Impact of the volume-based procurement for intraocular lenses combined with the diagnosis-related group's payment reform on hospitalization costs and expenditure structure among cataract patients: an interrupted time series analysis.

Background: Cataract surgery is one of the most resource-intensive procedures in China, with intraocular lens (IOL) costs accounting for a substantial proportion of total hospitalization expenditure. To address persistently high prices of high-value medical consumables, our hospital implemented the Beijing-Tianjin-Hebei "3 + N" regional alliance procurement for IOLs in January 2022, followed by DRG payment reform in January 2024. However, the synergistic effects of these two sequential policies on cataract surgery costs-particularly on both cost levels and expenditure composition-have not been systematically evaluated. Methods: We conducted a retrospective analysis of 8,458 cataract patients who underwent IOL implantation at a tertiary hospital in western China from January 2021 to December 2025. A multiple-phase interrupted time series model was used, with monthly medians of costs and cost proportions as outcomes. Two intervention points were defined: IOL-VBP implementation and DRG payment reform. Results: Immediately after VBP, total hospitalization cost, material cost, and surgical cost dropped significantly, though a rebound followed with total and material costs shifting to a monthly increase. Specifically, the median total hospitalization cost decreased from 27,403.68 CNY before the reform to 7,214.21 CNY after VBP, and further to 5,516.60 CNY after DRG-a cumulative reduction of 79.9%; the median material cost declined from 11,119.44 CNY to 4,382.92 CNY after VBP, and then to 2,741.10 CNY after DRG-a reduction of 75.4%. DRG reversed the rebound: total and material costs declined continuously, and the material cost proportion continued to fall. The surgical cost proportion rose from 27.44% to 35.35%, although the median surgical fee remained unchanged-a denominator effect driven by sharper declines in diagnostic and other cost components. Surgical volume nearly tripled over the study period, yet annual analysis using mean costs revealed that real per-case surgical revenue decreased, indicating that total revenue growth was entirely volume-driven. Conclusion: The VBP-DRG combination effectively contained costs and shifted expenditure structure toward services at the relative level. However, this structural improvement did not translate into higher absolute physician compensation. To address this, future reforms should consider dynamic adjustments of DRG weights and service prices to align cost containment with fair recognition of medical professionals' skills.