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New glaucoma risk tool helps determine when to begin treatment
Threshold to treat calculator bases predictions on IOP levels and what the patient is willing to tolerate.
A new estimation tool, based on IOP measurements, helps customize when to initiate treatment in patients with a 5-year predicted risk for glaucoma, according to a study.
In a study published in the Journal of Glaucoma, Henry Jampel, MD, MHS, and Michael V. Boland, MD, PhD, defined “threshold to treat” as “the IOP at which the eye care practitioner and the patient conclude that the benefits of IOP lowering exceed the downside.” That is, the threshold to treat is based on the level of risk that the patient and physician are willing to tolerate in the absence of treatment.
Risk calculator
“The threshold to treat can help clarify in the physician’s mind when, based on IOP level and all other things being equal, the initiation of treatment is indicated,” Jampel told Ocular Surgery News.
Using data from the Ocular Hypertension Treatment Study (OHTS) and the European Glaucoma Prevention Study (EGPS), researchers constructed 5-year risk calculators to predict development of glaucomatous optic nerve and visual field damage in patients with elevated IOP.
According to Jampel, the difference between existing risk calculators and the threshold to treat calculator is this: The OHTS risk calculator calculates risk as the dependent variable and age, IOP, cup-to-disc ratio, central corneal thickness and pattern standard deviation as independent variables; the threshold to treat estimator calculates IOP as the dependent variable and age, cup-to-disc ratio, central corneal thickness and pattern standard deviation as the independent variables.
“The conventional risk calculator takes age, IOP, cup-to-disc ratio, central corneal thickness and pattern standard deviation and calculates a 5-year risk of developing glaucoma. But say that you calculate the risk and it is 10%, and you and the patient decide that the risk at which treatment should be started at is 20%. It is difficult to determine what IOP would provide a 20% risk with the conventional risk calculator, but it is easy with the threshold to treat calculator,” Jampel said.
Once the decision is made to treat, laser trabeculoplasty or topical prostaglandin would be common next steps in patient management, Jampel said.
Some limitations
Because the threshold to treat calculator was developed using the populations in the OHTS and EGPS, its applicability is limited to patients with the same characteristics as those in the two studies, and it is subject to the same shortcomings as those prediction models, according to the study.
“Furthermore, a resultant threshold to treat of [less than] 22 mm Hg must be treated cautiously as the OHTS risk calculator was derived only from eyes with IOPs of 22 mm Hg or greater,” the study authors said.
The authors intend for the threshold to treat calculator to provide information that is complementary to the traditional OHTS risk calculator.
The threshold to treat calculator can be found at http://oil.wilmer.jhu.edu/threshold. – by Nhu Te
Reference:
Jampel H, et al. J Glaucoma. 2014;doi:10.1097/IJG.0b013e318294656d.For more information:
Henry Jampel, MD, MHS, can be reached at Wilmer Eye Institute, 600 N. Wolfe St., Baltimore, MD 21287; email: hjampel@jhmi.edu.Disclosure: Jampel has no relevant financial disclosures.
Perspective
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In my practice we regularly use a personalized approach to involve patients in helping them decide on treatment options for ocular hypertension. We discuss issues such as risk factors, medication’s side effects, challenges posed by long-term compliance and follow-up appointments. The aging population with the challenges that exist, such as memory loss or limited dexterity, are considered in the medical opportunities. As a busy glaucomatologist in these days of electronic medical records and meaningful use, I am mindful of practical concerns. While this risk calculator has the potential for improving treatment discussions with patients, today’s ophthalmologists may find it difficult to incorporate it into their routine. As we are pressed to see more patients every day, it could be impractical to go to a website, plug in numbers and incorporate the results into our patient discussions. To be really helpful, the risk calculator would have to be built into our information system along with imaging applications and IOP measurements.