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Results for “Intraocular fluid”

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At least 541 records · Page 30Linked to original sources
PubMed1990

Flow dynamics of extrusion needle vacuuming in a closed vitrectomy system.

The dynamics of pressure, flow, and ocular volume relationships were examined with respect to extrusion needle use in simulated vitrectomy. Glass-stoppered bottles used with infusion lines with drip chambers lowered the intraocular pressure 4 to 7 inches below the fluid level in the bottle, varying with the amount of fluid in the bottle. Compared with flow rates using the regular tip needle with the steel infusion cannula, the disposable infusion cannula lowered the flow rate by about 25% and the tapered tip extrusion needle decreased outflow by 40% to 50%. Tracer dilution rates were decreased by the use of the disposable infusion port or the aphakic model eye; however, 2 minutes of infusion at a 30-inch bottle height dilution was still sufficient to wash out the tracer to less than 5% of the original concentration.

Humans↗
PubMed1980

Intraocular carbon dioxide laser photosurgery.

Intraocular carbon dioxide laser has been used for photocautery and photo-incision as an adjunct to vitrectomy. This utilizes a new fluid-tissue interface application for the 10.6 micrometer wavelength infrared radiation. The use of an intraocular probe with an infrared transmitting window through a pars plana incision allows the placement of infrared energy in a fluid medium. The results of animal experimentation and of preliminary clinical trials in human patients are reported. The carbon dioxide laser appears to be a safe and reliable means of intraocular photocautery and photoincision.

Animals↗
PubMed1990

Fluid movement across the blood-retinal barrier: a review of studies by vitreous fluorophotometry.

Vitreous fluorophotometry was used to study the fluid movement across the blood-retinal barrier. The effect of plasma osmolality and intraocular pressure on the movement of the fluorescent tracer confirmed the interaction between the tracers and the fluid flow across the blood-retinal barrier. The measurement of outward and inward permeabilities to carboxyfluorescein revealed the existence of a posteriorly directed fluid flow in the vitreous cavity of cynomolgus monkey eyes with retinal detachment. Fluid movement across the blood-retinal barrier was shown to be inhibited by furosemide and enhanced by acetazolamide. Furthermore, vitreous fluorophotometry proved to be useful in estimating the in vivo fluid dynamics in the vitreous and across the human retina.

Animals↗
PubMedDate not supplied

Ischemic hypertension of pigeon eye.

PURPOSE: To determine the etiology of open-angle glaucoma in human eyes, we tested the hypothesis that ischemia of the endothelial cells lining Schlemm's canal alters the intraocular pressure (IOP) by affecting the transport of fluids out of the eye. METHODS: Experiments were conducted on pigeons. After blocking the two major arteries to the aqueous sinus artery of one eye by laser photocoagulation, the episcleral arteries of both eyes were cauterized. The IOP was measured with a Mentor pneumatonometer before, immediately, and several days after blocking the major arteries. RESULTS: After the episcleral cauterization, the IOP of the laser-treated eye rose significantly and was maintained for at least 3 hours. By day 2, the IOP had recovered to the pre-cauterization level. The IOP of the control eye remained unchanged throughout the experiment. CONCLUSION: These results strongly support the hypothesis that ischemia of the endothelial cells lining Schlemm's canal plays a role in the control of the IOP.

Animals↗
PubMed1994

Hydration changes in cadaver eyes prepared for practice and experimental surgery.

OBJECTIVES: To identify reliable and efficient methods of thinning postmortem corneas for surgical experiments and to develop methods of maintaining stable corneal thickness. METHODS: Three methods of corneal thinning were evaluated by group: group A, increased intraocular pressure; group B, exchange of anterior chamber fluid with dextran solution and immersion in dextran solution; and group C, immersion in dextran solution without aqueous replacement. The stability of the thinned central cornea was then evaluated by exposing 30 corneas thinned by methods used in groups B and C to air, Balanced Salt Solution drops (Alcon, Fort Worth, Tex), or dextran solution drops. RESULTS: By 1 hour, the thinning method used in group A resulted in only three of 11 eyes achieving normal central corneal thickness. The method used in group B resulted in normal central thickness in 14 of 14 corneas and in group C, in nine of 15 corneas, at 1 hour. Once thinned by methods used in group B or C, air exposure further thinned the 30 additional corneas by 22% to 26%, Balanced Salt Solution drops thickened the corneas by 16% to 22%, and dextran solution drops stabilized the corneas with only 5% to 13% additional thinning. CONCLUSIONS: Hyperosmolar solutions were more efficient than pressure gradients in thinning the cadaver central cornea. Hydration shifts of the de-epithelialized cornea were dramatic with use of Balanced Salt Solution drops or drying and were minimized with use of hyperosmolar topical solutions.

Aged↗
PubMed2004

Prolactin in eyes of patients with retinopathy of prematurity: implications for vascular regression.

PURPOSE: Disruption of the anti-angiogenic environment of the retina leads to neovascular eye diseases, including retinopathy of prematurity (ROP). Prolactin (PRL), the hormone originally associated with milk secretion, is proteolytically processed to 16K-PRL, a fragment with potent antiangiogenic, proapoptotic effects. Whether 16K-PRL is produced in eyes of patients with ROP and promotes the regression of intraocular blood vessels associated with this disease was investigated. METHODS: PRL was quantified in the aqueous humor, subretinal fluid, and serum from patients with stage 5 ROP and in patients with non-neovascular eye disorders. Intraocular expression of PRL was evaluated by RT-PCR, in situ hybridization, and Western blot analysis. AntiPRL antibodies were injected intravitreously in neonatal rats, and apoptosis of hyaloid vessels determined by TUNEL and ELISA. RESULTS: PRL was elevated in ocular fluids and serum from ROP patients. There was no correlation between PRL in ocular fluids and its level in serum, whereas PRL in aqueous humor and subretinal fluid were significantly correlated. PRL mRNA was expressed in blood vessels and leukocytes within retrolental fibrovascular membranes of ROP patients, and these membranes contained a 16 kDa immunoreactive PRL. The 16K-PRL isoform was more concentrated in subretinal fluid than in serum and was generated from PRL by subretinal fluid proteases. Intravitreous injection of neutralizing antiPRL antibodies inhibited the apoptosis of hyaloid vessels in neonatal rats. CONCLUSIONS: 16K-PRL derived from PRL internalized from the circulation or synthesized intraocularly can stimulate apoptosis-induced vascular regression and contribute to the development and progression of ROP.

Animals↗
PubMed1990

[Examinations by ocular pressure tonometry].

A new method has recently been suggested for the determination of the outflow resistance in the anterior chamber angle. In this method the intraocular pressure is set to 45 mmHg for 8 minutes. The intraocular pressure is measured after the removal of the suction cup. Values below 7 mmHg are obtained in healthy subjects. Values above 7 mmHg are thought to be indicative for glaucoma. By setting the intraocular pressure to 45 mmHg for the expression of fluid the authors claim to have brought normalization to tonography. We show here in a series of results that we can reproduce the results which have been published by Ulrich et al. For normalization of a tonographic test we need a pressure rise which effects a uniform expression of volume. According to the knowledge presently generally agreed upon a uniform expression of volume is obtained by increasing the intraocular pressure by a constant factor and not by increasing it to a constant level. In 30 healthy volunteers and in 30 glaucoma patients we have increased the intraocular pressure by the constant factor of 1.8. According to our results the glaucoma patients and the healthy subjects can no longer be differentiated. A better differentiation is possible by the initial intraocular pressure. Thus we have shown that the favorable results by ocular pressure tonometry are mainly due to the intraocular pressure before the test. We feel therefore that ocular pressure tonometry should not be incorporated in our diagnostic armamentarium for glaucoma diagnosis.

Diagnosis, Differential↗
PubMed1990

Somatostatin analogue and tissue cultures in the study of a human malignant glucagonoma.

A patient with metastasizing glucagonoma producing multiple molecular forms of glucagon is reported. The patient responded to symptomatic treatment with a somatostatin analogue (SMS 201-995). Glucagonoma tumour cells were studied in two tissue culture systems: intraocular transplants of immunosuppressed rats and long-term cell cultures. In both systems, several region-specific glucagon antisera gave a positive immunoreaction with tumour cells indicating synthesis of multiple molecular species. Intraocular tumour transplants released glucagon into the chamber fluid. In animals with unilateral transplants, glucagon was also detected in the contralateral eye chamber, indicating passage from the transplants via unknown mechanisms. Treatment of tumour cells during culture with SMS 201-995 inhibited rapidly the spontaneous release of glucagon without evident cytotoxic effects. The inhibitory effect decreased with time.

Adenoma, Islet Cell↗
PubMed1978

Central serous choroidopathy with bullous retinal detachment.

We report here a new type of secondary retinal detachment that has never been clearly defined. The characteristic features of the disease are: (1) prevalence in middle-aged males, (2) bilateral involvement, (3) frequent existence of prodromal lesions that over long periods resemble central serous retinopathy, (4) in the evolution stage, appearance of multiple yellowish white exudative flecks of one-half to one disc in diameter at or near the posterior pole of the fundus, (5) fluorescein studies revealing pronounced leakage of dye from the choroid into the subretinal space at the sites of exudates, (6) retinal detachment of various degrees with shifting subretinal fluid and without tears, (7) no evidence of intraocular inflammation, (8) no filling abnormalities seen in the choroidal fluorescence, (9) no response to medical therapy, including steroids and antibiotics, (10) photocoagulation to leakage sites leading to rapid resolution of retinal detachment; otherwise, spontaneous healing of detachment occurring within about 7-9 months, leaving fibroblastic macular scars and marked visual loss, and (11) no evidence of systemic findings that may be of etiologic significance. From this characteristic clinical picture, the idea of a new clinical entity must be considered. Our findings in 35 eyes from 18 Japanese patients are discussed.

Adult↗
PubMedDate not supplied

Anterior chamber collapse following vitreoretinal surgery with gas tamponade in aphakic eyes: incidence and risk factors.

PURPOSE: To report the risk factors associated with occurrence of anterior chamber collapse in aphakic eyes that underwent vitrectomy with gas tamponade. METHODS: A total of 314 eyes of 314 patients who underwent vitrectomy with gas tamponade and who were aphakic or were made aphakic intraoperatively were studied prospectively. Factors such as iris and pupillary integrity, depth of anterior chamber, gonioscopic grading, behavior of the anterior chamber on the operation table during fluid-air exchange, removal of crystalline lens or intraocular lens during surgery, and type of internal tamponade were noted. The anterior chamber was assessed postoperatively in supine and sitting position and with head bent forward. Statistical methods were used to identify risk factors for development of postoperative anterior chamber collapse using SPSS soft ware. RESULTS: Anterior chamber collapse occurred in 13 eyes (3.14%). Presence of preoperative shallow anterior chamber, removal of intraocular lens as a part of the procedure, occurrence of intraoperative anterior chamber collapse, and use of sulfur hexafluoride (SF6) were associated with higher risk of anterior chamber collapse postoperatively. CONCLUSIONS: The identification of potential risk factors in a given eye can alert the surgeon to the possibility of development of anterior chamber collapse postoperatively.

Adolescent↗
PubMed1960

Automatic tonometer with exact theory: various biological applications.

Methods for externally measuring pressure within body cavities exist. In tonometer form they are fast and gentle not requiring anesthetics for the cornea of the human eye. Readings are accurate and independent of tissue tension, corneal stiffness, astigmatic curvatures, and surface tension. There are also separate indications of corneal rigidity and relaxation, and tonographic fluid expression. Other applications include monitoring blood pressure, uterine contractions, and infant intracranial pressure.

Body Fluids↗
PubMed1989

Useful adjuncts for vitreoretinal surgery.

Many vitreoretinal procedures are performed in offices and hospitals where cost control is important. We describe three useful devices and techniques that facilitate these procedures at minimal expense and often greater convenience. These include an accurate method for localising the pars plana without the use of callipers, an inexpensive, reliable, pressure regulated air pump for fluid-air exchange, and an easy method for intraocular injection of silicone oil through 20 gauge instrumentation without the need for expensive pumps. These procedures and techniques should prove to be useful in the treatment of vitreoretinal disease.

Air Pressure↗