The best applanation tonometer for most US practices in 2026 is the Ezer ESL-Emerald-TN. It is a slit-lamp-mounted, Goldmann-type tonometer with a 3.06 mm applanation surface, a 0 to 80 mmHg range, a built-in cobalt filter and a compact 725 g body, and it is in stock with technical, spare-parts and warranty support from US Ophthalmic. If your lanes are built on Haag-Streit 900-series slit lamps, the matching Haag-Streit AT 900 is the natural alternative. For patients who cannot be positioned at a slit lamp, the Haag-Streit UK Perkins Mk3 and the Kowa HA-2 keep Goldmann-principle technique in a handheld body.
Applanation tonometry measures intraocular pressure by flattening a fixed area of the cornea and reading the force needed to do it; in Goldmann-type instruments that area is 3.06 mm across. This guide compares slit-lamp-mounted Goldmann-type tonometers (fixed R-type, removable T-type and swing-down designs), a digital Goldmann-type unit, handheld Perkins-style instruments and one strain-gauge handheld, the Reichert Tono-Pen AVIA. Rebound and non-contact (air-puff) tonometers are separate categories and are mentioned only as alternatives.
Every specification below comes from the manufacturer's product page or the US Ophthalmic product listing; where a figure is not published, we leave it out rather than guess. Pricing for all models is quote-based, so this comparison focuses on what actually separates these instruments in daily use: how they mount to your slit lamp, how the reading is displayed, measurement range, prism and tip options, calibration and who will service the unit after the sale.
Shopping for applanation? US Ophthalmic is a direct provider of applanation to eye care practices across the US. Tell us how your lane is set up and we will come back with the configurations that fit, plus current availability and lead times.
How to choose an applanation tonometer
- Slit lamp fit and mounting style: Goldmann-type tonometers are built for specific mounts. R-type units stay fixed on the microscope and swing into place, T-type units ride on a removable guide plate and can move between lanes, and some designs swing down from above or are made for Z-style or tower-illumination H-style lamps. Confirm your slit lamp make, model and interface before you compare anything else.
- Slit-lamp vs handheld form factor: A slit-lamp tonometer is the everyday workhorse for seated patients. A handheld Perkins-style or strain-gauge unit covers bed-bound, wheelchair, pediatric, nursing-home and home-visit patients. Many practices need one of each rather than choosing between them.
- Readout and measuring mechanism: Traditional units generate the measuring force with a leverage weight or spring and are read from a scale or dial; digital units such as the Keeler D-KAT show the value on an LED display. Strain-gauge pens like the Tono-Pen AVIA average several taps and display the result on an LCD.
- Measurement range and scale increments: Most slit-lamp Goldmann-type tonometers here list 0 to 80 mmHg; handhelds vary (the Kowa HA-2 lists 0 to 60 mmHg in 1 mmHg divisions and the Tono-Pen AVIA 5 to 55 mmHg). Check that the range and scale divisions suit the patients you see.
- Prism and tip options: Goldmann-type tonometers use reusable measuring prisms, and several accept single-use prisms such as Haag-Streit Tonosafe. Strain-gauge pens need single-use tip covers. Factor in your infection-control protocol, reprocessing time and which consumables the manufacturer approves for its device.
- Calibration and long-term service: A tonometer is only as good as its calibration. Look for an included calibration arm or check weights, a clear calibration procedure in the instructions for use, and a service partner in the US who can verify calibration and supply parts such as cone arms, prisms and bulbs.
#1 · Ezer ESL-Emerald-TN Applanation Tonometer (Ezer)
Best overall: a compact, in-stock Goldmann-type slit-lamp tonometer with US-based service and parts.
The ESL-Emerald-TN is the applanation tonometer from Ezer, the house brand US Ophthalmic manufactures, and it is the one model in this guide you can order from stock today. It mounts on the slit lamp microscope and uses a Goldmann-type measuring prism with a 3.06 mm applanation diameter (7.35 mm² area), which keeps the contact area small. The measuring force is generated by a spring and read on the measurement drum across a 0 to 80 mmHg range (0 to 10.64 kPa), and an included quick-reference table converts the drum reading to IOP without extra software or calculations. Illumination from your slit lamp passes through a built-in cobalt filter before it reaches the plastic measuring prism, giving reflection-free observation of the split images. Ezer designed it around its Emerald-line slit lamps, but states that it can be added to many microscopes from other manufacturers, which helps if your lanes are not all the same brand. At 725 g and 47 x 30 x 85 mm, it stays compact on the microscope. Because it is an Ezer product, warranty, service and spare parts run through US Ophthalmic's in-house technical and spare-parts departments rather than an overseas channel.
Pros: In stock and available to quote now · 0 to 80 mmHg range with a 3.06 mm applanation surface · Built-in cobalt filter for reflection-free split-image viewing · Designed for Ezer Emerald-line slit lamps and adaptable to many other microscopes · Supported by US Ophthalmic's in-house technical and spare-parts departments with a US warranty
Considerations: Scale-based reading rather than a digital display · Fit on a specific third-party slit lamp should be confirmed before ordering · Newer model name with less independent published history than the Haag-Streit line
Best for: Practices that want a dependable, quote-ready Goldmann-type tonometer for new or existing slit lamps, especially Ezer Emerald-line lanes.
View the Ezer ESL-Emerald-TN Applanation Tonometer & request a quote →
#2 · Haag-Streit Applanation Tonometer AT 900 (Models R, T, BQ) (Haag-Streit)
The long-standing Goldmann reference, and the obvious match if you already run Haag-Streit 900-series slit lamps.
Haag-Streit's AT 900 is the Swiss company's current Goldmann applanation tonometer line, and Haag-Streit describes Goldmann applanation as the gold standard it has offered for more than 65 years. It comes in three mounting versions. The BQ model mounts permanently on the microscope arm of BQ 900 and BP 900 slit lamps and has a parking position between measurements. The R model sits on top of the microscope on BI 900 and BM 900 lamps and, according to Haag-Streit, many third-party models, swiveling into working position when needed. The T model rides on a guiding platform over the slit lamp axis and is placed on the lamp only when you perform tonometry, with observation through either the right or left eyepiece. All three generate the measuring force with a leverage weight, cover 0 to 80 mmHg, include a meridian setting, and list a measurement deviation of at most ±1.5% of nominal (minimum ±0.49 mN) across the prism's measuring range. Weights run from 0.49 kg for the T model to 0.78 kg for the BQ. Reusable Goldmann prisms are standard and Tonosafe single-use prisms are optional. For Z-style slit lamps, Haag-Streit offers the spring-driven AT 870 instead.
Pros: Reference Goldmann design with decades of published clinical use · Three mounting versions matched to Haag-Streit 900-series slit lamps · 0 to 80 mmHg range with meridian setting · Tonosafe single-use prisms available as an option
Considerations: Designed around Haag-Streit slit lamps; third-party fit must be confirmed with Haag-Streit · Haag-Streit does not endorse non-Haag-Streit prisms on its tonometers · Not carried by US Ophthalmic, so service runs through Haag-Streit's own channel
Best for: Practices standardized on Haag-Streit BQ 900, BP 900, BI 900 or BM 900 slit lamps.
#3 · Haag-Streit UK Perkins Mk3 Handheld Applanation Tonometer (Haag-Streit UK)
The best-known handheld Goldmann-principle tonometer for patients who cannot sit at a slit lamp.
The Perkins tonometer was originally developed by Clement Clarke in the 1970s, and today's Perkins Mk3 is made by Haag-Streit UK, which describes it as the gold standard among hand-held applanation tonometers. It applies Goldmann principles in a portable body, so you still read applanation mires the way you do at the slit lamp rather than relying on a different sensing method. Haag-Streit UK designed it for patients who are often difficult to assess with traditional applanation tonometry: bed-bound and wheelchair-bound patients, children and community or home-visit patients. The Mk3 has precision counter-balanced movements, an integral rechargeable battery and built-in LED illumination that produces an enhanced image of the mires regardless of ambient lighting, with lower operating temperatures for operator and patient comfort. It accepts both reusable Goldmann tonometer prisms and Haag-Streit's Tonosafe single-use prisms through the Tonogrip prism holder, which gives you a disposable option without changing technique. Haag-Streit UK runs a dedicated tonometer service division for calibration checks and genuine parts. The manufacturer's product page does not publish a measurement range, and the product is sold through Haag-Streit UK, so confirm US availability and service arrangements before you plan around it.
Pros: Goldmann-principle readings in a handheld instrument · Works with reusable Goldmann prisms or Tonosafe single-use prisms · Integral rechargeable battery and LED illumination · Designed for bed-bound, wheelchair, pediatric and home-visit patients
Considerations: Requires the same applanation skill as slit-lamp Goldmann tonometry · Measurement range is not listed on the manufacturer's product page · Not carried by US Ophthalmic; confirm US availability and service
Best for: Home visits, nursing facilities, pediatrics and any patient who cannot be positioned at the slit lamp.
#4 · Keeler D-KAT Digital Applanation Tonometer (R-Type / T-Type) (Keeler)
Best digital Goldmann-type option for tower-illumination H-style slit lamps, with an LED readout to one decimal place.
Keeler's D-KAT is the digital version of the Keeler Applanation Tonometer. It still uses the Goldmann method, calculating the force required to flatten a constant 3.06 mm area of the cornea, but internal electronics drive an LED display that reads to one decimal place. Keeler says this reduces the potential for human error, and the bright display is easier to read in a darkened exam room than a dial. There are two versions for tower-illumination H-style slit lamps. The R-Type mounts on the optical body post for a secure fix, is fully rotatable and swings into and out of position without being removed. The T-Type mounts with a guide plate and can be taken away and shared between lanes in a multiple slit lamp practice. Each unit ships with a calibration arm assembly, a reusable tonometer prism and an AA battery, and Keeler highlights low battery usage. The D-KAT is designed, engineered and handmade in the UK. If you want to move from a dial to a numeric readout without changing your Goldmann technique, it is a logical candidate, provided your slit lamp is a tower-illumination H-style design.
Pros: LED display reading to one decimal place · Goldmann method with a constant 3.06 mm applanation area · Fixed R-Type or removable T-Type versions · Calibration arm assembly and reusable prism included
Considerations: Requires an AA battery · Designed for tower-illumination H-style slit lamps · Measurement range is not listed on Keeler's product pages; not carried by US Ophthalmic
Best for: Practices with tower-illumination H-style slit lamps that want a digital readout.
#5 · Reichert Tono-Pen AVIA Tonometer (Reichert)
Best strain-gauge handheld for fast measurements in any patient position, with no routine calibration.
The Tono-Pen AVIA is Reichert's current handheld tonometer and builds on the Tono-Pen XL, which Reichert calls the most widely used handheld tonometer. Reichert classifies the Tono-Pen as an applanation tonometer, but it works differently from a Goldmann prism: a micro strain gauge transducer takes readings as you gently tap the anesthetized cornea, then the unit averages them and shows a statistical confidence indicator. There are two measurement modes: the First Generation mode, which typically takes about five taps, and Quick-Tap mode, which can deliver a reading in as few as two taps and is useful for children and less cooperative patients. It is gravity independent, so it works for patients in a wheelchair or bed, and Reichert states that routine calibration is not required. Published specifications: 5 to 55 mmHg measurement range, 71 g, 16 cm long, a removable Powercel battery pack and dual-sided LCD screens for left- or right-handed users. Single-use Ocu-Film tip covers are required, and Reichert warns that non-Reichert covers can cause erratic readings. It is designed and assembled in Buffalo, New York.
Pros: Very light at 71 g and usable in any patient position · Quick-Tap mode can produce a reading in as few as two taps · Routine calibration not required, per Reichert · Simple one-button operation that is easy to delegate to technicians
Considerations: Strain-gauge measurement, not a Goldmann prism reading · Narrower 5 to 55 mmHg range than slit-lamp Goldmann-type units · Requires an ongoing supply of genuine Ocu-Film tip covers; not carried by US Ophthalmic
Best for: Technician screening, hospital or bedside consults, pediatrics and wheelchair patients.
#6 · Luxvision TN-150B Applanation Tonometer (Luxvision)
A flexible Goldmann tonometer that can run as a fixed R-type or a takeaway T-type.
The Luxvision TN-150B is a Goldmann applanation tonometer that US Ophthalmic carries, and its main selling point is mounting flexibility. It can be used in a fixed R-type configuration or on a T-type take-away guide plate, so the same model can stay on a primary lane or move from room to room as your practice changes. A notch position ensures exact centering of the prism with the left objective, and when you use the guide plate there are two positions, so you can observe through either the left or the right eyepiece. The listed measuring range is 0 to 80 mmHg in 2 mmHg increments, with a 3.06 mm measuring face, a stated accuracy of ±0.5 mmHg, a body of 47 mm wide by 30 mm high and a weight of 725 g. Like the ESL-Emerald-TN, it is backed by US Ophthalmic's in-house technical and spare-parts departments and a US warranty. It is currently out of stock, so ask US Ophthalmic about availability if the R/T flexibility is what you need; the in-stock ESL-Emerald-TN offers the same 0 to 80 mmHg range.
Pros: Works as a fixed R-type or a removable T-type tonometer · Two guide-plate positions for left- or right-eyepiece viewing · 0 to 80 mmHg range in 2 mmHg increments · Backed by US Ophthalmic service and spare parts
Considerations: Currently out of stock · Slit lamp interface should be confirmed before ordering
Best for: Multi-lane practices that want one tonometer model that can be fixed on one lamp or moved between rooms.
View the Luxvision TN-150B Applanation Tonometer & request a quote →
#7 · Luxvision TN-180B Applanation Tonometer (Luxvision)
A swing-down Goldmann-style tonometer that parks above the slit lamp when not in use.
The TN-180B is a Goldmann-style applanation tonometer that mounts to the slit lamp and swings down into position from above. When it is not in use it stays out of the way and does not interfere with normal slit lamp operation, which suits a busy lane where tonometry is one step among many. The listing describes direct IOP readings without a conversion table and notes that the measuring pressure can be calibrated. Listed specifications include a measuring range of 0 to 10.6 kPa (roughly 0 to 80 mmHg), a 7 mm probe diameter, a 3 mm probe moving range, light-circle movement of 1.53 x 2 = 3.06 mm, a weight of 950 g and an overall size of 210 x 150 x 85 mm. It is listed for slit lamps with a suspension-arm interface, so check how your lamp accepts accessories before ordering. US Ophthalmic carries it with in-house service and spare-parts support, but it is currently out of stock; ask about availability, or consider the in-stock ESL-Emerald-TN if you need a unit now.
Pros: Swing-down design parks above the slit lamp · Direct reading with no conversion table · Measuring pressure can be calibrated · Backed by US Ophthalmic service and spare parts
Considerations: Currently out of stock · Listed for slit lamps with a suspension-arm interface only · At 950 g, the heaviest slit-lamp unit here with a published weight
Best for: Busy lanes that want a tonometer permanently on the lamp but out of the way between measurements.
View the Luxvision TN-180B Applanation Tonometer & request a quote →
#8 · Kowa HA-2 Handheld Applanation Tonometer (Kowa)
A compact handheld Goldmann-prism tonometer for home visits and as a backup instrument.
The Kowa HA-2 is a handheld applanation tonometer that works on the Goldmann prism principle and uses industry-standard tonometer probes, and it is the handheld option US Ophthalmic carries. Kowa positions it for domiciliary situations and as a back-up tonometer. An internal one-spring mechanism allows accurate readings in any orientation, regardless of patient position or posture, and built-in illumination, interlocked with the thumb wheel, lets you use it whatever the room lighting. Pressure is read directly from a precision dial with no conversion tables, across a scale of 0 to 60 mmHg in 1 mmHg divisions. The HA-2 weighs 240 g, is 290 mm long, runs on a standard battery power source and has 6x magnification, with an optional 3x long eyepiece, a movable headrest and an optional interchangeable doubling prism. Compared with a strain-gauge pen, it keeps the split-mire Goldmann technique you already use at the slit lamp. It is currently out of stock; ask US Ophthalmic about availability and service.
Pros: Goldmann-prism technique in a 240 g handheld · Reads in any orientation thanks to its spring mechanism · Built-in illumination and direct-reading dial · 0 to 60 mmHg scale in 1 mmHg divisions
Considerations: Currently out of stock · Narrower 0 to 60 mmHg scale than slit-lamp models · Illumination relies on an interchangeable 2.5 V bulb
Best for: Home visits, nursing facilities and practices that want a Goldmann-prism backup tonometer.
View the Kowa HA-2 Handheld Applanation Tonometer & request a quote →
Feature comparison
| Model | Type | Mounting / form | Readout | Measurement range | Weight | Prism / tip | Carried by US Ophthalmic |
|---|---|---|---|---|---|---|---|
| Ezer ESL-Emerald-TN | Slit-lamp, Goldmann-type | Slit lamp microscope; designed for Emerald-line, adaptable to many others | Measurement drum plus quick-reference table (spring force) | 0-80 mmHg | 725 g | Plastic measuring prism, 3.06 mm; built-in cobalt filter | Yes (in stock) |
| Haag-Streit AT 900 (R, T, BQ) | Slit-lamp, Goldmann | R: top of microscope; T: guiding platform; BQ: microscope arm | Mechanical (leverage weight) | 0-80 mmHg | 0.49-0.78 kg by model | Reusable Goldmann prism; Tonosafe optional | No |
| Haag-Streit UK Perkins Mk3 | Handheld, Goldmann principle | Handheld; rechargeable battery, LED illumination | — | — | — | Reusable Goldmann prism or Tonosafe (Tonogrip holder) | No |
| Keeler D-KAT (R / T) | Slit-lamp, Goldmann, digital | R: optical body post; T: guide plate; tower-illumination H-style lamps | LED display, one decimal place | — | — | Reusable prism; calibration arm included | No |
| Reichert Tono-Pen AVIA | Handheld, strain gauge | Pen-style; usable in any position | Dual LCD screens | 5-55 mmHg | 71 g | Ocu-Film single-use tip covers | No |
| Luxvision TN-150B | Slit-lamp, Goldmann | R-type fixed or T-type guide plate | — | 0-80 mmHg (2 mmHg steps) | 725 g | 3.06 mm measuring face | Yes (out of stock) |
| Luxvision TN-180B | Slit-lamp, Goldmann-style | Swing-down from above; suspension-arm interface | Direct reading, no conversion table | 0-10.6 kPa | 950 g | 7 mm probe | Yes (out of stock) |
| Kowa HA-2 | Handheld, Goldmann prism | Handheld; battery powered, built-in illumination | Direct-reading dial | 0-60 mmHg (1 mmHg steps) | 240 g | Standard prism heads; doubling prism optional | Yes (out of stock) |
Why it’s our top pick
US Ophthalmic is a US-based ophthalmic equipment provider that manufactures its own house brand, Ezer, and also carries brands such as Luxvision and Kowa. That matters for a tonometer because the instrument is only useful while it stays calibrated and mechanically sound. US Ophthalmic sells new equipment only, new equipment comes with a US warranty, and it is supported by an in-house technical and repair department and a spare-parts department, so you are not waiting on an overseas service loop when a prism, arm or mount needs attention.
To be fair to the alternatives: if your practice is standardized on Haag-Streit 900-series slit lamps or tower-illumination H-style lamps, the matching AT 900 or Keeler D-KAT is a sensible choice, and a strain-gauge pen like the Tono-Pen AVIA fills a different role from a Goldmann prism. Where US Ophthalmic helps most is matching a tonometer to the slit lamps you already own or are buying, including Ezer Emerald-line lanes, and quoting the ESL-Emerald-TN, which is in stock, alongside the slit lamp and the rest of the exam lane.
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Frequently asked questions
What is the best applanation tonometer in 2026? For most practices buying in the US, the Ezer ESL-Emerald-TN is our top pick: it is a slit-lamp-mounted, Goldmann-type tonometer with a 0 to 80 mmHg range, a 3.06 mm applanation surface and a built-in cobalt filter, it is in stock, and it is supported by US Ophthalmic's in-house service and spare-parts teams. If you run Haag-Streit 900-series lamps, the Haag-Streit AT 900 is the natural match, and for handheld Goldmann-principle measurements, look at the Perkins Mk3 or the Kowa HA-2.
What is the difference between a Goldmann tonometer and a Perkins tonometer? Both use the Goldmann applanation principle. A Goldmann tonometer mounts on the slit lamp and is used with the patient seated at the chin rest. A Perkins tonometer is a handheld instrument that applies the same principle, so it can be used with patients who cannot be positioned at a slit lamp, such as bed-bound, wheelchair, pediatric or home-visit patients. The Haag-Streit UK Perkins Mk3 accepts reusable Goldmann prisms and Tonosafe single-use prisms.
Will an applanation tonometer fit my existing slit lamp? It depends on the mount. Haag-Streit's AT 900 comes in BQ, R and T versions for its 900-series lamps (the R model also fits many third-party lamps), and its AT 870 is made for Z-style lamps. Keeler's D-KAT is made for tower-illumination H-style lamps. The Luxvision TN-180B is listed for lamps with a suspension-arm interface, and the TN-150B can be used as a fixed R-type or with a T-type guide plate. The Ezer ESL-Emerald-TN is designed for Emerald-line lamps and can be added to many other microscopes. Send US Ophthalmic your slit lamp make and model to confirm fit before ordering.
Is a Tono-Pen an applanation tonometer, and can it replace a Goldmann tonometer? Reichert classifies the Tono-Pen AVIA as an applanation tonometer, but it measures with a micro strain gauge and averages several taps rather than using a Goldmann prism and mires. It is light, works in any patient position and does not require routine calibration, which makes it popular for screening and bedside use. Many practices keep a slit-lamp Goldmann-type tonometer as their primary instrument and use a handheld for patients who cannot sit at the slit lamp.
How do I keep a Goldmann-type tonometer calibrated? Follow the calibration procedure in the manufacturer's instructions for use. Some units ship with the tools to check it, for example the Keeler D-KAT includes a calibration arm assembly, and the Luxvision TN-180B listing notes that its measuring pressure can be calibrated. If a check is out of tolerance, have the tonometer serviced by a qualified technician; US Ophthalmic's in-house technical department and spare-parts department support the equipment it sells.
Should I use reusable or disposable tonometer prisms? Reusable Goldmann prisms are standard on most slit-lamp tonometers and must be cleaned and disinfected according to the manufacturer's instructions between patients. Single-use prisms such as Haag-Streit's Tonosafe remove that reprocessing step; Haag-Streit states they are calibrated to Goldmann standards and fit Goldmann tonometers. Check which prisms your tonometer's manufacturer approves, since Haag-Streit, for example, does not endorse non-Haag-Streit prisms on its devices.
Does US Ophthalmic sell used tonometers? No. US Ophthalmic sells new equipment only, with a US warranty and support from its in-house technical and spare-parts departments. It does offer open-box units in its clearance section, and all pricing is quote-based, so request a quote for the tonometer and slit lamp configuration you need.
The verdict
For a new or replacement slit-lamp tonometer, the Ezer ESL-Emerald-TN is the strongest overall choice in 2026 for US practices: it covers the standard 0 to 80 mmHg range with a 3.06 mm applanation surface and built-in cobalt filter, it is compact, it is in stock, and its service and parts come from US Ophthalmic's own departments. The Haag-Streit AT 900 remains the reference choice for practices built on Haag-Streit 900-series lamps, and the Keeler D-KAT is the pick if you specifically want a digital readout on a tower-illumination H-style lamp.
Most practices also need a handheld. If you want to keep Goldmann-principle technique, the Haag-Streit UK Perkins Mk3 and the Kowa HA-2 are the established options; if speed, any-position use and easy delegation matter more, the Reichert Tono-Pen AVIA is a different, strain-gauge tool for that job. Whatever you choose, confirm slit lamp fit and the calibration and service plan before you buy.
