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Carol B Toris - One of the best experts on this subject based on the ideXlab platform.
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Chapter 7 Aqueous Humor Dynamics I. Measurement Methods and Animal Studies
Current Topics in Membranes, 2020Co-Authors: Carol B TorisAbstract:Publisher Summary Intraocular pressure (IOP) is maintained by the Dynamics of ocular Aqueous Humor that involves its secretion, circulation throughout the anterior chamber, and drainage into the iridocorneal angle. The measurable components of Aqueous Humor Dynamics include Aqueous flow, outflow facility, uveoscleral outflow, and episcleral venous pressure. Multiple methods are available to assess these components. Interpretation of data collected by these methods requires an understanding of the inherent assumptions and limitations of each method applicable to the species of animal under investigation. Despite the inevitable problems associated with each method, invaluable information has been collected regarding normal circadian rhythms and interspecies differences in Aqueous Humor Dynamics. Additionally, studies of animal models of spontaneous and induced glaucoma have enhanced the understanding of human glaucoma and facilitated the design of improved pharmacological treatments and surgical procedures. This chapter describes various methods to assess Aqueous Humor Dynamics and summarizes findings from the animal species that have contributed the most to the understanding of Aqueous Humor Dynamics.
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Chapter 8 Aqueous Humor Dynamics II: Clinical Studies
Current Topics in Membranes, 2020Co-Authors: Carol B Toris, Carl B. CamrasAbstract:Publisher Summary A stable rate of production and drainage of Aqueous Humor is essential for the health of the eye and maintenance of normal visual function. This chapter reviews the contributions of Aqueous Humor Dynamics in normal and pathological conditions affecting intraocular pressure (IOP). IOP remains relatively stable throughout one's lifetime but subtle changes do occur in the outflow pathways that could increase IOP and the risk for glaucoma. Abnormalities in Aqueous Humor Dynamics have been found in various clinical syndromes that affect IOP. Most of the abnormalities have been localized to the Aqueous Humor outflow pathways. Surprisingly, Aqueous Humor production remains relatively stable in all of these conditions and ranges of IOPs. Some older drugs to treat elevated IOP work by reducing Aqueous Humor production, theoretically, placing the avascular lens and cornea at risk for damage from limited nutrients and accumulation of toxic metabolites. The recently approved drugs and the ones currently under development for future glaucoma therapy are those that target the outflow pathways. From a physiological perspective, this is a logical approach because this is the location of the pathology in glaucoma and the region in need of repair. These drugs and their effects on Aqueous Humor Dynamics also are discussed in this chapter.
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Time dependent effects of sympathetic denervation on Aqueous Humor Dynamics and choroidal blood flow in rabbits
Current Eye Research, 2020Co-Authors: Guilin Zhan, Carl B. Camras, David C. Ball, Corey J. Mayberger, Mark E. Tafoya, Carol B TorisAbstract:Purpose. This study investigates the time-dependent effects of superior cervical ganglionectomy (SCGx) on Aqueous Humor Dynamics and ocular blood flow in rabbits. Methods. Measurements were made at various times between 24 hours and 12 months after SCGx. Intraocular pressure (IOP) was measured by pneumatonometry, Aqueous flow by fluorophotometry and outflow facility by tonography. Uveoscleral outflow was determined by an intracameral tracer infusion technique and blood flow to the choroid was evaluated with fluorescent microspheres. Values in denervated eyes were compared with the contralateral, normallyinnervated eyes using a paired Student's two-tailed t-test. Results. At 24 hours after SCGx, IOP in denervated eyes was less than in normally-innervated eyes (14.6 ± 0.8 vs 20.1 ± 1.5mmHg, 27%, p < 0.002). At one month, IOPs were not different between eyes. Compared with normally-innervated eyes at 10-12 months, IOP in denervated eyes was greater (20.4 ± 0.7 vs 17.2 ± 0.9mmHg, 19%, p < 0.001), outflo...
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Daytime and nighttime effects of brimonidine on IOP and Aqueous Humor Dynamics in participants with ocular hypertension.
Journal of Glaucoma, 2020Co-Authors: Ankit Agrawal, Vikas Gulati, Donna G. Neely, Carol B TorisAbstract:The effects of brimonidine on daytime and nighttime intraocular pressure (IOP) and Aqueous Humor Dynamics were evaluated in volunteers with ocular hypertension (OHT).Thirty participants with OHT (58.6±1.7 years old, mean±SEM) were enrolled into this randomized, double-masked, cross-over study. For 6 weeks, participants self-administered 0.2% brimonidine or placebo 3 times daily. During daytime and nighttime visits, measurements included Aqueous flow (Fa) by fluorophotometry, outflow facility (C) by tonography, episcleral venous pressure (Pev) by venomanometry, and seated and supine IOP by pneumatonometry. Uveoscleral outflow (U) was calculated mathematically.When treated with placebo, nighttime supine Pev (11.2±0.25 mm Hg) was higher (P
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changes in parameters of Aqueous Humor Dynamics throughout life
2019Co-Authors: Carol B Toris, Padmanabhan PattabiramanAbstract:Steady-state intraocular pressure (IOP) results from the interplay of the inflow, outflow, facility, and pressure of Aqueous Humor Dynamics. A change in any one of these parameters may greatly affect IOP, while a simultaneous change in a second parameter might negate the effect of the first leaving IOP undisturbed. Some IOP changes could be rapid as when moving from a seated to a supine position. Other IOP changes are gradual such as seen seasonally. There is general agreement on the nighttime reduction in Aqueous Humor production but not on changes that occur during aging. Aging is confounded by many factors affecting IOP including systemic and ocular health, ethnic background, and recreational activities. Evidence suggests that Aqueous Humor Dynamics in children may change rapidly until sexual maturity is reached, but the scarcity of research on children has left a void in our understanding of the developing eye. Efficacy of IOP-lowering treatments can be altered by fluctuations in Aqueous Humor Dynamics, especially at night. The molecular and cellular aspects underlying the changes in Aqueous Humor Dynamics is a rapidly growing field. Effective mathematical modeling of ocular fluid Dynamics will benefit from a clearer understanding of the changes in Aqueous Humor Dynamics throughout life.
Paul L Kaufman - One of the best experts on this subject based on the ideXlab platform.
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effects of vitrectomy and lensectomy on older rhesus macaques oxygen distribution antioxidant status and Aqueous Humor Dynamics
Investigative Ophthalmology & Visual Science, 2017Co-Authors: Carla J Siegfried, Yingbo Shui, Baohe Tian, Michael T Nork, Gregg A Heatley, Paul L KaufmanAbstract:Purpose: The purpose of this study is to evaluate effects of vitrectomy (PPV) and lens extraction with intraocular lens implantation (PE/IOL) on molecular oxygen (pO2) distribution, Aqueous Humor antioxidant-oxidant balance, Aqueous Humor Dynamics, and histopathologic changes in the trabecular meshwork (TM) in the older macaque monkey. Methods: Six rhesus monkeys underwent PPV followed by PE/IOL. pO2, outflow facility, and intraocular pressure (IOP) were measured. Aqueous and vitreous Humor specimens were analyzed for antioxidant status and 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative damage. TM specimens were obtained for immunohistochemical and quantitative PCR analysis. Results: pO2 at baseline revealed steep gradients in the anterior chamber and low levels in the posterior chamber (PC) and around the lens. Following PPV and PE/IOL, pO2 significantly increased in the PC, around the IOL, and angle. IOP increased following both surgical interventions, with no change in outflow facility. Histopathologic analysis did not show changes in TM cell quantification, but there was an increase in 8-OHdG. Quantitative PCR did not reveal significant differences in glaucoma-related gene expression. Aqueous and vitreous Humor analysis revealed decreased ascorbate and total reactive antioxidant potential and increased 8-OHdG in the Aqueous Humor only in the surgical eyes. Conclusions: Oxygen distribution in the older rhesus monkey is similar to humans at baseline and following surgical interventions. Our findings of histopathologic changes of TM oxidative damage and alterations in the oxidant-antioxidant balance suggest a potential correlation of increased oxygen exposure with oxidative stress/damage and the development of open angle glaucoma.
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Effects of Vitrectomy and Lensectomy on Older Rhesus Macaques: Oxygen Distribution, Antioxidant Status, and Aqueous Humor Dynamics
Investigative Ophthalmology & Visual Science, 2017Co-Authors: Carla J Siegfried, Yingbo Shui, Baohe Tian, Gregg A Heatley, T. Michael Nork, Paul L KaufmanAbstract:The purpose of this study is to evaluate effects of vitrectomy (PPV) and lens extraction with intraocular lens implantation (PE/IOL) on molecular oxygen (pO2) distribution, Aqueous Humor antioxidant-oxidant balance, Aqueous Humor Dynamics, and histopathologic changes in the trabecular meshwork (TM) in the older macaque monkey. Six rhesus monkeys underwent PPV followed by PE/IOL. pO2, outflow facility, and intraocular pressure (IOP) were measured. Aqueous and vitreous Humor specimens were analyzed for antioxidant status and 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative damage. TM specimens were obtained for immunohistochemical and quantitative PCR analysis. pO2 at baseline revealed steep gradients in the anterior chamber and low levels in the posterior chamber (PC) and around the lens. Following PPV and PE/IOL, pO2 significantly increased in the PC, around the IOL, and angle. IOP increased following both surgical interventions, with no change in outflow facility. Histopathologic analysis did not show changes in TM cell quantification, but there was an increase in 8-OHdG. Quantitative PCR did not reveal significant differences in glaucoma-related gene expression. Aqueous and vitreous Humor analysis revealed decreased ascorbate and total reactive antioxidant potential and increased 8-OHdG in the Aqueous Humor only in the surgical eyes. Oxygen distribution in the older rhesus monkey is similar to humans at baseline and following surgical interventions. Our findings of histopathologic changes of TM oxidative damage and alterations in the oxidant-antioxidant balance suggest a potential correlation of increased oxygen exposure with oxidative stress/damage and the development of open angle glaucoma.
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Aqueous Humor Dynamics in monkeys in response to the kappa opioid agonist bremazocine
Transactions of the American Ophthalmological Society, 2007Co-Authors: Carol A Rasmussen, Bann T Gabelt, Paul L KaufmanAbstract:Purpose: To determine the effects of the kappa opioid agonist, bremazocine (BRE), on intraocular pressure (IOP) and Aqueous Humor Dynamics in normotensive cynomolgus monkeys. Methods: IOP, pupil diameter, refraction, Aqueous Humor flow, and mean arterial pressure (MAP) were measured following unilateral topical application of 1 to 100 µg BRE. IOP and MAP responses to 100 µg BRE were repeated during intravenous infusion of angiotensin II (ATII). IOP and MAP responses to BRE were also measured following pretreatment with the opioid receptor antagonists norbinaltorphimine (nor-BNI) or naloxone. Outflow facility was measured following unilateral intracameral exchange with 0.01 to 100 µg/mL BRE. IOP, Aqueous Humor flow, pupil, and MAP were measured after unilateral intracameral bolus injection of 1 µg of BRE. Results: Unilateral topical BRE caused a dose-related reduction in IOP and Aqueous Humor flow in both eyes and in MAP. Pupil miosis occurred at the 100-µg dose. There was no effect on refraction. IOP and MAP decreases after 100 µg of BRE were eliminated by ATII infusion. Differential IOP effects after 10-µg topical BRE doses were not eliminated by nor-BNI or naloxone. Unilateral intracameral bolus injection of BRE decreased IOP in both eyes but had no effect on MAP or Aqueous Humor flow. Outflow facility was unchanged after intracameral exchange with BRE. Conclusions: The IOP response to high doses of BRE in monkeys can be attributed to peripheral or central effects on MAP. The IOPlowering response to topical BRE is due to Aqueous Humor flow suppression via non-opioid receptor stimulation. Some components of the IOP response are mediated by unknown mechanisms.
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Aqueous Humor Dynamics in monkeys after topical r doi
Investigative Ophthalmology & Visual Science, 2005Co-Authors: Bann T Gabelt, Mehmet Okka, Tom R Dean, Paul L KaufmanAbstract:PURPOSE. To determine the effects of R-DOI, a selective 5-HT 2 agonist, on intraocular pressure (TOP) and Aqueous Humor Dynamics in monkeys. METHODS. Normotensive cynomolgus monkeys (n = 8) were treated topically once daily with four 5-μL drops of 0.5% R-DOI in one eye, vehicle in the opposite eye. The 6-hour IOP response (Goldmann applanation tonometry) was determined before the drug application and on the third day of treatment. Aqueous Humor formation, or flow (AHF, measured by fluorophotometry), was measured from hours 3 to 8 after the third dose. Beginning 3.5 hours after the fourth or fifth dose, AHF was measured by dilution of radio-iodinated monkey albumin perfused through the anterior chamber and flow to blood by accumulation of albumin in the general circulation. Uveoscleral outflow (Fu) was calculated. Flow to blood was determined at spontaneous and elevated pressures, allowing calculation of trabecular outflow facility. Total outflow facility was determined by two-level constant pressure perfusion from 3.5 to 5 hours and from 5.5 to 6.25 hours after R-DOI treatment. RESULTS. Reduction of IOP in treated eyes was compared to the opposite control eyes corrected for the 6-hour IOP baseline before the first dose. After the third dose of R-DOI, IOP was significantly (P < 0.01, n = 7) decreased by 1.4 to 4.7 mm Hg over the 6 hours. AHF (by fluorophotometry) increased by 13% (P < 0.05, n = 8) in treated compared with control eyes corrected for baseline. AHF (isotope dilution) increased by 30% (P < 0.01, n = 8), flow to blood decreased by 28% (n = 5), and Fu increased by 241% (P < 0.05, n = 5). Total and trabecular outflow facility were unchanged. CONCLUSIONS. R-DOI caused a small but significant increase in AHF and lowered IOP in normotensive monkeys primarily by increasing Fu.
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Aqueous Humor Dynamics in Monkeys After Topical R(+)–DOI
Investigative Ophthalmology & Visual Science, 2005Co-Authors: Bann T Gabelt, Mehmet Okka, Tom R Dean, Paul L KaufmanAbstract:PURPOSE. To determine the effects of R-DOI, a selective 5-HT 2 agonist, on intraocular pressure (TOP) and Aqueous Humor Dynamics in monkeys. METHODS. Normotensive cynomolgus monkeys (n = 8) were treated topically once daily with four 5-μL drops of 0.5% R-DOI in one eye, vehicle in the opposite eye. The 6-hour IOP response (Goldmann applanation tonometry) was determined before the drug application and on the third day of treatment. Aqueous Humor formation, or flow (AHF, measured by fluorophotometry), was measured from hours 3 to 8 after the third dose. Beginning 3.5 hours after the fourth or fifth dose, AHF was measured by dilution of radio-iodinated monkey albumin perfused through the anterior chamber and flow to blood by accumulation of albumin in the general circulation. Uveoscleral outflow (Fu) was calculated. Flow to blood was determined at spontaneous and elevated pressures, allowing calculation of trabecular outflow facility. Total outflow facility was determined by two-level constant pressure perfusion from 3.5 to 5 hours and from 5.5 to 6.25 hours after R-DOI treatment. RESULTS. Reduction of IOP in treated eyes was compared to the opposite control eyes corrected for the 6-hour IOP baseline before the first dose. After the third dose of R-DOI, IOP was significantly (P < 0.01, n = 7) decreased by 1.4 to 4.7 mm Hg over the 6 hours. AHF (by fluorophotometry) increased by 13% (P < 0.05, n = 8) in treated compared with control eyes corrected for baseline. AHF (isotope dilution) increased by 30% (P < 0.01, n = 8), flow to blood decreased by 28% (n = 5), and Fu increased by 241% (P < 0.05, n = 5). Total and trabecular outflow facility were unchanged. CONCLUSIONS. R-DOI caused a small but significant increase in AHF and lowered IOP in normotensive monkeys primarily by increasing Fu.
José Melena - One of the best experts on this subject based on the ideXlab platform.
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A comparative study of topical natural ergot alkaloids on the intraocular pressure and Aqueous Humor Dynamics in oclular normotensive and α-chymotrypsin-induced ocular hypertensive rabbits
Graefe's Archive for Clinical and Experimental Ophthalmology, 2007Co-Authors: Gustavo Puras, Juan Santafé, Manuel Garrido, José Segarra, José MelenaAbstract:Background Although it has been suggested that ergot derivatives may play a role in antiglaucoma therapy, little attention has been paid to the ocular hypotensive action of these drugs. Having previously reported that topical natural ergot alkaloids ergocristine α-ergocryptine and ergocornine dose-dependently reduce intraocular pressure in ocular normotensive and α-chymotrypsin-induced ocular hypertensive rabbits, the aim of the present work was to compare the effect of ergocristine, α-ergocryptine and ergocornine on the intraocular pressure and Aqueous Humor Dynamics in ocular normotensive and α-chymotrypsin-induced ocular hypertensive rabbits, in order to further explore the ocular actions of these compounds. Methods Experiments were conducted in albino ocular normotensive and hypertensive rabbits by intracameral injection of α-chymotrypsin. Intraocular pressure responses to drug vehicle and seven different doses of topical natural ergot alkaloids were examined, in order to obtain dose–response relationships for comparing the intraocular pressure-lowering effect and potency of these drugs. Tonographies were also performed to ascertain the actions of natural ergot alkaloids on Aqueous Humor Dynamics. Results All natural ergot alkaloids tested reduced intraocular pressure in a dose-related fashion. The ocular hypotensive effect was greater in α-chymotrypsin-induced ocular hypertensive rabbits for the three compounds tested. All natural ergot alkaloids tested decreased both tonographic outflow facility and, to a greater extent, Aqueous Humor inflow in ocular normotensive and in α-chymotrypsin-induced ocular hypertensive rabbits. Conclusion Taken together, our data suggest that these compounds decrease both tonographic outflow facility and, to a greater extent, Aqueous Humor inflow, which explains their final effect in ocular normotensive and in α-chymotrypsin-induced ocular hypertensive rabbits. Reductions in Aqueous Humor inflow observed after topical application of natural ergot alkaloids in α-chymotrypsin-induced ocular hypertensive rabbits can only be explained by a marked inhibition of active secretion of Aqueous Humor, since processes involved in Aqueous Humor formation may probably be altered after α-chymotrypsin injection.
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A comparative study of topical natural ergot alkaloids on the intraocular pressure and Aqueous Humor Dynamics in oclular normotensive and α-chymotrypsin-induced ocular hypertensive rabbits
Graefes Archive for Clinical and Experimental Ophthalmology, 2007Co-Authors: Gustavo Puras, Juan Santafé, Manuel Garrido, José Segarra, José MelenaAbstract:Background Although it has been suggested that ergot derivatives may play a role in antiglaucoma therapy, little attention has been paid to the ocular hypotensive action of these drugs. Having previously reported that topical natural ergot alkaloids ergocristine α-ergocryptine and ergocornine dose-dependently reduce intraocular pressure in ocular normotensive and α-chymotrypsin-induced ocular hypertensive rabbits, the aim of the present work was to compare the effect of ergocristine, α-ergocryptine and ergocornine on the intraocular pressure and Aqueous Humor Dynamics in ocular normotensive and α-chymotrypsin-induced ocular hypertensive rabbits, in order to further explore the ocular actions of these compounds.
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The effect of topical natural ergot alkaloids on the intraocular pressure and Aqueous Humor Dynamics in rabbits with α-chymotrypsin-induced ocular hypertension
Graefe's Archive for Clinical and Experimental Ophthalmology, 2002Co-Authors: Gustavo Puras, Juan Santafé, Manuel Garrido, José Segarra, José MelenaAbstract:Background: We previously reported that topical natural ergot alkaloids ergocristine, α-ergocryptine and ergocornine dose-dependently reduce intraocular pressure in ocular normotensive rabbits, most likely by decreasing Aqueous Humor inflow. In the present study, the effects of these compounds on intraocular pressure and Aqueous Humor Dynamics in a rabbit model for ocular hypertension were assessed. Methods: Experiments were conducted in albino rabbits made ocular hypertensive by intracameral injection of α-chymotrypsin. Intraocular pressure responses to drug vehicle and seven different doses of topical natural ergot alkaloids were examined in order to obtain dose–response relationships for comparing the intraocular pressure-lowering effect and potency of these drugs. Tonographies were also performed to ascertain the actions of natural ergot alkaloids on Aqueous Humor Dynamics in α-chymotrypsin-induced ocular hypertensive rabbits. Results: Topical application of the natural ergot alkaloids ergocristine, α-ergocryptine and ergocornine lowered intraocular pressure in α-chymotrypsin-induced ocular hypertensive rabbits in a dose-related fashion, with ergocristine displaying the greatest intraocular pressure-lowering effect. Tonographic studies revealed a decrease in the tonographic outflow facility following topical application of natural ergot alkaloids, although only the effects of both ergocristine and α-ergocryptine reached statistical significance. All natural ergot alkaloids tested significantly reduced the calculated Aqueous Humor inflow. Conclusion: This study suggests that the natural ergot alkaloids ergocristine, α-ergocryptine and ergocornine effectively decrease intraocular pressure in the α-chymotrypsin-induced model of ocular hypertension. Since these compounds reduce the tonographic Aqueous Humor outflow facility, their final ocular antihypertensive effect appears to result from a remarkable reduction of the Aqueous Humor inflow.
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Effects of Topical Natural Ergot Alkaloids on Intraocular Pressure and Aqueous Humor Dynamics in Ocular Normotensive Rabbits
Journal of Ocular Pharmacology and Therapeutics, 2002Co-Authors: Gustavo Puras, Juan Santafé, Manuel Garrido, José Segarra, José MelenaAbstract:Although it has been suggested that ergot derivatives may play a role in antiglaucoma therapy, little attention has been paid to the ocular hypotensive action of these drugs. Having previously reported in our laboratory that topical dihydroergocristine decreases intraocular pressure both in ocular normotensive and α-chymotrypsin-induced ocular hypertensive rabbits, the aim of the present work was to assess the effect of natural ergot alkaloids, ergocristine, α-ergocryptine and ergocornine, on the intraocular pressure and Aqueous Humor Dynamics in ocular normotensive rabbits in order to further explore the ocular actions of these compounds. Intraocular pressure was measured with a pneumatonometer manometrically calibrated for the rabbit eye. Changes in tonographic facility of Aqueous Humor outflow and rate of Aqueous Humor inflow were evaluated in anesthetized rabbits. Natural ergot alkaloids were found to reduce intraocular pressure in ocular normotensive eyes in a dose-related fashion. These compounds de...
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Aqueous Humor Dynamics in α chymotrypsin induced ocular hypertensive rabbits
Journal of Ocular Pharmacology and Therapeutics, 1999Co-Authors: José Melena, Juan Santafé, Jose Segarradomenech, Gustavo PurasAbstract:ABSTRACT Aqueous Humor Dynamics were studied in α-chymotrypsin-induced ocular hypertensive rabbits either by tonographic or two-level constant pressure perfusion techniques. A significant correlation was obtained between the values of outflow facility in α-chymotrypsin-induced ocular hypertensive rabbits as determined by tonography and constant pressure perfusion. The mean value of tonographic outflow facility in ocular hypertensive rabbits was not statistically different from that found in ocular normotensive rabbits. On the contrary, the estimated rate of Aqueous inflow in ocular hypertensive rabbits was about 1.5-fold higher than that of ocular normotensive ones. While topical timolol lowered intraocular pressure and Aqueous Humor inflow in ocular hypertensive rabbits, pilocarpine did not produce any significant effect. Aqueous Humor protein was significantly increased in ocular hypertensive eyes. The results of this study show that accurate measurements of outflow facility can be obtained in α-chymotr...
Carl B. Camras - One of the best experts on this subject based on the ideXlab platform.
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Chapter 8 Aqueous Humor Dynamics II: Clinical Studies
Current Topics in Membranes, 2020Co-Authors: Carol B Toris, Carl B. CamrasAbstract:Publisher Summary A stable rate of production and drainage of Aqueous Humor is essential for the health of the eye and maintenance of normal visual function. This chapter reviews the contributions of Aqueous Humor Dynamics in normal and pathological conditions affecting intraocular pressure (IOP). IOP remains relatively stable throughout one's lifetime but subtle changes do occur in the outflow pathways that could increase IOP and the risk for glaucoma. Abnormalities in Aqueous Humor Dynamics have been found in various clinical syndromes that affect IOP. Most of the abnormalities have been localized to the Aqueous Humor outflow pathways. Surprisingly, Aqueous Humor production remains relatively stable in all of these conditions and ranges of IOPs. Some older drugs to treat elevated IOP work by reducing Aqueous Humor production, theoretically, placing the avascular lens and cornea at risk for damage from limited nutrients and accumulation of toxic metabolites. The recently approved drugs and the ones currently under development for future glaucoma therapy are those that target the outflow pathways. From a physiological perspective, this is a logical approach because this is the location of the pathology in glaucoma and the region in need of repair. These drugs and their effects on Aqueous Humor Dynamics also are discussed in this chapter.
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Time dependent effects of sympathetic denervation on Aqueous Humor Dynamics and choroidal blood flow in rabbits
Current Eye Research, 2020Co-Authors: Guilin Zhan, Carl B. Camras, David C. Ball, Corey J. Mayberger, Mark E. Tafoya, Carol B TorisAbstract:Purpose. This study investigates the time-dependent effects of superior cervical ganglionectomy (SCGx) on Aqueous Humor Dynamics and ocular blood flow in rabbits. Methods. Measurements were made at various times between 24 hours and 12 months after SCGx. Intraocular pressure (IOP) was measured by pneumatonometry, Aqueous flow by fluorophotometry and outflow facility by tonography. Uveoscleral outflow was determined by an intracameral tracer infusion technique and blood flow to the choroid was evaluated with fluorescent microspheres. Values in denervated eyes were compared with the contralateral, normallyinnervated eyes using a paired Student's two-tailed t-test. Results. At 24 hours after SCGx, IOP in denervated eyes was less than in normally-innervated eyes (14.6 ± 0.8 vs 20.1 ± 1.5mmHg, 27%, p < 0.002). At one month, IOPs were not different between eyes. Compared with normally-innervated eyes at 10-12 months, IOP in denervated eyes was greater (20.4 ± 0.7 vs 17.2 ± 0.9mmHg, 19%, p < 0.001), outflo...
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Aqueous Humor Dynamics during the day and night in volunteers with ocular hypertension
Archives of Ophthalmology, 2011Co-Authors: Joseph J Hejkal, Vikas Gulati, Carl B. Camras, Susan Galata, Carol B TorisAbstract:Objective To evaluate the differences in Aqueous Humor Dynamics between nighttime and daytime in participants with ocular hypertension. Methods Thirty participants (mean [SD] age, 59.2 [11.1] years) with ocular hypertension were enrolled in the study, which included 1 daytime and 1 nighttime visit. During each visit, measurements included central cornea thickness by ultrasound pachymetry, intraocular pressure (IOP) by pneumatonometry, Aqueous flow by fluorophotometry, outflow facility by tonography, and blood pressure by sphygmomanometry. Uveoscleral outflow was calculated using the Goldmann equation. Daytime measurements were made only of episcleral venous pressure by venomanometry, anterior chamber depth by A-scan, and outflow facility by fluorophotometry. Repeated-measures analysis of variance and 2-tailed t tests were used for statistical comparisons. Results Compared with daytime seated IOP (21.3 [3.5] mm Hg), nighttime seated IOP (17.2 [3.7] mm Hg) was reduced (P Conclusions Significant ocular changes occur at night in individuals with ocular hypertension, including a reduction in seated IOP but an increase in habitual IOP, thickening of the cornea, and decreases in Aqueous flow and uveoscleral outflow. Outflow facility does not change significantly at nighttime.
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Aqueous Humor Dynamics during the day and night in healthy mature volunteers.
Archives of Ophthalmology, 2011Co-Authors: Vikas Gulati, Carl B. Camras, Lucinda J. Camras, G. Zhan, Deepta A Ghate, Carol B TorisAbstract:Objectives: To investigate the daytime vs nighttime differences in intraocular pressure (IOP), Aqueous Humor Dynamics, central cornea thickness, and blood pressure among a cohort of healthy volunteers. Methods: Thirty healthy volunteers (mean [SD] age, 57.0 [8.6] years) were enrolled in the study. Individuals underwent 1 daytime visit and 1 nighttime visit for the measurement of Aqueous Humor Dynamics. Measurements included IOP by pneumatonometry, Aqueous flow by fluorophotometry, outflow facility by fluorophotometry and tonography, uveoscleral outflow by mathematical calculation, central cornea thickness by pachymetry, and blood pressure by sphygmomanometry. Results between visits were compared by appropriate test. Dependence of the pneumatonometer probe results on position was tested in enucleated rabbit eyes at set pressures and probe positions. Results: Compared with daytime seated IOP, nighttime seated IOP was reduced by 16%, whereas nighttime supine IOP was increased by 17% (P
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Aqueous Humor Dynamics during the day and night in healthy mature volunteers
Archives of Ophthalmology, 2011Co-Authors: Vikas Gulati, Carl B. Camras, Deepta Ghate, Lucinda J. Camras, G. Zhan, Carol B TorisAbstract:OBJECTIVES: To investigate the daytime vs nighttime differences in intraocular pressure (IOP), Aqueous Humor Dynamics, central cornea thickness, and blood pressure among a cohort of healthy volunteers. METHODS: Thirty healthy volunteers (mean [SD] age, 57.0 [8.6] years) were enrolled in the study. Individuals underwent 1 daytime visit and 1 nighttime visit for the measurement of Aqueous Humor Dynamics. Measurements included IOP by pneumatonometry, Aqueous flow by fluorophotometry, outflow facility by fluorophotometry and tonography, uveoscleral outflow by mathematical calculation, central cornea thickness by pachymetry, and blood pressure by sphygmomanometry. Results between visits were compared by appropriate t test. Dependence of the pneumatonometer probe results on position was tested in enucleated rabbit eyes at set pressures and probe positions. RESULTS: Compared with daytime seated IOP, nighttime seated IOP was reduced by 16%, whereas nighttime supine IOP was increased by 17% (P < .001 for both). The IOP changes were independent of the pneumatonometer probe position. Central cornea thickness was increased at nighttime from a mean (SD) of 560 (37) μm to a mean (SD) of 574 (37) μm (P < .001). Compared with daytime Aqueous flow, nighttime Aqueous flow was reduced by 49% (P < .001). During the night, fluorophotometric outflow facility was reduced by 45% (P = .05), and tonographic outflow facility was reduced by 17% (P < .01). Uveoscleral outflow at night was decreased when calculated using tonographic outflow facility but not fluorophotometric outflow facility in the Goldmann equation. All other measurements were unchanged. CONCLUSIONS: Significant changes in Aqueous Humor Dynamics at night in healthy mature humans include reductions in Aqueous flow, outflow facility, and possibly uveoscleral outflow. Nocturnal changes in IOP are independent of the pneumatonometer probe position and are dependent on an individual's posture during the measurement.
Michael E Yablonski - One of the best experts on this subject based on the ideXlab platform.
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Aqueous Humor Dynamics in ocular hypertensive patients
Journal of Glaucoma, 2002Co-Authors: Carol B Toris, Scott A Koepsell, Michael E Yablonski, Carl B. CamrasAbstract:PurposeTo evaluate the mechanism of the intraocular pressure (IOP) elevation in ocular hypertension (OHT), Aqueous Humor Dynamics were compared in patients with OHT versus age-matched ocular normotensive (NT) volunteers.MethodsIn this retrospective study, one group included patients diagnosed with O
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effects of multiple dosing of epinephrine on Aqueous Humor Dynamics in human eyes
Journal of Ocular Pharmacology and Therapeutics, 2002Co-Authors: Yun Liang Wang, Michael E Yablonski, Mieko Hayashi, Carol B TorisAbstract:Numerous studies have provided conflicting evidence to explain the ocular hypotensive mechanism of action of epinephrine. Although epinephrine has been shown consistently to increase outflow facility, its effects on Aqueous flow and uveoscleral outflow are not as clear. The purpose of this study was to clarify the effects of multiple doses of topical epinephrine on Aqueous Humor Dynamics in human eyes. This was done by evaluating the four main parameters that determine steady state intraocular pressure. These parameters were assessed at baseline and after a week of twice-daily treatment of epinephrine hydrochloride 2% to one eye. Twenty-six human volunteers were enrolled in the study. Intraocular pressure was measured by pneumatonometry, Aqueous flow and trabecular outflow facility by fluorophotometry, episcleral venous pressure by venomanometry and uveoscleral outflow by mathematical calculation. In epinephrine-treated eyes compared to baseline, intraocular pressure and Aqueous flow were reduced from 21....
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Aqueous Humor Dynamics in monkeys with laser-induced glaucoma
Journal of Ocular Pharmacology and Therapeutics, 2000Co-Authors: Carol B Toris, Carl B. Camras, Guilin Zhan, Yun Liang Wang, Jian Zhao, Marsha A. Mclaughlin, Michael E YablonskiAbstract:This study determines the effects of laser-induced glaucoma on Aqueous Humor Dynamics of 18 cynomolgus monkeys. Baseline measurements of 12 monkeys included intraocular pressure (IOP) by pneumatonometry, Aqueous flow by fluorophotometry and outflow facility by tonography. Beginning 4 to 14 days later, the trabecular meshwork of one eye was treated repeatedly with laser photocoagulation until elevated IOP was induced. Thirty-six to 75 days after the last laser treatment, all measurements were repeated. Between 1.7 and 11.4 years after laser treatment, the same 12 monkeys plus 6 additional monkeys underwent IOP and Aqueous flow measurements. In addition, outflow facility was determined with fluorophotometry, and uveoscleral outflow was both calculated (n=18) and measured with an intracameral tracer (n=7). In glaucoma eyes compared to control eyes (n=12), IOP was increased (p
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Aqueous Humor Dynamics in monkeys with laser induced glaucoma
Journal of Ocular Pharmacology and Therapeutics, 2000Co-Authors: Carol B Toris, Carl B. Camras, Guilin Zhan, Yun Liang Wang, Jian Zhao, Marsha A. Mclaughlin, Michael E YablonskiAbstract:This study determines the effects of laser-induced glaucoma on Aqueous Humor Dynamics of 18 cynomolgus monkeys. Baseline measurements of 12 monkeys included intraocular pressure (IOP) by pneumatonometry, Aqueous flow by fluorophotometry and outflow facility by tonography. Beginning 4 to 14 days later, the trabecular meshwork of one eye was treated repeatedly with laser photocoagulation until elevated IOP was induced. Thirty-six to 75 days after the last laser treatment, all measurements were repeated. Between 1.7 and 11.4 years after laser treatment, the same 12 monkeys plus 6 additional monkeys underwent IOP and Aqueous flow measurements. In addition, outflow facility was determined with fluorophotometry, and uveoscleral outflow was both calculated (n=18) and measured with an intracameral tracer (n=7). In glaucoma eyes compared to control eyes (n=12), IOP was increased (p<0.04) by at least 8 mmHg at Time 1 (1 to 3 months) or Time 2 (3 to 4 years) after laser treatment; Aqueous flow was reduced (p=0.0007) by 46% at Time 1 but returned to baseline levels at Time 2; tonographic outflow facility was reduced (p=0.0008) by 71% at Time 1. In lasered eyes compared to control eyes, fluorophotometric outflow facility was reduced (p=0.0008; n=18) by 63%, and uveoscleral outflow was increased (p<0.05), whether calculated or measured with tracers at least 1 year after laser treatment. The increased IOP in monkeys with laser-induced glaucoma was caused by a sustained reduction in outflow facility. The uveoscleral outflow increase was not enough to prevent the rise in IOP.
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acute versus chronic effects of brimonidine on Aqueous Humor Dynamics in ocular hypertensive patients
American Journal of Ophthalmology, 1999Co-Authors: Carol B Toris, Carl B. Camras, Michael E YablonskiAbstract:Abstract PURPOSE: To report the acute vs chronic effects of brimonidine, a selective α 2 -adrenergic receptor agonist, on Aqueous Humor Dynamics in ocular hypertensive patients. METHODS: Brimonidine 0.2% was given topically twice daily for 29 days to one eye each of 28 ocular hypertensive volunteers in a randomized double-masked study. The fellow eye was similarly treated with vehicle. Aqueous flow (Fa) and outflow facility (C fl ) were determined with fluorophotometry. Intraocular pressure, outflow facility (C ton ), and episcleral venous pressure (Pev) were measured with pneumatonometry, tonography, and venomanometry, respectively. Uveoscleral outflow (Fu) was calculated from intraocular pressure, Fa, Pev, and C fl values. All measurements were taken on baseline day, day 8, and day 29 of treatment. Intraocular pressure and Fa only were measured after instillation of 1 drop of brimonidine on day 1. RESULTS: When measured 3 hours after instillation on days 1, 8, and 29 of treatment, brimonidine significantly ( P P P P CONCLUSIONS: The brimonidine-induced reduction in intraocular pressure in humans is associated initially with a decrease in Aqueous flow, and after chronic treatment with an increase in uveoscleral outflow.
