Geographic Information Systems Mapping of Diabetic Retinopathy in an Ocular Telemedicine Network

Abstract

Importance: Minimal information exists on the use of geographic information systems mapping for visualizing access barriers to eye care for patients with diabetes.

Objective: To use geographic information systems mapping techniques to visualize (1) the locations of patients participating in the North Carolina Diabetic Retinopathy Telemedicine Network, (2) the locations of primary care clinicians and ophthalmologists across the state, and (3) the travel times associated with traveling to the 5 primary care clinics in our study.

Design, setting, and participants: Cross-sectional study conducted from January 6, 2014, to November 1, 2015, at 5 Area Health Education Center primary care clinics that serve rural and underserved populations in North Carolina. In total, 1787 patients with diabetes received retinal screening photographs with remote expert interpretation to determine the presence and severity of diabetic retinopathy. Participants included patients 18 years or older with type 1 or type 2 diabetes who presented to these 5 clinics for their routine diabetes care.

Main outcomes and measures: Development of qualitative maps illustrating the density of patients with diabetes and their distribution around the 5 North Carolina Diabetic Retinopathy Telemedicine Network sites by zip code and the density of ophthalmologists and primary care clinicians by zip code relative to US Census Urban Areas. A travel time map was also created using road network analysis to determine all areas that can be reached by car in a user-specified amount of time.

Results: Mean (SD) age of patients was 55.4 (12.7) years. Women made up 62.7% of the study population. The study included more African American patients (55.4%) compared with white (35.5%) and Hispanic (5.8%) patients. The mean (SD) hemoglobin A1c level was 7.8% (2.4%) (to convert to proportion of total hemoglobin, multiply by 0.01), and the mean (SD) duration of diabetes was 9.2 (8.2) years. Whereas the clinics located in Greensboro, Asheville, and Fayetteville screened patients from more immediate surrounding areas, the Greenville site had the widest distribution of zip codes, suggesting that patients travel from greater distances to reach this facility. Primary care clinicians were spread somewhat uniformly across the state, whereas ophthalmologists were concentrated around urban centers. Also, the number and type of surface roads surrounding the clinics determined the distance and time patients must travel to receive care.

Conclusions and relevance: Geographic information systems mapping is a useful technique for visualizing geographic access barriers to eye care for patients with diabetes and may help to identify underserved areas that would benefit from the expansion of retinal screening programs via telemedicine.

Figure 1.. Patients With Diabetes in the North Carolina Diabetic Retinopathy Telemedicine Network (NCDRTN) per Zip Code

Figure shows density of patients with diabetes and their distribution around the 5 NCDRTN sites by zip code. Greenville clinic site has widest distribution of darkly shaded zip codes, suggesting patients travel from outlying rural areas to seek medical care at this facility. Greensboro, Asheville, and Fayetteville sites have more concentrated distributions of zip codes, suggesting patients travel from areas that are tightly clustered around the urban centers. Maps generated by Esri, HERE, DeLorme, MapmyIndia, USGS, NOAA, NPS, OpenStreetMap contributors, and the GIS user community.

Figure 2.. Density of Primary Care Professionals in North Carolina

Density of licensed primary care professionals throughout the state, shown using 1-to-3 dot density plotting. Figure demonstrates larger numbers of primary care professionals who are distributed more widely across both rural and urban areas of the state when compared against US Census Urban Areas (in green). Maps generated by Esri, HERE, DeLorme, MapmyIndia, USGS, NOAA, NPS, OpenStreetMap contributors, and the GIS user community.

Figure 3.. Density of Ophthalmologists in North Carolina

Density of licensed ophthalmologists throughout the state, shown using 1-to-1 dot density plotting. Figure demonstrates ophthalmologists are fewer in number and concentrated mainly within urban centers when compared against US Census Urban Areas (in green). Maps generated by Esri, HERE, DeLorme, MapmyIndia, USGS, NOAA, NPS, OpenStreetMap contributors, and the GIS user community.

Figure 4.. Driving Time to North Carolina Diabetic Retinopathy Telemedicine Network Sites

Travel time map allows for visualization of potential access barriers based on number and type of surface roads surrounding each clinic. Twenty-minute service area represents all areas that can be reached within 20 driving minutes. Forty-minute service area contains all areas that can be reached between 20 and 40 driving minutes. Sixty-minute service area contains all areas that can be reached between 40 and 60 driving minutes. Maps generated by Esri, HERE, DeLorme, MapmyIndia, USGS, NOAA, NPS, OpenStreetMap contributors, and the GIS user community.