The Relationship between Structure and Function Parameters in Diabetes and Prediabetes



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Purpose: Previous studies demonstrated structural and functional retinal changes in type 2 diabetes. (T2DM). However, less is understood in prediabetes, which is an important precursor to T2DM. In this thesis, we evaluate the microvasculature structure of the foveal avascular zone (FAZ) and how it is correlated to retinal function measured by multifocal electroretinograms (mfERG) and contrast sensitivity (CS). By evaluating different levels of glucose dysfunction, we uncover how T2DM and prediabetes alter this structure-function relationship. Methods: 33 subjects were included: 9 controls, 12 prediabetes, and 12 T2DM without retinopathy. Subjects were between 30-70 years, had BCVA of 20/25+, and had no confounding ocular conditions. Blood was collected via fingerstick to determine Hemoglobin A1c which along with previous diagnosis allowed determination of study grouping. Optical coherence tomography angiography (OCTA) was used to calculate the FAZ area (after correction for refractive error). FAZ area was measured by hand using the Heidelberg Spectralis software. mfERG (VERIS 6.4) metrics implicit time (IT) and amplitude (amp) were evaluated in the foveal region and averaged over the whole area of retina stimulated (“whole eye”). CS was measured by MARS chart. All testing was performed on the right eye. Regression analysis was performed between each study group parameter to determine significant relationships, and t-tests with corrections were used to compare groups. Results: FAZ area (superficial plexus) was negatively correlated with mfERG whole eye amp (P<0.008, R2= 0.30) and also with foveal amp (p=0.02 R2=0.17) across all 33 subjects. However, FAZ and mfERG metrics were not significantly different between study groups, with the exception of IT that was delayed in T2DM group. CS was not significantly associated with other metrics once age was considered. The relationship between IT and FAZ area was not significant in any of the groups alone, nor when compared in all study subjects as a single group. Conclusion: These data suggest a link between structural and functional metrics and overall retinal health. Evaluating OCTA and mfERG in subjects with and without T2DM may increase our knowledge of their retinal health and eventually lead to better clinical care.



OCTA, MfERG, Diabetes, Prediabetes