What is the value of a mm Hg reduction in intraocular pressure? Results from the Glaucoma Health Policy Model

Abstract

 

Purpose:

 

The Glaucoma Health Policy Model (GHPM) is a validated economic model designed to estimate the benefit of IOP lowering across the range of glaucoma.

 

Methods:

 

The GHPM estimates the probability of change in mean deviation (MD) over seven years using patient level data derived from CIGTS, OHTS, and AGIS studies. External validation of the model was conducted by comparing the model’s prediction to the observed outcome at year 5 in a sample of 150 patients from a large glaucoma practice. The model explained nearly 80% of the variation in outcome. Costs and health-related utilities used in the model were validated in a similarly rigorous manner. In this example, we used the GHPM to estimate the net benefit from a government payer’s perspective of an intervention that reduced IOP from 24 to 14 mm Hg and maintained that pressure reduction for seven years. The model used a microsimulation approach to recognize variation in expected outcome. We report cost savings, quality of life gained, and net economic benefit for twelve simulated patient cohorts with glaucoma stratified by age, race and glaucoma severity. Other magnitudes of IOP lowering effects can be modeled similarly.

 

Results:

 

Net benefit varied for the simulated cohorts, but was positive for all ranging from $253/year for a reduction in direct medical costs to over $2,000/year when quality of life benefits were considered. In general, the greater cost saving was seen in people with a larger loss of visual field at baseline (i.e., those with a starting MD of -10); those with less loss of visual field at baseline (i.e. a starting MD of -4) benefit from a smaller loss of quality of life.

 

Conclusions:

 

Sustained IOP reduction has a measurable and significant economic benefit. While we have examined a specific question (i.e. reduction of IOP from 24 to 14 mm Hg) the model allows for varying inputs in terms of cost and outcome such that treatment approaches for IOP control can be evaluated.The GHPM provides health policy and clinical decision makers a validated tool to evaluate the benefit of aggressive treatment and prevention of glaucoma.  

 

Keywords: clinical (human) or epidemiologic studies: health care delivery/economics/manpower • intraocular pressure • quality of life