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M F Refojo

Publications and source records attributed to M F Refojo.

At least 19 recordsLinked to original sources
PubMed1995

Scanning electron microscopy of the early host inflammatory response in experimental Pseudomonas keratitis and contact lens wear.

Because contact lens wear causes changes in tear film and corneal metabolism and can render the cornea susceptible to bacterial invasion, we examined the role of contact lens wear in Pseudomonas aeruginosa (P. aeruginosa) keratitis and its relation to the early defense mechanism, specifically whether the acute polymorphonuclear leukocyte (PMN) response is altered by contact lens wear. Thirty-three rabbit eyes were examined in an experimental model for P. aeruginosa keratitis. The development of bacterial invasion and PMN migration into the wound was studied during various time intervals in either the presence or absence of a soft hydrogel contact lens (SCL). Scanning electron microscopy revealed massive PMN accumulation in the P. aeruginosa-inoculated corneas without SCL and some, but distinctively fewer, PMNs in the bacteria-inoculated eyes with SCL. These observations demonstrate that P. aeruginosa inoculation evokes massive PMN reaction and suggests that SCL wear actually delays this early host inflammatory response. Thus, SCL wear seems to act as a barrier for the PMNs that presumably derive from the tear film.

Animals↗
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↗
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↗
PubMed1990

Time course of experimental Pseudomonas aeruginosa keratitis in contact lens overwear.

New perfilcon contact lenses (71% water) were placed on one eye of 36 rabbits under complete tarsorrhaphy for 7 days. The lenses were then removed, and 18 were incubated for 1 hour with a suspension of 1 x 10(8) colony-forming units per milliliter of Pseudomonas aeruginosa and replaced on their respective corneas. The remaining 18 eyes were inoculated with 0.1 mL of the P aeruginosa suspension; the lenses were not replaced. All eyes were again closed by tarsorrhaphy for 4, 8, 16, 24, 36 , or 48 hours. Ulcerative keratitis occurred in contact lens-wearing eyes only, as P aeruginosa penetrated the epithelium at 8 to 36 hours, and polymorphonuclear leukocyte migration began at 24 hours. Compared with conventional abrasion-wound models, the time course of infectious keratitis in this model was delayed, possibly due to less preexisting corneal trauma, but our findings suggest that soft contact lens wear facilitates bacterial invasion and also inhibits the host inflammatory response.

Animals↗
PubMed1990

Experimental Pseudomonas aeruginosa keratitis from extended wear of soft contact lenses.

We used a rabbit model to investigate the pathogenesis of soft contact lens-induced bacterial keratitis. Rabbit eyes underwent complete tarsorrhaphy for 7 days either with (group A, n = 14) or without (group B, n = 13) new sterile soft contact lenses. On day 7, an increase in mean corneal thickness (20.3% in group A and 17.2% in group B) was detected. New or rabbit-worn soft contact lenses were then inoculated with 10(7) colony-forming units of Pseudomonas aeruginosa or by 0.1 mL of P aeruginosa suspension. On day 9, conjunctival cultures of all eyes yielded P aeruginosa. Corneal infection developed in 11 of 14 eyes wearing new or worn, contaminated soft contact lenses. Bacterial keratitis did not develop in any of the 13 eyes inoculated with P aeruginosa suspension. Light and electron microscopy of infected eyes showed abundant polymorphonuclear neutrophils destroying the epithelium, basement membrane, and stroma. Few bacteria could be detected and only in the deep stroma. Since bacterial suspension alone caused no inflammation, soft contact lens-wear appears crucial to corneal infection in this model.

Animals↗
PubMed1990

Evaluation of a viscoelastic solution of hydroxypropyl methylcellulose as a potential vitreous substitute.

Hydroxypropyl methylcellulose (HPMC), an inert polymer that forms a viscoelastic solution in aqueous media, is useful for anterior segment surgery. A 2.2% solution of HPMC (MW 86,000 daltons) of 6,000 centistokes viscosity was evaluated as a vitreous substitute in rabbit eyes. Four days after perfluoropropane gas compression of the vitreous, the gas was exchanged with 0.5 ml HPMC. The aqueous was removed 1 and 2 weeks postinjection and at sacrifice, the vitreous was removed at sacrifice. HPMC concentrations in aqueous humor were: 0 hr, 0%; 48 hr, 0.002%; 1 week, 0.004%; 2 weeks, 0.001%; 4 weeks, 0%. HPMC concentrations in vitreous were: 48 hr, 93% of amount injected; 2 weeks, 88%; 4 weeks, 78%; 10 weeks, 0%. Hyaluronidase injected in the vitreous enhanced HPMC elimination. The effect of HPMC also was assayed on a cultured retinal pigment epithelial monolayer. Compared with controls, HPMC-treated cells maintained normal morphology at 5 days, and 2, 3, and 4 weeks as observed by light microscopy. Because of rapid intraocular decrease in viscosity, HPMC is not a good long-term vitreous replacement to support retinal tears. However, HPMC might be useful short-term to avoid postoperative hypotony, and to remove intraocular silicone oil and peel retinal membranes.

Animals↗
PubMed1990

Factors contributing to the emulsification of intraocular silicone and fluorosilicone oils.

Silicone oil (SiO) and fluorosilicone oil (FSiO) are used as vitreous substitutes during retinal detachment surgery. Emulsification of these oils causes complications in oil-injected eyes. One factor contributing to emulsification is interfacial tension (gamma i) of the oils. In general, the lower the gamma i, the more easily the oils are emulsified. We measured the gamma i of SiO and FSiO by the ring method at 37 degrees C; corrected the measured values by the Harkins-Jordan table or the Zuidema-Waters equation; and found that the gamma i between the oils and liquefied bovine vitreous was low compared with the gamma i between the oils and water (eg, gamma i of 1000 centistokes [cs]SiO against liquefied vitreous and water was 16.0 and 42.8 dyne/cm, and that of 1000 cs FSiO was 14.7 and 38.7 dyne/cm, respectively). When SiO or FSiO and liquefied vitreous were shaken in a partially filled vial, both oils were emulsified regardless of viscosity and purity. However, when the vial was filled completely (a situation in which the hydrodynamic condition of the oils may be similar to that in the eye), SiO of 1000 and 12,500 cs and FSiO of 10,000 cs did not emulsify, although FSiO of 1000 cs did emulsify. SiO was less emulsified than FSiO of the same viscosity, possibly because the smaller density difference between SiO and intraocular fluids makes agitation difficult compared with FSiO. High viscosity of the oils restricted mechanical emulsification, which was not prevented by eliminating low-molecular-weight components of the oils. Residual catalysts may relate to spontaneous emulsification, which was observed occasionally with high-viscosity SiO in water.

Animals↗