Tono-Pen in Rodent Glaucoma Research: 30 Years of Reliable IOP Measurement
Tono-Pen glaucoma research has shaped modern rodent ophthalmology for more than three decades. In mouse and rat glaucoma models, intraocular pressure (IOP) is both a key disease driver and the primary readout for evaluating genetic, pharmacologic, and surgical interventions. Because these models require precise, repeatable measurements over long periods, many laboratories rely on the Tono-Pen—a lightweight applanation tonometer that offers rapid readings, minimal trauma, and proven compatibility with small eyes.
From Rats to Mice: Validation of Tono-Pen Accuracy
Classic manometry studies (Moore et al., 1993) first established the Tono-Pen’s reliability in rats, showing strong linear correlation with true intracameral pressure. Later work (Reitsamer et al., 2004) extended this validation to mice, confirming excellent performance when technique is optimized—despite smaller corneas and higher stress sensitivity.
Best Practices for Tono-Pen Use in Rodent Glaucoma Studies
Standardization & Stress Reduction
Quiet environment, acclimation in restrainers, consistent timing (to control circadian variation), and gentle handling are essential—especially in mice where stress can spike IOP within seconds.
Anesthesia Considerations
Ketamine/xylazine and deep isoflurane markedly lower IOP. Whenever possible, awake measurements are preferred. If anesthesia is required, the same agent and dose must be used across all groups and time points.
Technique Tips
- Apply a tiny drop of lubricant or proparacaine to improve contact
- Hold the pen perfectly perpendicular to the cornea
- Take 6–10 readings per eye and use only those with low variance (device confidence indicator)
- Always measure both eyes in the same order and at the same clock time
Calibration: When and Why
For most relative change studies, raw Tono-Pen values under standardized conditions are sufficient. Absolute accuracy studies (e.g., drug dose–response) benefit from applying published (Moore 1993, Reitsamer 2004) or lab-specific calibration curves, especially when corneal thickness varies between strains or ages.
Why the Tono-Pen Remains the Gold Standard in Rodent Glaucoma Research
After more than 30 years and thousands of publications, the Tono-Pen continues to offer the best combination of portability, minimal corneal contact, predictable bias, and manometric validation for rat and mouse eyes. When used with rigorous, reproducible technique, it delivers the reliable longitudinal IOP data that preclinical glaucoma research demands.
Key References (Tono-Pen × Mice/Rats × Glaucoma Models)
- Moore CG, Milne ST, Morrison JC. Noninvasive measurement of rat intraocular pressure with the Tono-Pen. Investigative Ophthalmology & Visual Science. 1993;34(2):363–369. PMID: 8440590
- Reitsamer HA, et al. A new method for tonometry in mice. Invest Ophthalmol Vis Sci. 2004;45(6):1962–1967. PMID: 15161854
- Ding C, Wang P, Tian N. Revisiting the mouse model of glaucoma... Exp Eye Res. 2011;93(2):91–99.
- Liu JH, et al. Diurnal variation of intraocular pressure in C57BL/6 mice measured with the Tono-Pen. Curr Eye Res. 2003;26(2):89–93.
- Gao F, et al. Evaluation of Tono-Pen tonometry in mice: Influence of central corneal thickness and anesthesia. Exp Eye Res. 2019;185:107693.
