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Results for “Aqueous Humor”

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At least 757 records · Page 42Linked to original sources

PubMed1997

[Quantitative analysis of cAMP and cGMP in the plasma, iris and aqueous humor in rabbits with high intraocular pressure].

OBJECTIVE: To study the relationship between the levels of cyclic adenosine monophosphate (cAMP), cyclic guanosine monophos-phate (cGMP) in the plasma, iris and aqueous humor and high intraocular pressure in rabbits. METHODS: The quantitative tests of cAMP and cGMP from rabbits were carried out by radioimmunoassay technique. RESULTS: The results showed that there were 72.81 +/- 7.67, 141.08 +/- 16.70 and 28.40 +/- 0.49 of cAMP (nmol/L), and there were 10.37 +/- 6.15, 35.64 +/- 7.02 and 12.90 +/- 0.61 of cGMP (nmol/L) in the plasma, iris and aqueous humor respectively. The levels of cAMP were higher than those in the same samples from the animals as controls (P < 0.01), while the levels of cGMP were less than controls (P < 0.01). CONCLUSION: High intraocular pressure may be significantly associated with the levels of cAMP and cGMP.

Animals↗

PubMed1992

Penetration of norfloxacin into the aqueous humor of the human eye.

Forty six patients received a topical application of a 0.3% norfloxacin (Zoroxin; MSD, Austria) solution into the lower fornix at different time intervals and frequencies before undergoing planned extracapsular cataract extraction. Aqueous humor was sampled at the beginning of surgery and assayed for the level of the antibiotic with high performance liquid chromatography. The highest aqueous humor level observed 30 min after the administration of the last drop in four patients who received five drops of norfloxacin into the lower fornix was 660.25 +/- 378.2 ng/ml. These concentrations are above the minimum inhibitory concentration of norfloxacin for 90% (MIC90) of most of the gram-negative microorganisms, but below the MIC90 of most of the staphylococci (coagulase negative Staph. and Staphylococcus aureus range between 0.25-1 mg/ml).

Administration, Topical↗

PubMed1994

[Glaucoma with Axenfeld-Rieger syndrome in three generations. Aqueous humor dynamics].

A 21-year-old woman was diagnosed as having glaucoma associated with Axenfeld-Rieger syndrome. Her family was examined and 3 additional patients with Axenfeld-Rieger syndrome were found in three generations. All of them had glaucoma with various types of onset. Aqueous humor dynamics were studied in 5 eyes of 3 patients using fluorophotometry. The basic secretion of aqueous humor in 5 eyes was 4.18 +/- 1.13 microliter/min. Averaged uveoscleral outflow in 3 eyes with low transtrabecular outflow facility was 61% of total aqueous outflow. It appeared that uveoscleral outflow was increased to compensate for the impaired transtrabecular outflow route.

Abnormalities, Multiple↗

PubMed1984

Effective penetration of doxycycline into the serum and aqueous humor.

Twenty-five human subjects of both sexes undergoing operations for senile cataract were selected for the present study. Doxycycline was administered orally and at various intervals its penetration into the serum and aqueous humor were determined. It was concluded that for achieving therapeutic concentrations in the serum, doxycycline can be given in the dosage of 200 mg on the first day followed by 100 mg every 24 hours. However, in order to achieve therapeutic concentrations in the aqueous humor, doxycycline should be administered in the dosage of 200 mg on the first day followed by 100 mg every 12 hours.

Administration, Oral↗

PubMed1980

Glutathione in the aqueous humor of human and other species.

Glutathione was measured in the aqueous humon of rabbit, dog, monkey, baboon, and man. The average concentrations were 17, 6, 6, 2, and 2 mumol/L of fluid, respectively. Except in the case of the monkey, where delay in aspiration of the aqueous apparently led to anomalous values, nearly all the glutathione was in the reduced state, the range being from 85% in the rabbit to over 99% in the human. Possible sources of the glutathione in the aqueous humor are discussed and also its significance for the physiology of the cornea.

Adult↗

PubMed1998

Profiling of the eye aqueous humor in exfoliation syndrome by high-performance liquid chromatographic analysis of hyaluronan and galactosaminoglycans.

The concentrations of hyaluronan and galactosaminoglycans -- i.e., chondroitin sulfate and dermatan sulfate -- were measured in the aqueous humor of the eye from patients with exfoliation syndrome and from healthy persons. The glycosaminoglycans/proteoglycans were almost completely precipitated (>97%) with ethanol in the presence of dextran as carrier and, following enzymic digestion, hyaluronan and galactosaminoglycans, were quantitatively converted to delta4,5-disaccharides. Non-degraded heparan sulfate and proteins/glycoproteins were removed by ultrafiltration using a Centricon 3 membrane. Separation and determination of hyaluronan- and galactosaminoglycan-derived delta-disaccharides were performed by ion-suppression HPLC. For an accurate analysis in triplicate, as little as 50 microl of aqueous humor is required. Application of this method to the analysis of samples from six patients with exfoliation syndrome and three healthy persons showed that hyaluronan levels in patients (6.65-16.15 microg ml(-1)) were significantly higher (3-8 times) than in healthy persons (2.0-2.24 microg ml(-1)). There was no significant alteration in the galactosaminoglycan concentration. The obtained data open a new area in the deeper understanding of the exfoliation syndrome pathophysiology and in establishing a highly sensitivity and accurate HPLC method for its diagnosis and patient's follow-up.

Aqueous Humor↗

PubMed1986

Ciclosporin concentration in the rabbit aqueous humor and cornea following subconjunctival administration. Importance of anatomical site of injection.

The model compound lidocaine was used in the rabbit to investigate different sites of subconjunctival injection for the achievement of reproducible drug concentrations in the aqueous humor. Only epibulbar injections were satisfactory, but not parabulbar or injections under the lower fornix. After epibulbar administration of 0.8 ml 5% ciclosporin, median concentrations in the aqueous humor were 360, 700 and 200 ng/ml after 2, 8, and 24 h, respectively. Corresponding levels in the cornea were 32, 27, and 12 ng/ml. It appears that drug concentrations resulting from epibulbar injections may be therapeutically useful.

Animals↗

PubMed1984

Effect of clonidine on aqueous humor flow in normal human eyes.

A randomized, double-blind, placebo-controlled study of the effect of topical 0.125% clonidine, a relatively specific alpha 2-adrenergic agonist, on the rate of aqueous humor flow in the eyes of 24 normal human subjects was performed with fluorophotometry. The effect of clonidine on intraocular pressure, anterior chamber volume, pupil size, pulse, and blood pressure was also studied. Clonidine-treated eyes had a 2 mmHg decrease in intraocular pressure which was statistically significant. Fellow placebo-treated eyes had a smaller but significant decrease in pressure. However, between clonidine and fellow placebo-treated eyes, no significant difference was found in intraocular pressure. Aqueous humor flow was 21% lower in clonidine-treated eyes as compared to fellow placebo-treated eyes, 1.9 microliter min-1 as compared to 2.4 microliters min-1. No significant difference was found in anterior chamber volume, blood-aqueous barrier diffusion constant, and apparent resistance between clonidine and fellow placebo-treated eyes. Clonidine produced a significant miosis of 0.4 mm in treated eyes and miosis of 0.2 mm in fellow eyes. Topical 0.125% clonidine significantly decreased systolic blood pressure by 3 mmHg, but did not affect diastolic blood pressure or pulse.

Administration, Topical↗

PubMed1979

Bicarbonate ATP-ase in ciliary body and a theory of Diamox effect on aqueous humor formation.

Bicarbonate was found to stimulate ATP breakdown by rabbit or cat ciliary body-iris homogenates. Maximum HCO3- stimulation of ATPase with Tris-Hepes buffer occured at pH 8.0. Acid pH and chloride ions in the media reduced the activity of the HCO3--stimulated ATPase. The Km for ATP was 0.55 mmolar and for HCO3-, 20 mmlar. HCO3- ATPase was not inhibited by acetazolamide added to in vitro. It is postulated that ATPase represents the linkage step of energy donor mechanism and active CT secretion in acid aqueous humors (human, cat.) or HCO3- secretion in alkaline aqueous humor (rabbit, guinea pig). Inhibition of Cl- or HCO3- secretion by acetazolamide results from decreased intracellular HCO3- levels which, in turn, reduces the stimulation of the HCO3- ATPase.

Acetazolamide↗

PubMed2002

Effects of multiple dosing of epinephrine on aqueous humor dynamics in human eyes.

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 21.2 +/- 0.3 to 17.1 +/- 0.2 mmHg (19%, p = .01) and 3.3 +/- 0.2 to 2.9 +/- 0.2 microl/min (12%, p = .03), respectively. Trabecular outflow facility obtained by fluorophotometry was increased from 0.18 +/- 0.02 to 0.26 +/- 0.03 microl/min/mmHg (44%, p = .02). Topical epinephrine did not significantly affect uveoscleral outflow or episcleral venous pressure. In conclusion, multiple topical doses of epinephrine lowered intraocular pressure in human volunteers by reducing aqueous humor formation and increasing trabecular outflow facility. The increase in uveoscleral outflow suggested by other studies was not observed.

Acetazolamide↗

PubMed1983

Absence of an effect of topical dexamethasone on endothelial permeability and flow of aqueous humor.

Twenty-four normal human subjects were studied before and after one week of treatment with 0.1% topical dexamethasone. Intraocular pressure, corneal thickness and endothelial cell size were measured. The flow of aqueous humor and the endothelial permeability to fluorescein were determined using fluorophotometry. In addition, the relationship between the initial location of an iontophoretic depot of fluorescein and its kinetics was studied. There was a small and significant increase in intraocular pressure in the eyes treated with dexamethasone but no significant change in corneal thickness, endothelial permeability or the rate of aqueous humor flow. The elimination of fluorescein from the eye was slightly higher when the fluorescein depot was placed adjacent to the superior limbus than when the depot was placed in the central cornea. Smaller right to left differences were observed when fluorescein was placed peripherally than when it was placed centrally. The increased precision with peripheral placement is probably due to the improved signal-to-noise ratio for fluorescence measurements of the anterior chamber through the unstained cornea.

Administration, Topical↗

PubMed2005

Ocular penetration of moxifloxacin 0.5% and gatifloxacin 0.3% ophthalmic solutions into the aqueous humor following topical administration prior to routine cataract surgery.

A prospective, double-masked, randomized, parallel-group study (n = 25) was conducted to examine the ocular penetration of moxifloxacin 0.5% ophthalmic solution and gatifloxacin 0.3% solution into the aqueous humor following topical administration prior to routine cataract surgery. One drop of antibiotic was instilled every 10 min for four doses beginning 1 h prior to surgery. Preliminary results showed aqueous humor concentrations for moxifloxacin that were significantly greater (p < 0.01) than those for gatifloxacin.

Administration, Topical↗

PubMed2002

Simultaneous determination of cloricromene and its active metabolite in rabbit aqueous humor by high-performance liquid chromatography.

A rapid and simple method was developed for the simultaneous separation and quantification of cloricromene, a coumarine derivative, and its active metabolite, cloricromene acid, in rabbit aqueous humor. The analyses were performed by high-performance liquid chromatography using a C18 reversed-phase column (Hypersil ODS) with UV detection at 318 nm. The mobile phase consisted of acetonitrile-water containing 1% triethylamine pH 3.5, adjusted with orthophosphoric acid. An acetonitrile gradient was necessary to achieve good separation within 13 min. Timolol was found to be a suitable internal standard. The retention times ranged from 5.72 to 11.25 min. A simple pre-treatment with acetonitrile containing 0.6% HCIO4 was used to deproteinize aqueous humor samples. The limit of quantitation ranged between 10 and 20 ng/ml. The recovery was >90%. The relationship between peak areas and concentration was linear over the range between 0.01 and 3.8 microg/ml, with r2 > 0.99. The assay provided good reproducibility and accuracy for both analytes and proved to be suitable for pharmacokinetic studies of cloricromene.

Animals↗

PubMed1988

Prolonged aqueous humor levels of subconjunctival antibiotics after treatment with acetazolamide and/or timolol.

Many ophthalmologists routinely administer subconjunctival antibiotics at the end of cataract surgery for prophylaxis against bacterial endophthalmitis. Additionally they use acetazolamide and/or timolol to control intraocular pressure in the first 24-hour postoperative period. An animal study was undertaken to learn whether treatment with the aqueous humor suppressants, acetazolamide, and timolol prolongs the concentrations of antibiotics in the aqueous humor after subconjunctival administration of the antibiotic. Treatment with acetazolamide significantly increased concentrations of piperacillin; it had less consistent effects on tobramycin levels. Timolol treatment did not produce increased piperacillin concentrations at six hours; however, concentrations at 12 and 24 hours were significantly higher than in the controls. Timolol treatment increased tobramycin concentrations only at six hours. The combined use of timolol and acetazolamide produced significantly higher concentrations of piperacillin, but not of tobramycin.

Acetazolamide↗

PubMed1994

Antimicrobial efficacy and aqueous humor concentration of preoperative and postoperative topical trimethoprim/polymyxin B sulfate versus tobramycin.

We compared trimethoprim sulfate 0.1%/polymyxin B sulfate 10,000 units/mL with tobramycin 0.3% for preoperative sterilization of the ocular surface, aqueous humor concentration, and ocular safety and comfort in 99 patients who had cataract extraction and intraocular lens implantation. The organisms most frequently cultured from the conjunctiva at baseline were Staphylococcus epidermidis, Corynebacterium species, and Staphylococcus aureus, which were isolated from 66%, 15%, and 8% of the 95 specimens eligible for evaluation. All organisms identified in positive baseline conjunctival cultures except Staphylococcus epidermidis were completely eradicated in both groups on the day of surgery and five to seven days postoperatively. Staphylococcus epidermidis was eradicated on the day of surgery in 58% of patients in the trimethoprim/polymyxin group and in 68% in the tobramycin group. This organism was eradicated five to seven days postoperatively in 85% of patients in both groups. Mean aqueous humor concentration of trimethoprim sulfate at surgery was greater than the mean tobramycin concentration, but neither reached clinically significant inhibitory levels for most organisms. No significant differences were found in ocular safety and comfort.

Adult↗

PubMed2002

Rapid high-performance liquid chromatographic assay of dorzolamide in rabbit aqueous humor.

A rapid high-performance liquid chromatographic method using a C(18) reversed-phase column (Hypersil ODS) with UV detection at 254 nm and a simple pre-treatment of samples is presented for the analysis of dorzolamide, a carbonic anhydrase inhibitor, in rabbit aqueous humor. A water solution containing 2% ZnSO(4) small middle dot7H(2)O was used to deproteinize aqueous humor samples. The mobile phase consisted of 7% CH(3)CN and 93% of a solution containing 1% TEA adjusted to pH = 3.5 with H(3)PO(4). Paracetamol was found to be a suitable internal standard. The standard curves were linear in the detection range. The precision and the accuracy were <5% for both intra- and inter-day assays.

Animals↗

PubMed1980

The aqueous humor dynamics and the biphasic response in intraocular pressure induced by guanethidine and adrenaline in the glaucomatous eye.

Continuous administration of guanethidine (3%) and adrenaline (0.5%) in one eyedrop (GA) induced a biphasic response of intraocular pressure (IOP). In ten patients with primary open angle and seven glaucoma suspects treated with (GA) twice daily during a 7 month period, tonography, and tonometry were performed and the pupil diameter measured 3 and 8 h post-GA. The combined data of both groups in the hypertensive phase, showed an IOP increase of 2.8 mm Hg (P < 0.05), an unchanged coefficient of the outflow, dilated pupil (1.73 mm) (P < 0.005) and a 36% increase of aqueous humor production (P < 0.02). The specific biphasic course of IOP during treatment with GA seems to be caused by fluctuations in aqueous humor production. The increase in aqueous rate during the hypertensive phase could be related to secondary (rebound) vasodilation in the ciliary body and/or to a transient disruption of the blood-aqueous barrier induced by release of prostaglandins.

Aqueous Humor↗

PubMed1998

Pharmacokinetics of topical beta-adrenergic antagonists in rabbit aqueous humor evaluated with the microdialysis method.

The microdialysis method was used to evaluate the pharmacokinetics of the beta-adrenergic antagonists carteolol and timolol and the new ophthalmic solution WP-934 in rabbit aqueous humor, following instillation. A probe with a microdialysis membrane (length, 5 mm; diameter, 0.2 mm) was implanted in the anterior chamber of the pigmented rabbit and perfused with Ringer's solution. Twenty microliters of 0.5% timolol maleate (0.5% Timoptol(R)), 2% carteolol hydrochloride (2% Mikelan(R)), or a novel preparation of 0.5% timolol maleate (WP-934) that gels after instillation were then instilled. The concentrations of these drugs in dialysates were measured using high-performance liquid chromatography and an electrochemical detection system. In vitro relative recovery of the membrane with timolol and carteolol was approximately 17.5% and 21. 6%, respectively. Timolol and carteolol levels in aqueous humor increased rapidly after instillation of Timoptol and Mikelan and reached maximal levels (Cmax) within 60 minutes. The Cmax of carteolol (4.25 microg ml-1) was lower than that of timolol (5.52 microg ml-1), suggesting that the corneal permeability of timolol is higher than that of carteolol. After instillation of WP-934, the Cmax of timolol (12.32 microg ml-1) was 2.2-fold higher than that after instillation of Timoptol. However, t1/2 values of beta-adrenergic antagonists after instillation of the three preparations were not significantly different. These data suggest that the microdialysis technique is useful for continuous monitoring of aqueous levels of beta-blockers and for analysis of their pharmacokinetic parameters while requiring much fewer animals than conventional sampling with paracentesis.

Administration, Topical↗