title: Neurovascular dysfunction precedes neural dysfunction in the retina of patients with type 1 diabetes.
abstract: OBJECTIVE
  A variety of studies have shown that flicker-induced vasodilatation is reduced in patients with diabetes. It is, however, unclear whether reduced neural activity or abnormal neurovascular coupling is the reason for this phenomenon. In the present study, we hypothesized that retinal neurovascular dysfunction precedes neural dysfunction in patients with early type 1 diabetes.
  
  
  METHODS
  In the present study, 50 patients with type 1 diabetes without retinopathy and 50 healthy age- and sex-matched control subjects were included. The retinal vascular response to flicker stimulation was measured using the dynamic Retinal Vessel Analyzer. In addition, the response in retinal blood velocity to flicker stimulation as assessed with laser Doppler velocimetry was studied in a subgroup of patients. Pattern electroretinography (ERG) was used to measure neural retinal function.
  
  
  RESULTS
  The flicker responses of both retinal arteries and veins were significantly reduced in patients with diabetes (veins in the diabetic group: 3.5 ± 2.3% versus healthy control group: 4.6 ± 2.0%; P = 0.022 between groups, whereas arteries in the diabetic group: 2.0 ± 2.7% versus healthy control group: 3.8 ± 1.7%; P < 0.001 between groups). Likewise, the response of retinal blood velocity was reduced in patients with diabetes, although adequate readings could only be obtained in a subgroup of subjects (diabetic group [n = 22]: 19 ± 7%; healthy control group [n = 24]: 43 ± 19% P < 0.001 between groups). The parameters of pattern ERG were not different between the two groups.
  
  
  CONCLUSIONS
  The study confirms that flicker responses are reduced early in patients with type 1 diabetes. This is seen before alterations in pattern ERG indicating abnormal neurovascular coupling.
authors: Clinical Pharmacology, MedicalUniversity of Vienna, Vienna, Austria.
authors: Michael
authors: M
authors: Lasta
authors: Berthold
authors: B
authors: Pemp
authors: Doreen
authors: D
authors: Schmidl
authors: Agnes
authors: A
authors: Boltz
authors: Semira
authors: S
authors: Kaya
authors: Stefan
authors: S
authors: Palkovits
authors: Rene
authors: R
authors: Werkmeister
authors: Kinga
authors: K
authors: Howorka
authors: Alina
authors: A
authors: Popa-Cherecheanu
authors: Gerhard
authors: G
authors: Garhöfer
authors: Leopold
authors: L
authors: Schmetterer
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D003922:Diabetes Mellitus, Type 1 / Q000150:complications*; D003930:Diabetic Retinopathy / Q000175:diagnosis* / Q000503:physiopathology*; D004596:Electroretinography; D005260:Female; D005425:Flicker Fusion / Q000502:physiology; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D009410:Nerve Degeneration / Q000175:diagnosis / Q000503:physiopathology; D010775:Photic Stimulation; D012160:Retina / Q000473:pathology / Q000503:physiopathology; D012161:Retinal Artery / Q000503:physiopathology*; D012169:Retinal Vein / Q000503:physiopathology*; D014664:Vasodilation / Q000502:physiology