Differential activation of cerebral blood flow by stimulating amblyopic and fellow eye.
OBJECTIVE
Positron emission tomography (PET), the blood flow response in the primary visual cortex (V1) to two visual stimuli, low temporal frequency (6 Hz) to activate the parvocellular system, and high temporal frequency (25 Hz) to activate the magnocellular system were used to investigate pathophysiologic mechanism of amblyopia.


METHODS
Five women and one man who were aged between 26 and 60 years, who were ophthalmologically normal except for amblyopia, and who had corrected visual acuity in the amblyopic eye of 0.6 or worse were examined. An intravenous injection of the H(2)(15)O was given, and the regional cerebral blood flow was measured by PET during full-field stimulation with either 6 Hz or 25 Hz flicker to the amblyopic or the sound eye.


RESULTS
The activation of blood flow in the contra-lateral area V1 by the 6-Hz stimulation of the sound eye was greater than that during the stimulation of the amblyopic eye (P<0.05, small volume correction, n=6). With 25-Hz stimulation of the sound and amblyopic eyes, the blood flow in the contra-lateral and ipsi-lateral areas V1 was not significantly different.


CONCLUSIONS
The decreased activation of blood flow in the contra-lateral V1 by low temporal frequency stimuli supports the hypothesis that the parvocellular pathway in amblyopic eyes is depressed.
Mizoguchi
Shoichi
S
Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University Graduate School, Tokyo, Japan.
Suzuki
Yukihisa
Y
Kiyosawa
Motohiro
M
Mochizuki
Manabu
M
Ishii
Kenji
K
D000328:Adult; D000550:Amblyopia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001345:Autoradiography / Q000379:methods; D001921:Brain / Q000098:blood supply*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D018450:Disease Progression; D004585:Electrooculography; D005133:Eye Movements; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D010104:Oxygen Radioisotopes / Q000008:administration & dosage; D049268:Positron-Emission Tomography / Q000379:methods; D012039:Regional Blood Flow / Q000502:physiology*; D015203:Reproducibility of Results; D013268:Stimulation, Chemical; D014792:Visual Acuity; D014867:Water / Q000008:administration & dosage
D010104:Oxygen Radioisotopes; D014867:Water