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At least 631 records · Page 35Linked to original sources
PubMed1990

Vitrectomy retinotomy aspiration biopsy of choroidal tumors.

We used an investigational technique for the biopsy of intraocular tumors to aid in the diagnosis of three choroidal tumors. A three-port trans-pars plana vitrectomy was performed in conjunction with retinotomy, tumor biopsy, endophotocoagulation, and air-fluid exchange. Vitrectomy was used to decrease the amount of traction secondary to retained vitreous after intraocular surgery. Retinotomy sites were chosen under microscopic control to avoid large caliber retinal vessels. Then a modified tumor-aspiration technique, together with endophotocoagulation and aspiration of intraoperative vitreous hemorrhages, provided an opportunity to sample tumor tissue continually at varied depths. We have added standard vitreous surgery concepts, techniques, and instrumentation to produce vitrectomy retinotomy aspiration biopsy of choroidal tumors.

Adenocarcinoma↗
PubMedDate not supplied

Scleral buckling methods for rhegmatogenous retinal detachment.

Scleral buckling techniques are effective in treating most eyes with rhegmatogenous retinal detachment, and usually the final visual result is limited only by possible preexisting macular damage due to the detachment. Still, a variety of techniques are used, including exoplant or implant methods for the scleral buckle; cryotherapy, diathermy, or photocoagulation to cause the chorioretinal adhesion; and drainage or nondrainage of subretinal fluid. Also, recent development of alternative surgical techniques such as vitreous surgery and/or intraocular gas injection have raised questions about the current role of scleral buckling methods. This article reviews the principles and techniques of scleral buckling for retinal detachment and describes the methods we have found most useful.

Anesthesia, General↗
PubMed1983

Surgical techniques for selected giant retinal tears.

Based on clinical experience, improved methods for treating giant retinal tears with an inverted retinal flap are described. In all cases a broad encircling scleral buckle is used in conjunction with a broad zone of peripheral chorioretinal adhesion produced by cryotherapy and, often, supplemented by postoperative photocoagulation. This virtually eliminates recurrent retinal detachment from an anterior location, if the retinal flap can be properly unfolded and the retina is initially reattached. Vitrectomy is done in all these cases, and an intraocular bubble is used to unfold and reposition the retinal flap during or after surgery. If the retinal flap is especially stiff or foreshortened, special techniques are used to incarcerate the edge of the retinal flap in the pars plana or the peripheral choroid, or transvitreal suturing techniques are used to secure the edge of the retinal flap to the eyewall before fluid-gas exchange is performed. This insures proper unfolding of the flap by the intraocular bubble. Applying retinal cryotherapy before performing the vitrectomy seems to reduce the occurrence of postoperative proliferative vitreoretinopathy (PVR), perhaps because retinal pigment epithelial cells in the vitreous cavity are removed during vitrectomy. Frequent, detailed examination during the first three weeks after surgery and use of postoperative photocoagulation to supplement the cryotherapy seem to prevent recurrent detachment from anterior leakage of subretinal fluid beneath the retinal flap or through other anterior retinal breaks.

Humans↗
PubMed1983

Carbon dioxide laser trabeculostomy for the treatment of neovascular glaucoma.

During the past 24 months, 23 cases of advanced neovascular glaucoma, unresponsive to medical therapy, have been treated by a trabeculostomy procedure using a carbon dioxide laser. This procedure entails surgical entry into the anterior chamber from beneath either a conjunctival or scleral flap in such a way as to completely cauterize any neovascular tissue in the corneoscleral angle and to permit adequate drainage of the aqueous in fluid from the anterior chamber to the periocular space. The average intraocular pressure prior to carbon dioxide laser trabeculostomy was 54 mmHg and these pressures were lowered below 18 mmHg in over 70% of the cases followed for longer than six months postlaser therapy. Treatment was considered a failure in 16% of the cases where the intraocular pressure was not lowered substantially. Fourteen percent of the treated eyes sustained a pressure decrease to within the 26-35 mmHg range. Carbon dioxide laser trabeculostomy provides a new method of lowering the intraocular pressure in severe cases of neovascular glaucoma without the hazard of intraocular hemorrhage common with other filtration procedures or the ciliary destruction present with the cyclocautery operations. The indications, surgical technique, and complications will be discussed.

Diabetic Retinopathy↗
PubMedDate not supplied

Formation of the aqueous humor.

1. Glaucoma is a worldwide disease affecting approximately 1-2% of the population aged over 35 years in industrial countries and is a major cause of blindness. 2. Glaucoma is usually associated with an increased intraocular pressure reflecting an imbalance between the rate of production of fluid (the aqueous humor) by the ciliary epithelial cells and its drainage from the eye. Therefore, it is important to understand how this secretion is produced. This requires a knowledge of ciliary epithelial cell composition, which has, in the past, proved difficult to obtain in mammalian preparations. 3. We have recently used the technique of electron-probe X-ray microanalysis to determine this composition under a variety of in vitro conditions. 4. Our results have led to a new model for this secretion that emphasizes the potential secretory role of the Na+/K+/2Cl- cotransporter.

Animals↗
PubMed1986

Effect of amino acid input rates on lens metabolism in a perfusion culture system.

A perfusion system has been established for the organ culture of the lens. The system is designed so that a constant flow of fluid occurs past the lens and a separate channel of fluid simultaneously bypasses the lens. Lens metabolic activity can be determined by analyzing differences between these two samples of fluid. The system also maintains a level of pressure comparable to intraocular pressure. Apparatus for observation and photography of the lens is built into the system. The purpose of these studies was to determine if this perfusion system could maintain the rabbit lens close to the physiological state, to study the metabolic behavior of the lens under steady state conditions, and to determine the effect of increasing amino acid concentrations on the metabolic activity of the lens under steady state conditions. By increasing the amino acid concentrations in the medium we hoped to compensate for the lack of protein in the medium and to provide metabolic substrate to maintain the lens under perfusion conditions. The rabbit lens was cultured at a temperature of 33 degrees C for periods up to 100 h. A totally synthetic perfusion medium without proteins or antibiotics was devised. This medium imitates posterior chamber aqueous humour, except that it does not contain ascorbic acid because it was found that ascorbic acid readily auto-oxidizes and depletes the oxygen content of the medium. The amino acid concentration of the perfusion medium was adjusted so that its total nitrogen content was equivalent to the total nitrogen content of posterior chamber aqueous humour. To determine the metabolic behavior of the lens, 10 different metabolic substances were analyzed in the medium and 15 were analyzed in the lens. These substances are mainly metabolic substrates and end products. As a reference for the evaluation of the behavior of the lens in the perfusion system, the perfused lens was compared to the lens in the other eye of the rabbit. Standards for differences between the right and left lens and the first or second lens removed from the rabbit were developed in control studies. A series of experiments was devised to determine the effect of increased amino acid concentration in the medium on the metabolic behavior of the lens. Concentrations of amino acids from 0 to 7.26 times the posterior concentration of amino acids in chamber aqueous humour were studied. Seven studies were done with a flow rate of medium of about 2 g per h, with each experiment lasting from 80 to 100 h.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗
PubMed1982

Carbon dioxide laser trabeculostomy for the treatment of neovascular glaucoma.

During the past 18 months, 23 cases of advanced neovascular glaucoma, unresponsive to medical therapy, have been treated by a trabeculostomy procedure using a carbon dioxide laser. This procedure entails surgical entry into the anterior chamber from beneath either a conjunctival or a scleral flap in such a way as to completely cauterize any neovascular tissue in the iridocorneal angle and to permit adequate drainage of the aqueous fluid from the anterior chamber to the periocular space. The average intraocular pressure, prior to carbon dioxide laser trabeculostomy was 54 mm Hg and these pressures were lowered below 18 mm Hg in over 57% of the cases followed for longer than six months post-laser therapy. Treatment was considered a failure in 26% of the cases where the intraocular pressure was not lowered substantially, and 17% of the treated eyes sustained a pressure decrease to within the 25 to 35 mm Hg range. Carbon dioxide laser trabeculostomy or trabeculo-sclerostomy provides a new method of lowering the intraocular pressure in severe cases of neovascular glaucoma without the hazard of intraocular hemorrhage, common with other filtration procedures. These procedures have proved satisfactory in alleviating the high pressures of neovascular glaucoma in a relatively large proportion of the patients treated. If the eye is grossly hyperemic and irritated because of the high intraocular pressure and the deteriorated condition of the eye, it is suggested that the carbon dioxide laser trabeculostomy procedure with a scleral flap be performed with an implanted seton as the procedure of choice. If the eye is relatively quiet and has some visual reserve but an exceedingly high and intractable intraocular pressure, it is advisable to use either the carbon dioxide laser trabeculostomy procedure or the carbon dioxide laser trabeculo-sclerostomy operation as described. These procedures are being further refined, but the results of this investigation suggest that these procedures can be utilized judiciously, and should prove useful, particularly in those eyes with advanced neovascular glaucoma with useful vision still remaining.

Female↗
PubMed1996

[Hematogenic bacterial endophthalmitis. A rare infection with very poor functional prognosis].

Three men and one woman (mean age 52 years) were admitted to hospital for septicemia (2 cases), sudden partial loss of visual acuity (1 case) and suspected conjunctivitis (1 case). Three of the patients showed risk factors (diabetes, alcohol intoxication, immunosuppression). Panophthalmitis (affecting all tunics of the eye) was apparent from the initial examination in all 4 cases (2 bilateral and 2 unilateral). Ocular involvement was associated with endocarditis and meningitis (pneumococcus) in 1 case, with nocardiosis (pulmonary, cerebral and nodal) in 1 case, and with septicemia with bacterial arthritis (Escherichia coli, streptococcus A) in 2 cases. Hemocultures were positive in 3/4 cases. The micro-organism was also detected in the joint (n = 2), urine (n = 1) and cerebrospinal fluid (n = 1), during pulmonary transparietal puncture (n = 1) and in intraocular biopsy tissue (n = 1). All patients received appropriate antibiotic therapy intravenously and intraocularly. The infection was cured in all cases, but with severe functional sequelae: blindness in 2 cases, and unilateral enucleation in the other 2 cases.

Adult↗
PubMed1997

Mechanisms for vasopressin effects on intraocular pressure in anesthetized rats.

Continuous intracameral infusions of a balanced salt solution (0.175 microliter min-1) have been reported to raise intraocular pressure (IOP) in anesthetized rats. Palm et al. (1995) previously reported that this effect was attenuated significantly by inclusion of arginine-vasopressin (AVP, 10 ng 0.175 microliter-1) in the infusate. This study used experimental and computer simulation methods to investigate factors underlying these changes in IOP. First, constant intracameral infusions of artificial cerebrospinal fluid (aCSF) at different fixed rates (0.049-0.35 microliter min-1) were used to estimate the outflow resistance. Secondly, IOP responses were measured during an 2 hr intracameral infusion of either aCSF or AVP that was the sum of a small constant component (0.05 microliter min-1) and a larger periodic component (0.25 microliter min-1, cycling for 4 min on, then 4 min off); the mean infusion rate was 0.175 microliter min-1. As shown previously for 0.175 microliter min-1 constant infusions, the periodic aCSF infusion induced a significant rise in IOP that was attenuated by AVP administration. Complex demodulation analysis and the estimated gain parameter of a second order transfer function fit to the periodic responses indicated that outflow resistance increased significantly during the infusions in both aCSF and AVP groups, but that the indices of resistance did not differ significantly between aCSF and AVP infused eyes. This finding implies that changes in outflow resistance do not explain the difference in IOP responses to intracameral aCSF and AVP. The two responses differed significantly, though, in damping factors, such that the aCSF responses were considerably more underdamped than the AVP responses. It is hypothesized that aCSF-induced increase in IOP reflects both (1) a small component reflecting increased outflow resistance and (2) a larger non-resistive component. Since the non-resistive component is insensitive to pretreatment with acetazolamide, it is suggested that the aCSF-induced elevation in IOP reflects primarily vascular perfusion changes that are reduced by local vasoconstrictor actions of AVP. The latter mechanism likely maintains vascular perfusion of the globe when intraocular hypertension develops.

Animals↗
PubMedDate not supplied

Glycosaminoglycans and outflow pathways of the eye and brain.

The etiology of the majority of defects of the outflow pathways of aqueous humor (glaucoma) and cerebrospinal fluid absorption (hydrocephalus) is unknown. A considerable amount of evidence indicates that glycosaminoglycans have a role in regulating fluid movement through connective tissues such as the trabecular meshwork of the eye and the arachnoid of the brain. Both the eye and the brain outflow pathways have hyaluronic acid and chondroitin sulfate within the filtration barrier. The physiological significance of glycosaminoglycans in the outflow pathways may be their ability to form highly viscous and elastic gel-like solutions that function as a selective biological gel filtration system, which maintains normal intraocular and intracranial pressure. We suggest that glycosaminoglycans may act to maintain the unidirectional character, low-flow fluid movement, and pressure gradient between the trabecular lamellae and the drainage channels of the eye and the brain. This review of the outflow pathways of the eye and the brain discusses the cell biology of glycosaminoglycans in regulating normal aqueous outflow and cerebrospinal fluid absorption.

Animals↗
PubMedDate not supplied

[Effectiveness of laser treatment of narrow-angle glaucoma].

Forty-eight patients with narrow-angle glaucoma were treated with M-900 argon laser (Coherent Radiation, USA). Reduction of intraocular pressure as low as 20 +/- 1.82 mm Hg on an average was achieved. Fluid discharge efficacy coefficient has improved. The authors claim that laser cyclotrabeculospasis a sufficiently effective method for the treatment of primary narrow-angle glaucoma.

Adult↗
PubMed1988

Methylcellulose for endothelial cell protection.

A randomised trial of three types of endothelial cell protection for patients undergoing posterior chamber intraocular lens implant is described. The results confirm the superiority of a viscoelastic fluid over air as a form of endothelial cell protection. No statistically significant difference was found between sodium hyaluronate and hydroxypropylmethylcellulose (HPMC). As the cost of sodium hyaluronate is prohibitive, a manufacturing technique for HPMC is given.

Adult↗
PubMed1984

Gas-mediated vitreous compression: an experimental alternative to mechanized vitrectomy.

We have developed a simple technique in rabbit and baboon eyes that utilizes intravitreally injected perfluoropropane gas, which expands slowly to efficiently compress and displace nearly completely the vitreous body. There is cataract formation after extended contact of the gas bubble with the lens. However, it is rapidly reversible by reducing the duration of lens contact (gas-fluid exchange) and by using young animals. No long-term alterations in intraocular pressure or retinal function were observed, as determined by electroretinography, during the 4-month test period. Gross examination and scanning electron microscopy revealed that the vitreous cavity, shortly after full expansion of the gas bubble, was practically free of collagen. The vitreous body had been detached from most of the retina and compressed into a collagenous strand between the optic nerve head and lens in the rabbit eyes, and there was also a dense collagen accumulation on the inferior retinal surface and anterior vitreous base in the rabbits and the baboon. Large areas of the retina and medullary wings were stripped of overlying collagen. By the end of 4 months, the compressed vitreous body had expanded to become an irregular structure that remained separated from the retina in areas of previous detachment. Mechanized vitrectomy is a difficult procedure often needed in experimental work. We believe that the vitreous compression and gas-fluid exchange technique is a valid alterative to a mechanical approach. We also believe that we have a model that simulates the human situation of posterior vitreous detachment and vitreous syneresis.

Animals↗
PubMed1979

Experimental perfusions through the anterior and vitreous chambers with possible relationships to malignant glaucoma.

Enucleated eyes were perfused alternately via the anterior and vitreous chambers. At low intraocular pressure (IOP), vitreous humor presented considerable resistance to forward flow of perfusion fluid in calf eyes, but not in human eyes. In human eyes when the perfusion pressure was increased to 60 mm Hg, the resistance to flow forward from the vitreous body increased, but became practically nil again when the IOP was decreased. At high pressure the volume of the vitreous body apparently increases and the anterior hyaloid membrane probably presses against the ciliary body, reducing the area of hyaloid membrane through which fluid can flow. Whether increased perfusion pressure can in some other manner change the permeability of human vitreous to resemble that of the calf remains unanswered. Our results suggest that factors other than, or in addition to, simple diversion of aqeous humor must be important in malignant glaucoma.

Animals↗
PubMed1991

Experimental studies on the accumulation of subretinal fluid.

In an attempt to develop a rabbit model for serous detachment, we damaged the pigment epithelium with low-intensity laser burns, lowered intraocular pressure and administered dibutyryl adenosine 3',5'-cyclic phosphate (cAMP), to inhibit pigment epithelial water transport. We produced only small areas of edema or very low detachment that persisted for a few days at best. These experiments suggest that it is remarkably difficult to make fluid stay in the subretinal space, and more stringent conditions will be needed to mimic the size and persistence of clinical serous detachments.

Animals↗
PubMed1993

Intraocular lymphoma. Clinical and histopathologic diagnosis.

BACKGROUND: Intraocular lymphoma is associated with significant morbidity and mortality, but early diagnosis and treatment may improve prognosis. METHODS: The diagnostic features of 12 cases of intraocular lymphoma diagnosed at the National Eye Institute between 1984 and 1992 were retrospectively reviewed. RESULTS: A pathologic diagnosis of large B-cell lymphoma was made on vitrectomy specimens in ten patients, cerebral spinal fluid in one, and on an enucleation specimen in one. The mean time from onset of symptoms to diagnosis was 21.4 months (range, 1-66 months). All 12 patients were given a final diagnosis of non-Hodgkin's lymphoma of the central nervous system (NHL-CNS), based on the epidemiology, pathology, and clinical course of their tumors. Although an initial vitrectomy was negative for malignant cells in three of ten patients, a repeat vitrectomy specimen subsequently showed intraocular lymphoma. Results of examination of the cerebrospinal fluid (CSF) showed malignant cells in 5 of 11 patients, although malignant cells were only identified after repeat examination of additional samples of CSF in three of these patients. Malignant cells often are difficult to identify, and an experienced cytopathologist was critical in making the correct diagnosis. In addition, corticosteroids are lympholytic to the lymphoma cells, and they appeared to decrease the viability of tumor cells obtained in samples of vitreous and CSF. CONCLUSION: The prompt, appropriate handling of specimens and review by an experienced cytopathologist are critical to the diagnosis of intraocular lymphoma. Malignant cells often are present in the cerebral spinal fluid at the time that ocular lymphoma is diagnosed. Nevertheless, multiple vitrectomies and lumbar punctures may be necessary before the correct diagnosis is made.

Adult↗
PubMed1988

Intraocular pressure during hemodialysis.

In 14 patients undergoing hemodialysis, the intraocular pressure did not change significantly when measured at hourly intervals for 4 h. There was a loss in body weight because of fluid loss; also the Schirmer values decreased significantly at the conclusion of treatment. Blood osmolality decreased markedly in a linear fashion. The fluctuations of intraocular pressure during hemodialysis were likely dependent on the dynamics of dehydration and hypo-osmolality. Regulatory forces stabilized the intraocular pressure to such a degree that statistical significance in these fluctuations was not reached.

Adult↗