Pathological cupping in normal pressure glaucoma is probably not due to low CSF pressure.
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Adult↗
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Results for “Intraocular fluid”
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Ophthalmodynamometric estimation of cerebrospinal fluid pressure in pseudotumour cerebri.
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Cerebrospinal Fluid Pressure↗
Antimicrobial drug delivery to the eye.
A major obstacle in the treatment of ocular infections is the difficulty in obtaining adequate antimicrobial drug concentration at the site of infection. This article reviews the pharmacokinetic principles of ophthalmic drug delivery as it pertains to antimicrobial therapy. The administration of antimicrobials by topical application, subconjunctival injection, intravitreal injection, vitreous replacement fluid, and systemic administration are addressed. Representative data on the intraocular penetration of antimicrobials as well as recommended doses of drugs for ocular infections are presented.
Administration, Topical↗
A comparison of excimer laser (308 nm) ablation of the human lens nucleus in air and saline with a fiber optic delivery system.
BACKGROUND: Photoablation with excimer lasers has demonstrated precise tissue cutting and minimal thermal damage. Potential ophthalmic applications of these lasers include remodelling of the corneal surface, glaucoma treatment, and phacoablation. Ablation of human lens with a 308 nm XeCl excimer laser light delivered through a fiber has been demonstrated in preliminary experiments. Intraocular delivery of laser light must be done in a fluid medium to preserve the integrity of ocular structures. However, little information is available on the effect of the fluid media on the ablation process. Therefore, a series of experiments was conducted to determine whether the ablation of human lens nucleus at 308 nm via a fiber differs in air and saline media. METHODS: Ablation of human lens nuclei (n = 30) was conducted with a XeCI excimer laser (308 nm) coupled to a 600 microns core size fiber. Irradiation was performed at 2.8 mJ/cm2 energy density and 20 Hz. The fiberoptic was brought to contact with the lens nucleus and remained fixed for the duration of irradiation. Variables consisted of the medium (air or saline) and number of pulses delivered (100 to 10,000). Following establishment of the tissue shrinkage ratio, the depth of each crater and the tissue volume removed were measured histologically. The histological features of nucleus ablation in air and in saline were also examined with both light and scanning electron microscopy. RESULTS: Light microscopy revealed that the average zone of thermal damage adjacent to the crater is thinner in the presence of saline (60 microns, SD = 6 microns) than it is in air (90 microns, SD = 12 microns). In both media, the thickness of the zone of thermal damage is greater at the surface than it is at its base. Following irradiation in air, deep sharpedged craters with smooth walls are formed. Craters formed by irradiation in saline are characterized by reduced depth and irregular walls. For the same number of pulses applied (500, 1000, and 2000), the mean depth of ablation per pulse in air (8.6 to 2.7 microns/pulse) was greater by approximately a factor of two than that in saline (4.10 to 1.30 microns/pulse) at P < .01. However, the mean ablated volume removed per pulse was greater in saline (0.00250 to 0.00150 mm3/pulse) than in air (0.00120 to 0.00080 mm3/pulse), for the same number of pulses (1000, 2000) at P < .01. CONCLUSIONS: In comparing the data for the same number of pulses applied in air and in saline, it appears that the depth of crater formed by irradiation in air is deeper than that in fluid. The overall volume ablated is greater in fluid than it is in air at 1000 and 2000 pulses. Additionally, the zone of thermal damage is thinner in the presence of saline than it is in air. Smoother crater shapes were observed following irradiation in air than in saline. These results suggest that under this specific experimental setup, the ablation in saline is different from that in air.
Aged↗
[Choroidal detachment--pathogenesis, etiology and clinical features].
Serous choroidal detachment is characterized by exudative detachment of the retina and choroid following leakage of fluid from the choriocapillaris into suprachoroidal space. This accumulation of fluid has been known to be a complication of various intraocular surgeries (cataract, glaucoma and retinal detachment surgery), where hypotony is combined with postoperative inflammation. Among other non surgical conditions associated with uveal effusion are idiopathic (uveal effusion syndrome, microphthalmia) and inflammatory diseases (scleritis, sympathic ophthalmia, pars planitis, Harada's disease). Idiopathic serous detachment of choroids is caused by scleral abnormalities associated with hypoplasia or partial absence of the vortex venous system. The most cases of postoperative choroidal detachment resolve spontaneously. Resolution is usually associated with rapid normalization of the intraocular pressure and reduction of intraocular inflammation. The natural course of idiopathic condition is variable but tends to be prolonged with remissions and exacerbations. Surgical management involving vortex vein decompression and/or sclerotomy is the most effective treatment in this patients.
Choroid Diseases↗
Fluids in the anterior aprt of the optic nerve in health and disease.
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Animals↗
A feasibility study of 23Na magnetic resonance imaging of human and rabbit vitreal disorders.
PURPOSE: To assess the clinical feasibility of sodium magnetic resonance imaging for the visualization and characterization of intraocular tissues. METHODS: 23Na magnetic resonance images were obtained of enucleated human eyes and of rabbit eyes in vivo. The magnetic resonance imaging technique used in this study provided slices of < 2 mm thickness and in-plane resolution of < 2 x 2 mm. From each of these slices local values of spin-spin relaxation time (T2*) were calculated from pixel intensities in each of the eight echoes. RESULTS: The images clearly display normal anatomic details of the lens and vitreous humor, and important pathologic details such as intravitreal and subretinal hemorrhages, ocular melanoma, and retinal detachments. Intraocular tissue identifications based on relative spin-spin relaxation time values and pixel intensities correlate with those made by standard diagnostic techniques. CONCLUSIONS: 23Na magnetic resonance imaging may be used for the visualization and characterization of intraocular tissues. Differentiation among vitreous humor, lens, aqueous humor, subretinal fluid, or hemorrhage and tumor may be based on image intensity and/or spin-spin relaxation times.
Animals↗
Cytological factors relating to posterior capsule opacification following cataract surgery.
This paper discusses tissue culture experiments with human lens epithelial cells that demonstrate that cells from all parts of the anterior capsule have regenerative capacity, that the cells from younger patients proliferate more than those from older patients and that cells from cataractous lens retain their growth potential. Epithelial cells may be removed from the anterior capsule by EDTA in an infusion fluid and epithelial cells adhere more to PMMA than HEMA intraocular lenses. The clinical implications of these studies are discussed.
Aged↗
Intraocular penetration of the soluble antiviral, Ara AMP.
Earlier studies on intraocular penetration of the antiviral drugs idoxuridine and vidarabine (formerly Ara A) reveal that either inactive metabolites from the former or very low levels of less active metabolites from the latter actually enter the aqueous. Additionally, to achieve therapeutic levels, systemically administered vidarabine must be given in large fluid volumes because of poor solubility. The present time-curve study on the intraocular penetration of the highly soluble nucleotide form of vidarabine, Ara AMP, reveals that, in rabbits, very high aqueous levels of the antiviral metabolite, Ara Hx, are achieved after intravenous does in small fluid volume. Moderately low levels are attained after subconjunctival injection, extremely low levels are attained after subconjunctival injection, and extremely low levels are present after topical administration. This indicates that intravenous and possibly subconjunctival injection may be useful in treatment of deep ocular herpetic disease.
Administration, Topical↗
The molecular dynamics of hyaluronates in solution.
The dynamic properties of hyaluronate solutions are discussed with relevance to some problems in sensory physiology (mechanoelectrical transduction), renal physiology, interstitial fluid regulation, and especially to the causes of open-angle glaucoma. With respect to the last problem: as recent biochemical evidence indicates that the hyaloid membrane does not exist, it now seems worthwhile to consider the increase in intraocular pressure present in the eye with glaucoma to be due--at least in the open-angle case--to a change in the specific gravity and hydrophilic nature of the hyaluronic acid in the vitreous body in particular, as well as in the trabecular meshwork. Densimetric experimental evidence indicates that the hyaluronate system could, indeed, produce the pressure changes seen in glaucoma, if intraocular pH changed but slightly. A hypothesis concerning the effect of acetazol amide on intraocular pressure is also presented.
Body Fluids↗
[Experimental experiences with balloon-shaped capsular sac implantation with reference to accommodation outcome in intraocular lenses].
Implantation of a balloon into the capsular bag theoretically allows the injection of fluid materials for lens replacement, thus enabling accommodation. Leakage of the fluid can be avoided in this way, and a large variety of potential materials can be tested without taking into account their effect on ocular tissue. We tested ellipsoid balloons made of polydimethylsiloxane. The balloons had a maximum diameter of 11.0 mm and a wall thickness of 0.15 mm. After capsulorhexis of 2.5 mm and phacoemulsification, the balloons were implanted in enucleated pig eyes and filled with 2% methylcellulose or silicone oil through little tubes on the anterior side. Implantation of the balloons into the capsular sac was much more difficult than normal IOL implantation into the posterior chamber. We had to enlarge the tunnel incision to 4.5 mm, and it was technically difficult to leave the relatively strong capsule of the pig intact during implantation. Due to the additional surfaces we found increased reflection. Because of the difficulties described we cannot see any advantages over other refilling techniques.
Animals↗
Nonnecrotizing herpetic retinopathies masquerading as severe posterior uveitis.
OBJECTIVE: Aqueous humor analysis can be performed in severe atypical forms of posterior uveitis unresponsive to conventional treatment to exclude a viral infection. DESIGN: Noncomparative interventional case series. PARTICIPANTS: Thirty-seven immunocompetent patients seen with corticosteroid-resistant forms of posterior uveitis underwent extensive evaluation, including anterior chamber paracentesis, to rule out a nonnecrotizing viral retinopathy. INTERVENTION: Aqueous fluid samples were prospectively obtained. Polymerase chain reaction (PCR) and serologic evaluation of intraocular antibody production against herpesviruses were performed by molecular techniques and enzyme-linked immunosorbent assay. MAIN OUTCOME MEASURES: Polymerase chain reaction and local antibody production for herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus were determined on aqueous fluid samples. RESULTS: Viral infection was confirmed in 5 cases (13.5%). Clinical presentation included birdshot-like retinochoroidopathy, occlusive bilateral vasculitis, and cystoid macular edema. An antiviral regimen was initiated in all cases. Inflammation was stabilized, and steroid dosage could be significantly reduced. CONCLUSIONS: Identification of a viral agent during severe posterior uveitis can dramatically change therapeutic management.
Acyclovir↗
Intraocular gas measurement using A-scan ultrasound.
A-scan ultrasound was used to measure the position of the gas-fluid interface in eyes following vitrectomy and gas internal tamponade. Using 20 eyes of 19 patients it was found that in most instances the gas-fluid interface could be measured to within 0.5mm. The procedure was simple to perform and was well tolerated by the patients. This appears a useful way of monitoring changes in intraocular gas volume.
Eye↗
Effects of inhibition of angiotensin converting enzyme and carbonic anhydrase on fluid production by ciliary process, choroid plexus, and pancreas.
Inhibitors of angiotensin converting enzyme (ACE) (1) and of carbonic anhydrase (CA) (2,3) decrease intraocular pressure (IOP) in conscious rabbits. We asked whether ACE inhibition decreases IOP through effects on CA-dependent flow of aqueous humor (AH) and whether ACE inhibitors decrease other CA-dependent secretions. We show in anesthetized rabbits (a) that topical inhibitors of ACE decrease both IOP and AH flow as much as systemic inhibitors of CA; (b) that the maximal effects of ACE and CA inhibition are not additive, therefore these treatments may affect one or more components of a single system for fluid production; and that (c) ACE inhibitors do not work through inhibition of CA. Looking at other fluid production systems, we find (d) that cerebrospinal fluid (CSF) production is increased after ventriculocisternal perfusion with a potent ACE inhibitor and (e) that flow of pancreatic juice (PJ) is increased after systemic ACE inhibition.
Angiotensin-Converting Enzyme Inhibitors↗
A glass intraocular lens.
We designed a glass and polyimide iris-plane, iris-clip intraocular lens. It is sterilized in the autoclave and weighs approximately 6 mg in water. The optic is 0.3 mm thick for a 19-diopter lens and the flexible haptic is 0.05 mm thick. Two identical haptics and the optic are joined mechanically to form the intraocular lens. The round spatula-like portion of an insertional instrument secures the intraocular lens by passing through two opposing flexible haptic loops and behind the optic. Fluid or air is irrigated through the cannula as the implant is inserted in order to protect the endothelium.
Glass↗
Drug-induced glaucomas: mechanism and management.
Glaucoma comprises a heterogeneous group of diseases that have in common a characteristic optic neuropathy and visual field defects, for which elevated intraocular pressure is the major risk factor. The level of intraocular pressure within the eye depends on the steady state of formation and drainage of the clear watery fluid, called the aqueous humour, in the anterior chamber of the eye. An obstruction in the circulatory pathway of aqueous humour causes an elevation in intraocular pressure. Because intraocular pressure is the most modifiable parameter, therapeutic measures (medical and surgical) are aimed at reducing the pressure to protect against optic nerve damage. Glaucomatous optic neuropathy results from degeneration of the axonal nerve fibres in the optic nerve and death of their cell bodies, the retinal ganglion cells. Clinical examination of the optic nerve head or disc and the peripapillary nerve fibre layer of the retina reveals specific changes, and the resulting visual field defects can be documented by perimetry. Glaucoma can be classified into four main groups: primary open-angle glaucoma; angle-closure glaucoma; secondary glaucoma; and developmental glaucoma. Drug-induced glaucoma should be considered as a form of secondary glaucoma because it is brought about by specific systemic or topical medications. Although there is a high prevalence of glaucoma worldwide, the incidence of drug-induced glaucoma is uncertain. Drugs that cause or exacerbate open-angle glaucoma are mostly glucocorticoids. Several classes of drugs, including adrenergic agonists, cholinergics, anticholinergics, sulpha-based drugs, selective serotonin reuptake inhibitors, tricyclic and tetracyclic antidepressants, anticoagulants and histamine H(1) and H(2) receptor antagonists, have been reported to induce or precipitate acute angle-closure glaucoma, especially in individuals predisposed with narrow angles of the anterior chamber. In some instances, bilateral involvement and even blindness have occurred. In this article, the mechanism and management of drug-induced glaucomatous disease of the eye are emphasised. Although the product package insert may mention glaucoma as a contraindication or as an adverse effect, the type of glaucoma is usually not specified. Clinicians should be mindful of the possibility of drug-induced glaucoma, whether or not it is listed as a contraindication and, if in doubt, consult an ophthalmologist.
Drug-Related Side Effects and Adverse Reactions↗
Model of ionic transport for bovine ciliary epithelium: effects of acetazolamide and HCO.
The possible existence of transepithelial bicarbonate transport across the isolated bovine ciliary body was investigated by employing a chamber that allows for the measurement of unidirectional, radiolabeled fluxes of CO2 + HCO. No net flux of HCO was detected. However, acetazolamide (0.1 mM) reduced the simultaneously measured short-circuit current (I(sc)). In other experiments in which (36)Cl- was used, a net Cl- flux of 1.12 microeq. h(-1). cm(-2) (30 microA/cm(2)) in the blood-to-aqueous direction was detected. Acetazolamide, as well as removal of HCO from the aqueous bathing solution, inhibited the net Cl- flux and I(sc). Because such removal should increase HCO diffusion toward the aqueous compartment and increase the I(sc), this paradoxical effect could result from cell acidification and partial closure of Cl- channels. The acetazolamide effect on Cl- fluxes can be explained by a reduction of cellular H+ and HCO (generated from metabolic CO2 production), which exchange with Na+ and Cl- via Na+/H+ and Cl-/HCO exchangers, contributing to the net Cl- transport. The fact that the net Cl- flux is about three times larger than the I(sc) is explained with a vectorial model in which there is a secretion of Na+ and K+ into the aqueous humor that partially subtracts from the net Cl- flux. These transport characteristics of the bovine ciliary epithelium suggest how acetazolamide reduces intraocular pressure in the absence of HCO transport as a driving force for fluid secretion.
Acetazolamide↗
Angiotensin converting enzyme system in the normal canine eye: pharmacological and physiological aspects.
The function of the renin-angiotensin-aldosterone system (RAAS) in the mammalian eye remains unclear, although alterations in the concentrations of various pathway components can influence intraocular pressure and the electroretinogram. Angiotensin Converting Enzyme (ACE) has been localized to ocular tissues and fluids. Aqueous humor and serum values of ACE are increased in sarcoid uveitis patients. We used the dog to simultaneously examine the effects of a topically administered ACE inhibitor on the intraocular pressure (IOP), on components of the renin-angiotensin pathway in the serum and aqueous humor, and to monitor any systemic effects of the ACE inhibitor. The novel ACE inhibitor, SCH 33861 (Schering Corporation), decreased IOP in amounts similar to timolol when applied topically to the canine eye. Serum ACE values significantly decreased in SCH 33861 treated dogs, while aqueous ACE values were only slightly decreased. A decrease in heart rate, and systolic and diastolic blood pressure in these dogs during the treatment period indicated probable systemic absorption. Normal values of aqueous humor and serum angiotensin-I were established for the dog. Plasma renin activity and angiotensin-I values were not significantly changed for any of the treatment groups. Topical application of SCH 33861 to the canine eye is a useful model to further evaluate the role of the renin-angiotensin system in the eye.
Administration, Topical↗