The measurement of rate of aqueous flow
with iodide
Bernard Becker
Trace amounts of iodide are transported out of the rabbit eye in such a fashion that this union
accumulates in the aqueous humor of the anterior chamber exponentially toith time. Iodide is
therefore a useful anion for estimating the coefficient of aqueous flow and requires punctures
of the anterior chamber only. The method can be used in two eyes of one animal, or with the
use of two or more isotopes of iodide, can be applied to a single eye. The iodide methoddemonstrates a floiu coefficient of 1.5 per cent of the anterior chamber per minute in the normal
animal. It is reduced by some 45 to 50 per cent following acetazolamide, by 80 to 90 per cent
during hypothermia (18 to 20° C), and by an average of 17 per cent on the side of carotid
ligation. Topical pilocarpine appears to increase the flow coefficient by an average of 16 per
cent and atropine to decrease it by 21 per cent.
I
of the iodide method to normal rabbits as
well as those subjected to carbonic anhydrase inhibitors, hypothermia, unilateral
carotid ligation, or topical application to
one eye of pilocarpine or atropine.
odide is transported out of the rabbit
eye behind the iris.1 As a consequence of
this transport process, low concentrations
of iodide in the vitreous humor and posterior chamber aqueous humor have little
effect on the concentration in the anterior
chamber. In fact, after systemic administration of small doses of iodide, the concentration of the anterior chamber aqueous
humor rises exponentially with time; that
is, the turnover of iodide in the anterior
chamber is simplified to a single exponential.2 This makes possible the use of iodide
for the estimation of the rate of aqueous
flow from anterior chamber samples of the
two eyes of one animal, or even from single
punctures of the individual eye. This paper
presents the results of initial applications
Methods
Mathematical formulations.
dC.
= kap. ( a C p - C . ) - k r . C.
dt
yhere
"t
(1)
1 =i the rate of change in concentration of iodide in the anterior chamber aqueous humor
k,ipil = the coefficient of diffusional
exchange of iodide between
anterior chamber aqueous
humor and plasma (min."1)
kftt = fraction of anterior chamber
aqueous humor leaving the
eye each minute by flow
From the Department of Ophthalmology and the
Oscar Johnson Institute, Washington University
School of Medicine, St. Louis, Mo.
This investigation was supported in part by Research Grant B-621 from the National Institute
of Neurological Diseases and Blindness, National Institutes of Health, United States Public
Health Service.
a = the Donnan factor for iodide
(1.05)
Cn = the concentration of iodide in
the aqueous humor (as a
fraction of the concentration
in the plasma water)
52
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Volume 1
Number 1
Measurement of aqueous flow rate with iodide 53
Cp = the concentration of iodide in
the plasma water (corrected
for protein binding when
necessary)
This is essentially the equation of Kinsey3 but
disregards the contribution of the posterior
chamber.
If
ko =
k,lpn + kfn
infusion was set so as to maintain a constant
external counting rate over the animal's heart.
Aqueous humor was withdrawn from one eye at
approximately 20 to 40 minutes and from the
other eye 4 to 6 hours after the beginning of the
intravenous injection. Plasma counts (C P ) were
expressed per liter of water and corrected for
protein binding. With semilog paper, log
1
\
1 was plotted using the 4 to 6 hour
then equation (1) can be written:
r\C
1 =
(2)
kdpn a Cp - koC a
dt
At steady state,
dC.
dt
0, Ca
Ca 00
and
k0C
(3)
«Cp
Substituting in equation (2):
Ko ( C u 00
~
(4)
VJ
dt
and by integration:
Coo ~ Cn
Iog
Coo
, .
(5)
- kot
=
(6)
g
Therefore, plotting log
Cop
-
C
against
time in minutes provides a straight line of
slope, -ko. Furthermore, from the value for ko
obtained and C oo as measured, k,iPa can be calculated (equation [3]); then the flow coefficient,
With two eyes of one animal. Unanesthetized
male albino rabbits weighing 2 to 3 kilograms
were used for all experiments. All animals were
given 0.5 mg. per kilogram of sodium iodide (I127) 3 to 24 hours before the experiment to
saturate thyroidal and other binding sites. 1-131*
was administered in doses of 25 to 40 fie. In order
to maintain a constant blood level one third of the
total dose was injected intravenously and two
thirds intraperitoneally, or one third intravenously
followed by a continuous intravenous infusion
maintained with an infusion pump.f The rate of
•Obtained from Abbott Laboratories, Oak Ridge, Tenn.
fHarvard Apparatus Company, Dover, Mass.
values for
C
00
and the value at time t for
— . The slope of the line determined k0, and kfa
Cp
was calculated as indicated above.
This method was applied to 15 normal rabbits
as well as 15 rabbits treated with acetazolamide
(50 mg. per kilogram intravenously every 60
minutes). In addition, 13 rabbits were subjected
to immersion hypothermia (18 to 20° C.). In the
hypothermia experiments the anterior chambers
were tapped at 2 to 3 hours for C , and the
second eyes at from 10 to 12 hours for an approximation of CooWith, a single eye. Sodium iodide (1-127) was
administered intraperitoneally (0.5 to 1.5 mg. per
kilogram) 4 to 16 hours before puncture of the
anterior chamber. 1-131 was given (25 to 40 f*c)
either one third intravenously and two thirds
intraperitoneally, or by continuous intravenous infusion starting approximately 20 to 40 minutes
before the anterior chamber puncture. The iodide
(1-127) concentrations in the aqueous humor and
plasma were determined chemically by the eerie
sulfate-arsenious acid method for inorganic
iodide4 and provided a value for —!!—. 1-131
Cp
was counted in the same samples and estimated
Ca
The same type of semilog plot and calculaCp
tion was used as described above. This method
was applied to 5 eyes of animals treated with
acetazolamide. It was also used to study both
eyes of 10 rabbits treated in one eye with topical
pilocarpine (2 per cent every half hour), both
eyes of 10 rabbits treated in one eye with
atropine (2 per cent every half hour), and both
eyes of 10 animals subjected to unilateral carotid
ligation.
In some animals in order to obtain a third
point from the single anterior chamber puncture
and thus better characterize the plotted line,
1-130* was administered (25 to 40 fie) as well
"Obtained from Union Carbide Nuclear Company, Oak
Ridge National Laboratories, Oak Ridge, Tenn.
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Investigative Ophthalmology
February 1962
54 Becker
as the 1-131 and 1-127. In general, the 1-127 was
given 4 to 16 hours before the anterior chamber
puncture, 1-131 approximately 50 to 70 minutes
before the tap, and 1-130 approximately 20 to
40 minutes before the tap. 1-130 and 1-131 could
be distinguished and quantitated by counting the
sum of 1-131 and 1-130 in the samples of aqueous
humor and plasma at the time of the anterior
chamber puncture and repeating the counting
in the same samples 3 to 5 days later. At this
latter time 1-130 (half-life 12.5 hours) no longer
contributed to the counts and the 1-131 (half-life
8.07 days) levels could be corrected back to the
time of the tap. 1-130 values were then obtained
by difference. The three-isotope method was used
in 10 rabbits given topical atropine to one eye, 10
rabbits treated with pilocarpine in one eye, and
5 rabbits subjected to unilateral carotid ligation.
In each of these 25 animals the opposite eyes
were measured as untreated controls.
Results
Normal. In the untreated rabbit the mean
value for the flow coefficient, kfn, was 0.015
minr 1 (a ± 0.0017). This value was essentially the same for the method applied
to 2 eyes of a single animal (Table I) and
for multiple isotopes to a single eye (Tables
IV, V, and VI). The diffusion coefficient,
k(lpa, in all series averaged 0.009.
Acetazolamide. As indicated in Table II,
a series of 20 animals subjected to repeated
injections of acetazolamide had a mean
flow coefficient of 0.008 minr 1 (a ± 0.0012).
This decrease from the normal value
was highly significant statistically, and
amounted to some 45 to 50 per cent reduction in rate of aqueous flow following
systemic carbonic anhydrase inhibition.
The diffusion coefficient for iodide was not
changed significantly after acetazolamide
administration.
Hypothermia. The 13 animals subjected
to immersion hypothermia to levels of 18
to 20° C. demonstrated markedly reduced
turnover rates for iodide. The calculated
flow coefficient averaged 0.0022 minr 1 or
some 15 per cent of normal values (Table
III). The diffusion coefficient was also
markedly decreased in the hypothermic
rabbit.
Table I. Iodide turnover in 15 untreated
rabbits*
Rabbit
no.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
(minr1)
k0
CaCO
Cp
(minr1)
kfa
(minr1)
0.024
0.024
0.023
0.025
0.023
0.027
0.025
0.022
0.023
0.025
0.024
0.026
0.024
0.021
0.024
0.50
0.52
0.45
0.40
0.40
0.37
0.35
0.40
0.34
0.35
0.46
0.39
0.32
0.35
0.38
0.011
0.012
0.010
0.010
0.009
0.010
0.008
0.008
0.007
0.008
0.011
0.010
0.007
0.007
0.009
0.013
0.012
0.013
0.015
0.014
0.017
0.017
0.014
0.016
0.017
0.013
0.016
0.017
0.014
0.015
kdpa
0.024
Mean
0.40
Standard deviation ie)
0.009
0.015
±0.0015 ±0.0017
"Using 1-131 and tapping one eye at approximately 20 to
40 minutes and the other at 3 to 5 hours. For definition
of symbols and method of calculation see text.
Table II. Iodide turnover of 20 rabbits
treated with acetazolamide0
k0
Rabbit
no.f
(minr1)
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
0.019
0.014
0.016
0.019
0.020
0.016
0.014
0.018
0.017
0.018
0.020
0.018
0.019
0.018
0.014
0.017
0.017
0.014
0.017
0.015
CaOO
cP
0.65
0.47
0.50
0.58
0.60
0.55
0.55
0.55
0.52
0.43
0.69
0.56
0.66
0.57
0.49
0.55
0.50
0.60
0.40
0.58
kdpa
(minr1) (minr1)
0.012
0.006
0.008
0.011
0.011
0.008
0.007
0.009
0.008
0.007
0.013
0.010
0.012
0.010
0.007
0.009
0.008
0.008
0.007
0.008
0.007
0.008
0.008
0.008
0.009
0.008
0.007
0.009
0.009
0.011
0.007
0.008
0.007
0.008
0.007
0.008
0.009
0.006
0.010
0.007
Mean
0.017
0.009
0.55
0.008
Standard deviation (*)
±0.0019 ±0.0012
°25 mg. per kilogram intravenously every 30 minutes.
fRabbits nos. 16 to 30 received 1-131 and one eye was
tapped at approximately 20 to 40 minutes, the second eye
at 4 to 5 hours. Rabbits nos. 31 to 35 received 1-127 4
hours before and 1-131 20 to 40 minutes before tapping
of only one eye.
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Volume 1
Number 1
Measurement of aqueous flow rate toith iodide 55
Table III. Iodide turnover in 13 hypothermic rabbits*
Rabbit
ko
no.f
(minr1)
0.0050
36
37
0.0059
0.0054
38
0.0056
39
0.0050
40
0.0054
41
0.0050
42
0.0054
43
0.0047
44
0.0044
45
46
0.0041
47
0.0050
48
0.0050
Mean
0.0051
Standard deviation
Co oo
k,a
cP
(minr1) (minr1)
0.65
0.65
0.65
0.60
0.50
0.65
0.50
0.45
0.70
0.65
0.60
0.60
0.52
0.59
0.0031 0.0019
0.0022
0.0037
0.0032
0.0022
0.0032
0.0024
0.0024
0.0026
0.0032
0.0022
0.0026
0.0024
0.0023 0.0031
0.0032
0.0015
0.0027
0.0017
0.0023 0.0018
0.0029
0.0021
0.0025 0.0025
0.0022
0.0029
±0.00044 ±0.00042
"18 to 20° C. rectal temperature.
tin all rabbits one eye was tapped at 2 to 3 hours after
1-131 injection; second eye tapped at 10 to 12 hours after
injection.
Unilateral carotid ligation. After unilateral ligation of the common carotid
artery the flow coefficients were compared
on the nonligated and ligated sides. The
eye on the nonligated side demonstrated
a mean value of 0.015 minr1, and did not
differ from the normal rabbit eye. The eye
on the ligated side averaged 0.013 min."1.
As demonstrated in Table IV, the ligated
and nonligated sides could be compared in
the same animal. The ratio for flow coefficients on the ligated side to that on the
nonligated averaged 0.83 ± 0.087 (a). The
average decrease of 17 per cent in apparent rate of flow proved highly significant statistically. The diffusion coefficient
for iodide was decreased by an average
of 10 per cent on the ligated side.
Pilocarpine. The topical administration
of pilocarpine 2 per cent eveiy 30 minutes
to one eye of 20 rabbits resulted in an
increase in the aqueous flow coefficient
from a mean value of 0.015 in the untreated
eye to an average of 0.017 in the pilocarpine-treated eye. As demonstrated in
Table V, a comparison of the flow coefficients in the same animal provided
estimates for the ratio of the pilocarpinetreated eye to that of the untreated eye.
The ratio averaged 1.16 ±0.095 (a). The
16 per cent increase in the apparent rate
of aqueous formation in the pilocarpinetreated eye proved to be statistically significant. The diffusion coefficient for iodide
was increased even more than the flow
coefficient, averaging 34 per cent. This in-
Table IV. Iodide turnover in 15 rabbits with unilateral carotid ligation
Nonligated side
Ligated side
Co oo
Rabbit
ko
no.9
(minr1)
cP
49
0.023
0.46
0.022
0.38
50
51
0.31
0.020
52
0.39
0.019
53
0.33
0.019
54
0.35
0.021
0.47
0.020
55
0.41
56
0.023
0.41
57
0.023
0.46
0.022
58
0.33
0.018
59
0.47
60
0.018
0.39
61
0.019
0.40
62
0.020
0.42
63
0.019
0.40
Mean
0.020
Standard deviation (*)
kdpa
k,a
ko
(minr1)
(minr1)
(minr1)
0.010
0.008
0.006
0.007
0.006
0.007
0.009
0.009
0.009
0.010
0.006
0.008
0.007
0.008
0.008
0.008
±0.0013
0.013
0.014
0.014
0.012
0.013
0.014
0.011
0.014
0.014
0.012
0.012
0.010
0.012
0.012
0.011
0.013
±0.0013
0.027
0.027
0.020
0.023
0.023
0.025
0.025
0.027
0.026
0.024
0.021
0.023
0.024
0.021
0.023
0.024
Cooo
cP
0.40
0.35
0.37
0.37
0.32
0.34
0.46
0.35
0.36
0.46
0.28
0.42
0.41
0.45
0.40
0.38
fcdpa
kra
(minr1)
(minr1)
0.010
0.009
0.007
0.008
0.007
0.008
0.011
0.009
0.010
0.010
0.006
0.009
0.009
0.009
0.009
0.009
±0.0013
0.017
0.018
0.013
0.015
0.016
0.017
0.014
0.018
0.016
0.014
0.015
0.014
0.015
0.012
0.014
0.015
±0.0017
Ligated/
nonligated
(k,a)
0.77
0.78
1.08
0.80
0.81
0.82
0.79
0.78
0.88
0.86
0.80
0.71
0.80
1.00
0.79
0.83
±0.087
"Rabbits nos. 49 to 58 received 1-127 16 hours before and 1-131 20 to 40 minutes before anterior chamber taps. Rabbits
nos. 59 to 63 received 1-127 16 hours before, 1-131 50 to 70 minutes before, and 1-130 20 to 40 minutes before anterior
chamber taps.
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In vestigative O ph thalmology
February 1962
56 Becker
Table V. Iodide turnover in 20 rabbits treated with topical pilocarpine in one eye*
Untreated eye
Pilocarpine-treated eye
Rabbit
no.f
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
ko
(minr1)
0.028
0.030
0.022
0.026
0.028
0.028
0.025
0.027
0.028
0.024
0.035
0.028
0.032
0.031
0.028
0.028
0.025
0.031
0.030
0.032
CnOO
Cv
0.41
0.42
0.38
0.36
0.38
0.38
0.38
0.39
0.38
0.35
0.50
0.37
0.44
0.40
0.50
0.45
0.46
0.45
0.40
0.46
(minr1)
k,a
(minr1)
k0
(minr1)
0.022
0.017
0.025
0.018
0.018
0.014
0.023
0.017
0.024
0.018
0.024
0.018
0.022
0.016
0.025
0.017
0.022
0.018
0.023
0.016
0.029
0.018
0.020
0.018
0.028
0.019
0.020
0.019
0.022
0.015
0.020
0.016
0.021
0.014
0.028
0.018
0.025
0.019
0.027
0.018
0.023
Mean
0.028
0.41 0.011
0.017
Standard deviation (<r)
±0.0021
±0.0015
0.011
0.012
0.008
0.009
0.010
0.010
0.009
0.010
0.010
0.008
0.017
0.010
0.013
0.012
0.013
0.012
0.011
0.013
0.011
0.014
Pilocarpine/
normal
(minr1)
k,a
(minr1)
0.43
0.42
0.41
0.41
0.35
0.39
0.38
0.38
0.33
0.27
0.50
0.31
0.43
0.32
0.44
0.31
0.35
0.41
0.35
0.40
0.009
0.010
0.007
0.009
0.008
0.009
0.008
0.009
0.007
0.006
0.014
0.006
0.011
0.006
0.009
0.006
0.008
0.011
0.008
0.010
0.013
0.015
0.011
0.014
0.016
0.015
0.014
0.016
0.015
0.017
0.015
0.014
0.017
0.014
0.013
0.014
0.013
0.017
0.017
0.017
1.31
1.20
1.27
1.21
1.12
1.20
1.14
1.06
1.20
0.94
1.20
1.29
1.12
1.36
1.15
1.14
1.08
1.06
1.12
1.06
0.38
0.009
±0.0020
0.015
±0.0017
1.16
±0.095
Co oo
cP
(kf.)
"l'ilocarpine
2 IJUI
per Icent
every uu
30 minutes.
J. iiuv;iti i-Miit; it
C U L cveiy
minutes.
tRabbits nos. 64 to 73 received 1-127 4 to 5 hours before and 1-131 20 to 40 minutes before anterior chamber taps. Rabbits nos. 74 to 83 received 1-127 4 to 5 hours before, 1-131 50 to 70 minutes before, and 1-130 20 to 40 minutes before
anterior chamber taps.
crease also proved statistically significant.
Atropine. In 20 rabbits the administration of topical atropine 2 per cent every
30 minutes to one eye of 20 rabbits provided a comparison of the coefficient of
rate of flow in the treated and untreated
eyes. The atropine-treated eyes had a mean
flow rate of 0.012 min.-1 as compared with
0.015 min."1 in the untreated eyes. By comparing the two eyes of the same animal,
the mean value for the ratio offlowcoefficients in the atropine-treated to that in
the normal eye was 0.79 ± 0.090 (a). This
apparent reduction in rate of flow by 21
per cent proved statistically significant
(Table VI). The diffusion coefficient for
iodide was not altered significantly in the
eves treated with topical atropine.
Discussion
It is apparent that the iodide method is
a useful and relatively simple one for the
estimation of the coefficient of aqueous
flow. It is based upon the transport of
significant amounts of iodide out of the
eye behind the iris so that the turnover
in the aqueous humor of the anterior
chamber is a single exponential. The
method using two eyes of a single animal
is analogous to that described by Barany
and Wirth5 who used an infusion of paraaminohippurate (this anion is also transported out of the vitreous of the rabbit
eye). The use of the individual animal for
its own steady-state value as well as estimating the turnover rate is much more accurate than the use of a steady-state concentration obtained from the average of
other similar animals.0 The disadvantage
of the method as applied to two eyes of
one animal is that it assumes both eyes are
identical. Furthermore, it does not permit
a study of unilateral alterations in the
single animal.
The single eye method utilizes the suggestion of Linner7 of administering isotopes
at different time intervals before the
anterior chamber is sampled. It determines
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Volume 1
Number 1
Measurement of aqueous flow rate with iodide 57
the steady-state concentration of the same
eye used for the turnover rate. In addition,
this method affords ideal opportunities and
controls for studying such unilateral
changes as the effects of topical medication,
surgery, etc. The use of the same samples
for the determination of the several
isotopes also avoids or tends to cancel out
weighing and pipetting errors. It must be
recalled, however, that the flow coefficient,
kf,,, is measured as a fraction of the anterior
chamber volume. Thus, changes in anterior
chamber volume alone will alter the values
of kfll (and kd|m) as measured. It must also
be emphasized that the iodide method depends upon an intact and functional iodide
transport system out of the eye behind the
iris. Procedures or drugs that alter this
iodide transport system may preclude the
use of a single exponential for the anterior
chamber. In this regard, it has been demonstrated that acetazolamide administration or carotid ligation, as well as topical
pilocarpine or atropine, does not alter the
rate of loss of trace doses of iodide from
the rabbit vitreous humor. Furthermore, the
concentration of iodide in the posterior
chamber remains less than 15 per cent of
the plasma value in eyes treated with pilocarpine or atropine or subjected to carotid
ligation, acetazolamide, or hypothermia.
The value of 1.5 per cent of the
anterior chamber obtained for flow in
normal rabbits by the iodide method
agrees well with that determined by other
turnover studies.2-3> s> ° The effects of carbonic anhydrase inhibitors and hypothermia
are in accord with previously reported
values. Thus, as measured by a variety of
methods, acetazolamide reduces the rate
of aqueous formation by approximately 45
to 50 per cent" and systemic hypothermia
decreases this process to 10 to 15 per cent
of normal values.10; X1
After carotid ligation, the apparent reduction in rate of aqueous flow in the
Table VI. Iodide turnover in 20 rabbits treated with topical atropine in one eye'
Untreated eye
Atropine-treated eye
Rabbit
no.f
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
h,
1
C«OO
1
kfa
k0 1
C,.oo
1
kfn1
Atropine
/normal
(minr )
cP
(minr )
(minr1)
(minr )
0.021
0.021
0.021
0.021
0.020
0.024
0.021
0.023
0.025
0.018
0.021
0.019
0.017
0.017
0.020
0.025
0.017
0.015
0.022
0.021
0.52
0.42
0.52
0.50
0.44
0.44
0.48
0.49
0.50
0.46
0.37
0.45
0.45
0.47
0.43
0.40
0.48
0.36
0.44
0.44
0.010
0.008
0.010
0.010
0.008
0.010
0.010
0.011
0.012
0.008
0.007
0.008
0.007
0.008
0.008
0.010
0.008
0.005
0.009
0.009
0.011
0.013
0.011
0.011
0.012
0.014
0.011
0.012
0.013
0.010
0.014
0.011
0.010
0.009
0.012
0.015
0.009
0.010
0.013
0.012
0.023
0.025
0.024
0.026
0.025
0.026
0.025
0.025
0.025
0.020
0.028
0.021
0.021
0.020
0.024
0.027
0.020
0.018
0.025
0.023
0.41
0.42
0.35
0.40
0.34
0.36
0.46
0.40
0.55
0.36
0.34
0.35
0.40
0.36
0.31
0.37
0.39
0.30
0.40
0.35
0.009
0.010
0.008
0.010
0.008
0.009
0.011
0.010
0.013
0.007
0.009
0.007
0.008
0.007
0.007
0.010
0.007
0.005
0.010
0.008
0.014
0.015
0.016
0.016
0.017
0.017
0.014
0.015
0.012
0.013
0.019
0.014
0.013
0.013
0.017
0.017
0.013
0.013
0.015
0.015
0.79
0.87
0.69
0.69
0.71
0.82
0.79
0.80
1.08
0.77
0.74
0.79
0.77
0.69
0.7.1
0.88
0.69
0.77
0.87
0.80
0.45
0.009
±0.0016
0.012
±0.0017
0.024
0.38
0.009
±0.0018
0.015
±0.0018
0.79
±0.090
Mean
0.020
Standard deviation
Cv
(minr )
(minr )
(kfn)
•Atropine 2 per cent every 30 minutes.
fRabbits nos. 84 to 93 received 1-127 4 to 5 hours before and 1-131 20 to 40 minutes before anterior chamber taps. Rabbits nos. 94 to 103 received 1-127 4 to 5 hours before, 1-131 50 to 70 minutes before, and 1-130 20 to 40 minutes before
anterior chamber taps.
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Inoestigativc Ophthalmology
February 1962
58 Becker
homolateral eye by some 17 per cent is in
reasonable agreement with recent tonographic estimates which suggest a decrease of approximately 20 to 25 per cent.12
Such a change in aqueous flow must be
taken into account in the estimation of
ciliary body blood flow as proposed by
Linner13 and Langham.1'1 A revised estimation of the effects of carotid ligation on the
rate of blood flow in the ciliary processes
of the rabbit eye would suggest a decrease
to some 70 per cent of the rate on the nonligated side.
The findings that pilocarpine appears to
increase and atropine to decrease the rate
of flow in the rabbit eye are most interesting and provocative. They raise speculations as to neurohumoral control of aqueous
humor formation. These findings need confirmation in other species as well as by
other methods of measurement. It is particularly important to evaluate and correct for possible alterations in anterior
chamber volume induced by these agents.15
6.
7.
8.
9.
10.
11.
12.
I gratefully acknowledge the technical assistance
of Mrs. Tommie Tracy and Miss Carol Fritz.
13.
REFERENCES
1. Becker, B.: Iodide transport by the rabbit
eye, Am. J. Physiol. 200: 804, 1961.
2. Becker, B.: The turnover of iodide in the
rabbit eye, A. M. A. Arch. Ophth. 65: 832,
1961.
3. Kinsey, V. E.: Ion movement in the eye,
Circulation 21: 968, 1960.
4. Sandell, E. B., and Kolthoff, I. M.: Microdetermination of iodine by a catalytic method,
Mikrochem. acta. 1: 9, 1937.
5. Barany, E., and Wirth, A.: An improved
method for estimating rate of flow of aque-
14.
15.
ous humor in individual animals, Acta ophth.
32: 95, 1954.
Barany, E., and Kinsey, V. E.: The rate of
flow of aqueous humor: I. The rate of disappearance of para-aminohippuric acid, radioactive Rayopake and radioactive Diodrast
from the aqueous humor of rabbits, Am. J.
Ophth. 32: (Pt. 2) 177, 1949.
Linner, E.: A method for determination of
time-concentration curves using one single
sample and several test substances, Acta Soc.
med. upsal. 59: 241, 1953.
Becker, B.: The turnover of bromide in the
rabbit eye, A. M. A. Arch. Ophth. 65: 837,
1961.
Becker, B.: Carbonic anhydrase and the formation of aqueous humor, Am. J. Ophth. 47:
(Pt. 2) 342, 1959.
Pollack, I. P., Becker, B., and Constant, M.
A.: The effect of hypothermia on aqueous
humor dynamics. I. Intraocular pressure and
outflow facility of the rabbit eye, Am. J.
Ophth. 49: 1126, 1960.
Becker, B.: The effect of hypothermia on
aqueous humor dynamics. III. Turnover of
ascorbate and sodium, Am. J. Ophth. 51: (Pt.
2) 1032, 1961.
Pollack, I. P., and Becker, B.: The effect of
hypothermia on aqueous humor dynamics. IV.
Carotid artery ligation and blood flow, Am.
J. Ophth. 51: (Pt. 2) 1039, 1961.
Linner, E.: Ascorbic acid as a test substance
for measuring relative changes in the rate of
plasma flow through the ciliary processes. I.
The effect of unilateral ligation of the common carotid artery in rabbits on the ascorbic
acid content of the aqueous humor at varying
plasma levels, Acta physiol. scandinav. 26:
57, 1952.
Langham, M. E.: The use of ascorbic acid to
measure the rate of flow of plasma through
the ciliary processes, J. Physiol. 130: 1, 1955.
Bleeker, G. M.: Evaluation of three methods
of recording the anterior chamber depth of
the eye, A. M. A. Arch. Ophth. 65: 369,
1961.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/932888/ on 06/18/2017