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Although intracameral medication use in cataract surgery has several potential advantages, they should be weighed against the possible disadvantages and the benefits and risks of topical medication alternatives.
"We need sterile, premixed, preservative-free, unit doses of antibiotics, anesthetics, and anti-inflammatory agents used in cataract surgery," said Dr. Mamalis, professor of ophthalmology and visual sciences, University of Utah, and director of the Ophthalmic Pathology Laboratory, Moran Eye Center, Salt Lake City.
Advantages of using intracameral medications in cataract surgery for anesthesia, pupil dilation, or to prevent inflammation and endophthalmitis include ease of delivery, elimination of toxicity of topical drops, and avoidance of compliance issues, he said. In addition, by delivering the treatment directly to the target site, intracameral medications may offer enhanced efficacy, Dr. Mamalis added.
"Topical prednisolone and [non-steroidal anti-inflammatory drugs] are very effective for treating postoperative inflammation so that intracameral medication use for preventing inflammation may be unnecessary," Dr. Mamalis said. "There are toxicity risks associated with use of both preserved topical drops and intracameral injections for pupil dilation, and the toxicity of intracameral anesthetics must be weighed against the benefit of increased patient comfort."
The risk of toxic anterior segment syndrome is one of the biggest concerns, he said. This inflammatory reaction can occur through multiple mechanisms with intracameral medication use that relate to improper concentration, pH, or osmolarity as well as exposure to preservatives.
Use of lidocaine in a concentration exceeding 2% or bupivacaine in a concentration of more than 0.5% could cause corneal endothelial damage, he said. In addition, concern exists about dilution errors when mixing certain antibiotics that have a low therapeutic range, such as gentamicin.
To avoid pH-induced cell damage, custom-mixed medications may need to be buffered, and the range of acceptable osmolarity of solutions instilled within the anterior chamber is narrow because endothelial cell damage can occur with exposure to hyper-or hypo-osmolar solutions.
Many commercially available topical medications that might be used intracamerally also contain preservatives that potentially are toxic to the corneal endothelium. Surgeons also should be aware of the potential for corneal toxicity caused by stabilizing agents, such as bisulfites or metabisulfites found in preservative-free epinephrine.
Exposure to infectious contaminants is another safety concern with intracameral drug use, particularly if multiple doses for successive surgeries are drawn from the same vial. In addition, the potential for physicochemical incompatibilities exists when multiple drugs are combined, he said.