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PubMed1995

Corneal endothelial permeability and aqueous humor flow using a standard protocol.

BACKGROUND: The study was carried out to compare corneal endothelial permeability and aqueous flow values of healthy volunteers measured in different countries with identical fluorophotometers using a standardized protocol. METHOD: Healthy volunteers aged between 20 and 70 years were studied in five European cities. Fluorescence scans of the anterior segment of both eyes were made using a commercial fluorophotometer. Beginning 4 h after instillation of four drops of fluorescein 10%, 12 scans of the anterior segment of each eye were performed in 2 h. The values of corneal endothelial permeability and aqueous flow were calculated with standardized software from the decay of the fluorescein concentration in the cornea and anterior chamber. RESULTS: The mean permeability values (x 10(-4) cm.min-1) +/- SD were 3.7 +/- 1.6 (n = 19; Coimbra, Portugal), 4.3 +/- 1.1 (n = 19; Frankfurt, Germany), 3.9 +/- 0.9 (n = 19; Leiden, The Netherlands) and 5.4 +/- 1.2 (n = 10; Milan, Italy). The values were not significantly different (ANOVA, P > 0.3), except those in Milan. The mean flow values (microliters.min-1) +/- SD were 2.3 +/- 0.9 (n = 17; Coimbra), 1.9 +/- 0.7 (n = 10; Cologne, Germany), 2.6 +/- 1.2 (n = 19; Frankfurt), 2.0 +/- 0.6 (n = 19; Leiden) and 1.7 +/- 0.8 (n = 10; Milan). The values were not significantly different (Kruskal-Wallis test, P > 0.1). CONCLUSIONS: Permeability and flow values in the different cities had similar values and standard deviations. The Concerted Action demonstrated the usefulness of a standardized protocol.

Adult↗
PubMed1985

Studies on equine recurrent uveitis. I: Levels of immunoglobulin and albumin in the aqueous humor of horses with and without intraocular disease.

A radioimmunoassay was developed for detection of immunoglobulin in the aqueous of normal horses and horses with intraocular diseases. Levels of albumin were detected by radial immunodiffusion. Results of assays on samples from normal eyes from which aqueous was obtained by paracentesis under anesthesia were 32.10 +/- 21.50 microgram/ml for IgG, 0.05 +/- 0.01 microgram/ml for IgM, 0.04 +/- 0.02 microgram/ml for IgA and 34.0 +/- 38.0 microgram/ml for albumin. Results in 138 normal eyes sampled post mortem were 41.56 +/- 38.65 microgram/ml for IgG, 0.18 +/- 0.43 microgram/ml for IgM, 0.46 +/- 1.45 microgram/ml for IgE and 184 +/- 240 microgram/ml for albumin. Levels in abnormal eyes were some 50-120% greater, and very high levels were noted in cases of clinically documented uveitis. The aqueous to serum ratio of the proteins measured generally varied in relation to the molecular weights and was increased in diseased eyes. The ratio of IgG/albumin in the diseased eyes was less which suggested leakage of protein from an impaired blood/aqueous barrier rather than intraocular antibody synthesis.

Albumins↗
PubMed1991

Flow of aqueous humor in humans [The Friedenwald Lecture].

Based on clinical experiments with fluorophotometry, several observations can be made about aqueous flow through the chambers of the human eye. 1. The rate of flow is 2.75 +/- 0.63 microliters/min in normal subjects, as derived from measurements averaged during normal office hours. The normal range (95%) is 1.8 to 4.3 microliters/min. 2. There is a circadian rhythm of flow, with the highest rates during morning hours, slightly lower rates during afternoon hours, and rates during sleep that are approximately one half of those during the morning. The hormonal basis for this rhythm is unknown, but it is known to be present in both eyes of persons with unilateral Horner's syndrome. 3. A slight decline of the rate occurs after age 10 yr--3.2% per decade. There is no significant difference in aqueous flow between men and women. 4. Of the hundreds of drugs that are used clinically, most are unlikely to have a significant effect on aqueous flow. Exceptions are the beta-adrenergic agonists that, under certain circumstances, are able to increase flow, the corticosteroids that may have a stimulating effect on flow, and three classes of drugs that have therapeutically useful suppressing effects on flow: carbonic-anhydrase inhibitors, beta-adrenergic antagonists, and alpha 2-selective adrenergic agonists. 5. Timolol, which has a remarkably consistent suppressing effect on flow during the day, has no effect on the flow of sleeping subjects. By contrast, acetazolamide and apraclonidine are able to reduce the flow of sleeping subjects. 6. Acute doses of beta-adrenergic antagonists and alpha 2-agonists are not additive, but beta-adrenergic antagonists and carbonic-anhydrase inhibitors are partly additive. 7. The eye adapts partly to the chronic use of timolol and recovers from its effects when it is discontinued. 8. The rate of disappearance of the effect of beta-adrenergic antagonists is longer for the noncardioselective agents, such as timolol and levobunolol, but is relatively short for the cardioselective agent, betaxolol. 9. The rate of aqueous flow is insensitive to moderate changes of intraocular pressure. Clinical studies can provide suggestive leads for more basic investigations or test specific hypotheses. Biochemical, biologic, and pharmacologic approaches in simpler, more controlled experimental conditions are necessary to determine the fundamental processes that bring about aqueous formation in the living eye. The combination of many disciplines (eg, studying molecules, cells, tissues, organs, and the intact living system) has the best chance of furthering our understanding of the aqueous circulation.

Animals↗
PubMed1987

[Diffusion of fluoroquinolones in the aqueous humor and crystalline lens].

In 53 patients undergoing cataract extraction, the authors measured pefloxacin and ofloxacin penetration in aqueous humour and lens. Cataract removal was performed at varying times after either the end of one-hour infusion of pefloxacin, ofloxacin per os in one time, or pefloxacin per os during 3 days. In the two first schemes, acme concentrations in aqueous humour are 1.45 mg/l for pefloxacin, 1.14 mg/l for ofloxacin. These concentrations reach the MIC90 of most bacteria usually involved in endophthalmia. The steady state concentrations of pefloxacin are between 6 and 7 mg/l during the first 12 h: they reach the MIC of 80% of Streptococci. There is no evidence of accumulation of pefloxacin in lens; lenticular concentrations of ofloxacin are very low and rapidly decrease.

Administration, Oral↗