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Biomedical subjects

R L Gross

Publications and source records attributed to R L Gross.

At least 37 records · Page 2Linked to original sources
PubMed1995

Picosecond neodymium:yttrium lithium fluoride (Nd:YLF) laser peripheral iridotomy.

PURPOSE: We evaluated the picosecond neodymium:yttrium lithium fluoride (Nd:YLF) laser for performing peripheral iridotomies of predetermined size and shape in various types of irides. METHODS: In the first part of the study, we determined operating parameters from performing 60 iridotomies in human cadaver eyes. Subsequently, using the parameters obtained in cadaver eyes, iridotomies were created in eyes of patients with primary angle-closure glaucoma. RESULTS: In the cadaver eyes, the optimal parameters were a rectangular cutting pattern of 0.3 x 0.3 mm, 500-microns cutting depth, 50-microns spot separation, 200 to 400 microJ of energy per pulse, 200 to 400 pulses per second, and no focal offset distance. In 18 eyes of 11 patients, iridotomies with well-defined margins and size were created. Minimal hemorrhage occurred intraoperatively in ten of 18 eyes (55.6%), which did not affect the outcome of the procedure. Increases of postoperative intraocular pressure at one hour averaged 3.5 +/- 5.1 mm Hg, with an increase of more than 10 mm Hg in three eyes (16.7%), and a maximum of 12 mm Hg. We observed no corneal or retinal damage. CONCLUSION: The picosecond Nd:YLF laser seems to be an effective instrument for reliably performing peripheral iridotomies of precise size and shape using low energy per pulse levels. This laser, unlike the argon laser, is successful independent of iris thickness or color and can easily make a larger iridotomy than is often possible with the Nd:YAG laser.

Adult↗
PubMed1994

A human cadaver eye model for anterior and posterior segment laser applications.

We have developed a cadaver eye model that allows anterior and posterior segment laser procedures to be performed under closely simulated in vivo conditions. The model consists of a reusable container with an artificial cornea with a refractive power and an anterior radius of curvature similar to those of the human cornea, and a fresh cadaver eye, prepared by removing the cornea and adjusting the biometric parameters to normal values. This cadaver eye model appears to be a valuable tool for teaching and practicing anterior and posterior segment laser procedures, as well as for research on new laser systems and applications.

Anterior Eye Segment↗
PubMed1993

Collagen plug occlusion of Molteno tube shunts.

We report five patients in whom collagen lacrimal plugs were used to temporarily occlude the lumen of Molteno shunts to prevent early postoperative hypotony. Only one eye, with a double plate, developed hypotony and a flat anterior chamber that required reformation. However, in three patients, the collagen plugs did not dissolve and had to be removed surgically to lower the intraocular pressure. Although the semipermeability of collagen is desirable, its unpredictable degradation renders it unsuitable for temporary occlusion of tube shunts. Other biodegradable materials may be more appropriate for this purpose.

Aged↗
PubMed1992

Intraoperative application of 5-fluorouracil during trabeculectomy.

We report the preliminary results of the first 20 consecutive cases in which the antimetabolite 5-fluorouracil (5-FU) was applied directly beneath the conjunctival flap during trabeculectomy in high-risk patients. Seventeen were considered early successes, with 3-month postoperative intraocular pressures less than 21 mmHg, representing at least a 20% decrease from preoperative values. Successful blebs were pale, with conjunctival microcysts and without significant vascularization over the trabeculectomy site, similar to the appearance of blebs in eyes administered postoperative subconjunctival injections of 5-FU. There were no cases of corneal epithelial defects, and no eyes had lost more than one line of preoperative vision at the time of last follow up. Although the longer term efficacy of this method is unknown, these results suggest that it may represent a safe and effective alternative for administering 5-FU.

Adult↗
PubMed1990

Laser placement in noncontact Nd:YAG cyclophotocoagulation.

We treated 40 eyes of 40 patients by using noncontact transscleral Nd:YAG cyclophotocoagulation to determine whether treatment 1.5 or 3.0 mm posterior to the corneoscleral lumbus was preferable. Patients were randomly assigned to one of the treatment groups, and all other variables, including power, number, and distribution of laser applications, were kept constant. Six months postoperatively, those treated 1.5 mm posterior to the corneoscleral limbus had a lower intraocular pressure (P = .0047) than those treated 3.0 mm from the corneoscleral limbus. The 1.5-mm group also required fewer retreatment (P = .017) and had a slightly lower occurrence of visual acuity loss after this procedure. We believe it may be advantageous to locate the laser application approximately 1.5 mm posterior to the corneoscleral limbus, rather than further posteriorly, when performing noncontact transscleral Nd:YAG cyclophotocoagulation.

Aged↗
PubMed1990

Dendritic keratopathy associated with beta-blocker eyedrops.

Four patients with chronic open-angle glaucoma developed a dendriform corneal epithelial lesion. Two were associated with the use of topical betaxolol for 2 months and 6 weeks, and two were related to topical levobunolol. Resolution occurred within 2 weeks of discontinuation of the beta-blocker eyedrop. The distinctive pattern of dendritic epithelial keratopathy associated with these topical medications may be due to epithelial toxicity with subsequent regeneration.

Adrenergic alpha-Antagonists↗
PubMed1990

Effect of transscleral neodymium: YAG cyclophotocoagulation on intraocular lenses.

A neodymium: YAG laser operating in the thermal mode was used to irradiate isolated intraocular lenses (IOLs) and to perform transscleral cyclophotocoagulation on pseudophakic autopsy eyes to investigate the potential damage to IOL haptics such irradiation may cause. In the isolated IOLs, 70 mJ of energy deformed and partially melted both polymethylmethacrylate (PMMA) and polypropylene haptics. One of the capsular-fixated PC-IOL haptics in an autopsy eye partially melted when irradiated with the maximum energy level (8.8 J), with the aiming beam focused 1 mm posterior to the limbus and maximal posterior focus offset.

Humans↗
PubMed1989

Risk factors for the development of Tenon's capsule cysts after trabeculectomy.

Tenon's capsule cysts (TCCs) are a complication of glaucoma filtering surgery. They are frequently associated with substantial elevations in intraocular pressure (IOP) beginning 2 to 8 weeks postoperatively. To determine the incidence and possible risk factors for the development of TCCs, case records of all patients who received trabeculectomy over a 4-year period at the Wills Eye Hospital were reviewed. The incidence of TCCs was 28% in those who underwent trabeculectomy. Characteristics of patients after trabeculectomy in whom TCCs developed were compared with patients after trabeculectomy in whom TCCs did not develop. Both univariate and multivariate techniques were used to assess the association of characteristics associated with the development of TCCs. Factors associated with increased risk (P less than 0.05) were: history of prior TCCs, argon laser trabeculoplasty, male gender, and the use of preoperative sympathomimetics. The use of a compression shell was associated with decreased risk (P less than 0.05).

Adult↗
PubMed1988

Surgical therapy of chronic glaucoma in aphakia and pseudophakia.

Most glaucoma surgical procedures are less successful in aphakic or pseudophakic eyes. The authors reviewed 91 consecutive initial glaucoma procedures in aphakic patients from 1979 to 1986 to determine successful outcomes and complications. Success was defined as an intraocular pressure (IOP) of at least 30% below the preoperative value and less than 21 mmHg, less than 2 lines of Snellen acuity loss, and no further surgical intervention. At 9 months, success rates were: trabeculectomy, 4 of 15 patients; cyclodialysis, 3 of 20 patients; neodymium:YAG (Nd:YAG) cyclophotocoagulation, 1 of 8 patients; cyclocryotherapy, 9 of 22 patients; anterior chamber tube shunt (Schocket procedure), 3 of 6 patients; and argon laser trabeculoplasty, 2 of 20 patients. Severe complications included phthisis bulbi in 11% of cyclocryotherapy and severe visual loss in 20% with cyclodialysis and 14% with cyclocryotherapy. Results confirm the difficulty of surgical therapy in these patients.

Aged↗
PubMed1980

Characterization of cytochalasin B binding to adult rat liver parenchymal cells in primary culture.

The characterization of cytochalasin B binding and the resulting effect on hexose transport in rat liver parenchymal cells in primary culture were studied. The cells were isolated from adult rats by perfusing the liver in situ with collagenase and separating the hepatocytes from the other cell types by differential centrifugation. The cells were established in primary culture on collagen-coated dishes. The binding of [4-3H]cytochalasin B and transport of 3-O-methyl-D-[14C]glucose into cells were investigated in monolayer culture followed by digestion of cells and scintillation counting of radioactivity. The binding of cytochalasin B to cells was rapid and reversible with association and dissociation being essentially complete within 2 min. Analysis of the kinetics of cytochalasin B binding by Scatchard plots revealed that binding was biphasic, with the parenchymal cell being extremely rich in high-affinity binding sites. The high-affinity site, thought to be the glucose-transport carrier, exhibited a KD of 2.86 x 10(-7) M, while the low-affinity site had a KD of 1.13 x 10(-5) M. Sugar transport was monitored by 3-O-methyl-D-glucose uptake and it was found that cytochalasin B (10(-5) M) drastically inhibited transport. However, D-glucose (10(-5) M) did not displace cytochalasin B, and cytochalasin E, which does not inhibit transport, was competitive for cytochalasin B at only the low-affinity site, demonstrating that the cytochalasin B inhibition of sugar transport occurs at the high-affinity site but that the inhibition is non-competitive in nature. Therefore, the liver parenchymal cells may represent an unusually rich source of glucose-transport system which may be useful in the isolation of this important membrane carrier.

Animals↗
PubMed1979

I. Depressed immunological function in zinc-deprived rats as measured by mitogen response of spleen, thymus, and peripheral blood.

The in vitro responses of splenic, thymic, and peripheral blood lymphocytes to two T-cell mitogens (phytohemagglutinin and concanavalin A) and one B-cell mitogen (pokeweed mitogen) were investigated in zinc-deprived and pair-fed control rats. The responses to phytohemagglutinin of splenic, thymic, and peripheral blood lymphocytes from zinc-deprived animals were depressed by at least 50% in comparison with those of controls, and the difference between the two groups was significant for each tissue (P = 0.05). The responses to concanavalin A of splenic and peripheral blood lymphocytes were suppressed in zinc-deprived animals, and splenic and thymic responses to pokeweed mitogen were depressed by about 50% in comparison with those of controls; these results were significant at the P = 0.05 level. This study is the first to evaluate the effects of diet-induced zinc deprivation on lymphocyte transformation and immune function in rats.

Animals↗
PubMed1979

II. In vitro restoration by levamisole of mitogen responsiveness in zinc-deprived rats.

The effect of levamisole on the in vitro responses of splenic and peripheral blood lymphocytes to phytohemagglutinin were investigated in zinc-deprived and pair-fed control rats. The in vitro response of lymphocytes from zinc-deprived rats was markedly impaired in comparison with that of controls. The addition of levamisole to cultures of zinc-deprived splenic lymphocytes significantly improved their response to phytohemagglutinin by 54%. The addition of levamisole to cultures of zinc-deprived peripheral blood lymphocytes significantly improved their response by 116.2%. The addition of levamisole to control lymphocyte culture had no effect. This study may be the first to evaluate the beneficial effect of an immunomodulating agent on immune function in a nutritionally deprived host.

Animals↗