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Carol B Toris - One of the best experts on this subject based on the ideXlab platform.
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mechanism of action of selective laser trabeculoplasty and predictors of response
Investigative Ophthalmology & Visual Science, 2017Co-Authors: Vikas Gulati, Carol B Toris, Shan Fan, Bret J Gardner, Shane Havens, Marie T Schaaf, Donna G NeelyAbstract:Purpose This study was designed to evaluate the changes in aqueous humor dynamics (AHD) produced by selective laser trabeculoplasty (SLT) and to explore if baseline AHD parameters are predictive of IOP response to SLT. Methods Thirty-one consecutive subjects diagnosed with ocular hypertension or primary open-angle glaucoma scheduled to undergo SLT as their primary IOP-lowering therapy were enrolled in this prospective observational study. Subjects underwent baseline assessment of AHD in both eyes. Variables assessed were IOPs at 9 AM and noon, aqueous humor flow rate (Fluorophotometry), episcleral venous pressure (EVP, venomanometry), outflow facility (pneumatonography and Fluorophotometry) and uveoscleral outflow (calculated using modified Goldmann equation). All subjects underwent 360 degrees SLT and AHD measurements were repeated 3 months later. Results Compared with baseline, IOPs after SLT were significantly lower at 9 AM (22.9 ± 5.1 vs. 19.7 ± 3.0 mm Hg; P = 0.001) and noon (23.4 ± 4.6 vs. 20.0 ± 3.5 mm Hg; P < 0.001). Outflow facility by Fluorophotometry was significantly increased from 0.17 ± 0.11 μL/min/mm Hg at baseline to 0.24 ± 0.14 μL/min/mm Hg at 3 months (P = 0.008). Outflow facility by tonography (baseline: 0.16 ± 0.07 μL/min/mm Hg vs. 3 months: 0.22 ± 0.16 μL/min/mm Hg; P = 0.046) was similarly increased. No change in aqueous flow or EVP was observed. There were no changes in IOP or AHD in the contralateral untreated eye. Using multiple linear regression models, higher baseline aqueous flow, lower baseline outflow facility, and possibly lower uvescleral outflow were associated with more IOP lowering with SLT. Conclusions The IOP-lowering effect of SLT is mediated through an increase in outflow facility. There is no contralateral effect. Higher aqueous flow and lower outflow facility may be predictive of better response to SLT.
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aqueous flow measured by Fluorophotometry in the mouse
Investigative Ophthalmology & Visual Science, 2016Co-Authors: Carol B Toris, Shan Fan, Thomas V Johnson, Lucinda J Camras, Cassandra L Hays, H Liu, Bruce M IshimotoAbstract:PURPOSE A fluorophotometer designed to measure aqueous flow in murine eyes was tested with artificial fluorescein chambers and in live mice with different anesthesia regimens, aqueous flow suppressants, and an anterior chamber cannulation method. METHODS Two hours following topical fluorescein application, one group of CD-1 mice was anesthetized with ketamine/xylazine, 2,2,2-tribromoethanol, or ketamine alone. Cornea and anterior chamber fluorescein concentrations were measured periodically for 60 to 90 minutes by fluorophotometric scans to calculate aqueous flow. Later, a subgroup of mice underwent aqueous flow measurement by anterior chamber cannulation. A third group was treated with timolol, dorzolamide, and vehicle in a crossover manner 1 hour prior to fluorophotometric scans. RESULTS Aqueous flow with ketamine/xylazine anesthesia (0.09 ± 0.05 μL/min, mean ± SD, n = 24) was slower than with tribromoethanol or ketamine alone (P < 0.001). Timolol reduced aqueous flow from 0.20 ± 0.07 μL/min to 0.07 ± 0.03 μL/min (P = 0.001) under tribromoethanol anesthesia and from 0.14 ± 0.03 μL/min to 0.10 ± 0.02 μL/min (P = 0.004) under ketamine anesthesia but not under ketamine/xylazine anesthesia. Dorzolamide reduced aqueous flow from 0.09 ± 0.03 to 0.06 ± 0.03 μL/min (P = 0.04) under ketamine/xylazine anesthesia. Aqueous flow by anterior chamber cannulation (0.20 ± 0.13 μL/min) was greater (P = 0.05) than by Fluorophotometry (0.09 ± 0.07 μL/min). CONCLUSIONS A new noninvasive fluorophotometric method detected effects of general anesthesia and known aqueous suppressants on aqueous flow in mice. Aqueous flow measured by Fluorophotometry was slower than by cannulation, and was technically easier with less variability. The mouse fluorophotometer is useful for repeated measurements of aqueous flow in the murine eye making crossover and longitudinal studies possible.
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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, Carl B. Camras, Vikas Gulati, 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 juvenile and adult rabbits
Investigative Ophthalmology & Visual Science, 2010Co-Authors: M Zhao, Carl B. Camras, Joseph J Hejkal, Carol B TorisAbstract:PURPOSE: To determine the day and night differences in intraocular pressure (IOP), aqueous flow, outflow facility, uveoscleral outflow, and central corneal thickness (CCT) in juvenile and adult rabbits. METHODS: Studies were performed on twelve 3-month-old and ten 12-month-old male New Zealand White rabbits. Daytime measurements were made between 9 AM (3 hours after lights on) and 3 PM, and nighttime measurements were made between 11 PM and 5 AM. IOP was measured by pneumotonometry and aqueous flow by Fluorophotometry. Outflow facility was determined by both Fluorophotometry and tonography. Uveoscleral outflow was calculated by the Goldmann equation. CCT was measured by ultrasound pachymetry. Repeated-measures ANOVAs and Student's two-tailed t-tests were used for statistical comparisons. RESULTS: When nighttime versus daytime readings were compared, IOP, aqueous flow and uveoscleral outflow were higher, fluorophotometric outflow facility was lower, and CCT was thinner in both age groups. When the juvenile rabbits were compared to adult rabbits, IOP was lower, aqueous flow and uveoscleral outflow were higher, and fluorophotometric outflow facility and CCT were not different during the day or night. Tonographic outflow facility did not change in a 24-hour period in the juvenile rabbits. CONCLUSIONS: The increased IOP at night in rabbits can be explained mainly by a decrease in outflow facility. An increase in aqueous flow at night is counterbalanced by an increase in uveoscleral outflow. Although the rates of aqueous flow and uveoscleral outflow slow with maturity, their relative day/night differences remain the same.
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mechanism of action of bimatoprost latanoprost and travoprost in healthy subjects a crossover study
Ophthalmology, 2008Co-Authors: Carol B Toris, Jay W Mclaren, Sheng K Lim, Cherie B Nau, Megan M Obyrne, David O Hodge, Douglas H JohnsonAbstract:Purpose To study the effects of 3 prostaglandin analogs, bimatoprost, latanoprost, and travoprost, on aqueous dynamics in the same subjects and to compare techniques of assessing outflow facility. Design Experimental study (double-masked, placebo-controlled, randomized paired comparison, 4-period crossover). Participants Thirty healthy adult subjects. Methods Bimatoprost, latanoprost, travoprost, or a placebo was administered to the left eye once a day in the evening for 7 days, after a minimum 4-week washout period between each session. Tonographic outflow facility was measured by Schiotz tonography and pneumatonography on day 7. On day 8, the aqueous humor flow rate and fluorophotometric outflow facility were measured by Fluorophotometry. Uveoscleral outflow was calculated from the aqueous humor flow rate and outflow facility using the Goldmann equation. Main Outcome Measures Facility of outflow, aqueous humor flow rate, intraocular pressure (IOP), and calculation of uveoscleral outflow. Results All medications lowered IOP relative to a placebo. None of the drugs affected aqueous humor production. All medications increased outflow facility compared with placebo when measured by Schiotz and 2-minute pneumatonography ( P ≤0.02); the apparent increase of outflow facility measured with Fluorophotometry and 4-minute pneumatonography did not reach statistical significance. In contrast, uveoscleral outflow was significantly increased by all medications when calculated from 4-minute pneumatonography data, and Fluorophotometry and Schiotz data at higher episcleral venous pressures. The apparent increase found with 2-minute pneumatonography did not reach statistical significance. These differing results in the same patients indicate that differences in measurement techniques, and not differences in mechanism of action, explain previous conflicting published reports on the mechanism of action of the prostaglandins. Conclusions Bimatoprost, latanoprost, and travoprost have similar mechanisms of action. All 3 drugs reduce IOP without significantly affecting the aqueous production rate. All drugs increase aqueous humor outflow, either by enhancing the pressure-sensitive (presumed trabecular) outflow pathway or by increasing the pressure-insensitive (uveoscleral) outflow, but the assessment of the amount of flow through each pathway depends upon the measurement technique.
Günther Karl Krieglstein - One of the best experts on this subject based on the ideXlab platform.
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the influence of latanoprost 0 005 on aqueous humor flow and outflow facility in glaucoma patients a double masked placebo controlled clinical study
Graefes Archive for Clinical and Experimental Ophthalmology, 2004Co-Authors: Sven Dinslage, Arno Hueber, Michael Diestelhorst, Günther Karl KrieglsteinAbstract:Background Fluorophotometry and pneumotonography were performed to investigate the effect of Latanoprost 0.005% and Placebo on aqueous humor flow and total outflow facility in human glaucomatous eyes.
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the effect of trabeculectomy on the aqueous humor flow of the unoperated fellow eye
Graefes Archive for Clinical and Experimental Ophthalmology, 1991Co-Authors: M Diestelhorst, Günther Karl KrieglsteinAbstract:Computerized anterior-chamber Fluorophotometry was used to investigate the effect of unilateral antiglaucomatous trabeculectomy on the dynamics of aqueous humor in the unoperated fellow eye. In 14 patients with bilateral primary open-angle glaucoma, pigmentary glaucoma or exfoliation glaucoma, antiglaucomatous trabeculectomy was performed in one eye in which medical management of glaucoma had failed. The fellow eye in all patients had a well-defined history of glaucoma and had been treated with different sorts of medication. The medical management of the unoperated fellow eyes was continued throughout the study. Aqueous humor flow was measured in these eyes prior to surgery and on the 5th day after trabeculectomy. Systemic medication was discontinued from 48 h prior to surgery until second Fluorophotometry. The average postoperative flow in the fellow eyes increased from 2.56 to 2.92 μl/min (P<0.05%, paired t-test). The increase in flow in the fellow eyes was independent of topical antiglaucoma medication and of the diurnal rhythm of aqueous humor dynamics. The results of the study indicate that filtration surgery in one eye triggers a CNS-mediated, reflective increase in aqueous flow to maintain physiological stability in the anterior chamber of the surgically treated eye. Since this CNS reflex on aqueous humor dynamics affects both eyes, the clinical observation of intraocular pressure (10P) dysregulation in the unoperated fellow eye following unilateral trabeculectomy is now understandable.
S E Smith - One of the best experts on this subject based on the ideXlab platform.
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a comparison of the laser flare cell meter and Fluorophotometry in assessment of the blood aqueous barrier
Investigative Ophthalmology & Visual Science, 1993Co-Authors: S M Shah, David J. Spalton, R J Allen, S E SmithAbstract:PURPOSE To evaluate and compare the use of the Kowa laser flare cell meter and intravenous anterior chamber Fluorophotometry in assessment of the blood-aqueous barrier after cataract surgery. METHOD Laser flare and cell measurements and Fluorophotometry were performed at 1 and 3 months after surgery in 48 eyes of 44 patients admitted for routine cataract surgery. The fellow pseudophakic eyes of these patients were used as controls. RESULTS The two techniques measure different parameters, but both methods are able to document the integrity or breakdown of the blood-aqueous barrier. However, the laser flare cell meter is more sensitive in quantifying subtle changes in barrier function to large molecules (proteins). Various methods of assessing anterior chamber Fluorophotometry data were also compared. Measurement of a diffusion coefficient (requiring the measurement of plasma fluorescence) was not found to be more sensitive than other methods and did not alter the clinical significance of data obtained from the measurement of anterior chamber fluorescence alone. CONCLUSIONS Both the laser flare cell meter and Fluorophotometry provide a method for the assessment of the postoperative blood-aqueous barrier. However, the laser flare cell meter is rapid, noninvasive, and relatively easier to use. Therefore, for clinical use, it has great practical advantages over Fluorophotometry.
J. A. Oosterhuis - One of the best experts on this subject based on the ideXlab platform.
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Determination of basal tear turnover in insulin-dependent diabetes mellitus patients by Fluorophotometry.
International ophthalmology, 1991Co-Authors: Th. R. Stolwijk, H. H. P. J. Lemkes, R. J. W Keizer, J. A. Van Best, J. A. OosterhuisAbstract:The tear turnover was determined by Fluorophotometry in 25 insulin-dependent diabetes mellitus (IDDM) patients without retinopathy and 29 IDDM patients with (pre-)proliferative retinopathy. The results were compared with those in 34 healthy controls, to investigate the lacrimal gland function in diabetic patients. The tear turnover was calculated from the decay of the relative tear fluorescein concentration values measured after instillation of one μL of fluorescein.
S M Shah - One of the best experts on this subject based on the ideXlab platform.
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A Comparison of the Laser Flare Cell Meter and Fluorophotometry in Assessment of the Blood-Aqueous Barrier
2020Co-Authors: S M Shah, ^ David, J Spalton, Raymond ] Allen, Stephen E Smith\Abstract:Purpose. To evaluate and compare the use of the Kowa laser flare cell meter and intravenous anterior chamber Fluorophotometry in assessment of the blood-aqueous barrier after cataract surgery. Method. Laser flare and cell measurements and Fluorophotometry were performed at 1 and 3 months after surgery in 48 eyes of 44 patients admitted for routine cataract surgery. The fellow pseudophakic eyes of these patients were used as controls. Results. The two techniques measure different parameters, but both methods are able to document the integrity or breakdown of the blood-aqueous barrier. However, the laser flare cell meter is more sensitive in quantifying subtle changes in barrier function to large molecules (proteins). Various methods of assessing anterior chamber Fluorophotometry data were also compared. Measurement of a diffusion coefficient (requiring the measurement of plasma fluorescence) was not found to be more sensitive than other methods and did not alter the clinical significance of data obtained from the measurement of anterior chamber fluorescence alone. Conclusions. Both the laser flare cell meter and Fluorophotometry provide a method for the assessment of the postoperative blood-aqueous barrier. However, the laser flare cell meter is rapid, noninvasive, and relatively easier to use. Therefore, for clinical use, it has great practical advantages over Fluorophotometry. Invest Ophthalmol Vis Sci. 1993;34:3124-3130
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a comparison of the laser flare cell meter and Fluorophotometry in assessment of the blood aqueous barrier
Investigative Ophthalmology & Visual Science, 1993Co-Authors: S M Shah, David J. Spalton, R J Allen, S E SmithAbstract:PURPOSE To evaluate and compare the use of the Kowa laser flare cell meter and intravenous anterior chamber Fluorophotometry in assessment of the blood-aqueous barrier after cataract surgery. METHOD Laser flare and cell measurements and Fluorophotometry were performed at 1 and 3 months after surgery in 48 eyes of 44 patients admitted for routine cataract surgery. The fellow pseudophakic eyes of these patients were used as controls. RESULTS The two techniques measure different parameters, but both methods are able to document the integrity or breakdown of the blood-aqueous barrier. However, the laser flare cell meter is more sensitive in quantifying subtle changes in barrier function to large molecules (proteins). Various methods of assessing anterior chamber Fluorophotometry data were also compared. Measurement of a diffusion coefficient (requiring the measurement of plasma fluorescence) was not found to be more sensitive than other methods and did not alter the clinical significance of data obtained from the measurement of anterior chamber fluorescence alone. CONCLUSIONS Both the laser flare cell meter and Fluorophotometry provide a method for the assessment of the postoperative blood-aqueous barrier. However, the laser flare cell meter is rapid, noninvasive, and relatively easier to use. Therefore, for clinical use, it has great practical advantages over Fluorophotometry.