection amount on an extraocular muscle during strabismus surgery, and lid and canthal distances in oculoplastic work. The figure is read off the graduated scale on the instrument.

Why does a Jameson caliper have the scale on the instrument?

So the figure can be read while the points are still set. A Jameson caliper graduated scale is cut into the frame itself. In a small deep field, transferring a setting to a separate ruler is the step where a number gets lost, and on a muscle recession the number is the operation.

Is a Jameson caliper the same as a Castroviejo caliper?

No. They overlap in use but the Castroviejo is a 20 mm graduated caliper with a thumbscrew and a choice of straight or curved points, and it is the one most ophthalmic trays carry for corneal and graft measurement. The Jameson is the strabismus marking instrument.

Can a Jameson caliper be used outside eye surgery?

It can, wherever the distances are small and the field is tight, and some plastic surgery and dental users keep one for exactly that. It is not the right instrument for anything measured in centimeters.

Is the Jameson caliper reusable and autoclavable?

Yes. Solid steel with one moving joint, nothing to replace, and it runs through a standard autoclave cycle with the rest of the tray.

Related products and categories

The 20 mm graduated caliper most ophthalmic trays carry alongside it is the Castroviejo caliper 20mm, and for a longer range the Ginsberg caliper 0-40mm reaches four times as far. For straight distances outside the socket the surgical ruler graduated in mm and inches is the simpler answer.

Jameson’s name is on a retractor, a hook and a pair of scissors as well as this caliper, so a catalogue search on the surname alone will turn up instruments that are nothing like this one. The item code on this page is the way to be sure.

The rest of the family sits under marking and measuring instruments, and the wider set for this kind of work is under facelift and neck lift instruments.