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M F Refojo

Publications and source records attributed to M F Refojo.

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

Retinoic acid in silicone and silicone-fluorosilicone copolymer oils in a rabbit model of proliferative vitreoretinopathy.

PURPOSE: The authors evaluated the effect of retinoic acid (RA) in silicone oil (SiO) and in silicone-fluorosilicone (SiFO) copolymer oil in a new rabbit model of proliferative vitreoretinopathy (PVR). METHODS: To create the PVR model, three groups of rabbits were administered vitreous injections of approximately 100,000 homologous fibroblasts, 75,000 platelet-rich plasma (PRP), and fibroblasts + PRP, respectively. These rabbits were followed up ophthalmoscopically and histopathologically for as long as 2 months. Five additional groups of rabbits underwent gas-compression vitrectomy in one eye. Four days later, group 1 was administered intravitreous RA in SiFO (9 micrograms/ml) with approximately 150,000 fibroblasts and 70,000 PRP. Group 3 was administered the same amount of fibroblasts and PRP as group 1 with RA in SiO (9 micrograms/ml). Groups 2, 4, and 5 were administered the same amount of fibroblasts and PRP as groups 1 and 3 with 1 ml of SiFO, SiO, or balanced salt solution only, respectively. To evaluate RA toxicity, RA was injected in SiO (15 and 20 micrograms/ml) and RA in SiFO (10 micrograms/ml). RESULTS: All eyes that were administered fibroblasts or PRP developed vitreous membranes, but those with PRP alone did not develop proliferative changes or retinal detachment; fibroblasts alone produced proliferative changes and retinal detachment after 2 to 3 weeks; fibroblasts + PRP produced similar changes within 3 days of injection. Retinoic acid (15 micrograms/ml) in SiO and RA (10 micrograms/ml) in SiFO was well tolerated. Retinal atrophic changes were found in eyes with 20 micrograms/ml RA in SiO. The retinal detachment rate was lower (P < 0.05) in the eyes that were administered fibroblasts + PRP and RA than in the controls. Significant differences were found in the degrees of PVR among the groups. CONCLUSIONS: RA could be useful in PVR treated with SiO or for eyes treated intraoperatively with heavier-than-water SiFO when it is used as a short-term retinal tamponade.

Animals↗
PubMed1995

Effect of poloxamer 407 on the adherence of Pseudomonas aeruginosa to corneal epithelial cells.

The effect of poloxamer 407 on Pseudomonas aeruginosa adherence to cultured epithelial cells from rabbit corneas was investigated. Three methods of bacterial quantification were used to assess P. aeruginosa adherence: scanning electron microscopy (SEM) counts, radioactivity counts, and viable bacteria counts. Confluent monolayers of rabbit corneal epithelial cells were incubated in agitation for 30 min at room temperature with H3-labeled or nonradiolabeled P. aeruginosa (10(10) bacteria/ml) in a solution of poloxamer 407 [2% or 4% in phosphate-buffered saline (PBS)] or PBS as control. Cell monolayers were washed to remove nonadherent bacteria and fixed with 2.5% glutaraldehyde and processed for SEM or processed for radioactivity counting or for culture on agar plates. The results showed that both solutions of poloxamer 407 inhibited approximately 75% of the bacterial adherence to epithelial cells (p < 0.05). Similar percentages of bacterial inhibition were obtained using the three methods of bacterial quantification. The use of an antiadherent agent such as poloxamer 407 in eye drops could possibly be a prophylactic approach to P. aeruginosa keratitis.

Animals↗
PubMed1994

Poloxamer 407 as a bacterial adhesive for hydrogel contact lenses.

Bacterial adherence and colonization of biomedical prosthetic implants is one of the main causes for implant withdrawal. The abhesive (anti-adhesive) effect of poloxamer 407 on several Gram-positive and Gram-negative strains and the site of action of its effect have been investigated. Poloxamer 407 significantly inhibited 92-99% of Pseudomonas aeruginosa adherence to hydrophilic contact lenses (P < .05). This adherence inhibition was concentration-dependent. A reduction of about 50-60% was obtained for Staphylococcus strains, and 50-70% for Gram-negative strains other than Pseudomonas. The poloxamer seems to act on the bacteria surface, but not on the contact lens surface. Poloxamer 407 could potentially prevent implant-related infections and keratitis associated with contact lens wear, by inhibiting bacterial adherence onto the implant or contact lens surface.

Bacterial Adhesion↗
PubMed1994

Histopathology of rabbit eyes with intravitreous silicone-fluorosilicone copolymer oil.

Silicone-fluorosilicone copolymer oil is characterized by being heavier than water (density, 1.16 g cm-3) and low viscosity (175-185 centistokes) compared with currently used intraocular silicone oils (density, 0.97 g cm-3 and 1000-5000 centistokes). This oil is potentially useful as an operative tool and a tamponade on the inferior retina in complicated retinal detachment. We evaluate the ocular response clinically and histopathologically within 8 weeks in rabbit phakic eyes to the purified silicone-fluorosilicone copolymer oil after vitreous cavity injection, and compared the oil tolerance with purified silicone oil (0.97 g cm-3, 5000 centistokes) and perfluorotetradecahydrophenanthrene for ophthalmic use (Vitreon, 2.03 g cm-3, 8.03 centistokes) which are currently used as operative tools and as internal retinal tamponade agents in retinal detachment surgery. Because of their low viscosity, silicone-fluorosilicone copolymer oil and perfluorotetradecahydrophenanthrene were easier to inject into the eye than silicone oil. Silicone-fluorosilicone copolymer oil and perfluorotetradecahydrophenanthrene occupied the inferior portion in the eye, and silicone oil occupied the superior portion. Fewer discrete oil droplets and weaker vessel attenuation of medullary rays than in the perfluorotetradecahydrophenanthrene-injected eyes were seen in silicone-fluorosilicone-copolymer-oil-injected eyes. Histopathologically, all retinas injected with silicone-fluorosilicone copolymer oil were normal within 4 weeks. The silicone-fluorosilicone copolymer oil dispersion did not induce histopathological changes within 8 weeks. However, thinning or disappearance of the outer plexiform layer was seen in the inferior retina in some silicone-fluorosilicone-copolymer-oil-injected eyes at 6-8 weeks. A similar effect was found in the superior retina of a silicone-oil-injected eye at 8 weeks. More severe changes such as thinning or disappearance of the outerplexiform layer, thinning and disorganization of the photoreceptor layer, and migration of the receptor cell nuclei to the photoreceptor layer were found in the inferior retina of perfluorotetradecahydrophenanthrene-injected eyes after 2 weeks. Intraocular silicone-fluorosilicone copolymer oil tolerance until about 2 months post-injection is similar to silicone oil and better than perfluorotetradecahydrophenanthrene. Silicone-fluorosilicone copolymer oil may be useful intraoperatively and as a temporary vitreous substitute in cases of inferior retinal detachment.

Animals↗
PubMed1993

Reduced bacterial adhesion to heparin-surface-modified intraocular lenses.

Bacterial adherence to intraocular lenses (IOLs) could be the cause of endophthalmitis following cataract surgery and lens implantation. There are previous reports that heparin bound to the surface of poly(methyl methacrylate) (PMMA) IOLs reduces cell adhesion. In this study, the in vitro adherence of Staphylococcus epidermidis, Staphylococcus aureus, and Pseudomonas aeruginosa to regular PMMA IOLs and to heparin-surface-modified (HSM) PMMA IOLs was investigated. The three bacterial strains attached in significantly lower numbers to HSM-PMMA IOLs than to PMMA IOLs (P < .01). Heparin in solution also inhibited attachment of Staphylococcus epidermidis to regular PMMA IOLs. Heparin may reduce adherence by placing a highly hydrated layer between the bacteria and the IOL surface. Therefore, the use of HSM-PMMA IOLs could diminish the incidence of endophthalmitis.

Bacterial Adhesion↗
PubMed1993

Effect of Pseudomonas aeruginosa concentration in experimental contact lens-related microbial keratitis.

Pseudomonas aeruginosa adherence in vitro to perfilcon A (ionic, 71% H2O) extended wear soft contact lenses--both new and after 7 days of continuous wear on closed rabbit eyes--was found to be related directly to the bacterial concentration in the contaminating solution. Thirty rabbits wore perfilcon A lenses for 7 days with complete lid closure to mimic contact lens overwear. After 7 days, conjunctival cultures showed no growth of pathogens, but all corneas had developed epithelial cell exfoliation and/or epithelial defects and stromal edema. The lenses were then incubated in various concentrations (10(7), 10(6), 10(5), 10(4), and 10(2) colony-forming units per milliliter or saline control; n = 5/group) of P. aeruginosa suspensions and replaced on their respective corneas with tarsorrhaphies for an additional 48 h. By day 9, corneal thickness had increased significantly, and P. aeruginosa keratitis had developed in 13 of 25 bacterially exposed eyes but not in 5 control eyes. Although with decreasing P. aeruginosa concentration the prevalence of ulcerative microbial keratitis also decreased, the initial concentration of bacteria or the initial extent of soft contact lens-induced corneal damage had no influence on the ultimate clinical severity of the disease.

Animals↗
PubMed1993

Silicone oil as a delivery vehicle for BCNU in rabbit proliferative vitreoretinopathy.

The antiproliferative properties of a single intravitreous injection of BCNU [carmustine; 1,3-bis(2 chloroethyl)-1-nitrosourea] dissolved in 1 ml of medical grade, 1,000-centistoke silicone oil were evaluated in a rabbit model of proliferative vitreoretinopathy (PVR). 10 micrograms and 15 micrograms of BCNU in 1 ml silicone oil resulted in a 46% and 27% reduction in the incidence of retinal detachments, respectively. Chi-square tests showed a significant statistical difference (P < 0.05) between the control and treated groups. However, histopathologic examination of the eyes injected with BCNU and silicone oil indicated some retinal disorganization even at the lower therapeutic levels. With a therapeutic index of < 1.0, BCNU in silicone oil has a low margin of safety for treatment of PVR. Nevertheless, this study demonstrates that silicone oil when used for retinal tamponade in PVR may be the vehicle for delivery of a lipophilic antiproliferative agent.

Animals↗
PubMed1993

Sustained delivery of retinoic acid from microspheres of biodegradable polymer in PVR.

PURPOSE: The aims were to obtain a controlled intravitreous release of retinoic acid (RA) by injecting drug loaded microspheres of biodegradable polymers and to study the potential use of this RA delivery system in a rabbit model of proliferative vitreoretinopathy (PVR). METHODS: The release of RA in vitro from 15 mg of 50-50 poly(DL-lactide-co-glycolide) (PLGA) in 1 ml of water at room temperature was measured with a spectrophotometer. In a rabbit model of PVR, 11 eyes were injected with 5 mg of microspheres containing 22 micrograms of RA/mg of PLGA, and seven control eyes were injected with microspheres of the same polymer that did not contain RA. In a third group, six rabbits were injected with 5 mg (n = 3) and 10 mg (n = 3) of microspheres containing RA. RESULTS: The initial concentration of RA was 20.8 micrograms/mg of PLGA. The release curve showed a fairly constant daily release of 7 micrograms/d for about 30 days. At 40 days, the release rate decreased to about 6 micrograms/d. After 40 days, 82.8% of the RA was released. Four of 11 treated rabbits (36%) and 7/7 (100%) controls showed tractional retinal detachment (TRD) (P < 0.01) after 2 months. Histopathologically, a mild, localized, foreign body reaction was observed. CONCLUSIONS: The authors obtained a sustained release of RA from PLGA microspheres in vitro for 40 days. A single injection of RA-loaded microspheres in suspension in BSS was effective in reducing the incidence of TRD after 2 months in a rabbit model of PVR.

Animals↗
PubMed1993

Antiproliferative effect of retinoic acid in intravitreous silicone oil in an animal model of proliferative vitreoretinopathy.

PURPOSE: To evaluate, in vitro, the solubility and stability of all-trans RA in silicone oil (SiO) and, in vivo, the stability and the antiproliferative effect of all-trans RA in SiO on an experimental model of PVR. METHODS: The solubility and stability of RA in SiO, in vitro and in vivo, were evaluated by HPLC. Rabbits underwent unilateral gas-compression vitrectomy and gas-SiO exchange. Rabbits received 10 micrograms (n = 17), 5 micrograms (n = 11), and 2 micrograms (n = 9) of all-trans RA in SiO, and SiO only (n = 12). All rabbits received an intravitreous injection of 150,000 fibroblasts. RESULTS: RA is stable in SiO in vitro, but some isomerization from all-trans to 13-cis was observed under light exposure. In vivo, after 1 week, trace amounts of RA in SiO were observed in the controls and in the experimental animals, suggesting a steady state between the release of RA from the SiO and from the retina to the SiO. The rate of fractional retinal detachment was significantly lower in the animals that received 10 and 5 micrograms of RA than in the controls (P < 0.05). No statistical differences were found between the eyes treated with 10 and 5 micrograms of RA. Eyes that received 2 micrograms of RA showed no difference from the control group. CONCLUSIONS: The in vivo data suggest that retinoic acid might be useful as an antiproliferative agent in human eyes.

Animals↗
PubMed1992

Long-term complications of the MAI hydrogel intrascleral buckling implant.

Seven cases in which long-term complications developed from swelling of the MAI hydrogel intrascleral buckling implant are reported herein. Micro-Fourier transform infrared spectroscopic analysis of two recovered implants demonstrated the occurrence of chemical changes leading to increased swelling. Clinical problems with the implants appeared 7 to 11 years after surgery, suggesting the need for periodic, long-term follow-up. It is possible that the present-day MIRAgel implant, which has the same chemical composition as the MAI implant, may require similar precautions.

Adolescent↗
PubMed1992

In vitro adhesion of Pseudomonas aeruginosa and Staphylococcus aureus to surface passivated poly(methyl methacrylate) intraocular lenses.

Bacterial attachment to intraocular lenses (IOLs) can be a cause of infectious endophthalmitis following cataract surgery. In this study, Pseudomonas aeruginosa and Staphylococcus aureus adhered in vitro to untreated poly(methyl methacrylate) (PMMA) and to surface passivated PMMA lenses. The IOLs were placed in bacterial suspensions (1 x 10(7) cfu/ml) in vitro. Significantly fewer S. aureus attached (P < .05) to the normal PMMA IOLs (4,535 +/- [SD] 3,052 bacteria/mm2) and to passivated PMMA IOLs (8,720 +/- 10,040 bacteria/mm2) than did P. aeruginosa (normal PMMA: 67,808 +/- 45,070 bacteria/mm2, passivated PMMA: 85,795 +/- 70,647 bacteria/mm2). The differences in bacterial attachment to surface passivated IOLs and to untreated PMMA lenses were not significant.

Bacterial Adhesion↗
PubMed1992

Attachment of Pseudomonas to human-worn, disposable etafilcon A contact lenses.

After 7 days of continuous wear, Acuvue (Vistakon, Jacksonville, FL, U.S.A.; etafilcon A) lenses were soaked in a Pseudomonas aeruginosa suspension (1.4 x 10(8) cfu/ml). New Acuvue lenses served as controls. A single strain of P aeruginosa harvested from a human corneal ulcer was used throughout the experiment. Lenses were examined by culture and scanning electron microscopy (SEM). We found significantly greater (p less than 0.05) bacterial attachment to new Acuvue lenses [culture, 3.1 x 10(4) (+/- 0.82 x 10(4)) cfu/mm2; SEM, 2.6 x 10(4) (+/- 0.47 x 10(4)) bacteria/mm2] compared with those previously worn [culture, 1.0 x 10(4) (+/- 0.17 x 10(4)) cfu/mm2; SEM, 0.73 x 10(4) (+/- 0.21 x 10(4)) bacteria/mm2]. No statistical difference was found among the individuals. Our findings demonstrate that the biological coating resulting from 1 week of continuous contact lens wear restricts P. aeruginosa attachment to the Acuvue lens when comparing new and used lenses.

Bacterial Adhesion↗
PubMed1992

Intravitreal silicone and fluorosilicone oils: pathologic findings in rabbit eyes.

The effects of medical-grade intraocular silicone and commercial-grade fluorosilicone oils were studied in rabbit eyes. The experimental model consisted of lensectomized and vitrectomized eyes that did not undergo further treatment (Group 1), and three groups of lensectomized and vitrectomized eyes that were injected intravitreously 3 months earlier with medical-grade silicone oil of 1000 cs (Group 3), and 10,000 cs (Group 4). The silicone oil-injected eyes developed proliferative membranes. The fluorosilicone oil caused an intravitreous inflammatory reaction with vacuolated macrophages present around the oil that may have been due to the higher concentration of low-molecular-weight components found in the oil.

Animals↗
PubMed1991

Corneal edema after overnight lid closure of rabbits wearing silicone rubber contact lenses.

Elastofilcon A silcone rubber contact lenses induce less corneal swelling than no lens wear during sleep, and increasing the central thickness and volume of the lens does not influence its overnight performance. We sought to elucidate whether a silicone rubber lens can promote the distribution of atmospheric O2 on the cornea through a small interpalpebral opening under closed-eye conditions. Three groups of rabbit eyes comprised 12 eyes wearing Silflex (Dk 79.8 barrer) lenses, 12 with elastofilcon A (Dk 340 barrer) lenses, and 12 without lenses. All eyes were surgically closed overnight; six eyes in each group had a complete lid closure and six eyes had a partial tarsorrhaphy that left a small, central gap approximately 3 mm in length. When the lids were opened the next morning, the partially closed elastofilcon A eyes showed less corneal swelling (6.2 +/- 1.4%) than the partially closed no-lens eyes did (9.6 +/- 1.3%) (p less than 0.01), whereas the partially closed Silflex eyes were significantly more swollen (12.8 +/- 2.1%) (p = 0.01) than the other two partially closed groups were. The completely closed eyes showed no significant difference in corneal swelling among the groups. These results indicate that small lid gaps during sleep may lead to less corneal swelling when elastofilcon A lenses are used than with no lenses.

Animals↗
PubMed1991

Pseudomonas attachment to low-water and high-water, ionic and nonionic, new and rabbit-worn soft contact lenses.

The authors determined the attachment of a single strain of Pseudomonas aeruginosa to seven brands of hydrogel soft contact lenses (SCLs): nonionic, low-water (polymacon and crofilcon); nonionic, high-water (lidofilcon); ionic, high-water (bufilcon, etafilcon, and perfilcon); and surface-neutralized, high-water (bufilcon). The lenses were exposed to a 1 X 10(8) colony-forming units (CFU)/ml P. aeruginosa suspension either when new and sterile or after 24 hr of continuous wear in rabbit eyes. Quantitative scanning electron microscopy showed that, regardless of lens type, significantly fewer bacteria attached to worn than to new SCLs (P less than 0.05). The bacterial attachment on new, unworn SCLs was significantly lower (Wilcoxon rank-sum test) (P less than 0.05) on polymacon and crofilcon than on all other lenses tested except perfilcon; on etafilcon than on bufilcon; and on perfilcon than on all SCLs tested except polymacon. The bacterial attachment on rabbit-worn SCLs was significantly lower (P less than 0.05) on polymacon than on all other lenses tested except crofilcon and perfilcon; on crofilcon than on bufilcon; on lidofilcon and on surface-neutralized bufilcon than on crofilcon and perfilcon; on etafilcon than on crofilcon, bufilcon, and perfilcon; and on perfilcon than on crofilcon and bufilcon. The results did not show a consistent relationship between hydration and surface charge and P. aeruginosa adherence. Among the SCLs tested, no one lens had a decisive advantage over another, because all, both new and worn, can bind amounts of P. aeruginosa that could potentially produce bacterial keratitis on predisposed eyes.

Animals↗
PubMed1991

Ocular toxicity of low-molecular-weight components of silicone and fluorosilicone oils.

Silicone oil (SiO) and fluorosilicone oil (FSiO) are injected into the vitreous cavity in difficult cases of retinal detachment surgery. SiO and FSiO contain linear and cyclic low-molecular-weight components (LMWC) that are thought to cause ocular toxicity. Using the purified oils (without LMWC) and some of the individual LMWC, the authors evaluated the relation of the LMWC to the short-term ocular toxicity of the oils. When octamethylcyclotetrasiloxane or other single small species of linear and cyclic LMWC of SiO were injected into the rabbit anterior chamber, severe inflammation and corneal edema were induced. The ocular responses to the single species of the LMWC of SiO decreased with an increase of the molecular weights. Cyclic LMWC of FSiO (a mixture of trimethyl-3,3,3-trifluoropropylcyclotrisiloxane and tetramethyl-3,3,3-trifluoropropylcyclotetrasiloxane) also induced inflammation and corneal edema. However, unpurified SiO and FSiO, as well as purified oils (via solvent fractionation), did not cause significant adverse ocular response, presumably because the amounts of LMWC (especially the smallest species) in the oils were relatively small. Using gas chromatography, the authors analyzed SiO and FSiO recovered from rabbit and human vitreous cavities up to 2 yr after injection. In most of the cases, the concentrations of LMWC in SiO decreased after injection. This is consistent with the possibility that LMWC diffused from the oils into the ocular tissues. The long-term effect of LMWC in intraocular SiO and FSiO has not been determined. However, diffusion of LMWC into ocular tissues may relate to the chronic ocular toxicity of the oils.

Animals↗