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Fundamentals of Clinical Ophthalmology - part 9

Ngoài ra, chính quyền kháng sinh tại chỗ có chọn lọc có thể làm tăng số lượng sinh vật kháng thuốc trên bề mặt mắt. Nền văn hóa mắt trước phẫu thuật không có giá trị đáng kể tiên đoán bởi vì đôi mắt khỏe mạnh đã được chứng minh cảng Staphylococcus aureus và pathogens | CATARACT SURGERY numbers of organisms in the conjunctival sac 10 but this effect is short lived. In addition the administration of topical antibiotics may selectively increase the numbers of resistant organisms on the ocular surface. Preoperative eye cultures have no significant predictive value because many healthy eyes have been demonstrated to harbour Staphylococcus aureus and other potential intraocular pathogens.11 As a consequence the routine administration of preoperative antibiotic eye drops has fallen out of favour other than in eyes with manifest risk factors such as blepharitis or chronic nasolacrimal infection in which their benefit is unproven. Routine use of preoperative norfloxacin was not shown to reduce the incidence of Figure 12.2 5 Povidine iodine placed into the conjunctival sac before surgery. aqueous contamination in one study.12 Ocular surface disinfection at the time of surgery with 5 povidone iodine Figure 12.2 significantly reduces bacterial counts13 14 and the risk of endophthalmitis 15 and this is considered the most reliable method of surface decontamination for intraocular surgery. Isolation of the eyelids and eyelashes from the surgical field by careful draping is advisable Figure 12.3 and unnecessary contact of instruments or lens implants with the ocular surface should be avoided. Addition of antibiotics to infusion fluids has been shown to reduce the incidence of positive cultures from aqueous fluids at the end of surgery 16 17 but there is little evidence to show a real reduction in the risk of endophthalmitis with this strategy. A persuasive argument against the unnecessary use of vancomycin in a hospital setting is the increasing spread of resistance to vancomycin among bacteria and the problem of methicillin resistant S. aureus MRSA . Addition of heparin18 19 to the infusion or use of heparin surface modified lens implants20 is reported to be associated with less intraocular inflammation. However these theoretical benefits have