Scotopic electrophysiology of the retina during transient hyperglycemia in type 2 diabetes.
OBJECTIVE
To examine dark-adapted retinal function in subjects with type 2 diabetes during transient hyperglycemia.


METHODS
Twenty-four subjects with type 2 diabetes and minimal diabetic retinopathy were randomized to an oral glucose tolerance test (OGTT) or a fasting regimen. One study eye was kept in the dark-adapted state at all times. Full-field electroretinography (ffERG) and blood glucose measurements were performed at baseline and after 20, 80, 140, and 200 minutes.


RESULTS
Mean capillary glucose had increased 162% from the fasting baseline value when the concentration peaked in the OGTT group after 80 minutes (P < 0.0001). Concomitantly, rod b-wave amplitude had increased by 34% (P = 0.0007), whereas the a- and b-wave amplitudes of the standard combined rod-cone response had increased by 17% (P = 0.0013 and P = 0.0064). The dark-adapted 30-Hz flicker response was unaffected by hyperglycemia. The scotopic ffERG amplitudes rose and fell in phase with the glycemia. Implicit times did not change with the rise and fall in glycemia.


CONCLUSIONS
The change in scotopic signaling amplitude in the outer and middle layers of retina in subjects with diabetes was proportional to the change in capillary glucose. Cone amplitude was not influenced by hyperglycemia in this study.
Holfort
Stig Kraglund
SK
Department of Ophthalmology, Glostrup Hospital, University of Copenhagen, Copenhagen, Denmark. stig_holfort@hotmail.com
Klemp
Kristian
K
Kofoed
Peter Kristian
PK
Sander
Birgit
B
Larsen
Michael
M
D001786:Blood Glucose / Q000032:analysis; D003623:Dark Adaptation; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000503:physiopathology*; D004596:Electroretinography; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D006943:Hyperglycemia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D055254:Night Vision; D012160:Retina / Q000503:physiopathology*
D001786:Blood Glucose