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Results for “Aqueous Humor”

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At least 865 records · Page 48Linked to original sources
PubMed1989

[Intra aqueous humor penetration of ciprofloxacin in humans].

Authors have studied the penetration of ciprofloxacin in the aqueous humor of 30 patients (30 eyes). The concentration in the anterior chamber was on average 0.73 mg/l (33% of serum level), from 1.30 hours after a single oral dose (1000 mg) till the 5th hour after this dose. The samples were assessed by a microbiological method. These results are over the minimal inhibitory concentration for many bacterial agents found in endophthalmitis. So this antibiotic may be proposed in the treatment of endophthalmitis, with further investigations assessing the safety of this procedure.

Aged↗
PubMed1979

Method of measuring aqueous humor flow and corneal endothelial permeability using a fluorophotometry nomogram.

A new method of measuring aqueous humor flow and corneal endothelial permeability to fluorescein using a fluorophotometry nomogram is described. This method is compared to four other methods, two of which have been described previously. All five methods were carried out simultaneously in a group of 20 normal human subjects. All methods give closely comparable results in most of the eyes tested. A tabular comparison of the results of the nomographic method and the published results of other investigators, which are in good agreement, is given. The relative advantages and disadvantages of the nomographic technique are discussed.

Adult↗
PubMed1989

[Tonography and fluorophotometry in the clinical study of aqueous humor dynamics].

We used Grant's tonography and fluorophotometry (the Jones and Maurice method) to study the aqueous humor dynamics in normal and glaucomatous eyes. The results of the two methods were compared. The mean facility and rate of aqueous flow in normal eyes were similar. In glaucomatous eyes the tonographic outflow facility (C-value) varied greatly, and the calculated rate of aqueous flow (F-value) also had a large standard deviation. To study the inflow rate, fluorophotometry is a more accurate method. Further calculation of uveoscleral flow and the "pseudofacility" from the tonographic F-value and fluorophotometric C-value was therefore of only limited accuracy.

Adult↗
PubMed1976

Indentification and radioimmunologic estimation of sexual steroid hormones in aqueous humor and vitreous of rabbit eye.

The occurrence of testosterone, estrone, and estradiol-17 alpha in aqueous humor and vitreous body of the rabbit eye was demonstrated. The identity of the steroid hormones was confirmed by their chromatographic properties, microreactions, and radiochemically by crystallization to constant specific activity of their labeled acetates. The levels of testosterone and estrogens in rabbit male and female plasma, aqueous, and vitreous were determined by radioimmunologic assay. The concentrations of the steroid hormones in plasma are higher than in aqueous and vitreous. However, testosterone in aqueous circulates in free form and lacks the binding to sexual hormone-binding globulin as in plasma.

Animals↗
PubMed1978

Effects of transcorneal freezing on protein content of aqueous humor and intraocular temperature in rabbit and cat.

The effects of transcorneal freezing on protein content of aqueous humor and intraocular temperature at the posterior surface of the cornea, the angle, the iris, and the ciliary processes were determined in rabbits and cats. Normal aqueous protein concentration was 40 +/- 2 mg/dl in rabbits and 43 +/- 4 mg/dl in cats. In rabbits, total aqueous protein content reached its highest level (2790 +/- 302 mg/dl) for 3 hr after transcorneal freezing, decreased by 50% after 4 hr, and was not significantly different than normal at 7 days. In cats, total aqueous protein content also reached its highest level (1610 +/- 290 mg/dl) 3 hr after corneal freezing. Fluctuations occurred thereafter, but protein content was not significantly different from normal after 7 days. The temperature at the corneal endothelium always decreased to below 0 degrees C with a 10 to 25 sec application of the cryoprobe to the cornea in rabbit and cat. Intraocular temperature did not decrease below 24 degrees C at the angle or ciliary processes during application of the cryoprobe for up to 25 sec, whereas the temperature at the pupillary margin of the iris sometimes decreased to near 0 degrees C with a 15 to 25 sec application.

Animals↗
PubMed2007

Model of pulsatile-flow of aqueous humor through the iris-lens canal.

PURPOSE: To present a model of pulsatile-flow of aqueous humor from posterior (PC) to anterior chamber (AC) and to analyze the sensitivity of this novel model in detecting typical high risk conditions predisposing to pupillary block. METHODS: The model assumes noncontinuous flow of aqueous through the iris-lens canal. Aqueous that fills the canal will be ejected toward the AC-side of the canal at certain time intervals, and between 2 events of aqueous ejection there is no actual flow through this canal. Pupillary pumping rate (PPR) was calculated from the aqueous flow rate and the calculated volume of iris-lens canal. RESULTS: PPR values were generated by incorporating pupillary diameter (1 to 8 mm), aqueous flow rate (1 to 2.5 microL/min), and iris-lens canal width (0.5 to 2 mm) and height (3-9 microm) in numerical experimentation with the present model. PPR showed inverse dependence on iris-lens canal height and pupillary diameter and was directly proportional to aqueous flow rate, in agreement with the steady-flow model. However, contrary to the steady-flow model, PPR showed inverse dependence on iris-lens canal width and predicted the anticipated PC-AC pressure gradient changes at simulated light-dark transition in eyes of patients with clinically narrow angles and ultrasound biomicroscopy evidenced pupillary block. CONCLUSIONS: Upon the incorporation of real ultrasound biomicroscopy measurements in numerical experimentations with both models, the present pulsatile-flow model, contrary to the steady-flow model, showed good predictability of PC-AC pressure gradient changes in a typical condition predisposing to pupillary block.

Anterior Chamber↗
PubMed2005

Glaucoma medication and aqueous humor dynamics.

PURPOSE OF REVIEW: This review evaluates current concepts regarding the effects of glaucoma medication on aqueous humor dynamics and the impact of this on intraocular pressure control and drug selection in clinical practice. RECENT FINDINGS: Calculations based on the Friedenwald and Goldmann equations have predicted that glaucoma medications that increase pressure-sensitive aqueous outflow will dampen intraocular pressure spikes and therefore may be advantageous over drugs that do not increase outflow facility. SUMMARY: Further experimental research is required to verify the influence of increased outflow facility on intraocular pressure fluctuation and the effect of this on glaucoma progression.

Animals↗
PubMed2000

Latrunculins' effects on intraocular pressure, aqueous humor flow, and corneal endothelium.

PURPOSE: To determine the effects of latrunculin (LAT)-A or -B on intraocular pressure (IOP), aqueous humor flow (AHF), anterior chamber (AC) protein concentration ([protein]AC), corneal endothelial permeability and morphology, and corneal thickness in living cynomolgus monkeys. METHODS: Topical LAT-A or LAT-B was administered to one eye, and vehicle to the other. IOP was measured by Goldmann tonometry, AHF and corneal endothelium transfer coefficient (ka) by fluorophotometry, [protein]Ac by Lowry assay, corneal endothelial cell morphology by specular microphotography, and corneal thickness by ultrasound pachymetry. RESULTS: LAT-A began to lower IOP at 6 hours and maximally reduced IOP by 4.6 mm Hg at 9 hours. LAT-B lowered IOP within 1 hour and maximally reduced IOP by 3.1 mm Hg at 6 hours. LAT-A increased AHF by 87% for 3 hours and increased ka by 94% over 6 hours; LAT-B increased ka by 39% over 6 hours without affecting AHF. LAT-A increased IV fluorescein entry into the cornea approximately 10 fold, but did not affect IV fluorescein entry into the AC. LAT-A increased [protein]AC by 25% at 2 hours but not 5.5 hours. LAT-B variably and insignificantly increased [protein]AC: at 1 hour but not at 6.5 hours. LAT-A induced extensive corneal endothelial pseudoguttata within 1 hour, with normal cell counts by 7 days. LAT-B increased central corneal thickness maximally by 47 microm at 3.5 hours. CONCLUSIONS: LAT-A and -B significantly reduced IOP and were consistent in their facility-increasing effect, indicating that pharmacologic disorganization of the actin cytoskeleton in the trabecular meshwork by latrunculins may be a useful antiglaucoma strategy. However, effects on corneal endothelium or ciliary epithelium are a potential safety issue.

Animals↗
PubMed1984

The drainage routes for aqueous humor in monkeys as revealed by scanning electron microscopy of corrosion casts.

The outflow routes for aqueous humor from the anterior chamber in cynomolgus monkeys were studied. The routes were filled with a mixture of Mercox CL2R and methyl methacrylate, 4:6, which had a low viscosity. Polymerization was delayed by cooling. Some experiments were performed after fixation with glutaraldehyde. Scanning electron microscopy was used to study the casts after dissolution of the tissue. The casts indicate inflow into the first intertrabecular space through a limited number of 10-100 microns openings. The first space is an irregular circular plexus. Subsequent uveal intertrabecular spaces also constitute complex channels. In the ciliary muscle the plastic entering from the uveal intertrabecular spaces could pass through narrow spaces into the supraciliary and suprachoroidal spaces. The intertrabecular spaces in the corneoscleral meshwork were thinner than those in the uveal meshwork. The outermost layer which tended to fill incompletely especially in fixed preparations communicated with the spaces of the juxtacanalicular tissue. In this tissue there was very limited filling even in unfixed preparations. On the casts of the canal of Schlemm there were remnants of communications with the juxtacanalicular tissue. These remnants indicated that only pores with diameters of 2-3 microns or more had been large enough to drain plastic into the canal. The collector channels formed a deep scleral plexus at many places. This plexus and direct collector channels drained into superior and inferior episcleral veins. Apparently the casting technique permitted visualization of most of the uveal and corneoscleral intertrabecular spaces and of preferential channels through the juxtacanalicular tissue and the inner wall of Schlemm's canal. The number of such channels was about 10-20/mm2 of inner wall.

Animals↗
PubMed1994

The presence of biologically significant concentrations of glucocorticoids but little or no cortisol binding globulin within aqueous humor: relevance to immune privilege in the anterior chamber of the eye.

PURPOSE: Immunosuppressive factors in aqueous humor (AH) contribute to the immune-privileged status of the anterior chamber of the eye. One such factor is transforming growth factor-beta (TGF-beta); other relevant inhibitors have not been fully identified. The authors examined AH to search for other putative inhibitors and to determine their effect on TGF-beta inhibitory activity. METHODS: Radioimmunoassays (RIA) were used to detect the presence of hydrocortisone, corticosterone, cortisol binding globulin (CBG), and alpha-melanocyte stimulating hormone (alpha-MSH) in AH. The ability of these factors to inhibit murine thymocyte proliferation stimulated by phytohemagglutinin-interleukin 1 (PHA/IL-1) and proliferation of a TGF-beta-sensitive cell line (CCL64) in vitro was examined. The ability of hydrocortisone to inhibit a one-way mixed lymphocyte reaction (MLR) and the ability of epidermal cells to present soluble tumor-associated antigens (TAA) for elicitation of immunity in mice in the concentration range present in AH was also examined. RESULTS: Hydrocortisone was detected in mouse, rat, and human AH (10.8 +/- 1.1 ng/ml, 9.3 +/- 2.1 ng/ml, and 18.0 +/- 1.0 ng/ml, respectively; mean +/- SEM), as was corticosterone (2.7 +/- 0.9 ng/ml, 2.2 +/- 0.3 ng/ml, and 0.7 +/- 0.1 ng/ml, respectively). Whereas normal plasma contains a binding protein for corticosteroids (i.e., CBG), the concentration in mouse, rat, and human AH was less than the level detectable by an RIA. Hydrocortisone inhibited PHA/IL-1-stimulated murine thymocyte proliferation and CCL64 cell proliferation in the concentration range present in AH. When hydrocortisone was combined with TGF-beta 2 (125 pg/ml), the degree of inhibition observed was greater than with either alone. Corticosterone inhibited thymocyte costimulation only slightly at concentrations present in AH but was inhibitory for CCL64 cells. alpha-MSH was also detected in AH. The concentration present had only slight inhibitory effects for CCL64 cell proliferation and did not enhance TGF-beta 2-mediated (62 pg/ml to 250 pg/ml) inhibition of CCL64 or thymocyte proliferation. Hydrocortisone inhibited the one-way MLR in the concentration range present in AH and, at 10 ng/ml, inhibited the ability of epidermal cells to present TAA for elicitation of delayed-type hypersensitivity in tumor-immune mice. CONCLUSIONS: These results show that AH contains biologically relevant concentrations of glucocorticoids and that CBG is relatively absent so that glucocorticoids present are largely free, and they suggest that regional sites take advantage of the activities of multiple factors to maintain an immune-privileged status.

11-Hydroxycorticosteroids↗