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Aqueous humor dynamics in the enucleated deer eye
Camp. Biochem. Physiol. Vol. 78A, No. 4, pp. 155-156, 1984
0300-9629/84 $3.00+ 0.00 0 1984Pergamon Press Ltd
Printed in GreatBritain
AQUEOUS HUMOR DYNAMICS IN THE ENUCLEATED DEER EYE Departments
BRENDA K. COLASANTI of Ophthalmology and Pharmacology & Toxicology, West Virginia University Medical Center, Morgantown, WV 26506, USA. Telephone: (304) 293-3371 (Received 21 November 1983)
Abstract-l. Facility of outflow of aqueous humor was determined in ten deer (Odocoileus virginianus) eyes enucleated within 1 hr post-mortem. 2. Although both outflow facility and anterior chamber volume were much greater than values reported in the literature for a variety of other species, calculated values for aqueous humor turnover were within the reported range for other animals as well as for man. 3. These results strengthen the hypothesis that the rate of turnover of aqueous humor is quite similar in eyes of vastly differing dimensions.
during deer season. All five deer had been killed with rifles. Eyes were placed in jars on saline-soaked cotton and refrigerated until perfusion. Determinations of aqueous outflow facility were made at intervals ranging from 7 to 20 hr after death of the animal. Facility was measured by the two-level constant pressure perfusion technique (BirBny, 1964) using mock aqueous humor. Eyes were mounted in a Styrofoam holder with a surrounding layer of saline-soaked gauze and maintained at 37°C by means of a hot plate. Two needles were placed mechanically in the anterior chamber of each eye, one for pressure recording and one for infusion. Immediately after anterior chamber cannulation, intraocular pressure was adjusted to 10mmHg by means of a reservoir. Successive perfusions were then begun at two pressure levels, one 24 and the second 9-12 mmHg above the initial pressure value. At the end of each experiment, anterior chamber volume was determined after aspiration of the chamber contents. The rate of aqueous humor turnover was calculated by dividing the aqueous flow rate (facility times resting intraocular pressure) by the anterior chamber volume, assuming that the episcleral venous pressure was zero (Macri and Cevario, 1974).
INTRODUCTION Studies conducted three decades ago (BArAny, 1951) initially suggested that the rate of turnover of aqueous humor in different species is quite similar even in eyes of widely differing dimensions. This work provided data from eyes as small as the hen’s to those as large as the cat%. Data on turnover rates obtained over the years from many of these same species by a variety of methods have corroborated this observation (Cole, 1974). In contrast with results for aqueous humor turnover, facility of aqueous outflow was found early to vary dramatically between species with different eye sizes (Becker and Constant, 1956). Moreover, outflow facility varied linearly with the volume of the anterior chamber; values for the small eye of the guinea pig were quite low, while those for the large cat eye were quite high. A more precise linear relationship between chamber volume and outflow facility was obtained for eyes of the same species (Becker and Constant, 1956). The present study was undertaken to determine outflow facility and aqueous humor turnover in an eye much larger than those previously studied, that of the deer. The results indicate that the relationships between inflow and outflow of aqueous humor and eye dimension are quite similar to those previously reported for eyes with smaller anterior chamber volumes.
RESULTS The data derived from these experiments in enucleated deer eyes are summarized in Table 1. While the calculated aqueous flow rate is reasonably similar to that of the cat eye, values for outflow facility are considerably higher than those reported for the cat (Macri et al., 1965). Average anterior chamber volume of the deer eye amounted to 1400 f 90~1 (N = 10 eyes). The rate of aqueous humor turnover, i.e 0.9% per min per volume of the anterior chamber,
METHODS Ten eyes from five deer (Odocoileus virginianus) were enucleated within 1 hr post-mortem at a check-in station Table 1. Aqueous humor Measured Outiow Resting Calculated Aqueous Aqueous
dynamics
of the enncleated
parameters facility intraocular pressure parameters humor flow rate humor turnover constant
Values for the measured
parameters
deer (Odocoileusvirginianus)eye 1.29 * 0.20 ~l/min/mmHg 9.8 k 0.48 mmHg
0.9% per minute represent
12.7 pl/min of anterior
the mean ? SEM for 10 eyes. 755
chamber
volume
756
BRENDA
Aqueoushumor turnover in eyes from several species
Table 2.
..~_
K. COLASANTI
Species
Turnover.__---_-constant(B)
.~.
1.4 1.1
Guinea pig
Albino rabbit (American)
0.9 1.7 1.4 1.0
Albino rabbit [Swedish)
White Leghorn hen Cat Human
REFERENCES
Turnover constants are expressed as % per min of volume of anterior
chamber. The data are those from the original work of BBr&ny (1951).
thus falls in the range observed for a variety of other species (Table 2). DISCUSSION The outflow
facility
determinations
deer eyes rendered values considerably
in enucleated
higher than
those reported for a variety of other species in studies on aqueous humor turnover (Cole, 1974). Outflow facility in the deer eye, on the other hand, is comparable to that reported for the large cattle eye, which has
been utilized pe~odically for studies on resistance to outflow anterior
(B&r&y, chamber
1954, Epstein et aZ., 1981). The volume of the deer eye is likewise
considerably larger than that reported for a variety of other species (Cole, 1974). These results support the existence aqueous
of a linear relationship outflow and anterior
(Becker and Constant, The aqueous
humor
between facility of chamber volume
1956). turnover
rate calculated
variety of species with smaller eyes (Table 2). This finding adds support to the original contention of BArAny (1951) that the rate of turnover of aqueous humor in different species is quite similar even in eyes of widely differing dimensions.
for
the large deer eye is similar to that reported for a
B&&y E. (1951) Rate of flow of aqueous humor in normal and scorbutic guinea pigs. Ar&s 0~~~~~~~0~. 46, 32&336. B&&y E. H. (1954) In vitro studies of the resistance to Row through the angle of the anterior chamber. Acta Sac. med. Ups&e&s 59, 2%276. BBriny E. H. (1964) Simultaneous measurement of changing intraocular pressure and outflow facility in the vervet monkey by constant pressure infusion. Invest. Ophthalmol. 3, 135-143. Becker B. and Constant M. A. (1956) Species variation in facility of aqueous outflow. Am. J. Ophthalmol. 42, 189-194. Cole D. F. (1974) Comparative aspects of the intraocular fluids. In The Eye, Vol. 5. Comparative PhysioZogy (Edited by Davson H. and Graham L. T.), pp. 71-161. Academic Press, New York. Epstein D. L., Hashimoto J. M., Anderson P. J. and Grant W. M. (1981) Effect of iodoacetamide perfusion on outflow facility and metabolism of the trabecular meshwork. Invest. Op~tth~imoi. 20, 625-63 1.
Macri F. .I. and Cevario S. J. (1974) A pharmacodynamic study of the inhibitory effects of I-norepinephrine, Iepinephrine, and d,l-isoproterenol on aqueous humor formation in the enucleated, arterially perfused cat eye. Invest. Ophthalmol. 13, 392-395. Macri F. J., Dixon R. L. and Rall D. P. (1965) Aqueous humor turnover rates in the cat. I. Effect of acetazolamide. Invest. Ophthalmol. 4, 927-934.
0300-9629/84 $3.00+ 0.00 0 1984Pergamon Press Ltd
Printed in GreatBritain
AQUEOUS HUMOR DYNAMICS IN THE ENUCLEATED DEER EYE Departments
BRENDA K. COLASANTI of Ophthalmology and Pharmacology & Toxicology, West Virginia University Medical Center, Morgantown, WV 26506, USA. Telephone: (304) 293-3371 (Received 21 November 1983)
Abstract-l. Facility of outflow of aqueous humor was determined in ten deer (Odocoileus virginianus) eyes enucleated within 1 hr post-mortem. 2. Although both outflow facility and anterior chamber volume were much greater than values reported in the literature for a variety of other species, calculated values for aqueous humor turnover were within the reported range for other animals as well as for man. 3. These results strengthen the hypothesis that the rate of turnover of aqueous humor is quite similar in eyes of vastly differing dimensions.
during deer season. All five deer had been killed with rifles. Eyes were placed in jars on saline-soaked cotton and refrigerated until perfusion. Determinations of aqueous outflow facility were made at intervals ranging from 7 to 20 hr after death of the animal. Facility was measured by the two-level constant pressure perfusion technique (BirBny, 1964) using mock aqueous humor. Eyes were mounted in a Styrofoam holder with a surrounding layer of saline-soaked gauze and maintained at 37°C by means of a hot plate. Two needles were placed mechanically in the anterior chamber of each eye, one for pressure recording and one for infusion. Immediately after anterior chamber cannulation, intraocular pressure was adjusted to 10mmHg by means of a reservoir. Successive perfusions were then begun at two pressure levels, one 24 and the second 9-12 mmHg above the initial pressure value. At the end of each experiment, anterior chamber volume was determined after aspiration of the chamber contents. The rate of aqueous humor turnover was calculated by dividing the aqueous flow rate (facility times resting intraocular pressure) by the anterior chamber volume, assuming that the episcleral venous pressure was zero (Macri and Cevario, 1974).
INTRODUCTION Studies conducted three decades ago (BArAny, 1951) initially suggested that the rate of turnover of aqueous humor in different species is quite similar even in eyes of widely differing dimensions. This work provided data from eyes as small as the hen’s to those as large as the cat%. Data on turnover rates obtained over the years from many of these same species by a variety of methods have corroborated this observation (Cole, 1974). In contrast with results for aqueous humor turnover, facility of aqueous outflow was found early to vary dramatically between species with different eye sizes (Becker and Constant, 1956). Moreover, outflow facility varied linearly with the volume of the anterior chamber; values for the small eye of the guinea pig were quite low, while those for the large cat eye were quite high. A more precise linear relationship between chamber volume and outflow facility was obtained for eyes of the same species (Becker and Constant, 1956). The present study was undertaken to determine outflow facility and aqueous humor turnover in an eye much larger than those previously studied, that of the deer. The results indicate that the relationships between inflow and outflow of aqueous humor and eye dimension are quite similar to those previously reported for eyes with smaller anterior chamber volumes.
RESULTS The data derived from these experiments in enucleated deer eyes are summarized in Table 1. While the calculated aqueous flow rate is reasonably similar to that of the cat eye, values for outflow facility are considerably higher than those reported for the cat (Macri et al., 1965). Average anterior chamber volume of the deer eye amounted to 1400 f 90~1 (N = 10 eyes). The rate of aqueous humor turnover, i.e 0.9% per min per volume of the anterior chamber,
METHODS Ten eyes from five deer (Odocoileus virginianus) were enucleated within 1 hr post-mortem at a check-in station Table 1. Aqueous humor Measured Outiow Resting Calculated Aqueous Aqueous
dynamics
of the enncleated
parameters facility intraocular pressure parameters humor flow rate humor turnover constant
Values for the measured
parameters
deer (Odocoileusvirginianus)eye 1.29 * 0.20 ~l/min/mmHg 9.8 k 0.48 mmHg
0.9% per minute represent
12.7 pl/min of anterior
the mean ? SEM for 10 eyes. 755
chamber
volume
756
BRENDA
Aqueoushumor turnover in eyes from several species
Table 2.
..~_
K. COLASANTI
Species
Turnover.__---_-constant(B)
.~.
1.4 1.1
Guinea pig
Albino rabbit (American)
0.9 1.7 1.4 1.0
Albino rabbit [Swedish)
White Leghorn hen Cat Human
REFERENCES
Turnover constants are expressed as % per min of volume of anterior
chamber. The data are those from the original work of BBr&ny (1951).
thus falls in the range observed for a variety of other species (Table 2). DISCUSSION The outflow
facility
determinations
deer eyes rendered values considerably
in enucleated
higher than
those reported for a variety of other species in studies on aqueous humor turnover (Cole, 1974). Outflow facility in the deer eye, on the other hand, is comparable to that reported for the large cattle eye, which has
been utilized pe~odically for studies on resistance to outflow anterior
(B&r&y, chamber
1954, Epstein et aZ., 1981). The volume of the deer eye is likewise
considerably larger than that reported for a variety of other species (Cole, 1974). These results support the existence aqueous
of a linear relationship outflow and anterior
(Becker and Constant, The aqueous
humor
between facility of chamber volume
1956). turnover
rate calculated
variety of species with smaller eyes (Table 2). This finding adds support to the original contention of BArAny (1951) that the rate of turnover of aqueous humor in different species is quite similar even in eyes of widely differing dimensions.
for
the large deer eye is similar to that reported for a
B&&y E. (1951) Rate of flow of aqueous humor in normal and scorbutic guinea pigs. Ar&s 0~~~~~~~0~. 46, 32&336. B&&y E. H. (1954) In vitro studies of the resistance to Row through the angle of the anterior chamber. Acta Sac. med. Ups&e&s 59, 2%276. BBriny E. H. (1964) Simultaneous measurement of changing intraocular pressure and outflow facility in the vervet monkey by constant pressure infusion. Invest. Ophthalmol. 3, 135-143. Becker B. and Constant M. A. (1956) Species variation in facility of aqueous outflow. Am. J. Ophthalmol. 42, 189-194. Cole D. F. (1974) Comparative aspects of the intraocular fluids. In The Eye, Vol. 5. Comparative PhysioZogy (Edited by Davson H. and Graham L. T.), pp. 71-161. Academic Press, New York. Epstein D. L., Hashimoto J. M., Anderson P. J. and Grant W. M. (1981) Effect of iodoacetamide perfusion on outflow facility and metabolism of the trabecular meshwork. Invest. Op~tth~imoi. 20, 625-63 1.
Macri F. .I. and Cevario S. J. (1974) A pharmacodynamic study of the inhibitory effects of I-norepinephrine, Iepinephrine, and d,l-isoproterenol on aqueous humor formation in the enucleated, arterially perfused cat eye. Invest. Ophthalmol. 13, 392-395. Macri F. J., Dixon R. L. and Rall D. P. (1965) Aqueous humor turnover rates in the cat. I. Effect of acetazolamide. Invest. Ophthalmol. 4, 927-934.