title: A Quantitative Analysis of the Relationship between Medicare Payment and Service Volume for Glaucoma Procedures from 2005 through 2009.
abstract: OBJECTIVE
  To calculate the association between Medicare payment and service volume for 6 commonly performed glaucoma procedures.
  
  
  METHODS
  Retrospective, longitudinal database study.
  
  
  METHODS
  A 100% dataset of all glaucoma procedures performed on Medicare Part B beneficiaries within the United States from 2005 to 2009.
  
  
  METHODS
  Fixed-effects regression model using Medicare Part B carrier data for all 50 states and the District of Columbia, controlling for time-invariant carrier-specific characteristics, national trends in glaucoma service volume, Medicare beneficiary population, number of ophthalmologists, and income per capita.
  
  
  METHODS
  Payment-volume elasticities, defined as the percent change in service volume per 1% change in Medicare payment, for laser trabeculoplasty (Current Procedural Terminology [CPT] code 65855), trabeculectomy without previous surgery (CPT code 66170), trabeculectomy with previous surgery (CPT code 66172), aqueous shunt to reservoir (CPT code 66180), laser iridotomy (CPT code 66761), and scleral reinforcement with graft (CPT code 67255).
  
  
  RESULTS
  The payment-volume elasticity was nonsignificant for 4 of 6 procedures studied: laser trabeculoplasty (elasticity, -0.27; 95% confidence interval [CI], -1.31 to 0.77; P = 0.61), trabeculectomy without previous surgery (elasticity, -0.42; 95% CI, -0.85 to 0.01; P = 0.053), trabeculectomy with previous surgery (elasticity, -0.28; 95% CI, -0.83 to 0.28; P = 0.32), and aqueous shunt to reservoir (elasticity, -0.47; 95% CI, -3.32 to 2.37; P = 0.74). Two procedures yielded significant associations between Medicare payment and service volume. For laser iridotomy, the payment-volume elasticity was -1.06 (95% CI, -1.39 to -0.72; P < 0.001): for every 1% decrease in CPT code 66761 payment, laser iridotomy service volume increased by 1.06%. For scleral reinforcement with graft, the payment-volume elasticity was -2.92 (95% CI, -5.72 to -0.12; P = 0.041): for every 1% decrease in CPT code 67255 payment, scleral reinforcement with graft service volume increased by 2.92%.
  
  
  CONCLUSIONS
  This study calculated the association between Medicare payment and service volume for 6 commonly performed glaucoma procedures and found varying magnitudes of payment-volume elasticities, suggesting that the volume response to changes in Medicare payments, if present, is not uniform across all Medicare procedures.
authors.affiliation: Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, Connecticut.
authors.forename: Dan
authors.initials: D
authors.lastname: Gong
authors.affiliation: Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, Connecticut.
authors.forename: Lin
authors.initials: L
authors.lastname: Jun
authors.affiliation: Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, Connecticut; Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York Eye and Ear Infirmary of Mount Sinai, New York, New York. Electronic address: jtsai@nyee.edu.
authors.forename: James C
authors.initials: JC
authors.lastname: Tsai
mesh_terms: D000368:Aged; D016208:Databases, Factual; D005260:Female; D018463:Filtering Surgery / Q000706:statistics & numerical data*; D005500:Follow-Up Studies; D005901:Glaucoma / Q000601:surgery*; D020327:Glaucoma Drainage Implants / Q000706:statistics & numerical data; D017048:Health Care Costs / Q000706:statistics & numerical data*; D006302:Health Services Research; D006801:Humans; D032801:Iridectomy / Q000706:statistics & numerical data; D017075:Laser Coagulation / Q000706:statistics & numerical data; D008297:Male; D016345:Medicare Part B / Q000191:economics*; D009885:Ophthalmology / Q000706:statistics & numerical data*; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data; D012189:Retrospective Studies; D014130:Trabeculectomy / Q000706:statistics & numerical data; D014481:United States