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PubMed1991

Radio-isotopic determination of hydrogen peroxide in aqueous humor and urine.

The concentrations of hydrogen peroxide in the aqueous humor and urine of several animal species and humans have been determined. The determinations are based on peroxide-dependent decarboxylation of I-[14C]-alpha-ketoglutaric acid and measurement of the resulting 14CO2 by quantitating the radioactive disintegration. The levels of H2O2 in most animals varied between 5.0 and 41 microM for aqueous, and 115 and 187 microM for urine. The levels of peroxide in the urine of steer, cat and baboon were lower and fell out of the above range. In the aqueous of humans with cataracts, the levels ranged from 33 to 324 microM, the overall average being 189 +/- 88 microM. The source of such high levels in the aqueous of cataract patients is currently being studied.

Aged↗
PubMed1986

Isolation of the human T-cell leukemia/lymphotropic virus type III from aqueous humor in two patients with perivasculitis of the retinal vessels.

The human T-cell leukemia/lymphotropic virus type III (HTLV-III) has been isolated from aqueous humor in two patients with perivasculitis of the peripheral retinal vessels, an AIDS-related ocular manifestation. Both patients had antibodies to HTLV-III and although they presented with herpes zoster ophthalmicus, they did not present other symptoms known to be associated with HTLV-III infection. The isolation of HTLV-III from aqueous humor in these two patients with retinal perivasculitis suggests that the virus itself may play a role in the etiology of this ocular sign. The presence of infectious HTLV-III in the anterior chamber further emphasises the necessity to discard corneas from HTLV-III infected donors.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Measurement of aqueous humor flow by fluorophotometry in the presence of a dilated pupil.

PURPOSE: To determine by means of fluorophotometry whether pharmacologic dilation of the pupil can interfere with the measurement of aqueous flow. METHODS: Ten normal human volunteers underwent dilation with tropicamide, phenylephrine, and a combination of the two drugs. Before and after dilation, the rate of aqueous flow was measured by the rate of disappearance of fluorescein from the cornea and the anterior chamber. RESULTS: Dilation of the pupil with tropicamide alone had no effect on the rate of clearance of fluorescein. Dilation with phenylephrine increased the rate of clearance of fluorescein by 40% and caused a small increase in the variability among subjects. Dilation with a combination of tropicamide and phenylephrine caused clearance of fluorescein at more than double the normal rate and a marked increase in variability among subjects. CONCLUSIONS: When the pupil is dilated sufficiently to permit mixing of aqueous humor in the posterior and anterior chambers, fluorescein can leave the system by a posterior route, and its rate of clearance may not be an accurate measure of the net rate of aqueous humor flow through the anterior chamber.

Adult↗
PubMed1999

Aqueous humor dynamics in anesthetized rats infused with intracameral apraclonidine.

We studied the acute effects of the ocular hypotensive drug, apraclonidine (AP), on intraocular pressure (IOP) and aqueous humor dynamics of anesthetized rats during infusion-induced ocular hypertension. Two infusions were made into the anterior chamber of the eye: one was constant at a rate of 0.05 microl/min, the other was cyclic, at a rate of 0.25 microl/min, with the pump on for 4 min, then off for 4 min. Data were processed by complex demodulation and analysis of a second-order transfer function. This permitted separate calculations of resistive components (Ao), i.e., trabecular meshwork and uveoscleral outflows, and residual pressure (RP) estimating nonresistive components, i.e., aqueous synthesis and episcleral venous pressure. A balanced salt solution (BSS) and AP (0. 0005%) were tested. AP markedly delayed the within-group rise in IOP: 20 min for BSS vs. 60 min for AP (p < 0.001). IOP of AP rats was less than control for 100 min (p < 0.05). The infusions raised Ao in both groups (p < 0.05). AP initially had a transient inhibitory effect (p < 0.05). Infusions raised RP in both groups. AP had a strong inhibitory effect for the first 8 cycles (p < 0.05). These data document that the acute effects of AP in this in vivo rat model of ocular hypertension were to delay increases in IOP, mainly by reducing nonresistive components of aqueous humor dynamics. Transient inhibition of resistive mechanisms also occurred.

Adrenergic alpha-Agonists↗
PubMed1994

The effect of the water-drinking test on aqueous humor dynamics in healthy volunteers.

In 19 healthy volunteers (9 men, 10 women) we studied the effect of drinking 1000 ml of water within 10 min on aqueous humor dynamics. Fluorescein was applied topically five times, 6 h before measurements. All readings were taken during the afternoon. The Wilcox-on signed-rank test was used to evaluate the statistical relevance of the data. Aqueous humor flow was measured 60 min before (F1) and 10 min (F2), 30 min (F3), 60 min (F4) and 90 min (F5) after drinking 11 of water. Flow (mean +/- SD) changed as follows: F1, 2.25 +/- 1.2 microliters/min; F2, -3.29 +/- 3.4 microliters/min (P < 0.0000); F3, 1.69 +/- 1.0 microliters/min (P = 0.007); F4, 2.39 +/- 0.9 microliters/min (P = 0.25); F5, 2.64 +/- 0.9 microliters/min (P = 0.02). Three to four days later the identical procedure was performed in each individual: F1, 2.06 +/- 1.0 microliters/min; F2, -3.12 +/- 2.4 microliters/min (P < 0.0000); F3, 1.09 +/- 0.6 microliters/min (P < 0.0001); F4, 1.76 +/- 0.6 microliters/min (P = 0.15); F5, 2.54 +/- 0.8 microliters/min (P = 0.01). The correlation coefficient for the left and night eyes (F1-F5, both days) was r = 0.85. The mean flow in the 19 healthy volunteers during the afternoon hours was 2.25 +/- 1.0 microliters/min. Water load consistently led to a reflux of unbound fluorescein into the eye about 10 min later. This is documented as a negative flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2001

Penetration of topical fluconazole into human aqueous humor.

The purpose of this study was to determine the aqueous levels and pharmacokinetics of topical fluconazole 0.2% upon single and multiple drop applications. Forty-nine patients undergoing cataract surgery were given topical fluconazole 0.2%. They either received single drop or a loading dose of 1 drop per 5 min for 20 min. Aqueous samples were obtained during surgery 5, 15, 30, 45 and 60 min after the last drop. The samples were analysed by high-pressure liquid chromatography to determine aqueous concentrations. After single and loading dose applications peak aqueous levels were achieved at 15 min (3.35 +/- 0.64 and 7.13 +/- 0.79 microg ml(-1), respectively). Both had a steady decrease in concentration at 30, 45 and 60 min down to 4.06 +/- 0.37 microg ml(-1)with loading dose and undetectable levels with single dose application. Comparing the concentrations with the minimum inhibitory concentrations (MIC) of yeasts determined by the National Committee for Clinical Laboratory Standards showed that concentrations achieved with single dose applications were higher than MICs of Candida albicans and Candida parapsilosis and concentrations achieved after loading dose applications were higher than MICs of C. parapsilosis, C. albicans and Candida tropicalis. We concluded that topical fluconazole 0.2% penetrates into the aqueous humor in concentrations that satisfy MICs of most of the Candida strains. It can be a good alternative to Amphotericin B for treatment of Candida keratitis.

Administration, Topical↗
PubMed1983

Azlocillin concentrations in human aqueous humor after intravenous and subconjunctival administration.

Twenty-nine patients received either 4 g intravenous infusion or 100 mg subconjunctival application of azlocillin 1-12 h before cataract extraction. After intravenous application the mean aqueous humor concentration of azlocillin was 4.4 micrograms/ml after 3 h. The subconjunctival dose produced a mean aqueous humor concentration of 78 micrograms/ml and 3.4 micrograms/ml after 3 and 12 h, respectively. These levels are above the minimum inhibitory concentration of azlocillin for sensitive organisms.

Aqueous Humor↗
PubMed1988

The effect of YAG laser anterior capsulotomy on prostaglandin concentration in aqueous humor.

The YAG (yttrium aluminum garnet) laser has been recommended for anterior capsulotomies. One major complication is elevated intraocular pressure. We report a study of the biochemical content of the aqueous humor after a YAG laser anterior capsulotomy. We analyzed 6-keto-prostaglandin F1 alpha, thromboxane B2 and protein concentrations in the aqueous humor of human eyes. The average values of protein, 6-keto-prostaglandin F1 alpha, and thromboxane B2 in the control eyes were 81.3 +/- 14.0 mg/dL, 17 +/- 30 pg/mL, and 10 +/- 10 pg/mL, respectively. These values were elevated to 182.4 +/- 81.3 mg/dL, 401 +/- 55 pg/mL, and 576 +/- 148 pg/mL, respectively, after YAG laser anterior capsulotomy. The samples with a moderate level of 6-keto-prostaglandin F1 alpha (less than 300 pg/mL) had negligible changes of thromboxane. The elevation of thromboxane was obvious only when prostaglandin levels rose above 300 pg/mL.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Atriopeptin lowers aqueous humor formation and intraocular pressure and elevates ciliary cyclic GMP but lacks uveal vascular effects in the bovine perfused eye.

The effects of atriopeptin (AP) on intraocular pressure (IOP), aqueous humor formation (AHF) and ciliary cyclic GMP in bovine eyes perfused in vitro through a ciliary artery were investigated. AHF was monitored fluorophotometrically by perfusing the anterior chamber with Bárány's mock aqueous humor containing fluorescein. To study the effect of AP on cyclic GMP synthesis, eyes were injected with an intra-arterial bolus of AP prior to dissection of the ciliary processes. For comparison, individual ciliary processes, or isolated ciliary epithelial cells were incubated with AP. Cyclic GMP was extracted by homogenization, aqueous partition and column chromatography, and measured by radioimmunoassay (RIA). Decreases in IOP or AHF were seen approximately 15 min after the injection of AP and persisted throughout a 60-80 min perfusion. Arterial perfusion pressure was not significantly altered by AP, even when vascular tone was raised by adding noradrenaline to the perfusate. In whole eyes, ciliary cyclic GMP increased in response to AP. Cyclic GMP in isolated ciliary processes, or cultured ciliary epithelial cells incubated with AP also increased. We conclude that the decrease in IOP in the bovine eye by AP is due to a reduction in AHF, which is independent of any vascular effect. Ciliary cyclic GMP may be the intracellular mediator involved.

Adrenergic alpha-Agonists↗
PubMed1980

[Zinc concentration in the aqueous humor (author's transl)].

The zinc concentration in normal human aqueous humor was determined with the help of an atomic absorption spectrophotometer. The mean value was 0.359 ppm with a scatter range of 0.27 to 0.44 ppm. The spectrophotometer permits simultaneous determination of two metals, in this case zinc and copper. It was possible to demonstrate an interaction of the two metals.

Aqueous Humor↗
PubMed1996

Neuropeptide Y levels in the aqueous humor of rabbits.

The concentration of neuropeptide Y in the aqueous humor (NPYaq) did not change during the circadian cycle in rabbits. However, NPYaq also did not decrease after superior cervical ganglionectomy or preganglionic section of the cervical sympathetic trunk (decentralization). Nor did NPYaq change after either stimulation, with para-aminoclonidine, or blockade, with rauwolscine, of prejunctional ocular alpha2-adrenergic receptors. Therefore, NPYaq does not reflect NPY release from ocular sympathetic nerves in rabbits.

Adrenergic alpha-Agonists↗
PubMed1984

Biochemical studies on the use of sodium hyaluronate in the anterior eye segment. I. Variation of protein and ascorbic acid concentration in rabbit aqueous humor.

To investigate the safety of the use of sodium hyaluronate in anterior segment surgery, the changes in protein, ascorbic acid and hyaluronate concentration in the aqueous humor, and intraocular pressure were followed after sodium hyaluronate was injected into the anterior chamber. When a 1% solution of sodium hyaluronate with a molecular weight of 800K was injected, the recovery patterns of protein and ascorbic acid concentration to normal levels were the same as the recovery patterns after injection of phosphate buffered saline which was the solvent for sodium hyaluronate. However, when a 1% solution of sodium hyaluronate with a molecular weight of 1640K or a 2% solution with a molecular weight of 800K was injected, it was observed that the recovery times of protein and ascorbic acid concentration to normal levels were longer than that required after injection of 1%, 800K sodium hyaluronate. Further, the recovery time of the aqueous humor components to normal levels was associated with the clearance time of sodium hyaluronate from the anterior chamber. The transient increase in intraocular pressure by injection of sodium hyaluronate was observed, but it disappeared in 12 hrs. The recovery time of intraocular pressure to normal level was independent of molecular weight and concentration of sodium hyaluronate tested.

Animals↗
PubMed1989

A study of the relation between intraocular pressure and aqueous humor flow in the pigment dispersion syndrome.

Forty subjects with pigment dispersion syndrome with and without intraocular pressure (IOP) elevation were compared with 40 age-matched controls. Intraocular pressure, resistance to outflow, and the rate of flow of aqueous humor were compared. Eyes with higher IOP and higher resistance to outflow were found to have a normal rate of aqueous flow. The results are interpreted as demonstrating that moderate and chronic elevation of IOP in the adult human eye does not induce a chronic compensatory reduction of aqueous humor flow.

Adult↗
PubMed1985

Ceftriaxone. A new cephalosporin with aqueous humor levels effective against enterobacteriaceae.

One- or two-gram doses of ceftriaxone were administered intravenously to 30 patients before cataract extraction. With the 1-g dose, mean aqueous humor concentrations of 0.93 and 0.88 microgram/mL were found at approximately 2 and 12 hours after administration, respectively. With the 2-g dose, a mean level of 2.47 micrograms/mL was observed at two hours; levels of more than 2 micrograms/mL were found in two patients 13 hours after administration. Both the 1- and 2-g doses thus produce aqueous humor levels many times higher than the minimum inhibitory concentration of ceftriaxone for 90% of most Enterobacteriaceae, excluding Pseudomonas. Concentrations adequate for Staphylococcus aureus and Staphylococcus epidermidis were not, however, obtained.

Adult↗
PubMed2001

Modeling passive mechanical interaction between aqueous humor and iris.

Certain forms of glaucoma are associated with displacement of the iris from its normal contour. We present here a mathematical model of the coupled aqueous humor-iris system that accountsfor the contribution of aqueous humor flow and passive iris deformability to the iris contour. The aqueous humor is modeled as a Newtonian fluid, and the iris is modeled as a linear elastic solid. The resulting coupled equation set is solved by the finite element method with mesh motion in response to iris displacement accomplished by tracking a pseudo-solid overlying the aqueous humor. The model is used to predict the iris contour in healthy and diseased eyes. The results compare favorably with clinical observations, supporting the hypothesis that passive iris deformation can produce the iris contours observed using ultrasound biomicroscopy.

Aqueous Humor↗
PubMed1982

Penetration of intravenous moxalactam into human aqueous humor.

Intraocular penetration of moxalactam disodium, a new broad-spectrum oxa-beta-lactam antibiotic, was studied in 18 patients undergoing cataract surgery. The antibiotic was administered in a 2-g single dose by intravenous drip during a 20-minute period. After 40 to 230 minutes, moxalactam aqueous humor concentrations ranged from 1.1 to 5.0 micrograms/mL (mean, 2.3 micrograms/mL). The ratio of aqueous humor concentrations to concomitant serum concentrations ranged from 1.6% to 9.8%. The achievable aqueous moxalactam concentrations were well above the minimum inhibitory concentrations of most Gram-negative enteric bacilli but not of Pseudomonas and staphylococci.

Aged↗