BLOG: Always set a goal for IOP

I think it’s very important to set a goal.

Imagine this somewhat familiar scenario. You’re following a patient for glaucoma suspicion. Her pressures are creeping up over the months and years and now they are consistently around 22 mm Hg. The rim seems more excavated, and suspicious field defects are starting to develop. You decide to pull the trigger and start IOP-lowering therapy.

You prescribe a prostaglandin and see the patient back in 1 month, and the IOP drops to 16 mm Hg. Great, right? Right. Then over the next several years her pressure fluctuates slightly, and her IOP creeps up to 19 mm Hg. But each visit, the IOP is only 1 mm Hg higher than the last visit. So basically she’s stable, right? And now you’re seeing a glaucoma patient with IOPs of 19, mm Hg, and that’s not so bad, right?

Except that this is only around 10% lower than what her maximum IOP (TMax) was. This slow creep might not have gone under your radar if you set an IOP goal at the moment you decided to start treatment. Without an IOP goal it’s very difficult to know what is an acceptable IOP for the patient (or at least without reviewing dozens of records each time your patient visits the office), because one patient’s lowest IOP ever is another’s TMax.

Always set a goal. It’s not just my advice, it’s considered standard of care. “Estimate an IOP below which further optic nerve damage is unlikely to occur” is high on the list of mandates in treating the glaucoma patient, second only to “Document the status of optic nerve structure and function on presentation,” according to the American Academy of Ophthalmology.

But where to start? The Collaborative Normal-Tension Glaucoma Study Group and the Early Manifest Glaucoma Trial Group both found that lowering pre-treatment IOPs by 25% showed a significant reduction in glaucoma progression. So most of us, myself included, start with a goal of 25% off the TMax. Of course, if the TMax is a large outlier, then the best strategy is to instead use an average of the highest IOPs that are generally representative of the IOP profile. But in most cases, 25% reduction from the TMax will suffice as a “TGoal.”

Of course, this goal can change. Patients who have more advanced glaucoma at initial exam should have a more aggressive goal, and patients who are shown to have progression even while under the target pressure should have their TGoals lowered. The reason we keep repeating visual fields, retinal nerve fiber layer optical coherence tomographies and optic nerve assessments is to assess the adequacy and validity of the TGoal. If the patient worsens, then the TGoal needs to be lowered, and if the goal is now unattainable by medication, then surgical options need to be considered.

Sometimes a TGoal can be raised. From the Collaborative Initial Glaucoma Treatment Study: “Choosing a less aggressive target IOP may be reasonable if the risks of aggressive treatment outweigh the benefits (e.g., if a patient does not tolerate medical therapy well and surgical intervention would be difficult or if the patient's life expectancy is short).”

So, choose a TGoal for your patient when starting IOP therapy (or even when you see him or her next for follow-up). It is a little more work up front, but your life will be easier at follow-up, and it’s really the best way to stay vigilant against an IOP creep. Plus it’s a nice tool for patient education and compliance, allowing them a part in their own care and giving them something to root for and a reason to be adherent to the schedule you provided.

I have a few more thoughts on IOP.

Don’t forget about post-dilation pressures. This was beat into my head during my residency, as I had a mentor who would always ask me to check the patient’s post dilation pressures. Keep in mind that this is evidence-based: cycloplegics have been shown to cause significant IOP elevation in only 2% of the apparently normal population, but that increases to 23% of patients with known primary open angle glaucoma.

Lastly, a question for you. Is there an IOP value for which you would treat regardless of optic nerve appearance, pachymetry and visual field status? If so, then what is that number? Most of us would not necessarily treat every IOP of 24 mm Hg that we see. But how about 30 mm Hg? 40 mm Hg? Or does it always depend on the other factors? Assume no recent surgeries.

Post a comment below or send me an email with your opinion, if you don’t mind. I’m collecting some data on this and will write more in later blogs. My email address is under my photo to the left.

References:

Collaborative Normal-Tension Glaucoma Study Group. Am J Ophthalmol. 1998;126:487-497.

Harris LS. Arch Ophthalmol. 1968;79:242–246.

Harris LS, et al. Arch Ophthalmol. 1971;86:12–14.

Leske MC, et al. Early Manifest Glaucoma Trial Group. Arch Ophthalmol. 2003;121:48-56.

Musch DC, et al. Ophthalmology. 2009;116:200-207.

Portney GL, et al. Ann Ophthalmol. 1975;7:31–34.