Disparity of ophthalmic surgeries in Japan

Clinical Snapshot

Key Findings

• P Value: Not reported for primary outcomes

• Effect Size: Fold-variation: cataract surgery 1.8x, vitrectomy 3.3x, glaucoma surgery 7.8x

• Primary Outcome: Prefecture-level surgical rates per 100,000 population varied substantially across procedure types

• Nnt Or Sensitivity: Gini coefficients: cataract 0.064, vitrectomy 0.125, glaucoma 0.190, corneal transplant 0.351

• Confidence Interval: Not reported

Clinical Application

Methodology could be replicated using Australian Medicare Benefits Schedule data for similar analysis Relevant for Australian healthcare planning - similar analysis could inform RACGP rural health initiatives and specialist distribution policies Healthcare planners and ophthalmologists in countries with similar healthcare delivery systems

Abstract

PURPOSE: Although regional disparities in access to surgical care have been reported across medical specialties, nationwide evaluations of variation in ophthalmic surgical services remain limited. This study examined prefecture-level differences in major ophthalmic surgeries in Japan using publicly available claims data. METHODS: We analyzed the ninth release of the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB Open Data) for fiscal year 2022 (April 2022-March 2023). Prefecture-level procedure counts were extracted for cataract surgery (K282), vitrectomy (K279-K281 and related codes), glaucoma surgery (relevant K-codes), and corneal transplantation. To reduce potential underestimation in non-Diagnosis Procedure Combination settings, ophthalmology-related procedures reimbursed under the Short-Stay Surgery Basic Fee 3 (A400) were identified and incorporated according to predefined mapping rules. Surgical rates per 100,000 population and per board-certified ophthalmologist were calculated. Regional inequality was quantified using population-weighted Gini coefficients. Associations between ophthalmologist density and surgical volume were assessed using Pearson's correlation coefficients. RESULTS: Nationwide totals were 1,777,502 cataract surgeries, 154,336 vitrectomies, 80,753 glaucoma surgeries, and 2,895 corneal transplantations. Prefecture-level surgical rates per 100,000 population varied 1.8-fold for cataract surgery, 3.3-fold for vitrectomy, and 7.8-fold for glaucoma surgery. Several prefectures reported no corneal transplantation cases. Population-weighted Gini coefficients were 0.064 for cataract surgery, 0.125 for vitrectomy, 0.190 for glaucoma surgery, and 0.351 for corneal transplantation. Similar patterns were observed after adjusting for age structure, indicating that regional disparities were not solely explained by demographic differences. Ophthalmologist density varied 2.5-fold across prefectures and was positively correlated with surgical volume for cataract surgery and vitrectomy, but not for glaucoma surgery. CONCLUSIONS: Using nationwide claims data, we identified substantial regional variation in major ophthalmic surgical procedures in Japan, with greater inequality observed for more specialized surgeries. These findings provide a population-level description of ophthalmic surgical distribution and may inform future evaluations of healthcare resource allocation.

References

1. 1.Shiga, T., Tanaka, A., Fukuda, Y., & Kashiwagi, K. (2026). Disparity of ophthalmic surgeries in Japan. PLoS One. https://doi.org/10.1371/journal.pone.0347587