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Biomedical subjects

M F Refojo

Publications and source records attributed to M F Refojo.

At least 91 records · Page 5Linked to original sources
PubMed1980

Tolerance of normal rabbit eyes to the antineoplastic carmustine.

Various dosages of the anticancer agent 1,3-bis(2-chloroethyl)-1-nitrosourea (carmustine, BCNU) were administered to 28 normal rabbit eyes. Single injections and series of injections were given to determine the tolerance and toxicity levels of this drug when injected directly into the vitreous cavity, the anterior chamber, or the subtenon-retrobulbar space. During a follow-up period of 3 weeks to 4 months, no significant ocular changes were noted following a single injection of BCNU into the vitreous (0.002--0.50 mg) or anterior chamber (0.001--0.250 mg), or 10 daily subtenon-retrobulbar injections (0.5--1.0 mg each). When the daily dosage was increased to 1.5--2.0 mg, corneal damage with stromal infiltration, edema, and vascularization were found after the course of the 10 subtenon-retrobulbar injections in 3 of 6 test animals.

Animals↗
PubMed1979

Mechanism of gas transport through contact lenses.

The transport of oxygen and carbon dioxide through contact lenses is important for maintaining normal corneal physiology. Gas permeation through a lens depends on the solubility and the diffusivity of the lens for that gas. Gases pass through spaces between the flexible polymer segments in plastics and rubbers. Gases diffuse through the water of hydration in hydrogel lenses, and gas permeation increases exponentially with hydration. The driving force behind gas permeation is the difference in partial pressure of the gas across the lens. The amount of gas passing through a given lens, in unit time, doubles by halving the lens thickness. Carbon dioxide permeation through any lens is several times greater than is oxygen permeation through that lens. Thus, it suffices to know the oxygen permeability in order to predict the physiological performance of a lens. The oxygen permeability coefficients of representative hard, hydrogel, and silicone rubber lenses are tabulated for easy reference.

Carbon Dioxide↗
PubMed1979

Sustained release of BCNU for the treatment of intraocular malignancies in animal models.

Sustained release of 1,3-bis(2)chloroethyl)-1-nitrosourea (BCNU) via an episcleral implanted silicone device was used to treat Brown-Pearce epithelioma in the anterior chamber of rabbit eyes. One group of test eyes received BCNU dissolved in sesame oil; a second group received BCNU in pure ethanol. Control eyes received only the diluent, sesame oil or pure ethanol. The effectiveness of the various dosages and diluents was compared by clinical observation, by weight of the enucleated eyes, and by histopathologic examination. Sustained release of BCNU via an episcleral implanted silicone device delayed the growth of Brown-Pearce epithelioma in rabbit eyes of both test groups. The most effective action resulted from administration of BCNU in pure ethanol.

Animals↗
PubMed1979

Scleral buckling with a soft xerogel implant: II. Experiments in vivo.

Experimental scleral buckling was obtained in rabbits by using soft xerogel implants placed either episclerally or intrasclerally. After implantation of 1 x 1.5 x 2 mm or 1 x 2 x 2.5 mm implants, buckle heights ranged from 1.3 to 4.0 mm. Intrascleral implantation produced a higher buckle than episcleral implantation. The follow-up period extended from 6 months to 1 year. No significant inflammatory reactions, wound dehiscence, or extrusions or intrusions of the poly(2-hydroxyethyl acrylate), PHEA, implant were observed either clinically or histologically. Our impression is that HEA can be a useful material for treatment of retinal detachment, particularly when a localized high buckle is required or for patients with thin and weak sclera.

Acrylic Resins↗
PubMed1978

Intravitreous silicone balloon: an experimental study.

A specially designed silicone balloon, expanded in vivo with normal saline, was tested for possible use as a retinal tamponade in desperate cases of rhegmatogenous retinal detachment. In six pigmented rabbits there were extensive postoperative complications, but in eight owl monkeys results were noticeably better. When the seam of the balloon was in contact with the retina there were adverse effects; seamless areas of the balloon did not appear to disturb the retina. Histopathologic studies indicated that excessive expansion of the balloon can cause significant damage, but that carefully controlled expansion can probably minimize complications. The presence of the balloon appears to alter electroretinographic response, but without necessarily causing histopathologic changes. Balloons of this type have been used in treatment of a small number of otherwise inoperable cases of retinal detachment with promising results.

Animals↗
PubMed1978

Direct delivery of anticancer agents: experimental treatment of intraocular malignancy.

Two anticancer agents, one lipophilic, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), and one hydrophilic, 5-(3,3-dimethyl-1-triazeno) imidazol-4-carboxamide (DTIC), were used to treat Brown-Pearce epithelioma in the anterior chamber of rabbit eyes. The BCNU test animals were divided into three groups: one treated by direct injection of the drug into the subconjuntival space or the anterior chamber, the second by both direct injections and intravenous administration, and the third by intravenous injection alone. The DTIC test animals were treated with only local injection into the subconjunctival space or anterior chamber. Dosage, delivery system, and effectiveness were compared following clinical observation and histopathologic examination. Direct delivery of BCNU or DTIC in subconjuntival space or anterior chamber delayed the growth of Brown-Pearce epithelioma in rabbit eye. The effectiveness of this treatment was significnatly enhanced by combining direct injection with systemic administration of a lower dose of BCNU.

Animals↗
PubMed1978

Experimental scleral buckling with a soft xerogel implant. I. Properties of poly(hydroxyethyl acrylate) compared with gelatin and other swelling implants.

Scleral buckling can be obtained with insoluble hydrophilic polymers that are implanted in the dry state (xerogels, which then expand to a predetermined size by imbibing tissue fluids. Absorbable gelatin, nonabsorbable poly(hydroxyethyl methacrylate) (PHEMA), and poly(glyceryl methacrylate) (PGMA), have been implanted as xerogels in scleral buckling procedures. Gelatin, PHEMA, and PGMA are soft when hydrated, but are hard and brittle in the dehydrated state. However, poly(hydroxyethyl acrylate) (PHEA) is soft not only in the dehydrated state. However, poly(hydroxyethyl acrylate) (PHEA) is soft only when hydrated but also when dehydrated. Dry PHEA can be carved easily to shape and size, and because it is soft it could be very useful for operations on thin, weakened sclera. We have implanted PHEA intrasclerally and suprasclerally in rabbit eyes. Tolerance of PHEA appears to be as good as that of other materials in clinical use. We have impregnated PHEA and gelatin implants with antibiotics to achieve prolonged antibiotic delivery to the surgical site. When dried impregnated gels were assayed for antibiotic activity in agar plates with Sarcina lutea, both gels displayed high but rapidly decreasing activity.

Acrylic Resins↗
PubMed1975

Expandable silicone implants for scleral buckling. III. Experiments in vivo.

Experimental scleral buckling was obtained in rabbits by using expanded silicone rubber implants under scleral trap doors. Buckle heights ranged from 2.3 to 4mm after injection of 0.05 to 0.15 ml of fluid into the implants. Therate of decrease in buckle height followed up opthalmoscopically for five months, was found to be slow and continous and was caused mainly by loosening by the scleral flaps rather than by the diffusion of fluid from the implants. Implants expanded with chorampenicol solutions provided sustained release of the antibiotic in the area of the operation. This was confirmed in agar plantes by inhibition of the growth of Sarcina lutea around subimplant tissues and the expanded implants that were recovered post mortem. These implants provided an opportunity of modify the buckle height easily, either during the procedure or postoperatively.

Animals↗
PubMed1975

Expandable silicone implants for scleral buckling. IV. Experiments with an explant for macular breaks.

A new expandable silicone rubber explant used to indent the sclera at the macula was tested experimentally in rabbits. The device consists of a Dacron-reinforced silicone rubber strip that has an expandable portion (or balloon) at its midpoint connected to a silicone filling tube. The explant was expanded with 0.03 to 0.06 ml of an antibiotic solution. Smooth, round buckles that exerted even indentation were produced. A decrease in height of 20% to 50% was observed ophthalmoscopically during six months of follow-up. The degree of buckling can be easily controlled during operation and may be modified postoperatively.

Animals↗
PubMed1975

Wettability of hydrogels. I. Poly (2-hydroxyethyl methacrylate).

The wettability characteristics of the contact lens material, PHEMA, with respect to water have been determined by using the sessile drop, and the captive air bubble techniques of contact angle goniometry. It is concluded that on PHEMA gels water does not spread spontaneously. Large hysteresis has been observed in the advancing and receding contact angles. This suggests that this hydrogel surface is capable of changing its free energy through reorientation of the polymer side chains and chain segments depending on the nature of the adjacent phase. The water content of the gels does not appear to have an effect on water wettability in the hydration range investigated. The minor wettability differences among the various gels studied were most likely due to differences in surface structure and segmental mobility due to inherent variations in the method of preparation. Small but consistent differences were found between the contact angles measured by the captive bubble method and those obtained by the sessile drop method, the former values being higher. These differences may not be method-related artifacts and cannot be explained at the present time.

Acrylates↗