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Query: UMLS:C0022568 (keratitis)
 5,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Collagen shields applied to the corneas of patients with bacterial keratitis degrade rapidly, often within a few hours. Once treatment brings the infection under control, subsequently applied collagen shields degrade more slowly. In vitro models were established to evaluate the significance of these observations. Twenty-four and 72-hour collagen shields were incubated with collagenase from Clostridium histolyticum. The in vitro rate of digestion of the shields was directly proportional to the concentration of collagenase, with the rate of digestion of the 24-hour shields being greater than that of the 72-hour shields. Therefore, the rate of collagen shield degradation may be a clinically useful index of collagenase activity on the ocular surface. Ultrastructural studies of collagen shields from patients with acute bacterial keratitis revealed irregular degradation of shield matrix with no evidence of adherence of microorganisms or inflammatory cells. Co-incubation of deepithelialized rabbit corneas and collagen shields resulted in inhibition of the digestion of the rabbit corneas when the weight:weight ratio of collagen shield:rabbit cornea was increased to greater than or equal to 2:1. Collagen shields may inhibit corneal collagen degradation in infectious ulceration and melting disorders by effectively competing for collagenase on the ocular surface.
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PMID:The collagen shield as a collagenase inhibitor and clinical indicator of collagenase activity on the ocular surface. 131 47

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.
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PMID:Collagen shields containing tobramycin for sustained therapy (24 hours) of experimental Pseudomonas keratitis. 142 60

An intrastromal injection of endotoxin lipopolysaccharide (LPS) in one eye of New Zealand albino rabbits induced a prominent keratitis characterized clinically and microscopically by edema and infiltration. Polymorphonuclear leukocytes (PMNs) constituted the primary invading leukocytic element. Collagen synthesis was measured by pulsing the corneas with 3H-proline before inducing inflammation. The invasion of the cornea by leukocytes did not alter the conversion of proline to hydroxyproline significantly in the stroma during the 14-day observation period, signifying that there were only negligible changes in the rate of collagen synthesis. However, the percentage of total stromal protein represented by collagen (ie, collagen/total protein) was only 50% of that in comparable corneas receiving an injection of phosphate-buffered saline. Some animals were rendered leukopenic by intravenous nitrogen mustard before intrastromal LPS injection caused a less severe corneal inflammatory response, characterized microscopically by fewer infiltrating leukocytes. Similarly, in nonleukopenic rabbits, topical therapy with 1% prednisolone acetate markedly reduced the corneal inflammatory response which also was characterized by fewer invading leukocytes. In neither instance was there extreme collagen loss, suggesting that the loss of stromal collagen is related to PMN infiltration.
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PMID:Quantification of stromal destruction in the inflamed cornea. 200 34

External devices have been used to enhance drug delivery. This article reviews the role of collagen shields, iontophoresis, and pumps used to deliver ophthalmic medications. Collagen shields have been used to deliver drugs and promote corneal epithelial healing. Presoaked collagen shields deliver many drugs to the eye as well as or better than traditional methods such as frequent topical therapy or subconjunctival injection. The efficacy of drug delivery by collagen shields was demonstrated in animal models of graft rejection and bacterial keratitis. Iontophoresis uses an electrical current to carry an ionized drug across tissue. Transcorneal iontophoresis delivers high concentrations of a drug to the anterior segment of the eye. Transscleral iontophoresis bypasses the lens-iris diaphragm and produces adequate vitreous levels. Pumps deliver fluid to the eye for extended periods of time via a tube with its distal opening in the conjunctival sac, corneal stroma, anterior chamber, or vitreous cavity. Clinical acceptance of the collagen shield for drug delivery to the anterior segment is better than iontophoresis or pumps, probably because the collagen shield is simpler and more convenient to use.
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PMID:Device drug delivery to the eye. Collagen shields, iontophoresis, and pumps. 206 8

Collagen shields made of porcine collagen were placed in a solution containing tobramycin sulfate (40 or 200 mg/ml) for five minutes, then applied to rabbit eyes. One, four, or eight hours after application, the corneas, aqueous humor samples, and shields were assayed for antibiotic. At all intervals, the concentration of antibiotic in the corneas and aqueous humor samples exceeded the mean inhibitory concentration for tobramycin, as determined for most strains of Pseudomonas. Shields immersed in 200 mg/ml tobramycin produced significantly higher concentrations of antibiotic in the cornea at one hour than subconjunctival injections of tobramycin (20 mg) (P = .0001). Shields immersed in 40 mg/ml tobramycin produced higher, although not significantly higher, concentrations of antibiotic in the cornea at one hour than subconjunctival injections of tobramycin (20 mg) (P = .318). Shields immersed in commercially available tobramycin drops or injectable tobramycin solution (40 mg/ml) caused no epithelial damage visible by slitlamp examination. Collagen shields containing antibiotics can serve as a vehicle for drug delivery and may prove superior to current methods for preoperative and postoperative antibiotic prophylaxis and the initial treatment of bacterial keratitis.
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PMID:Collagen shield drug delivery: therapeutic concentrations of tobramycin in the rabbit cornea and aqueous humor. 318 30

Treatment of staphylococcal keratitis includes tobramycin drops at repeated intervals, a prolonged therapy that is disruptive to the patient. To identify a regimen involving less frequent drug application, we compared the efficacy of fortified tobramycin (1.36%) administered by collagen shields or in topical drop form to rabbit corneas intrastromally infected with staphylococci. Eyes were treated with shields hydrated in and supplemented with fortified tobramycin drops (1.36%) applied every 1, 2, 5, or 10 h, from 10 to 20 h postinfection. For topical drop treatment alone, tobramycin was applied following the identical regimen. Untreated corneas contained 10(6) colony forming units. Shields supplemented with tobramycin drops applied every 1, 2, or 5 h sterilized 100% of the corneas. Shields supplemented with tobramycin drops applied at 10 h sterilized 58% of the corneas. Topical delivery of tobramycin every h sterilized all corneas; drops alone applied at longer intervals, such as 2, 5, or 10 h, sterilized 83%, 17%, and 0% of the corneas, respectively. Collagen shield delivery of tobramycin with supplemental topical drops can eradicate staphylococci in this model with less frequent dosing intervals than are required with topical therapy alone.
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PMID:Efficacy of tobramycin drops applied to collagen shields for experimental staphylococcal keratitis. 772 Mar 94

Collagen corneal shields were developed as a corneal bandage lens and are currently indicated for ocular surface protection following surgery and in traumatic and nontraumatic corneal conditions. Collagen shields are manufactured from porcine or bovine collagen and three different collagen shields are currently available with dissolution times of 12, 24, and 72 hours. The theoretical, experimental, and clinical evidence supports a role for collagen corneal shields as a drug delivery device and in the promotion of epithelial and stromal healing. Presoaking the collagen shield in a pharmacological agent with adjunctive topical treatment represents the most efficacious method of utilizing collagen shields for drug delivery. In microbial keratitis collagen shields can enhance drug delivery, promote epithelial and stromal healing, neutralize collagenases, and reduce corneal inflammation. This review will examine the evidence that supports the role of collagen shields in drug delivery and corneal wound healing. Despite a large volume of experimental (animal) work, studies on human subjects, particularly randomized controlled trials, are lacking. The authors are advocating the reassessment of the application and benefits of corneal collagen shields to clinical practice.
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PMID:Collagen corneal shields. 1268 15

Several infiltrates appeared in the upper midperipheral cornea of a 29-year-old woman who had had uneventful corneal collagen crosslinking (CXL) with riboflavin and ultraviolet-A light (UVA) for the treatment of keratoconus in the right eye. Staphylococcus epidermidis keratitis was confirmed by microbiological studies, which guided treatment with topical fortified antibiotic agents. Before CXL, the best spectacle-corrected visual acuity (BSCVA) in the right eye was 20/25, the manifest refraction was -0.25 -0.25 x 125, and the anterior segment was normal under biomicroscopy. Five months after the procedure, the BSCVA was 20/22, the manifest refraction was +1.00 -2.50 x 40, and slitlamp examination revealed a mild residual haze in the upper midperipheral cornea. Collagen crosslinking with riboflavin-UVA is a minimally invasive method but traditionally requires epithelial removal, which could be a predisposing factor to bacterial keratitis.
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PMID:Microbial keratitis after corneal collagen crosslinking. 1946 3

Collagen cross-linking (CXL) using UVA light and riboflavin (vitamin B2) was introduced as a clinical application to stabilize the cornea by inducing cross-links within and between collagen fibers. CXL has been investigated extensively and has been shown clinically to arrest the progression of keratoconic or post-LASIK ectasia. With its minimal cost, simplicity, and proven positive clinical outcome, CXL can be regarded as a useful approach to reduce the number of penetrating keratoplasties performed. Small case series have also indicated that CXL is beneficial in corneal edema by reducing stromal swelling behavior and in keratitis by inhibiting pathogen growth. Despite these encouraging results, CXL remains a relatively new method that is potentially associated with complications. Aspects such as side effects and recurrence rates have still to be elucidated. In light of the growing interest in CXL, our paper summarizes present knowledge about this promising approach. We have intentionally endeavored to include the more relevant studies from the recent literature to provide an overview of the current status of CXL.
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PMID:Collagen cross-linking: current status and future directions. 2228 5

Purpose. To review the newer treatments for bacterial keratitis. Data Sources. PubMed literature search up to April 2012. Study Selection. Key words used for literature search: "infectious keratitis", "microbial keratitis", "infective keratitis", "new treatments for infectious keratitis", "fourth generation fluoroquinolones", "moxifloxacin", "gatifloxacin", "collagen cross-linking", and "photodynamic therapy". Data Extraction. Over 2400 articles were retrieved. Large scale studies or publications at more recent dates were selected. Data Synthesis. Broad spectrum antibiotics have been the main stay of treatment for bacterial keratitis but with the emergence of bacterial resistance; there is a need for newer antimicrobial agents and treatment methods. Fourth-generation fluoroquinolones and corneal collagen cross-linking are amongst the new treatments. In vitro studies and prospective clinical trials have shown that fourth-generation fluoroquinolones are better than the older generation fluoroquinolones and are as potent as combined fortified antibiotics against common pathogens that cause bacterial keratitis. Collagen cross-linking was shown to improve healing of infectious corneal ulcer in treatment-resistant cases or as an adjunct to antibiotics treatment. Conclusion. Fourth-generation fluoroquinolones are good alternatives to standard treatment of bacterial keratitis using combined fortified topical antibiotics. Collagen cross-linking may be considered in treatment-resistant infectious keratitis or as an adjunct to antibiotics therapy.
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PMID:New treatments for bacterial keratitis. 2299 50


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