Outcome of the keratoprosthesis surgery varied markedly with preoperative diagnosis. Most favorable was graft failures in non-cicatrizing conditions, whereas Stevens-Johnson syndrome was the worst. Ocular cicatricial pemphigoid and chemical burns occupied a middle ground. The difference between the groups seemed to correlate with the degree of past preoperative inflammation.
Purpose
To formulate and characterize a drug-eluting contact lens designed to provide extended, controlled release of a drug.
Methods
Prototype contact lenses were created by coating PLGA (poly[lactic-co-glycolic acid]) films containing test compounds with pHEMA (poly[hydroxyethyl methacrylate]) by ultraviolet light polymerization. The films, containing encapsulated fluorescein or ciprofloxacin, were characterized by scanning electron microscopy. Release studies were conducted in phosphate-buffered saline at 37°C with continuous shaking. Ciprofloxacin eluted from the contact lens was studied in an antimicrobial assay to verify antimicrobial effectiveness.
Results
After a brief and minimal initial burst, the prototype contact lenses demonstrated controlled release of the molecules studied, with zero-order release kinetics under infinite sink conditions for over 4 weeks. The rate of drug release was controlled by changing either the ratio of drug to PLGA or the molecular mass of the PLGA used. Both the PLGA and the pHEMA affected release kinetics. Ciprofloxacin released from the contact lenses inhibited ciprofloxacin-sensitive Staphylococcus aureus at all time-points tested.
Conclusions
A prototype contact lens for sustained drug release consisting of a thin drug-PLGA film coated with pHEMA could be used as a platform for ocular drug delivery with widespread therapeutic applications.
Alkali burns to the eye constitute a leading cause of worldwide blindness. In recent case series, corneal transplantation revealed unexpected damage to the retina and optic nerve in chemically burned eyes. We investigated the physical, biochemical, and immunological components of retinal injury after alkali burn and explored a novel neuroprotective regimen suitable for prompt administration in emergency departments. Thus, in vivo pH, oxygen, and oxidation reduction measurements were performed in the anterior and posterior segment of mouse and rabbit eyes using implantable microsensors. Tissue inflammation was assessed by immunohistochemistry and flow cytometry. The experiments confirmed that the retinal damage is not mediated by direct effect of the alkali, which is effectively buffered by the anterior segment. Rather, pH, oxygen, and oxidation reduction changes were restricted to the cornea and the anterior chamber, where they caused profound uveal inflammation and release of proinflammatory cytokines. The latter rapidly diffuse to the posterior segment, triggering retinal damage. Tumor necrosis factor-α was identified as a key proinflammatory mediator of retinal ganglion cell death. Blockade, by either monoclonal antibody or tumor necrosis factor receptor gene knockout, reduced inflammation and retinal ganglion cell loss. Intraocular pressure elevation was not observed in experimental alkali burns. These findings illuminate the mechanism by which alkali burns cause retinal damage and may have importance in designing therapies for retinal protection.
Objectives:To determine the effect of amniotic membrane transplantation (AMT) on persistent corneal epithelial defects (PEDs) and to compare the efficacy between inlay and overlay techniques.Methods: Thirty patients (30 eyes) underwent AMT for PED. The use of AMT was restricted to patients in whom all previous measures, including bandage contact lens and tarsorrhaphy, had failed. The amniotic membrane was placed on the surface of the cornea in overlay (group A) or inlay (group B) fashion.
Eyes that have experienced alkali burn to the surface are excessively susceptible to subsequent severe glaucoma and retinal ganglion cell loss, despite maximal efforts to prevent or slow down the disease. Recently, we have shown, in mice and rabbits, that such retinal damage is neither mediated by the alkali itself reaching the retina nor by intraocular pressure elevation. Rather, it is caused by the up-regulation of tumor necrosis factor-α (TNF-α), which rapidly diffuses posteriorly, causing retinal ganglion cell apoptosis and CD45 cell activation. Herein, we investigated the involvement of peripheral blood monocytes and microglia in retinal damage. Using CX3CR1::CCR2 reporter mice and bone marrow chimeras, we show that peripheral CX3CR1CD45CD11bMHC-II monocytes infiltrate into the retina from the optic nerve at 24 hours after the burn and release further TNF-α. A secondary source of peripheral monocyte response originates from a rare population of patrolling myeloid CCR2 cells of the retina that differentiate into CX3CR1 macrophages within hours after the injury. As a result, CX3CR1CD45CD11b microglia become reactive at 7 days, causing further TNF-α release. Prompt TNF-α inhibition after corneal burn suppresses monocyte infiltration and microglia activation, and protects the retina. This study may prove relevant to other injuries of the central nervous system.
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