A Quantitative Analysis of the Relationship between Medicare Payment and Service Volume for Glaucoma Procedures from 2005 through 2009

A Quantitative Analysis of the Relationship between Medicare Payment and Service Volume for Glaucoma Procedures from 2005 through 2009

A Quantitative Analysis of the Relationship between Medicare Payment and Service Volume for Glaucoma Procedures from 2005 through 2009 Dan Gong, BA,1 ...

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A Quantitative Analysis of the Relationship between Medicare Payment and Service Volume for Glaucoma Procedures from 2005 through 2009 Dan Gong, BA,1 Lin Jun, MD, PhD,1 James C. Tsai, MD, MBA1,2 Purpose: To calculate the association between Medicare payment and service volume for 6 commonly performed glaucoma procedures. Design: Retrospective, longitudinal database study. Subjects: 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. Main Outcome Measures: 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 ¼ 0.61), trabeculectomy without previous surgery (elasticity, 0.42; 95% CI, 0.85 to 0.01; P ¼ 0.053), trabeculectomy with previous surgery (elasticity, 0.28; 95% CI, 0.83 to 0.28; P ¼ 0.32), and aqueous shunt to reservoir (elasticity, 0.47; 95% CI, e3.32 to 2.37; P ¼ 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 ¼ 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. Ophthalmology 2015;122:1049-1055 ª 2015 by the American Academy of Ophthalmology.

Glaucoma is a leading cause of blindness, prevalent in 2.2 million people across the United States.1 It represents the most common cause of blindness in Hispanic persons, the second most common cause in black persons, and the third most common cause in white persons.2 Among all Americans with visual impairment, an estimated 6.1% have primary open-angle glaucoma, and estimates predict that 3.4 million Americans will have glaucoma by 2020.3 As a disease of aging, glaucoma represents a significant portion of annual Medicare expenditures: in 2000, $1.2 billion was spent on glaucoma treatment, second only to cataract-related expenditures among major eye diseases.4 Rising Medicare spending on eye care remains a concern amidst national

 2015 by the American Academy of Ophthalmology Published by Elsevier Inc.

policy discussions about effective means to curb healthcare spending. Congress first introduced the modern-day physician fee schedule for rendered Medicare services in the Omnibus Budget Reconciliation Act of 1989, then later introduced the sustainable growth rate formula in 1997 to contain Medicare spending based on overall economic growth. Since the implementation of the Medicare Physician Fee Schedule (MPFS), the Health Care Financing Administration (now Centers for Medicare and Medicaid Services [CMS]) and the Congressional Budget Office assumed that in response to fee reductions, physicians would recuperate one half of lost revenue by increasing the volume and complexity of

http://dx.doi.org/10.1016/j.ophtha.2014.12.006 ISSN 0161-6420/15

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Ophthalmology Volume 122, Number 5, May 2015 services, which the Health Care Financing Administration termed the 50% behavioral offset.5 This assumption was based largely on empirical work conducted by the Physician Payment Review Commission (now the Medicare Payment Advisory Commission).6,7 However, the last major study to examine this relationship used data from 1994 to 1996, and there is a dearth of quantitative studies on the association between Medicare payment and service volume for glaucoma procedures. The purpose of this study was to provide a timely, 5-year, quantitative analysis of Medicare payment and glaucoma service volume using data for the entire United States. We included 6 commonly performed glaucoma procedures in our analysis: 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).

Methods Data Sources Medicare service volume data were obtained using the CMS Part B National Summary Data Files8 and Part B Carrier Summary Data Files.9 These files contain the total number of allowed services by CPT code, which includes billed services for the physician or surgeon, assistant surgeon, and ambulatory surgery center facility service charge. The national data file includes all procedures performed on Part B Medicare beneficiaries in the United States, and the carrier data file contains all procedures performed within each Medicare Part B carrier, organizations contracted by CMS that exercise jurisdiction over a defined geographical area, usually a state, to administer Medicare policies. Payment data was extracted from the MPFS,10 which lists the fee schedule and relative value units for procedures by CPT code. All fees were adjusted for inflation according to the Consumer Price Index11 using 2005 as the base year. For each carrier, CMS has published data from 2005 through 2011. In this study, we included data from 2005 up to 2009 but not beyond because of a change in the MPFS’s payment formula midway through 2010. The conversion factor for relative value units into a dollar amount was updated on June 1, 2010, resulting in a different fee schedule for the second half of the year compared with that of the first half.12 Because volume data are provided by year, data for 2010 and 2011 were excluded to ensure accurate matches in the timing of payment and service volume data.

Regression Analysis To describe the relationship between Medicare payment and glaucoma service volume, we conducted a retrospective longitudinal analysis of Medicare Part B carriers representing all 50 states and the District of Columbia. Using a fixed-effects regression model, a standard technique used by the Physician Payment Review Commission and other research groups to assess the volume response to payment changes,7,13,14 we calculated payment-volume elasticitiesddefined as the percent change in Medicare service volume per 1% change in Medicare paymentdfor CPT code 65855 (laser trabeculoplasty), CPT code 66170 (trabeculectomy without previous surgery), CPT code 66172 (trabeculectomy with previous surgery), CPT code 66180 (aqueous shunt to reservoir), CPT code 66761 (laser iridotomy), and CPT code 67255 (scleral

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reinforcement with graft). This definition of elasticity is adopted from the standard definition of price elasticity used in the health economics literature.15 In our model, the Medicare Part B carrier where the surgery was performed served as the independent unit of analysis. Across carriers, there exists a large degree of variation in the absolute volume of glaucoma services because of patient factors such as demand, population, and demographics, and physician factors such as the number of ophthalmologists and practice behaviors. Rather than comparing the level of glaucoma service volume and Medicare payment, the fixed-effects model calculates the association between changes in service volume and payment while controlling for both carrier-specific characteristics and national trends in glaucoma service volume. Taking advantage of adjustments in the MPFS formula by the Geographic Practice Cost Index that accounts for regional variations in practice costs,16 the regression model focuses on the differences in year-to-year Medicare payment changes across carriers. Variation in the Medicare fee schedule across both years and carriers creates a natural experiment to isolate the association between Medicare payment and service volume within a single carrier.17 A dummy variable representing each Medicare Part B carrier was included in the regression model to account for intercarrier heterogeneity that was stable over time, such as time-invariant regional variations in patient demand and demographics and physician practices. We included an additional time variable to control for national trends in service volume because of factors that affected the entire country. The regression model also controlled for carrier-level changes in Medicare beneficiary population, number of ophthalmologists, and income per capita obtained from the Area Health Resources File,18 in addition to heteroscedasticity to account for non-normally distributed standard errors as determined by the modified Wald test. Mathematically, the carrier and time fixed-effects regression model can be represented as follows: Vijk¼ b0 þ b1 Pijk þ b2 Ajk þ b3 Bjk þ b4 Cjk þ aj  gk þ εijk In this model, Vijk is the service volume and Pijk is the Medicare fee for procedure i in carrier j and year k. Ajk, Bjk, and Cjk represent the number of Medicare beneficiaries, number of ophthalmologists, and income per capita, respectively, in carrier j and year k. b0 is the fixed-effects parameter representing the y-intercept, aj is the fixedeffects parameter that represents the stable characteristics of each carrier, gk is the correction for the national trend in service volume, and εijk is the error term. b1, b2, b3, and b4 are the regression coefficients to be estimated and represent the effect of their respective covariates on service volume. Because each variable was log transformed, b1 can be interpreted as the percent change in service volume per 1% change in Medicare payment, or the payment-volume elasticity. Statistical analyses were conducted using StataMP 13 (StataCorp LP, College Station, TX) with 2-sided significance testing and statistical significance set at P ¼ 0.05. Institutional review board approval was not obtained because this research did not involve human subjects, humanderived materials, or human medical records and did not fall under the Department of Health and Human Services Office for Human Resource Protections regulation 45 CFR part 46.

Results National Trends From 2005 to 2009, the 3 highest paid glaucoma procedures by Medicare were trabeculectomy with previous surgery ($1097.49e$1171.62), trabeculectomy without previous surgery

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($873.62e$940.67), and aqueous shunt to reservoir ($858.69e$978.26; Table 1). For all 6 glaucoma procedures studied, average Medicare payment across carriers representing all 50 states and the District of Columbia decreased over the 5 years. Payments for trabeculectomy without and with previous surgery were the most stable with real value declines of only 5.3% and 4.4%, respectively, whereas payments for laser trabeculoplasty and scleral reinforcement with graft declined the most at 18.0% and 12.0%, respectively. During the period studied, the 2 most highly performed glaucoma procedures were laser trabeculoplasty (889 641 billed services) and laser iridotomy (457 414 billed services), followed by trabeculectomy without previous surgery (165 535 billed services), aqueous shunt to reservoir (73 231 billed services), trabeculectomy with previous surgery (69 682 billed services), and scleral reinforcement with graft (47 916 billed services). The volume of billed services for 2 of the 6 procedures, trabeculectomy without and with previous surgery, decreased from 2005 to 2009. The 2 procedures with the greatest increase in Medicare service volume were aqueous shunt to reservoir and scleral reinforcement with graft, which saw increases of 36.5% and 61.9%, respectively.

Regression Results Using a fixed-effects regression model controlling for timeinvariant carrier-specific characteristics, carrier-level changes in Medicare beneficiary population, number of ophthalmologists, income per capita, and national trends in glaucoma service volume, we calculated the payment-volume elasticity for each procedure to describe the association between Medicare payment and glaucoma service volume (Table 2). For 4 of the 6 glaucoma procedures studieddlaser trabeculoplasty, trabeculectomy without previous surgery, trabeculectomy with previous surgery, and aqueous shunt to reservoirdthe regression coefficients were nonsignificant at the 0.05 level. Thus, there is a lack of evidence to suggest an association between changes in Medicare payment and changes in service volume for these 4 procedures. The regression coefficients were significant for 2 procedures: laser iridotomy and scleral reinforcement with graft. For laser iridotomy, the payment-volume elasticity was 1.06 (95%

confidence interval [CI], 1.39 to 0.72; P < 0.001): for every 1% decrease in Medicare payment for CPT code 66761, laser iridotomy service volume increased 1.06%. For scleral reinforcement with graft, the payment-volume elasticity was 2.92 (95% CI, 5.72 to 0.12; P ¼ 0.041): for every 1% decrease in Medicare payment for CPT code 67255, scleral reinforcement with graft service volume increased 2.92%.

Discussion From 2005 through 2009, Medicare payments for laser trabeculoplasty, trabeculectomy without and with previous surgery, aqueous shunt to reservoir, laser iridotomy, and scleral reinforcement with graft demonstrated a real-value decline ranging from 4.4% to 18.0%. Over this same period, every procedure except for the 2 types of trabeculectomies had an increase in Medicare service volume ranging from 7.0% to 61.9%. The decline in the number of trabeculectomies performed has been well documented and is thought to be secondary to the introduction of new drug therapies for lowering intraocular pressure.19,20 Based on descriptive data alone, it is difficult to determine any relationship between Medicare payment and glaucoma service volume. To date, the most thorough prior study examining this relationship concluded that argon laser therapy and trabeculectomy volume seem unrelated to reimbursement rates using national trend data.19 However, these figures do not take into account a number of factors that influence nationwide practice patterns for glaucoma management, including greater awareness of new technologies and procedures, better diagnostic tools such as anterior segment imaging, and changes in practice guidelines for the use of laser therapy and surgery versus medical management. In our study, we controlled for these factors by including a time variable to capture the national trend in glaucoma service volume and also accounted for unmeasured carrier-specific characteristics that were stable

Table 1. Trends in Medicare Payment and Glaucoma Service Volume, 2005e2009 Procedure Laser trabeculoplasty (CPT code 65855) Average payment (in 2005 $) Service volume (services/yr) Trabeculectomy without previous surgery (CPT code 66170) Average payment (in 2005 $) Service volume (services/yr) Trabeculectomy with previous surgery (CPT code 66172) Average payment (in 2005 $) Service volume (services/year) Aqueous shunt to reservoir (CPT code 66180) Average payment (in 2005 $) Service volume (services/year) Laser iridotomy (CPT code 66761) Average payment (in 2005 $) Service volume (services/year) Scleral reinforcement with graft (CPT code 67255) Average payment (in 2005 $) Service volume (services/year)

2005

2006

2007

2008

2009

$315.41 175 910

$310.55 173 459

$281.23 167 866

$260.99 184 216

$258.67 188 190

$940.67 39 051

$926.54 36 402

$925.17 32 147

$873.62 30 231

$891.04 27 704

$1171.62 15 808

$1148.32 15 565

$1159.93 13 316

$1097.47 12 921

$1119.51 12 072

$978.26 11 674

$955.42 13 160

$916.04 16 014

$858.69 16 451

$881.26 15 932

$371.15 83 429

$367.40 83 671

$361.36 83 739

$340.35 103 113

$339.63 103 462

$717.75 7472

$704.73 8639

$673.93 9574

$626.91 10 135

$631.51 12 096

CPT ¼ Current Procedural Terminology.

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Ophthalmology Volume 122, Number 5, May 2015 Table 2. Relationship between Medicare Payment and Glaucoma Service Volume, Fixed Effects Model, 2005e2009 Procedure Laser trabeculoplasty (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)*

Scleral reinforcement with graft (CPT code 67255)*

Variable CPT code 65855 payment (% change) Medicare beneficiary population (% change) No. of ophthalmologists (% change) Income per capita (% change) Year 2006 2007 2008 2009 CPT code 66170 payment (% change) Medicare beneficiary population (% change) No. of ophthalmologists (% change) Income per capita (% change) Year 2006 2007 2008 2009 CPT code 66172 payment (% change) Medicare beneficiary population (% change) No. of ophthalmologists (% change) Income per capita (% change) Year 2006 2007 2008 2009 CPT code 66180 payment (% change) Medicare beneficiary population (% change) No. of ophthalmologists (% change) Income per capita (% change) Year 2006 2007 2008 2009 CPT code 66761 payment (% change) Medicare beneficiary population (% change) No. of ophthalmologists (% change) Income per capita (% change) Year 2006 2007 2008 2009 CPT code 67255 payment (% change) Medicare beneficiary population (% change) No. of ophthalmologists (% change) Income per capita (% change) Year 2006 2007 2008 2009

% Change in Volume (95% Confidence Interval)

P Value

L0.27 (L1.31 to 0.77) 4.07 (1.36 to 9.51) 0.16 (1.22 to 1.54) 0.80 (0.93 to 2.52)

0.61 0.14 0.82 0.36

0.11 (0.31 to 0.08) 0.17 (0.38 to 0.04) 0.25 (0.56 to 0.06) 0.29 (0.62 to 0.04) L0.42 (L0.85 to 0.01) 1.58 (1.09 to 4.26) 0.39 (1.13 to 0.35) 0.40 (1.65 to 0.85)

0.25 0.10 0.11 0.087 0.053 0.24 0.30 0.52

0.12 (0.24 to 0.01) 0.26 (0.45 to 0.07) 0.34 (0.61 to 0.07) 0.50 (0.81 to 0.19) L0.28 (L0.83 to 0.28) 0.23 (3.03 to 2.58) 0.27 (1.57 to 1.03) 0.69 (e0.57 to 1.94)

0.065 0.009y 0.013z 0.002y 0.32 0.87 0.68 0.28

0.10 (0.25 to 0.05) 0.25 (0.47 to 0.03) 0.36 (0.67 to 0.05) 0.37 (0.66 to 0.08) L0.47 (L3.32 to 2.37) 0.87 (1.71 to 3.45) 1.85 (3.34 to 0.36) 1.45 (0.062.83)

0.18 0.025z 0.025z 0.012z 0.74 0.50 0.016z 0.041z

0.11 (0.33 to 0.10) 0.003 (0.37 to 0.37) 0.06 (0.66 to 0.55) 0.03 (0.56 to 0.50) L1.06 (L1.39 to L0.72) 2.54 (0.844.25) 0.23 (0.73 to 1.19) 0.35 (0.66 to 1.36)

0.30 0.99 0.85 0.91 <0.001x 0.004y 0.64 0.49

0.19 (0.24 to 0.04) 0.16 (0.32 to 0.004) 0.09 (0.30 to 0.11) 0.11 (0.32 to 0.10) L2.92 (L5.72 to L0.12) 3.78 (0.24 to 7.80) 1.10 (2.49 to 0.28) 1.15 (0.18 to 2.47)

0.009y 0.044z 0.38 0.32 0.041z 0.065 0.12 0.088

0.10 0.20 0.48 0.35

0.37 0.26 0.11 0.26

(0.31 (0.54 (1.07 (0.96

to to to to

0.11) 0.15) 0.11) 0.26)

CPT ¼ Current Procedural Terminology. *Fixed-effects model controlling for carrier-level changes in Medicare beneficiary population, number of ophthalmologists, and income per capita and for national trends in glaucoma service volume. y P ¼ 0.01. z P ¼ 0.05. x P ¼ 0.001. Boldface values represent the payment-volume elasticity and corresponding confidence interval and P value for each procedure.

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Medicare Payment and Glaucoma Service Volume

across time and for carrier-level changes in demographic and provider numbers. With these appropriate controls, we found that only 2 of the 6 procedures studieddlaser iridotomy and scleral reinforcement with graftdhad a significant association between Medicare payment and service volume. In 2009, these 2 procedures accounted for less than one-third of the total service volume for the 6 glaucoma procedures included in our analysis. Previous research conducted using methodology similar to the fixed-effects regression model used by the current study has remained mixed about the relationship between the volume of Medicare services rendered and payment. Although initial studies conducted by the Physician Payment Review Commission suggested a 50% behavioral offset, subsequent research by both the Health Care Financing Administration Office of the Actuary and independent researchers have found the physician volume-andintensity response for Medicare payment reductions to be lower at 30% to 40%.13,21 Yet, another study examining cataract procedures from the same period concluded that there is no association between Medicare payment and surgical volume.22 Although there is a dearth of previous studies examining Medicare payment and volume for glaucoma procedures, one group has studied the relationship between remuneration fees and procedure rates of trabeculoplasties, trabeculectomies, and glaucoma drainage device implantations in Canada from 1992 through 2007.23 Using a regression model that used within-province comparisons and controlled for temporal trends in procedure rates, the authors found no influence of physician remuneration fee on procedure rates for these 3 procedures, consistent with our findings for CPT codes 65855, 66170, 66172, and 66180. Because our analysis did not include physician-level data, it was not possible to determine the degree of income recouped that would be seen after payment reductions for laser iridotomy and scleral reinforcement with graft. As a result, the calculated payment-volume elasticities cannot be compared directly with the 30% to 50% behavioral offset or physician response from prior studies. However, it is clear from our study that different procedures, even within the same subspecialty, can have varying magnitudes of payment-volume elasticities. Therefore, assigning a single number as the volume response to changes in the Medicare fee schedule may oversimplify the relationship between Medicare reimbursement rates and procedural volume. Our findings also suggest that most glaucoma procedures may not have any association between Medicare payment and service volume, raising further flags about grouping all Medicare procedures and services together when discussing how healthcare providers and consumers respond to changes in Medicare payment. We raise an additional concern about how the relationship between Medicare payment and service volume should be characterized moving forward. Two ways that this relationship has been referred to in the literature are behavioral offset and physician response, suggesting that physicians are engaging in behavior to recoup lost income from declines in Medicare reimbursement by recommending more medical care services to patients. However, without examining

patient and physician decision making more closely, it may be misleading to conclude that only physicians drive shifts in procedural volume. Although a strong income effect can explain why physicians would increase the volume of Medicare services rendered when faced with declining Medicare payment, a downward-sloping demand curve representing patients’ preferences also can explain why decreasing Medicare fees would increase patient demand for services. Lower prices for medical care services can induce Medicare beneficiaries to seek more care because of lower out-of-pocket expenses from reduced coinsurance payment. In our research, we elected to use the term payment-volume elasticity as a descriptive term to refer to the association between Medicare payment and Medicare service volume. Future streams of research should examine data at physician and patient levels to determine how the supply and demand for procedures influence payment-volume elasticities. For laser iridotomy, increased physician and patient awareness of angle-closure glaucoma suspects may be important to study as a factor that impacts both supply and demand. An additional variable to consider is the role of increased billing charge capture for both laser iridotomy and scleral reinforcement with graft. Whether driven by decreasing reimbursement levels or unrelated to Medicare payments, increased capture could explain the increased service volume for both procedures. In addition, because our findings suggest that different procedures for glaucoma treatment can have varying payment-volume elasticities, further research on procedures both within ophthalmology and in other fields of medicine is needed to characterize better the variation in the volume response to changes in the Medicare fee schedule across different procedures. As part of this characterization, a central question that remains unexplored is determining which attributes of a procedure result in that procedure having a significant association between payment and service volume. From the provider perspective, one such factor to explore is the relationship between the extent to which a procedure accounts for a practice’s total revenue and that procedure’s payment-volume elasticity. Procedures accounting for a greater percentage of a provider’s income may have more significant associations between payment and service volume. Another factor to consider is how a procedure’s elective or nonelective nature may affect the impact of Medicare reimbursements on service volume: consistent with our findings for trabeculectomy, we expect nonelective procedures to have less significant or nonsignificant associations between Medicare payment and service volume. Identifying the specific factors that make one procedure more elastic than another can help policy makers predict future Medicare spending after changes in the Medicare Physician Fee Schedule. Our analysis of 6 glaucoma procedures from 2005 through 2009 suggest that there may not be a significant association between Medicare payment and service volume for many glaucoma procedures. Among those procedures that have a significant relationship, different elasticities are observed, suggesting that the volume response to changes in Medicare payments is not uniform across all Medicare procedures. Approaching the relationship between Medicare payment and service volume with a more nuanced

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Ophthalmology Volume 122, Number 5, May 2015 perspective will help policy makers attain a more accurate picture of the impact of changes in the Medicare physician payment system. With forthcoming discussions ranging from a repeal of the sustainable growth rate formula to the creation of a value-based per-patient payment system,24e26 a better understanding of both patient and physician behavior will lead to more accurate projections about future Medicare spending.

References 1. Friedman DS, Wolfs RC, O’Colmain BJ, et al. Prevalence of open-angle glaucoma among adults in the United States. Arch Ophthalmol 2004;122:532–8. 2. Congdon N, O’Colmain B, Klaver CC, et al. Causes and prevalence of visual impairment among adults in the United States. Arch Ophthalmol 2004 Apr;122:477–85. 3. Klein R, Klein BE. The prevalence of age-related eye diseases and visual impairment in aging: current estimates. Invest Ophthalmol Vis Sci 2013;54:ORSF5–13. 4. Salm M, Belsky D, Sloan FA. Trends in cost of major eye diseases to Medicare, 1991 to 2000. Am J Ophthalmol 2006;142:976–82. 5. Department of Health and Human Services, Health Care Financing Administration. Medicare program: fee schedule for physicians’ services: final rule. Federal Register November 25, 1991;56:59502e811. 6. Physician Payment Review Commission. Annual Report to Congress 1993. Washington, DC: Physician Payment Review Commission; 1993. 7. Ginsburg PB, Hogan C. Physician response to fee changes. A contrary view. JAMA 1993;269:2550–2. 8. Centers for Medicare and Medicaid Services. Part B National Summary Data File. Available at: http://www.cms.gov/ Research-Statistics-Data-and-Systems/Files-for-Order/NonId entifiableDataFiles/PartBNationalSummaryDataFile.html. Accessed September 15, 2013. 9. Centers for Medicare and Medicaid Services. Part B Carrier Summary Data File. Available at: http://www.cms.gov/ Research-Statistics-Data-and-Systems/Files-for-Order/NonId entifiableDataFiles/Part-B-Carrier-Summary-Data-File.html. Accessed September 15, 2013. 10. Centers for Medicare and Medicaid Services. Medicare Physician Fee Schedule. Available at: http://www.cms.gov/apps/ physician-fee-schedule/overview.aspx. Accessed September 15, 2013 11. Bureau of Labor Statistics. CPI Inflation Calculator. Available at: http://data.bls.gov/cgi-bin/cpicalc.pl. Accessed September 15, 2013.

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12. American Medical Association. CMS to Begin Processing Claims with 2.2 Percent Increase. Available at: http://www. ama-assn.org/ama/pub/physician-resources/solutions-managingyour-practice/coding-billing-insurance/medicare/medicareclaims-payment.page. Accessed September 15, 2013. 13. Nguyen NX, Derrick FW. Physician behavioral response to a Medicare price reduction. Health Serv Res 1997;32:283–98. 14. Mitchell JB, Cromwell J. Impact of Medicare payment reductions on access to surgical services. Health Serv Res 1995;30:637–55. 15. Andreyeva T, Long MW, Brownell KD. The impact of food prices on consumption: a systematic review of research on the price elasticity of demand for food. Am J Public Health 2010;100:216–22. 16. American Medical Association. Overview of RBRVS. Available at: http://www.ama-assn.org/ama/pub/physicianresources/solutions-managing-your-practice/coding-billinginsurance/medicare/the-resource-based-relative-value-scale/ overview-of-rbrvs.page. Accessed November 1, 2013. 17. Allison PD. Fixed Effects Regression Models. Thousand Oaks, CA: Sage; 2009. 18. U.S. Department of Health and Human Services. Area Health Resources File. Available at: http://ahrf.hrsa.gov/download. htm. Accessed September 15, 2013. 19. Paikal D, Yu F, Coleman AL. Trends in glaucoma surgery incidence and reimbursement for physician services in the Medicare population from 1995 to 1998. Ophthalmology 2002;109:1372–6. 20. Ramulu PY, Corcoran KJ, Corcoran SL, Robin AL. Utilization of various glaucoma surgeries and procedures in Medicare beneficiaries from 1995 to 2004. Ophthalmology 2007;114: 2265–70. 21. Codespote SM, London WJ, Shatto JD. Physician volume & intensity response. Available at: http://www.cms.gov/ResearchStatistics-Data-and-Systems/Research/ActuarialStudies/Down loads/PhysicianResponse.pdf. Accessed September 15, 2013. 22. Escarce JJ. Effects of lower surgical fees on the use of physician services under Medicare. JAMA 1993;269:2513–8. 23. Buys YM, Austin PC, Campbell RJ. Effect of physician remuneration fees on glaucoma procedure rates in Canada. J Glaucoma 2011;20:548–52. 24. House Ways & Means and Senate Finance Committee Staff. SGR Repeal and Medicare Physician Payment Reform. October 2013. Available at: http://waysandmeans.house.gov/ uploadedfiles/sgr_discussion_draft.pdf. Accessed January 15, 2014. 25. Wilensky GR. Improving value in Medicare with an SGR fix. N Engl J Med 2014;370:1–3. 26. Chien AT, Rosenthal MB. Medicare’s physician value-based payment modifierdwill the tectonic shift create waves? N Engl J Med 2013;369:2076–8.

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Footnotes and Financial Disclosures Originally received: August 4, 2014. Final revision: December 9, 2014. Accepted: December 9, 2014. Available online: January 23, 2015.

Manuscript no. 2014-1232.

1

Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, Connecticut. 2 Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York Eye and Ear Infirmary of Mount Sinai, New York, New York. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. Support for this study was provided in part by an Unrestricted Departmental Grant from Research to Prevent Blindness, Inc, New York, New York, and the Robert R. Young Professorship. Research to Prevent Blindness, Inc, and

the Robert R. Young Professorship had no role in the design and conduct of the study; the collection, management, analysis, and interpretation of the data; the preparation, review, or approval of the manuscript; or the decision to submit the manuscript for publication. Presented at: American Academy of Ophthalmology Annual Meeting, October 2014, in Chicago, Illinois. Abbreviations and Acronyms: CI ¼ confidence interval; CMS ¼ Centers for Medicare and Medicaid Services; CPT ¼ Current Procedural Terminology; MPFS ¼ Medicare Physician Fee Schedule. Correspondence: James C. Tsai, MD, MBA, New York Eye and Ear Infirmary of Mount Sinai, 310 East 14th Street, New York, NY 10003. E-mail: [email protected].

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