Study assesses macaque-specific tonometry mode for primate IOP: full analysis

Version 2 — Full analysis

A new study summary reports that the macaque-specific measurement mode of the iFalcon™ V100 rebound tonometer performed strongly in an ex vivo non-human primate model, showing excellent agreement with an invasive pressure sensor across a wide intraocular pressure range of 5–90 mmHg. The headline result, an R² of 0.99, points to a potentially useful new tool for measuring intraocular pressure in macaques used in ophthalmic research. (pmc.ncbi.nlm.nih.gov)

The development fits into a broader push to refine tonometry for species used in translational eye research. Non-human primates are especially important in glaucoma and retinal research because of their ocular similarities to humans, but accurately measuring intraocular pressure in these animals has been a persistent challenge. Prior studies in rhesus and cynomolgus macaques found rebound tonometry can be practical and reasonably accurate, yet also showed that readings may be influenced by central corneal thickness, eye position, body position, and whether the animal is anesthetized. (tonovet.com)

That background helps explain why a species-specific mode matters. The iFalcon V100 is marketed as a multi-species rebound tonometer, and a recent rabbit-eye validation study described built-in species modes for rabbit, cat, horse, dog, monkey, and rodent. In that rabbit study, the device tracked pressure changes well overall but still showed range-dependent bias, including underestimation at higher pressures and instability below 10 mmHg, suggesting that calibration and species-specific algorithms are central to how these devices perform. (pmc.ncbi.nlm.nih.gov)

The new macaque assessment appears to be an early-stage technical validation rather than a clinical field study. Based on the available summary, investigators compared the macaque mode against invasive pressure sensing in an ex vivo setup and found strong correlation and agreement across a broad pressure range. That’s encouraging, but ex vivo performance doesn’t fully answer how the device will behave during routine use in living animals, where tear film, corneal hydration, movement, restraint, sedation, and operator technique can all affect readings. (pmc.ncbi.nlm.nih.gov)

Direct outside commentary on this specific study was not readily available in the sources reviewed, but the wider literature points in the same direction: tonometers used in non-human primate research should be calibrated carefully, and ideally to the species or even the individual eye when precision matters. One prior review-style analysis concluded that tonometers in experimental glaucoma work should be calibrated to the individual eye, highlighting how small measurement errors can complicate interpretation in research settings. (pmc.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals working in research, preclinical development, or specialty ophthalmology, the practical value here is less about a new gadget and more about better confidence in a key biomarker. Intraocular pressure is central to glaucoma studies, ocular toxicology, and peri-procedural monitoring. If a macaque-specific mode can reduce systematic error compared with generalized settings, it could improve study consistency, reduce noise in longitudinal datasets, and potentially lower the number of repeat measurements needed. At the same time, the ex vivo nature of the evidence means veterinary teams should be cautious about overextending the findings until live-animal validation is published. (pmc.ncbi.nlm.nih.gov)

There’s also a welfare and workflow angle. Rebound tonometry is valued because it’s portable, fast, and often doesn’t require topical anesthesia, advantages documented in earlier macaque work with other devices. In research colonies, a reliable species-specific mode could make ocular monitoring easier to standardize across handlers, protocols, and study sites. But the same historical literature also shows that handling conditions and physiologic variables can shift readings, so standard operating procedures will still matter as much as hardware. (tonovet.com)

What to watch: The next step is publication of the full macaque dataset, followed by in vivo studies that test repeatability, inter-operator variability, and performance under real-world research conditions, particularly in normal versus elevated intraocular pressure ranges. If those data hold up, species-specific rebound tonometry could become a more meaningful part of non-human primate ophthalmic monitoring. (pmc.ncbi.nlm.nih.gov)