Prevention of endophthalmitis by collagen shields presoaked in fourth-generation fluoroquinolones versus by topical prophylaxis

PURPOSE: To compare the prophylaxis of collagen shields presoaked in antibiotics versus antibiotic drops after bacterial anterior chamber challenge. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. METHODS: Forty rabbits received bilateral 0.03 mL intracameral injections of Staphylococcus epidermidis (5 x 10(8) colony-forming units). Four groups of 10 rabbits had their eyes randomized to receive (1) 3 mg/mL gatifloxacin (Zymar) drops or shield in Zymar, (2) Zymar drops or shield in 10 mg/mL gatifloxacin (Tequin), (3) 5 mg/mL moxifloxacin (Vigamox) drops or shield in Vigamox, or (4) balanced salt solution (BSS) drops or shield in BSS. Each eye received Zymar, Vigamox, or BSS 4 times 1 hour before injection. The antibiotic-BSS was administered every 2 hours (5 doses total). One day later, signs of endophthalmitis were scored under the slitlamp. RESULTS: Groups 1 and 2 had significantly lower endophthalmitis incidences (total score > or = 8) than the BSS controls. Shield scores were not significantly different from those of the counterpart drops. The comparison between drops was not significant (P = .0513); the difference between shields (P = .0232) and the post-comparison Zymar versus BSS shields (P = .0021) were significant. CONCLUSIONS: Topical therapy with gatifloxacin before and after intraocular bacteria challenge led to lower incidences of endophthalmitis in rabbits. Prophylaxis with presoaked collagen shields was not statistically different than that with topical drops.     

Delivery of fluorescein to the anterior chamber using the corneal collagen shield

Collagen corneal shields show promise as an alternative method of drug delivery to the eye. The authors quantified collagen shield delivery of sodium fluorescein to the aqueous humor in human volunteers using fluorophotometry. Collagen shields that had been immersed in 0.01% sodium fluorescein were applied to eyes of human volunteers. The shields delivered significantly more fluorescein to the aqueous humor at 2 and 4 hours compared with drops of the same concentration instilled every 30 minutes for 4 hours (P less than 0.0001 and P = 0.0003, respectively) or daily wear soft contact lenses presoaked in 0.01% fluorescein (P less than 0.0001 and P less than 0.0025, respectively). Collagen shields did not induce damage to the corneal epithelium over a 2-hour wearing period. These results suggest that the collagen shield may be superior to topical drops in delivering water-soluble compounds to the cornea and aqueous humor.     

Collagen shield delivery of amphotericin B

By using a high-pressure liquid chromatography assay, we investigated the ability of collagen shield therapeutic contact lenses to release amphotericin B and deliver it to the anterior segment of rabbit eyes. In vitro studies showed that presoaked collagen shields released most of the amphotericin B within the first hour of elution. We compared the corneal and aqueous humor amphotericin B levels produced by collagen shields soaked in amphotericin B and frequent-drop therapy at four time points over a six-hour period. The collagen shields soaked in amphotericin B produced corneal levels that were higher than those produced by frequent-drop therapy at one hour, equivalent to drop therapy at two and three hours, and lower than drop therapy at six hours. There were no differences in amphotericin B levels in aqueous humor at any time point between rabbits treated with collagen shield delivery and rabbits treated with frequent-drop delivery. The results of this study suggest that amphotericin B delivery to the cornea by collagen shields is comparable to frequent-drop delivery but has the potential benefit of added convenience and compliance.     

Collagen shield delivery of trifluorothymidine

Corneal and aqueous levels of topically applied trifluorothymidine (F3T) were compared with and without the collagen shield in normal and damaged rabbit eyes. Shields were presoaked in 1% F3T for 15 minutes prior to application. Rabbits received either a presoaked shield, 1% F3T drops every two hours, or both. Corneal and aqueous levels of F3T were measured at 30 minutes, two, four, and eight hours. If 5 mm epithelial defects were created, the collagen shield and topical F3T drops produced significantly higher levels of F3T than drops alone at all periods tested (P less than .05). A presoaked shield alone produced greater levels of F3T than drops alone at 30 minutes and two hours (P less than .05). Collagen shields did not enhance F3T levels in eyes with intact epithelium. Implications for treatment of herpetic keratouveitis are discussed.     

Collagen shields containing tobramycin for sustained therapy (24 hours) of experimental Pseudomonas keratitis.

We compared collagen shields hydrated in 1.36% tobramycin with topical 1.36% tobramycin for sustained treatment of experimental Pseudomonas keratitis in rabbits. Antibiotic therapy for a total of 24 hours was initiated 14 hours after an intrastromal injection of 10(3) logarithmic phase Pseudomonas aeruginosa. Seven groups were treated as follows: groups 1-3, collagen shields hydrated in tobramycin supplemented with topical 1.36% tobramycin drops at 4, 6, or 8 hour intervals; group 4, collagen shields hydrated in tobramycin without any further topical supplementation; group 5, topical tobramycin therapy, initially every half-hour for 4 hours, then hourly; group 6, collagen shields hydrated in balanced saline solution; and group 7, no treatment. Each group contained four eyes. The groups treated with collagen shields supplemented every 4 or 6 hours with topical tobramycin had significantly fewer colony forming units (CFU) than those receiving topical or collagen shield therapy alone (P < 0.001). The group treated with collagen shields hydrated in sterile saline had 10(7) CFU per cornea, which was not significantly different from the untreated group (P > 0.2). Collagen shields hydrated in tobramycin and supplemented with topical tobramycin were effective in sustained treatment of experimental Pseudomonas keratitis.     

Efficacy of tobramycin-soaked collagen shields vs tobramycin eyedrop loading dose for sustained treatment of experimental Pseudomonas aeruginosa-induced keratitis in rabbits.

We compared the efficacy of a fortified tobramycin-soaked collagen shield to the efficacy of a single loading dose (four 50-microliters drops) of fortified tobramycin eyedrops in the treatment of New Zealand White rabbits with Pseudomonas aeruginosa-induced keratitis. Eyedrop loading-dose efficacy was evaluated with and without lateral tarsorrhaphy. Six hours after a single treatment, significantly fewer Pseudomonas colonies were present in the corneas of all three drug-treated groups as compared to the number of colonies in the corneas of balanced salt solution-treated control rabbits (P less than .006). Although no significant difference was observed between any of the drug-treated groups, lateral tarsorrhaphy was associated with a greater than tenfold decrease in the number of colony-forming units (P = .073). We found no significant difference in efficacy between a collagen shield presoaked in tobramycin, and a single loading dose of tobramycin eyedrops, in the treatment of rabbits with P. aeruginosa-induced keratitis.     

Evaluation of corneal collagen shields as a drug delivery device for the treatment of experimental Pseudomonas keratitis.

PURPOSE: To clarify the role of corneal collagen shields as a drug delivery device for the treatment of bacterial keratitis, the authors studied the effectiveness of topical gentamicin treatment, with and without the use of corneal collagen shields, in a rabbit model of Pseudomonas keratitis. METHODS: Forty-eight New Zealand white rabbits were infected by injecting 500 colony-forming units (CFU) of Pseudomonas aeruginosa into the corneal stroma, and treatment was begun 24 hours later. A 13.6 mg/ml solution of gentamicin was topically administered during a 24-hour period. Collagen shields were soaked in gentamicin 13.6 mg/ml for 5 minutes before placing them on the cornea. Corneas were quantitatively cultured 1 hour after the treatment period ended. Six different groups of rabbits were tested, with the results analyzed as the mean log10 of bacterial CFU. RESULTS: An untreated control group had significantly more bacteria (7.96 +/- 0.74) than any of 5 treatment groups. No difference was found between groups given a loading dose of antibiotic drops at the beginning of treatment, either with (4.90 +/- 2.41) or without (6.25 +/- 0.54) an antibiotic-impregnated collagen shield. A group treated with a collagen shield augmented with gentamicin drops every 3 hours had fewer bacteria (1.52 +/- 1.82) than a group receiving drops alone (4.15 +/- 1.83) (P less than 0.05). However, treatment with a collagen shield supplemented with drops every 3 hours was not as effective as gentamicin drops administered every 30 minutes (no bacterial growth) (P less than 0.05). CONCLUSION: These results show that antibiotic-impregnated collagen shields should not replace traditional antibiotic drop therapy as the mainstay of treatment but may be a useful adjunct to treatment with topical antibiotics.     

Toxicological evaluation of micafungin ophthalmic solution in rabbit eyes.

There have been no reports of the topical application of micafungin to the eye. The aim of this study was to evaluate the safety of topical instillation of 0.1% micafungin ophthalmic solution in rabbit eyes. In New Zealand white rabbits (n = 6), 50 microL of 0.1% micafungin solution was topically instilled to 1 eye, and 50 microL of sterile saline was applied to the other eye. Both eyedrops were administered hourly from 7 A.M. for 7 days. Measurements were conducted on corneal thickness, intraocular pressure, endothelial cell density, and lactate dehydrogenase (LDH) activity of tear samples. The eyes were examined slit-lamp biomicroscopically and histopathologically. Topical micafungin application for 1 week did not induce any changes in intraocular pressure, endothelial cell density, and tear LDH. Corneal thickness after instillation was slightly, but significantly, smaller in the micafungin group than in the control group (P = 0.0156, paired t test), but this difference disappeared within 24 hours after the final instillation. Biomicroscopy and histopathology revealed no significant toxic influence of micafungin application on the cornea. Topical instillation of micafungin solution had no apparent toxicity to the cornea. These results warrant future studies on the efficacy of micafungin ophthalmic solution against corneal fungal infection.     

Lysozyme in corneal ulcer.

In the present experimental study the role of lysozyme drops in healing of corneal ulcer of staphylococcal origin (sensitive to chloramphenicol) was studied on 16 albino rabbits. In 8 rabbits, in one eye placibo drops (distilled water) and in the other eye lysozyme 1% were put 4 times daily. In the other 8 rabbits, in one eye chloramphenicol drops 0.4% and in the other eye chloramphenicol drops 0.4% + lysozyme drops 1% were instilled 4 times daily. It was observed that the rate of healing of corneal ulcer was much earlier in the eyes which had local instillation of chloramphenicol drops + lysozyme in comparison to the eyes which had only chloramphenicol drops, lysozyme drops, or distilled water.     

Intravitreal corticosteroids in the treatment of exogenous fungal endophthalmitis.

A rabbit model of exogenous Candida albicans endophthalmitis was used to determine if intravitreal corticosteroids combined with an efficacious antifungal agent enhanced fungal proliferation and ocular destruction, or if the combination can suppress the inflammatory and immunogenic response that causes retinal and uveal destruction. Exogenous Candida albicans endophthalmitis was experimentally induced in 20 rabbit eyes. Eight eyes received intravitreal amphotericin B alone; eight eyes received amphotericin B plus dexamethasone. Four eyes served as controls. By clinical grading on the fourth day after infection, the vitreous of the eyes in the two drug-treated groups was significantly clearer in comparison to that of eyes in the control group. By the seventh day after infection, the eyes treated with amphotericin B plus dexamethasone had significantly clearer vitreous in comparison to the eyes receiving only amphotericin B (P = 0.0017). Quantitative culture results were negative in both treatment groups, and histopathologic examination confirmed the clinical grading. Contrary to current beliefs, there was no evidence that the addition of corticosteroids impaired antifungal activity or enhanced fungal proliferation.     

Cyclosporine-containing collagen shields suppress corneal allograft rejection

Thirty-seven rabbit eyes with penetrating keratoplasty grafts placed in vascularized beds to enhance the possibility of graft rejection were treated with cyclosporine delivered in collagen shields or drops of olive oil. Treatment was begun either immediately after grafting or at the first sign of immune graft reaction. Mean survival time of the grafts in the collagen shield treated eyes was significantly longer than in the eyes treated with drops. In the eyes treated at the first sign of graft reaction, cyclosporine in collagen shields halted the rejection process; seven of these eyes survived the 120-day observation period, compared to one of the eyes treated with drops. These results indicate that the collagen shield is an effective delivery system for cyclosporine and the topically administered cyclosporine is effective in suppressing the initiation of graft rejection and in reversing a graft reaction in progress.     

Keratomycosis caused by Candida albicans

A 78-year-old female patient developed mycotic keratitis in her right eye three months after penetrating keratoplasty. Multiple myeloma is presumed to have been the predisposing factor. Candida albicans was isolated from the aqueous humor at the time of surgery. Treatment consisted of systemic ketoconazole (p.o.) and miconazole (i.v.); miconazole eye drops were applied topically and amphotericin B was instilled into the anterior chamber. Resolution of the corneal infection was ultimately achieved with this therapy.     

Effect of amniotic membrane transplantation on the healing of bacterial keratitis

PURPOSE: To study, with the use of an animal model, the efficacy of amniotic membrane (AM) transplantation as adjunctive treatment in corneal healing after bacterial keratitis. METHODS: Staphylococcus aureus keratitis was induced in 47 rats by injection of bacteria into the corneal stroma. Treatment was started 48 hours later with one of three randomly assigned protocols: cefazolin drops (50 mg/mL) and AM transplantation (n = 16); nonpreserved 0.9% saline drops and AM transplantation (n = 15); or cefazolin without AM transplantation (n = 16). Cefazolin and saline drops were administered every 30 minutes for 6 hours, then hourly for 6 hours. AM was transplanted 24 hours after termination of cefazolin or saline treatment. Results were clinically assessed 7 days after AM transplantation or at the corresponding time in the nontransplanted animals. The rats were then killed, and their corneas were removed for bacterial counts or histopathologic examination. RESULTS: The best clinical results were observed in the group treated with cefazolin and AM transplantation, manifested by the least corneal haze and neovascularization (P = 0.007 and P = 0.014, respectively) and minimal bacterial counts (28 colony-forming units [CFU]/mL compared with 160 CFU/mL and 240 CFU/mL, respectively). Histopathologic examination showed that the central corneal vessels from rats treated with cefazolin and AM were smaller and less congested than those from the other two groups. CONCLUSIONS: AM transplantation is a useful adjunctive treatment after bacterial keratitis in this rat model. The transplanted AM improved the healing process, resulting in decreased corneal haze and less neovascularization.     

Differences in response in vivo to amphotericin B among Candida albicans strains

A group of ten Candida albicans strains previously determined to be resistant or susceptible to topical amphotericin B in vivo and in vitro were exposed to treatment with different concentrations of the drug in a quantitative model of candidal keratitis in Dutch-belted rabbits. After 5 days of topical treatment with amphotericin B eye drops in concentrations of 0.3%, 0.03%, or 0.003%, quantitative isolate recovery in treated animals was compared with that of untreated controls. A dose response was observed for all five susceptible strains. The two strains that were most sensitive to amphotericin B in vitro also were the most susceptible in vivo. At each dose level there was a two- to eightfold reduction in isolate recovery among highly susceptible strains compared with less susceptible strains (P less than 0.05). The five resistant strains remained so even when the 0.3% concentration was used. Among strains of C. albicans susceptible to amphotericin B, there appeared to be a variation in degree of susceptibility in vivo that correlated with the minimum inhibitory concentration.     

Collagen shields as a drug delivery system for the fourth-generation fluoroquinolones

PURPOSE: To evaluate the penetration of commercially available gatifloxacin and moxifloxacin into the anterior chamber of a rabbit eye using collagen shields presoaked in the antibiotics as a drug delivery system. METHODS: Collagen shields, presoaked for 10 min in commercially available solutions of gatifloxacin (diluted intravenous Tequin) or moxifloxacin (Vigamox) with the same concentration, were placed on the surface of each of the corneas of 12 rabbits for a total of 24 eyes (12 in each group). Aqueous humor samples were taken 3 and 6 h later. RESULTS: The concentrations of both antibiotics were high after 3 h (3.1 +/- 1.3 microg/ml for moxifloxacin and 2.3 +/- 0.8 microg/ml for gatifloxacin, p = 0.22). The concentration of gatifloxacin after 6 h was statistically significantly higher than for moxifloxacin (0.76 +/- 0.33 microg/ml vs. 0.29 + 0.14 microg/ml, respectively, p = 0.03). CONCLUSION: Our results suggest that collagen shields can be effective as a drug delivery system for the fourth-generation fluoroquinolones with a longer effect for gatifloxacin.     

Efficacy of liposome-bound amphotericin B for the treatment of experimental fungal endophthalmitis in rabbits

The efficacy of intravitreally administered amphotericin B was evaluated. Experimental fungal infections were produced by inoculation of Candida albicans organisms into the vitreous cavities of 46 rabbit eyes. After 72 hr, eight eyes received intravitreal injections of 10 micrograms of free amphotericin B; and ten eyes each received 10 micrograms, 20 micrograms, and 40 micrograms of liposome-bound amphotericin B. The remaining eight eyes served as controls: four eyes received dextrose solution and four eyes received empty liposomes. Histopathologic examination 8 weeks after inoculation showed clear vitreous without retinal damage in groups treated with either 10 micrograms free amphotericin B or 20 micrograms of liposome-bound drug. All eyes in the control group and six eyes (60%) in the group treated with 10 micrograms of liposome-bound amphotericin B developed vitreous abscesses with evidence of fungal infection. In eyes treated with 40 micrograms of liposome-bound amphotericin B, fungal infection was successfully eradicated, but retinal damage was detected in all eyes by light microscopy. It is proposed that a reduced toxicity of intravitreally injected liposome-bound drugs is accompanied by reduced efficacy. In the treatment of fungal endophthalmitis, an increased dosage of liposome-bound amphotericin B (above that dosage of free drug which would be required) is suggested.     

Efficacy of topical caspofungin in experimental fusarium keratitis

PURPOSE: To evaluate the efficacy of caspofungin in an experimental rabbit model of Fusarium keratitis and to compare it with amphotericin B. METHODS: Eighteen New Zealand white rabbits were randomly divided into 2 treatment groups and 1 control group. One cornea of each rabbit was inoculated with Fusarium solani spores. The first group received topical amphotericin B 0.15%, the second group received topical caspofungin 1%, and the control group received topical balanced salt solution hourly for 2 days and then 4 times daily for 3 additional days. Treatment effects were evaluated by clinical assessment at days 3 and 5 and by fungal culture after 5 days of treatment. RESULTS: In the treatment groups, progression of keratitis was inhibited, and cultures were sterile at the end of the study. In the control group, keratitis progressed, and cultures were positive for F. solani. CONCLUSIONS: Topical caspofungin is effective in Fusarium keratitis, and clinical efficacy studies seem justified.     

Experimental keratomycosis in a mouse model

PURPOSE: To establish a murine model of corneal candidiasis that permits molecular evaluation of fungal adherence and invasion. METHODS: Corneas of immunocompetent, methylprednisolone-treated, and cyclophosphamide-treated adult NIH Swiss and BALB/c mice were topically mock inoculated or inoculated with 10-fold increasing amounts between 100 and 100 million colony-forming units (CFU) of Candida albicans after unilateral corneal scarification. Mock-inoculated eyes served as the control. Eyes were scored daily on a 12-point scale to categorize corneal inflammation and were enucleated for quantitative fungal cultures, analysis by polymerase chain reaction (PCR), and histopathologic examination. RESULTS: At least 100 CFU of C. albicans initiated measurable corneal infection, but 1 million or more colony-forming units were needed to induce consistent keratitis. Treatment with methylprednisolone increased disease severity in infected BALB/c mice and fungal persistence in both BALB/c and NIH Swiss mice. Treatment with cyclophosphamide increased disease severity and fungal persistence in both strains of mice. Infectious organisms were recovered by quantitative culture, and candidal DNA was detectable by PCR. C. albicans, inflammatory cells, and stromal necrosis were histologically evident within ocular tissue. CONCLUSIONS: Although mice are innately resistant to Candida infection after corneal inoculation, moderate to severe keratomycosis can be established in immunocompromised mice by the route of corneal scarification. Although differences between mouse strains and among immunosuppressive regimens remain to be explored, this murine model provides the basis for understanding the pathogenesis of fungal infections of the cornea.     

The effect of collagen shields on epithelial wound healing in rabbits

We evaluated the effect of a collagen shield on epithelial healing in keratectomy wounds in rabbit eyes. Superficial keratectomies 6 mm in diameter were created in 12 eyes of six rabbits. Six eyes received collagen shields every eight hours; six eyes received no treatment (control group). Epithelial healing was significantly faster (P less than .01) in corneas treated with collagen shields (47.8 +/- 1.1 microns/hr) compared to untreated control corneas (40.8 +/- 1.6 microns/hr). Regression analysis gave a projected time for closure of treated corneas of 73.96 hours, compared to 83.41 hours for untreated corneas. Scanning electron microscopy of collagen shields after eight hours of wear showed a large number of polymorphonuclear leukocytes entrapped in the collagen matrix. Light microscopy of healed corneas showed that the appearance of the regenerated epithelium in treated and untreated corneas was similar. These results demonstrate that collagen shields speed reepithelialization of keratectomy wounds in the rabbit cornea.     

Determination of aqueous and vitreous concentration of moxifloxacin 0.5% after delivery via a dissolvable corneal collagen shield device

PURPOSE: To determine the penetration of moxifloxacin 0.5% in the human aqueous and vitreous when delivered by a presoaked collagen shield. SETTING: University-based clinical practice. METHODS: Moxifloxacin 0.5% was administered before vitrectomy surgery in 10 patients using a 24-hour dissolvable cross-linked corneal collagen shield delivery device. Aqueous and vitreous samples were obtained after the shield was placed for 4 hours in the first 5 patients and for 24 hours in the second 5 patients. Assays were performed using high-performance liquid chromatography. RESULTS: Delivery of moxifloxacin via a collagen shield revealed a mean aqueous concentration of 0.30 microg/mL +/- 0.17 (SD) 4 hours after placement (n = 5). Vitreous levels at 4 hours and aqueous and vitreous levels at 24 hours were negligible using this route of administration. Peak aqueous moxifloxacin levels occurred soon after shield placement. This is when high concentrations of moxifloxacin are most needed to clear the aqueous of bacteria. The minimum inhibitory concentration at which 90% of the isolates were inhibited for organisms commonly responsible for endophthalmitis was exceeded in the 4-hour aqueous group. Negligible concentrations were detected at 24 hours. CONCLUSIONS: Although aqueous moxifloxacin levels achieved through the use of a collagen shield delivery device are lower than via topical drops, there are several advantages to this route of delivery that make it appealing in the immediate postoperative period. Future studies will be needed to define precisely the role of fourth-generation fluoroquinolones and presoaked collagen shields in the prophylaxis or management of intraocular infections.