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Biomedical subjects

M B Landers

Publications and source records attributed to M B Landers.

At least 19 recordsLinked to original sources
PubMed1997

Antiviral chemoprophylaxis after occupational exposure to human immunodeficiency virus: why, when, where, and what.

PURPOSE: To update ophthalmologists on recent developments in the area of antiviral chemoprophylaxis after occupational exposure to human immunodeficiency virus (HIV). Background information is provided by which to make an informed decision about whether to initiate antiviral chemoprophylaxis against HIV infection. METHODS: We discuss why HIV postexposure prophylaxis should be considered; when prophylaxis should be initiated; where prophylaxis medications should be located in the operating or emergency room; and what medications might be used and the factors influencing their selection. Recent provisional recommendations by the United States Centers for Disease Control and Prevention and the International AIDS Society-USA are reviewed along with literature dealing with antiviral chemoprophylaxis against HIV infection. RESULTS: Recommendations are made for specific antiviral chemoprophylaxis after occupational exposure to HIV based on the Centers for Disease Control and Prevention and the International AIDS Society-USA provisional recommendations. Uncertain areas and the minor discrepancies in these two reports are discussed. CONCLUSIONS: Prevention of HIV transmission after accidental occupational exposure is possible. Combination therapy is more effective than monotherapy in treating HIV infections. Zidovudine (AZT or ZDV) is effective in postexposure prophylaxis; the combination of zidovudine and lamivudine (3TC) and indinavir (IDV) has greater antiretroviral activity than zidovudine alone does. The requirements for effective HIV postexposure prophylaxis may be somewhat different than those for optimum HIV treatment in the chronically ill HIV-positive patient. Ophthalmologists should have an in-depth knowledge of current thinking regarding HIV pathophysiology and treatment.

Antiviral Agents↗
PubMed1996

An infusion temporary keratoprosthesis for pars plana vitrectomy.

PURPOSE: To develop a temporary keratoprosthesis with integrated infusion cannula to minimize retinal complications during pars plana vitrectomy in eyes with an opaque cornea. METHODS: The wide-field temporary keratoprosthesis has been modified to include an integrated infusion cannula. The 20-gauge cannula runs from the periphery of the corneal flange, bends 90 degrees, and enters the eye after passing through the periphery of the corneal cylinder. RESULTS: The infusion wide-field temporary keratoprosthesis has been used successfully in three cases without the need to place a separate infusion, which risks iatrogenic retinal breaks or retinal dialyses. Droplet condensation on the posterior surface of the infusion temporary keratoprosthesis was reduced compared with the standard temporary keratoprosthesis. CONCLUSION: We have developed a wide-field temporary keratoprosthesis with an integrated infusion cannula for use during pars plana vitrectomy in eyes with severe corneal opacity. This device eliminates the risk of complications related to the pars plana infusion cannula.

Catheterization↗
PubMed1996

Fibrinolysis of experimental subretinal haemorrhage without removal using tissue plasminogen activator.

AIMS/BACKGROUND: Human recombinant tissue plasminogen activator (rt-PA) fibrinolysis of subretinal haemorrhage with concomitant removal has been shown to reverse the natural history of photoreceptor degeneration in experimental subretinal haemorrhages if evacuated within 7 days. The aim of the study was to determine whether fibrinolysis of subretinal haemorrhage without concomitant removal would offer a simpler approach with similar photoreceptor sparing. METHODS: A neodymium YAG laser was used to create experimental subretinal haemorrhages beneath the holangiotic retina of the cat. Tissue plasminogen activator (10 micrograms/ml) was injected into 4 day old subretinal haemorrhages to evaluate its effect on altering the natural history of retinal degeneration. Light and electron microscopy were used to study the histopathological effect. RESULTS: The injection of rt-PA into large 4 day old subretinal haemorrhages without concomitant removal did not alter the natural history of retinal degeneration. In fact, a second focus of retinal degeneration occurred at a gravity dependent inferior site where the subretinal haemorrhages had migrated. CONCLUSIONS: There was no therapeutic benefit from the injection of rt-PA into subretinal haemorrhages without con-comitant removal in this cat model.

Animals↗
PubMed1995

Comparison of techniques for transscleral diode photocoagulation in the rabbit.

PURPOSE: To assess the optimum probe design and treatment parameters for transscleral diode laser retinopexy. METHODS: Transscleral diode photocoagulation was performed on the eyes of Dutch-belted rabbits using three different transscleral probes: a straight, 400-microns diameter probe; a prism-tipped 400-microns diameter probe; and a prism-tipped 900-microns diameter probe. RESULTS: Transscleral diode photocoagulation with all three probe types was an effective method of ablating the retina and creating chorioretinal adhesions. Both the burn diameter and the mean radiant output energy requirement increased as the burn duration and probe aperture diameter was increased. Explosive retinal holes were encountered in 12% of the burns created with the straight probe. The use of the prism-tipped probes significantly reduced the incidence of retinal holes to < 4% (P < 0.005). Histopathologically, all burns were grade III in intensity with severe choroidal injury. In many of the burns, there was histopathologic evidence of thermal injury to the inner sclera. The frequency of these inner scleral changes was reduced with a long burn duration (5 seconds). CONCLUSION: This study confirms that diode transscleral photocoagulation is a feasible method of thermal retinopexy. The use of the prism-tipped probes and long duration burns resulted in the fewest adverse reactions.

Animals↗
PubMed1994

Fibrinolytic-assisted removal of experimental subretinal hemorrhage within seven days reduces outer retinal degeneration.

PURPOSE: To better determine the surgical window for removing experimental subretinal hemorrhages in the cat model and to compare the histopathologic effect of such removal with the natural history of untreated subretinal hemorrhages. METHODS: Twenty-three large experimental subretinal hemorrhages were created with a neodymium:YAG laser focused through a performed retinal bleb in a cohort of cats. Fourteen subretinal hemorrhages were observed without treatment, six were removed at 7 days through a micropipette after injecting 10 micrograms/ml of human recombinant tissue plasminogen activator (rt-PA) into the subretinal space, and three were removed through an access retinotomy without the use of rt-PA. The tissues from these eyes were examined with light and electron microscopy 14 to 28 days after creation of the subretinal hemorrhages. RESULTS: Severe outer retinal degeneration was evident by day 14 in all of the untreated subretinal hemorrhages 3 disc diameters or greater in size. In contrast, the outer retinal architecture was better preserved in the eyes that underwent rt-PA-assisted removal of their subretinal hemorrhage that was 3 disc diameters or greater on day 7. In these eyes, mild abnormalities such as abnormally short and misaligned photoreceptor outer segments with vacuolization were present within the retina that was formerly located over the hemorrhage center. The eyes that underwent subretinal hemorrhage removal through an access retinotomy without rt-PA on day 7 had a low-lying retinal detachment and outer retinal degeneration. CONCLUSION: Removing experimental subretinal hemorrhages within 7 days of their occurrence with the assistance of rt-PA and an ultramicrosurgical approach may reduce outer retinal degeneration in the cat model.

Animals↗
PubMed1993

A comparison of argon and diode photocoagulation combined with supplemental oxygen for the treatment of retinopathy of prematurity.

The efficacy of argon and diode laser photocoagulation of the avascular peripheral retina for threshold retinopathy of prematurity (ROP) was compared in a prospective trial. The study group included 9 premature infants (17 eyes). In each infant, one eye was treated with the diode laser indirect ophthalmoscope (LIO), and the fellow eye was treated with the argon LIO. Supplemental oxygen therapy was administered after laser treatment to all nine infants. The mean duration of the follow-up period was 9.7 +/- 2.6 months. All 17 eyes (100%) had complete regression of ROP and favorable outcomes. The diode and argon LIO appear to be equally effective in treating threshold ROP. Two patients sustained burns of the tunica vasculosa lentis and anterior lens capsule in the argon laser treated eye but not in the fellow diode treated eye. Photocoagulation with either the diode or argon LIO, combined with supplemental oxygen treatment, appears to be a promising treatment for retinopathy of prematurity.

Combined Modality Therapy↗
PubMed1992

Intraocular fluid cultures after primary pars plana vitrectomy.

To determine what organisms enter the eye and remain in the eye after pars plana vitrectomy, vitreous cavity aspirates were cultured postoperatively. Two of 33 (6%) consecutive eyes undergoing primary pars plana vitrectomy had positive cultures. One sample grew a single colony of Staphylococcus epidermidis, the second grew two colonies of Acinetobacter lwoffi. Neither of these eyes developed endophthalmitis. This study demonstrates that bacteria enter the eye at a low rate during pars plana vitrectomy and that the eye on which a vitrectomy has been performed is capable of clearing a low inoculum of bacteria.

Acinetobacter↗
PubMed1992

Ultramicrosurgical removal of subretinal hemorrhage in cats.

Subretinal hemorrhages are associated with progressive degeneration of the outer retina and a corresponding poor visual prognosis. Mixed results have been reported in previous attempts to remove such subretinal hemorrhages. We developed an ultramicrosurgical system that used the control of a stereotactic micromanipulator to direct a micropipette tip through a small retinotomy into the subretinal space in three cat eyes. Low-dose recombinant tissue plasminogen activator was then introduced into the subretinal space around the subretinal hemorrhage via a controlled microinfusion system. The recombinant tissue plasminogen activator solution facilitated clot lysis and subsequent removal through the micropipette. Light- and electron-microscopic analysis of histopathologic specimens disclosed good preservation of retinal architecture in the three cat eyes in which experimental subretinal hemorrhages were removed. This was in contrast to the retinal degeneration observed in similar but untreated experimental subretinal hemorrhages.

Animals↗
PubMed1992

Treatment of retinopathy of prematurity with argon laser photocoagulation.

Fifteen eyes of nine infants were treated for retinopathy of prematurity by confluent photocoagulation of the avascular retina using an argon laser indirect ophthalmoscope. All treated eyes presented at or beyond threshold of stage 3 retinopathy of prematurity with "plus" disease. Three treated eyes had retinopathy of prematurity in zone I. Early complete regression of extraretinal proliferation was seen in 13 eyes. At 6 month's [corrected] minimum follow-up, 11 (73%) of the treated eyes demonstrated a favorable outcome, while four eyes (27%) progressed to an unfavorable outcome. No intraocular hemorrhages occurred during any laser treatment.

Cryosurgery↗
PubMed1992

Antifibrotic and uveitogenic properties of gamma interferon in the rabbit eye.

The feasibility of gamma (gamma)-interferon injection for the treatment of ocular fibrotic conditions was studied in rabbits using recombinant rabbit gamma-interferon and the cell-injection model of tractional detachment. A toxicity study revealed that intravitreal injection of greater than 10(4) units gamma-interferon consistently produced panuveitis. For tractional detachment, 250,000 rabbit dermal fibroblasts were injected intravitreally into 20 eyes; 1 day later, 5 of these eyes received intravitreal injections of 10(4) units gamma-interferon, another 5 were given 10(6) units, and the remaining 10 received balanced salt solution. Slit-lamp examination and fundus photography were performed at regular intervals for 21 days and were graded by a masked observer. The eyes were then enucleated and processed for histology. Doses of 10(4) units gamma-interferon significantly reduced the severity of detachments, but injections of 10(6) units induced panuveitis.

Animals↗
PubMed1992

Comparison of photocoagulation with the argon, krypton, and diode laser indirect ophthalmoscopes in rabbit eyes.

PURPOSE: The purpose of this study is to compare photocoagulation with the argon green, krypton red, and diode infrared laser indirect ophthalmoscopes in an experimental setting. METHODS: Photocoagulation was performed with each of the laser indirect ophthalmoscopes in a grid pattern within one sector of the same eye of 14 Dutch-belted rabbits. Treatment was performed either with or without scleral depression. Measurements of the retinal burn diameters were performed after hemisecting the globes, and the burns were examined with light microscopy. RESULTS: Variation in burn intensity and diameter (10% to 28%) was common with all 3 laser indirect ophthalmoscopes. Five times more output energy was required to make equivalent burns with the diode laser indirect ophthalmoscope than with the argon or krypton laser indirect ophthalmoscopes. Choriovitreal hemorrhages only occurred during scleral depression. Histopathologically, the argon green laser indirect ophthalmoscope burns spared the choroid and inner sclera, while the intense krypton and diode burns had full-thickness choroidal involvement and even thermal injury to the inner sclera. Scleral depression reduced the mean energy required to create equivalent burns with all three laser indirect ophthalmoscopes. There was a 10% to 40% reduction in the mean retinal burn diameter with scleral depression (argon green, P < 0.0005; krypton red, P < 0.0005; and diode, P < 0.025). CONCLUSION: Photocoagulation with the argon green, krypton red, or diode infrared laser indirect ophthalmoscopes is a safe and effective method of retinal ablation. Decreasing the posterior nodal distance of the eye with scleral depression will produce a smaller spot on the retina with the laser indirect ophthalmoscope.

Animals↗
PubMed1992

An experimental model of ectropion uveae and iris neovascularization in the cat.

Neovascularization of the iris (NVI) is one of the most frequently studied intraocular vascular proliferations in animal models. Ectropion uveae has not been a consistent finding in these studies. In this study, a surgical model of ectropion uveae and iris neovascularization was developed that involved lensectomy, vitrectomy, bipolar cautery and transection of all three principal branch veins in the cat eye. Twelve of 14 eyes that received this procedure developed postoperative retinal detachments with a clinical picture of hemorrhagic retinopathy. These eyes progressed to a clinical picture of NVI within 1-7 wk. Eight eyes developed ectropion uveae for as much as 300 degrees. At the light microscopic level, a fibrovascular membrane was apparent on the anterior iris stroma in 9 of 14 eyes and further involved the angle in six eyes.

Animals↗
PubMed1991

A new inexpensive pump for vitreoretinal surgery.

An inexpensive and reliable fluid-gas exchange system has been developed for vitreous surgery. The system relies on a fish-tank air pump and was compared with the Grieshaber Air System in several laboratory and operating room situations. No significant differences were found between the two systems. Details of the Davis Ocular Air Pump are provided along with a cost analysis.

Drainage↗