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At least 361 records · Page 20Linked to original sources
PubMed1995

The influence of cerebrospinal fluid pressure on the lamina cribrosa tissue pressure gradient.

PURPOSE: To measure the tissue pressure gradient through the optic disk and to determine the relationship between intraocular, cerebrospinal fluid, and retrolaminar tissue pressures. The relationship of optic nerve subarachnoid space pressure to intracranial cerebrospinal fluid pressure also was explored. METHODS: Micropipettes coupled to a pressure transducer were passed through pars plana and vitreous to enter the optic disk in the anesthetized dog. Using a micromanipulator, pipettes penetrated the optic disk in steps while pressure measurements were taken. In some animals, pipettes also were passed into the optic nerve subarachnoid space. Lateral ventricle cerebrospinal fluid pressure, intraocular pressure, and arterial blood pressure were measured concurrently, and the effect of raising CSF pressure was explored. RESULTS: Retrolaminar tissue pressure was largely dependent on the surrounding cerebrospinal fluid pressure, which was on average 8.6 +/- 3.5 mm Hg (SD, n = 8) higher, and was independent of intraocular pressure. Most (85% +/- 15% [SD, n = 8]) of the pressure drop between intraocular pressure and retrolaminar pressure occurred across the anterior 400 microns of disk tissue. When the intraocular pressure was 21 mm Hg and the cerebrospinal fluid pressure was zero, retrolaminar tissue pressure averaged 7 mm Hg and the translaminar pressure gradient was 3.08 +/- 0.29 mm Hg/100 microns tissue (SD, n = 3). Optic nerve subarachnoid space pressure was equivalent to lateral ventricular pressure. CONCLUSIONS: These results show that cerebrospinal fluid pressure largely determines retrolaminar tissue pressure; hence, along with intraocular pressure, it is of major importance in setting the translaminar tissue pressure gradient. Results also demonstrate hydrostatic continuity between the optic nerve subarachnoid space and the lateral ventricle. That the translaminar pressure gradient can vary independently of intraocular pressure may be of importance in understanding the pathophysiology of glaucoma.

Animals↗
PubMed2000

Vitreoretinal surgery through multifocal intraocular lenses compared with monofocal intraocular lenses in fluid-filled and air-filled rabbit eyes.

PURPOSE: To compare vitrectomy procedures and visualization of posterior segment structures through multifocal silicone intraocular lenses (IOLs) with the same procedures through monofocal silicone IOLs in rabbit eyes. DESIGN: Experimental study. PARTICIPANTS: Twelve eyes of six rabbits. METHODS: Each rabbit eye underwent phacoemulsification of the lens and posterior chamber implantation of a silicone multifocal or silicone monofocal IOL. The type of IOL (monofocal vs. multifocal) implanted in the first eye of each rabbit was randomly decided. The fellow eye then received the other IOL type. Vitrectomy procedures were performed through the IOLs by using a flat contact lens (part 1) or wide-angled contact lens (part 2) for visualization through fluid-filled (parts 1 and 2) and air-filled (part 2) eyes. MAIN OUTCOME MEASURES: Image quality, stereopsis, and contrast were subjectively graded on a scale of 0 (none) to 4 (excellent) for each eye by each surgeon. RESULTS: In part 1, image quality averaged 4 for the monofocal IOL and 3.6 for the multifocal IOL. Stereopsis averaged 4 for the monofocal IOL and 4 for the multifocal IOL. Contrast averaged 4 for the monofocal IOL and 3.9 for the multifocal IOL. Vitrectomy with retinal surface maneuvers was successfully performed in both pigmented and nonpigmented rabbit eyes through both IOL types. In part 2, image quality, stereopsis, and contrast were rated as 4 for both multifocal and monofocal silicone IOLs. Air-fluid exchange was performed without difficulty. Image quality, stereopsis, and contrast were rated as 4 for air-filled eyes. CONCLUSIONS: Visualization of posterior segment structures through multifocal silicone IOLs was sufficient for retinal surface maneuvers during vitrectomy procedures in both fluid-filled and air-filled rabbit eyes.

Air↗
PubMed1988

Detection and quantification of S-100 protein in ocular tissues and fluids from patients with intraocular melanoma.

S-100 protein is a 21,000 dalton acidic calcium-binding protein present in ocular melanomas and some normal ocular tissues. Ocular fluids and extracts of ocular tumours were examined by a sensitive radioimmunoassay that could detect less than 5 ng of S-100 protein in minute volumes of fluid. Three ocular melanoma biopsy specimens had S-100 protein at levels between 25 and 1300 ng/ml, comparable to that found in a cutaneous melanoma biopsy specimen (1000 ng/ml). (SI conversion: ng/ml = microgram/l.) Six melanoma culture lines had 1000 to 125,000 ng/ml. Four lymphoblastoid cultures had less than 2 ng/ml, and three colon carcinoma cultures had 180 ng/ml. Subretinal fluid from 23 melanoma-containing eyes had 10 to 76,800 ng/ml. Lesser amounts were found in eyes with small, anteriorly located, lightly pigmented tumours. Vitreous from 3 melanoma-containing eyes had 10,000 to 11,000 ng/ml. Vitreous obtained from three eyes during tractional retinal detachment repair had 500 to 1600 ng/ml, and vitreous obtained at necropsy from six normal eyes had 2 to 120 ng/ml. Aqueous from six melanoma-containing eyes had 10 to 30 ng/ml, levels not significantly different from those observed in three normal eyes (80-120 ng/ml). This approach provides new insight into the interaction of ocular tumours and adjacent ocular fluids and may, with more specific tumour markers, have diagnostic applications.

Aqueous Humor↗
PubMed2005

Intraocular humidity immediately after fluid-air exchange in pars plana vitrectomy.

PURPOSE: To study vitreous cavity humidity during fluid-air exchange in pars plana vitrectomy. METHODS: Intraocular humidity in the vitreous cavity was recorded for 2 min in six artificial eyes, six enucleated pig eyes, and ten patient eyes, after the eyes had been filled with either humidified air (75% humidity) or dry air (8% humidity). RESULTS: In artificial eyes the humidity levelled off at a value that was approximately equal to the humidity of the infused air, i.e., a mean of 71.9% when humidified air was used and a mean of 14.4% when dry air was used. In enucleated pig eyes humidity increased slightly with humidified air and remained stable with dry air. In patients intraocular humidity increased to over 90%, regardless of whether humidified or dry air was used. CONCLUSION: In the living eye, dry air deprives the retinal tissue of humidity, which is lost into the vitreous cavity. This effect can be reduced by using humidified air.

Acetates↗
PubMed1980

Intraocular irrigating and replacement fluid.

The transparency of the rabbit cornea is regulated by an toward directed bicarbonate ion pump located in the corneal endothelium. The activity of the pump may be measured directly by measuring the electrical phenomena associated with it (current, potential, tissue resistance) or indirectly with a pachymeter or specular microscope with which one may measure fluid flows into or out of the stroma. Both methods give the same results. In human corneas we find that specular microscopy can give unreliable results (the scleral clamping phenomenon) but electrical investigations of endothelial inability are reliable and very similar in magnitude to those found in the rabbit. We have investigated the effects ov various aqeuous media on the human corneal endothelium, measuring viability with our experimental set-up, and have developed one which seems to cause no trauma to these clinically important cells.

Animals↗
PubMed1997

Management of condensation on a foldable acrylic intraocular lens after vitrectomy and fluid-air exchange.

PURPOSE: To describe the management of condensation on the posterior surface of a foldable acrylic intraocular lens during vitrectomy and fluid-air exchange. METHODS: A 70-year-old pseudophakic man with a foldable acrylic intraocular lens and open posterior capsule underwent vitrectomy and fluid-air exchange for repair of rhegmatogenous retinal detachment. RESULTS: During pars plana vitrectomy and fluid-air exchange, condensation immediately formed on the posterior surface of the foldable acrylic intraocular lens. This condensation, which prevented a view of the retina, was eliminated by wiping the posterior surface of the intraocular lens with a soft-tipped cannula. CONCLUSION: Although condensation may rapidly form on acrylic intraocular lenses during vitrectomy and fluid-air exchange, it can be managed readily by wiping with a soft-tipped cannula.

Aged↗
PubMed1987

Effects of intraocular pressure and other factors on subretinal fluid resorption.

We observed the effects of intraocular pressure (IOP), vitreous pressure and gravity on the resorption of small retinal detachments (blebs) made with Hanks' solution or autologous serum. Raising the IOP decreased the absorption time moderately and lowering the IOP increased it. These effects were greater when the RPE had been damaged by sodium iodate or laser burns, but we conclude that IOP makes only a small, limited contribution to normal subretinal fluid absorption. Neither liquefaction of the vitreous nor retinal weight had a significant influence on fluid absorption.

Animals↗
PubMed1987

Simulation of spaceflight with whole-body head-down tilt: influence on intraocular pressure and retinocortical processing.

Cephalad fluid shifts occur in the microgravity environment of spaceflight. Whole-body head-down tilt was used to simulate the influence of these fluid shifts upon intraocular pressure (IOP) and the bioelectrical activity of neural elements in the retinocortical pathway. Noninvasive techniques were used to monitor IOP, pattern reversal electroretinograms (prERGs), and pattern reversal visual evoked cortical potentials (prVEPs) when subjects were oriented either upright or in a head-down position (6 degrees or 90 degrees). The results indicate that there is a significant elevation in IOP when an individual is oriented in a head-down position. Significant alterations of neurophysiological processing in the retinocortical pathway also occur when individuals are oriented in a head-down position.

Adult↗
PubMedDate not supplied

Interface fluid after laser in situ keratomileusis.

PURPOSE: To describe a case of interface fluid after laser in situ keratomileusis (LASIK) and review the literature on this rare complication after LASIK. METHODS: We present a case report and literature review. Articles for this review were chosen from electronic database and manual literature searches. MEDLINE searches were made from 1990 to April 2002, using the key words "interface fluid" and "LASIK." RESULTS: A 40-year-old man had uneventful LASIK for residual refractive error from previous penetrating keratoplasty in his right eye. Diffuse lamellar keratitis began 1 day postoperatively. Topical corticosteroids were administered. Six weeks after LASIK, a layer of interface fluid developed. Intraocular pressure was 9 mmHg when measured centrally by Goldmann applanation tonometry and 30 mmHg by Tono-pen tonometry. The interface fluid resolved with antiglaucoma agents and corticosteroids combined with cyclosporine. CONCLUSIONS: This case, along with other reported cases, demonstrate the clinical features of interface fluid after LASIK.

Adult↗
PubMed1987

Intraocular pressure assessment in gas-filled eyes following vitrectomy.

The accuracy and precision of tonometric methods in measuring intraocular pressure (IOP) was assessed in 24 eye-bank eyes subjected to pars plana lensectomy/vitrectomy and air-fluid exchange. Intraocular pressure was measured in masked fashion with a Perkins' applanation tonometer, pneumatic applanation tonometer; a mercury manometer served as a reference standard. Pneumatic tonometry underestimated actual IOP by as much as 25%, and Schiotz' indentation tonometry underestimated actual IOP by as much as 79%. Perkins' applanation tonometry was significantly more accurate in estimating actual IOP in gas-filled eyes than pneumatic tonometry or Schiotz' indentation tonometry.

Humans↗
PubMed1982

[Effects of anterior chamber perfusion on the rabbit corneal endothelium: a scanning electron microscopy study (author's transl)].

The effects of intraocular irrigating solutions (TC Earle and NaCl 9%) on the rabbit corneal endothelium were evaluated utilizing scanning electron microscopy. Introcular pressure was maintained at 15 or 50 mm Hg. Rate of perfusion was between 50 microliter/min and 2 ml/min. With NaCl 9%, in eyes exposed to high pressure (50 mm Hg) for 2 hours with a rate of 50 microliter/min changes could be detected: rupture of apical junctions and minimal structural changes. Similar lesions appeared with a pressure of 15 mm Hg at a rate of ml/min. With Earle solution, no lesions were seen after 3 hours and minimal changes after 4 hours. Intraocular irrigating solution seems to be more toxic than increased intraocular pressure on the structure of endothelial cells, as seen on scanning electron microscopy. Greater sensitivity of endothelium to perfusion fluid than intraocular pressure probably explains the paradoxical appearance of corneal edema in diseased states, and suggests that endo-ocular surgical procedures require modification.

Animals↗
PubMed2001

[Enhancement of laboratory diagnosis specificity in human toxocariasis].

The aim of the study was to enhance specificity of immunological diagnosis in toxocarosis. The investigations concern: detection of circulating parasite antigens using dot-ELISA technique and detection of specific IgG antigodies using ELISA test with low molecular weight (< or = 30 kD) excretory-secretory (ES) larval T. canis antigens. The circulating antigens were investigated in 60 sera and 20 anterior chamber fluids from children with ocular form of toxocarosis. These antigens were present only in 3 sera and 2 anterior chamber fluids in children with active intraocular inflamation and fluid antibodies titers 1:5120 and 1:20 000. Comparative study with different ELISA tests indicated that use of low molecular weight antigens increase specificity of reaction.

Animals↗
PubMed2002

Supraciliochoroidal fluid in the eyes indicates good intraocular pressure control despite absence of obvious filtering bleb after trabeculectomy.

PURPOSE: To examine the presence of supraciliochoroidal fluid (SCF) by ultrasound biomicroscopy in posttrabeculectomy eyes that show good intraocular pressure (IOP) control despite the absence of an obvious filtering bleb. PATIENTS AND METHODS: Eyes were selected retrospectively according to the following criteria: IOP < 15 mm Hg, no antiglaucoma medication, no filtering bleb or a flattened bleb without microcystic spaces, and no ophthalmoscopic choroidal detachment after trabeculectomy with mitomycin C. The SCF was examined using 50-MHz ultrasound biomicroscopy (Zeiss-Humphrey). RESULTS: Ultrasound biomicroscopy detected SCF in five (63%) of eight eyes that met the study criteria. The extent of SCF in two of the eyes was four quadrants and one or two quadrants in three eyes. CONCLUSION: The presence of the SCF may explain increased uveoscleral outflow and may represent an IOP-lowering mechanism after trabeculectomy with mitomycin C, especially when IOP control is good and a filtering bleb is not obvious.

Anterior Eye Segment↗