Quantitative retinal and choroidal blood flow during light, dark adaptation and flicker light stimulation in rats using fluorescent microspheres

Curr Eye Res. 2013 Feb;38(2):292-8. doi: 10.3109/02713683.2012.756526. Epub 2013 Jan 14.


Purpose: The present study aimed to quantify retinal and choroidal blood flow (BF) during light, dark adaptation and flicker light stimulation using the microsphere technique.

Materials and methods: Adult male Sprague-Dawley rats were anesthetized with isoflurane. Eyes were dark (Group I, n = 8), light (Group II, n = 8) adapted or stimulated with 10 Hz flicker light (Group III, n = 10). Retinal and choroidal BF were measured by a previously established method, using a mixture of 8 µm yellow-green and 10 µm red fluorescent microspheres. The microspheres were counted ex vivo in the dissected retina and choroid and in the reference arterial blood under a fluorescent microscope.

Results: The choroidal BF was 64.8 ± 29 µl/min (mean ± SD) during dark adaptation, not significantly different from that during light adaptation (66.0 ± 17.8 µl/min). The retinal BF was 13.5 ± 3.2 µl/min during 10 Hz flickering light stimulation, significantly higher than that during dark adaptation in the control fellow eyes (9.9 ± 2.9 µl/min). The choroidal BF values were not statistically different between flicker stimulation and dark adaptation. Retinal BF was 11.6 ± 2.9 µl/min during light adaptation. Dark adaptation did not increase retinal BF (Group I, 8.2 ± 2.4 µl/min; Group II, 9.9 ± 2.9 µl/min).

Conclusions: These findings argue against a dark-induced or flicker-induced functional hyperemia in the choroid as a result of the demands of the outer retina. Retinal BF was not higher during dark adaptation. Our data support the conclusion that the inner retina has a higher energy demand in flicker conditions relative to dark.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adaptation, Ocular / physiology*
  • Animals
  • Blood Pressure / physiology
  • Carbon Dioxide / blood
  • Choroid / blood supply
  • Choroid / physiology
  • Dark Adaptation / physiology*
  • Flicker Fusion / physiology*
  • Fluorescence
  • Hydrogen-Ion Concentration
  • Male
  • Microspheres
  • Models, Cardiovascular
  • Photic Stimulation
  • Rats
  • Rats, Sprague-Dawley
  • Regional Blood Flow / physiology
  • Retina / physiology
  • Retinal Vessels / physiology*


  • Carbon Dioxide