Biomedical Engineering Reference
In-Depth Information
Appendix 1:
Technical Details
of Functional
Retinography
The monkeys were anesthetized by a mixture of 70% N
2
O, 30%
O
2
supplemented with 1.0-1.5% of isoflurane and were paralyzed
with vecuronium bromide (0.1-0.2 mg/ kg/ hour). Before the
recordings, the pupils were fully dilated with topical tropicamide
(0.5%) and phenylephrine hydrochloride (0.5%). A modified dig-
ital fundus camera system (NM-1000, Nidek, Aichi, Japan) was
used to observe and measure the light reflectance changes from
the ocular fundus. The fundus images were recorded with a CCD
camera (PX-30BC, Primetech Engineering, Tokyo, Japan), and
the images were digitized with an IBM/PC-compatible computer
equipped with a video frame grabber board (Corona II, Matrox,
Quebec, Canada: gray level resolution, 10 bits; spatial resolution,
640 x 480; temporal resolution, 1/30 s). The camera was focused
on the macular vessels, and the area recorded covered 45 degrees,
which included the macula, superior and inferior vascular arcades,
and the optic disk.
The fundus was continuously monitored with light from a
halogen lamp filtered through a red (610-650 nm) or infrared
(840-900 nm) interference filter. Each recording trial consisted
of three hundred video frames collected at 30 frames/sec for a
total recording time of 10 s. A Xenon flash (duration: 1 msec)
was given to the whole posterior pole of the ocular fundus, 500
msec after the initiation of data acquisition. The flash intensity
measured at the cornea was 1.54
10
2
cd
s/m
2
. The timing of
the data acquisition and stimulus delivery was under computer
control. Changes in light reflectance from the ocular fundus
following the stimulus, such as a darkening (a decrease in light
reflectance) or a brightening (an increase in light reflectance),
were measured. The optical signal was calculated as follows:
(1)
The gray-scale values of the image obtained after the stimulus
were divided, pixel by pixel, by those obtained during a 0.5-s
period before the stimulus, and
(2)
This ratio was rescaled to
256 levels of gray-scale resolution to show the stimulus-induced
reflectance changes.
×
8. Appendix 2:
Technical Details
of fOCT
System
We used a fiber-based OCT imaging system (
Fig. 6.7B
). It
consists
of
a
Mach-Zehnder-type
heterodyne
interferometer
