JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
To optometrist distribution, a zip code database was downloaded from Federalgovernmentzipcodes.us; this database contained latitude and longitude data for each US zip code. Optometrist data was compared to ophthalmologist data using Microsoft Excel to determine all US zip codes containing only optometry offices (“isolated optometry offices”), Table 2. Using a brute force method with Excel, every isolated optometry office was paired with every ophthalmology office in each state. “Brute force” means that every row was calculated with every column, and the distance between their two zip codes was calculated using the Spherical Law of Cosines, 10 as follows: the distance between two points on Earth’s surface is calculated as determine ophthalmologist and
This communication seeks to ascertain the accuracy of these assertions by analyzing the National Medicare Database.
Materials and Methods
The Physician Compare National downloadable file was downloaded from Medicare.gov. This file was dated June 26, 2014. Microsoft Access was used to access these data. Ophthalmology practice addresses and optometry practice addresses were identified and saved into separate files. Note that this database contains data for the 50 states, as well as the District of Columbia, the Commonwealth of Puerto Rico, and the US territories of Guam, US Virgin Islands, and the Northern Mariana Islands. Unique National Provider Identifier (NPI) numbers were then identified for each address. These were tabulated by state using Microsoft Excel. These data are summarized in Table 1.
d= acos ( sin φ1 • sin φ2 + cos φ1 • cos φ2 • cos [λ2 – λ1] ) • R
where (φ1, λ1) are the latitude and longitude of point one, (φ2, λ2) are the latitude and longitude of point two, and R is the radius of the Earth in miles.
Table 1
MD ADDRESSES
MD UNIQUE NPI 29
OD ADDRESSES
OD UNIQUE NPI
MD / OD ADDRESSES
160.00% 64.49% 77.63% 62.09% 29.29% 47.88% 44.95% 50.88% 80.36% 49.35% 81.99% 362.50% MD / OD NPI 60.77% 36.38% 31.65% 61.05% 34.72% 30.75% 47.26% 69.19% 108.00% 132.75%t
STATE
AK
55 215 351 545 5138 474
248 430 751
99 307 485 568 2642 535 361 24 107 1538 670
150.00% 95.74% 92.67% 63.94% 22.18% 50.00% 46.74% 48.79% 122.92% 54.36% 88.17% 393.55% 52.82% 36.18% 31.51% 82.35% 36.48% 33.61% 63.28% 79.10% 174.18% 145.54%
AL AR AZ CA CO CT DC DE FL GA GU HI IA ID IL IN KS KY LA MA MD
147 218 289 2123
1117 4180
264 296
872 465 31 141
410 122 135
87 69 1194 416 8
2201
2375 1126 8
12 720 187 250 92
5
110 171 69 776 293 151 224 566 270 535
354 691 292
181 470 218 1271
1824 1280 735
1502 467 247
844 491 474 818 250 403
417 980 634
659
1239 364
1029
707
150 J La State Med Soc VOL 169 NOVEMBER/DECEMBER 2017
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