CLINICAL: Glaucoma

Threshold IOP

“When does my pressure need treatment?”

A healthy, 56-year-old male returned for an IOP check. He has been followed for years without treatment, displaying slightly elevated IOPs (24 mmHg to 25 mmHg) in the presence of otherwise overall normal ocular findings and ancillary testing.

Specifically, pachymetry shows average corneal thickness measurements (545 µ), gonioscopy reveals a visible ciliary body in all four quadrants with light trabecular meshwork pigment, and the clinical exam shows a clear lens with otherwise normal ocular health OU. Additionally, the patient has no other pertinent risk factors (e.g. strong family history of glaucoma, low corneal hysteresis, systemic comorbidities, etc.).

Threshold to treat calculation.
Image courtesy of Dr. Austin Lifferth and

After discussing these findings with the patient and the collaborative decision to continue monitoring him without treatment, the patient asked, “Well, how high does my eye pressure need to be to start treatment?”

Here, I explain how to answer this challenging question and the chosen treatment approach I took with this ocular hypertension patient and why.


The Ocular Hypertension Treatment Study shows that the risk of patients with ocular hypertension developing glaucoma over the course of 5 years without treatment is 9.5% compared to 4.4% of those patients who undergo treatment.1 From these transformative study results, and combined with the European Glaucoma Prevention Study Group, a risk assessment calculator was developed and validated.2

As a corollary to this risk calculator, there is a threshold to treat calculator that also provides an evidence-based guide for provider and patients (with similar demographic study profiles). It can be accessed on the following link: . From this information ­— and if there are no other pertinent patient risk factors — this number alone may be a helpful initial guide to discuss when considering observation without treatment vs. initiating treatment.3

For our patient, and with an estimated proposed 10% threshold risk of progression over 5 years, as shown here, his personalized threshold to treat IOP number is 28 mmHg.


Based on these findings, and due to the absence of any other contributory risk factors, we decided that it was still reasonable to continue monitoring the patient every 6 to 9 months without treatment at this time. Moving forward, however, we did discuss the need to continually re-evaluate the decision to initiate treatment in the context of future test results, increasing age and other potential systemic risk factors, such as diabetes, hypertension or obstructive sleep apnea.4


With this more evidence-based foundation, we can personalize the threshold IOP in many patients and, thus, avoid over treating patients who have a relatively low risk of progression. OM


  1. Kass MA, Heuer DK, Higginbotham EJ, et al. The ocular hypertension treatment study: a randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002; 120: 701–713.
  2. Gordon MO, Torri V, Miglior S, et al. Ocular Hypertension Treatment Study Group; European Glaucoma Prevention Study Group. Validated prediction model for the development of primary open-angle glaucoma in individuals with ocular hypertension. Ophthalmology. 2007; 114: 10–19.
  3. Jampel H, Boland MV. Calculating the “threshold to treat” in ocular hypertension. J Glaucoma. 2014; 23: 485.
  4. McMonnies CW. Glaucoma history and risk factors. J Optom. 2017; 10: 71–78.