iStent for Adults With Glaucoma: A Health Technology Assessment.

backgroundGlaucoma is a condition that causes progressive damage to the optic nerve, which can lead to visual impairment and potentially to irreversible blindness. The iStent and iStent inject are devices implanted in the eye during a type of minimally invasive glaucoma surgery (MIGS) to reduce intraocular pressure by increasing trabecular outflow by bypassing the trabecular meshwork. We summarized two health technology assessments and additional recent publications that evaluated iStent for people with glaucoma, including effectiveness, safety, cost-effectiveness, the budget impact of publicly funding iStent, and patient preferences and values.

methodsWe summarized two health technology assessments recently completed in Canada. In addition, we summarized new evidence we identified through expert consultation and scoping of the literature. We reported the quality of the body of clinical evidence as reported by the included health technology assessments, according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria.

resultsComparing iStent with pharmacotherapy, there may be no difference in comparative clinical effectiveness (GRADE: Very low to Low). There was uncertainty around the comparative clinical effectiveness of iStent compared with filtration surgery and of iStent plus cataract surgery compared with a different MIGS procedure plus cataract surgery (GRADE: Very low). iStent with cataract surgery may improve comparative clinical effectiveness (reduced intraocular pressure and number of medications) compared with cataract surgery alone (GRADE: Low).iStent may be cost-effective compared with pharmacotherapy (incremental cost-effectiveness ratios [ICER]: $14,120-$25,596/quality-adjusted life-year [QALY]; 60%-76% and 65%-100% of iterations cost-effective at willingness-to-pay values of $50,000/QALY and $100,000/QALY, respectively). iStent with cataract surgery may not be cost-effective compared with cataract surgery alone (ICERs: $108,934-$112,380/QALY; 17%-46% and 46%-68% of iterations cost-effective at willingness-to-pay values of $50,000/QALY and $100,000/QALY, respectively). iStent may not be cost-effective compared with filtration surgery (iStent was less effective and more expensive than filtration surgery). These estimates are influenced by the long-term effectiveness of iStent.The iStent device costs approximately $1,250 (for two iStent or iStent inject devices). Based on a recent analysis by Quebec's Institut national d'excellence en santé et en services sociaux (INESSS) and our previous analysis on MIGS, publicly funding iStent may reduce some spending on glaucoma medication but, overall, iStent is likely to lead to additional costs for the public health care system. In Ontario, publicly funding MIGS over 5 years is estimated to cost a total of $40 million if uptake is slow (25,000 people) and $199 million, if uptake is fast (100,000 people). In Quebec, publicly funding iStent over 3 years is estimated to cost a total of $29 million (15,000 people).People with glaucoma with whom we spoke reported that pharmacotherapy can be challenging and that they relied on trust in their physician to determine if surgery was necessary to avoid potential consequences of glaucoma, such as blindness. Those who received MIGS procedures found it beneficial, with minimal side effects and recovery time. However, they were often unaware what type of MIGS procedure they received, so they could not specifically comment on iStent.

conclusionsWe are uncertain about the comparative clinical effectiveness of iStent compared with filtration surgery, as well as iStent combined with cataract surgery versus other MIGS procedures combined with cataract surgery. There may be no difference in the comparative clinical effectiveness of iStent compared with pharmacotherapy. iStent combined with cataract surgery may improve clinical effectiveness (mainly intraocular pressure and number of medications) when compared with cataract surgery alone.In some instances, iStent may be cost-effective (i.e., when compared with pharmacotherapy) but in other instances it may not be cost-effective (i.e., when iStent combined with cataract surgery is compared with cataract surgery alone or when iStent is compared with filtration surgery). Publicly funding iStent may reduce some spending on pharmacotherapy but, overall, is likely to lead to additional costs for the public health system. People with glaucoma reported that pharmacotherapy adherence could be challenging, and that avoiding blindness was their main priority for treatment. Experiences with MIGS procedures were positive, although patients were unable to comment on iStent specifically.