In the wake of concerns about increasing rates of postoperative endophthalmitis and antibiotic resistance, continuing efforts are made to find the most effective prophylactic method for preventing postoperative infections. Despite this, endophthalmitis continues to be one of the most devastating complications of cataract surgery. Several factors are suggested to be involved in this process, such as the surgical technique, the intraoperative contamination of the anterior chamber and the increasing age of patients undergoing phacoemulsification.
Intraocular contamination is known to occur during cataract extraction or within the first hours after surgery. Anterior chamber aspirates obtained during cataract phacoemulsification show contamination rates ranging from 2 to 43%.11,12 Propionibacterium acnes and other conjunctival flora are the most commonly isolated microorganisms. In fact, the number of bacterial isolates in preoperative conjunctival cultures in patients older than 75 years old seems to be significantly higher than those in younger patients,13 suggesting a correlation between age and bacterial load.
Several advantages have been attributed to the use of intracameral injections over traditional topical drops regimens. Achieving intraocular drug levels above the minimum inhibitory concentration (MIC) against conjunctival flora pathogens is of primary importance due to the absence of vascular structures in the cornea and aqueous humor, and the need to avoid the development of bacterial resistance. This is better accomplished with intracameral injections since ocular penetration of topical antibiotics is mostly restricted by corneal epithelium and lacrimal drainage system. Antibiotic delivered directly to the anterior chamber provides high initial intracameral levels immediately after the injection. These aqueous humor levels should be enough to eradicate intracameral bacteria at the end of the surgery and the first hours of the postoperative period. Another relevant issue is the need to ensure prolonged intraocular levels of antibiotics after injection, which is directly related to the antibiotic half-life and the aqueous humor turnover. The half-life of intracameral cefuroxime has been reported to be approximately of 1-2 hours, exhibiting drug levels above the MIC for at least 4 hours.14 On the other hand, vancomycin half-life has been estimated to range from 2 to 3 hours.14,15 Based on these observations, vancomycin levels in aqueous humor should exceed the MIC for most frequent microorganisms for a longer period of time. This could be in part responsible for the intensity of the anterior chamber reaction observed in the vancomycin group 24 hours after surgery.
Since the ESCRS study evaluated the effectiveness of intracameral cefuroxime and established the clinical benefits of a dose of 1 mg cefuroxime after cataract extraction,2 the use of intracameral antibiotics has gained worldwide acceptance. Vancomycin is one of the...