Glaucoma Utility Instrument May Help Identify Cost-Effective Interventions

Eva Fenwick, PhD

A glaucoma-specific instrument for utility estimation across the severity spectrum may be useful for cost-effectiveness analyses of treatments and interventions.

A team led by Eva Fenwick, PhD, developed/validated the preference-based Glaucoma Utility Instrument (Glau-U), determining whether there were any associations between Glau-U utilities and glaucoma severity.

“The direct and indirect costs of glaucoma and its treatments are substantial, but the cost-effectiveness and quality-adjusted life-year (QALY) gains associated with existing and emerging treatments are unclear because of the lack of a valid glaucoma,” Fenwick and colleagues wrote, contextualizing the purpose of their study.

The Study

As such, they conducted a cross-sectional study in 2 stages at the Singapore National Eye Centre glaucoma clinics.

In Stage 1, the investigators identified and pretested 6 Quality of Life [QOL] attributes, including activities of daily living, lighting and glare, movement, eye discomfort, other effects of glaucoma, and social and emotional effects.

In Stage 2, they developed and administered to participants a discrete choice experiment (DCE) survey and tasks, which they conducted between May 7, 2018 – December 11, 2019. Utility weights were then developed using the questionnaire; mixed logit regression was used to determine the utility weights for each health state.

“Glau-U utility weights across better- or worse-eye glaucoma and vision impairment severity were calculated using 1-way analysis of variance,” the investigators explained. “Correlations between Glau-U utilities and better- or worse-eye visual fields and EuroQol 5-Dimension utilities were ascertained to assess convergent and divergent validity.”

Results

A total of 304 participants with mean age of 68.3 years were evaluated.

Of the population, 92.4% had no vision impairment in the better eye, 4.3% had mild impairment, and 3.3% had moderate to severe vision impairment in their better eye.

The team further reported that mean Glau-U utilities decreased with increasing glaucoma severity (none: 0.73 [0.21]; mild: 0.66 [0.21]; moderate: 0.66 [0.20]; severe: 0.60 [0.28]; and advanced or end-stage: 0.22 [0.38]; P<.001), “representing reductions of 20.7% to 76.1% in quality-adjusted life-years compared with a health state that included preperimetric glaucoma” 

“Similar to findings from other studies, the results of the present study emphasize the importance of early detection and intervention to prevent or slow glaucoma progression and avert substantial QOL loss,” Fenwick and colleagues wrote.

As better-eye vision impairment worsened from 0.67 (none) to 0.58 (mild) to 0.46 (moderate to severe), mean Glau-U utilities also decreased.

There were also moderate correlations between Glau-U utilities and better-eye (r = 0.45; P< .001) and worse-eye (r = 0.33; P<.001) mean deviation scores — as well as low correlations between Glau-U utilities and EuroQol 5-Dimension utilities (r = 0.22; P<.001).

The EuroQol 5-Dimension was unable to discriminate between either glaucoma or vision impairment severity, underscoring limitations in use of generic utilities in eye-related studies and supporting the need for valid glaucoma-specific utility instruments.

“The new, validated Glau-U can estimate disutility associated with glaucoma and related vision impairment across the spectrum of the disease, demonstrating large decrements in QALYs that are associated with late-stage glaucoma,” the investigators concluded.

“Glau-U could be useful in estimating the cost-effectiveness of alternative interventions for glaucoma and in informing the resource allocation policies for glaucoma and vision loss.”

The study, “Development and Validation of a Preference-Based Glaucoma Utility Instrument Using Discrete Choice Experiment,” was published online in JAMA Ophthalmology.