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Invest Ophthalmol Vis Sci. 2006 Feb;47(2):715-21.

Visual stimulus-induced changes in human near-infrared fundus reflectance.

Author information

  • 1Department of Ophthalmology and Visual Sciences, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242, USA. michael-abramhoff@uiowa.edu

Abstract

PURPOSE:

Imaging studies from anesthetized feline, primate, and human retinas have revealed near-infrared fundus reflectance changes induced by visible light stimulation. In the present study, the spatial and temporal properties of similar changes were characterized in normal, awake humans.

METHODS:

Five normal human subjects were studied. A modified fundus camera was used to image changes in retinal reflectance of 780-nm near-infrared light imaged onto a 12-bit charge-coupled device (CCD) camera in response to a green (540 nm) visual stimulus. During 60 seconds of recording (frame rate, 3 Hz) 10 cycles were recorded, during each of which 3 seconds of blank and then 3 seconds of either vertical bar or blank stimulus was projected. The change in the average near-infrared reflectance of the stimulated retinal region relative to an equal-sized nonstimulated region (r is the ratio of reflectance between the two retinal areas) was analyzed with a mixed model for repeated measures.

RESULTS:

The mixed model showed a significant average decrease in r of 0.14% (95% CI, -0.25 to -0.03) over all subjects induced by bar stimulus cycles, with a gradual return to baseline after stimulus offset, compared with only a 0.04% (95% CI, -0.11-+0.20) decrease in r induced by blank, nonstimulated cycles. The mixed model for individuals showed a decreasing linear trend in r over time during bar stimulation, but no decrease for blank cycles in three of five subjects.

CONCLUSIONS:

There was a localized decrease in reflectance in response to 780-nm near-infrared light in the retinal region exposed to a visual stimulus, which was significant in three of five subjects. It is presumed that the reflectance change represents the functional activity of the retina in response to a visual stimulus.

PMID:
16431972
[PubMed - indexed for MEDLINE]
PMCID:
PMC1473026
Free PMC Article

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