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From the editor

Endophthalmitis

Mamalis, Nick MD

Journal of Cataract & Refractive Surgery: May 2002 - Volume 28 - Issue 5 - p 729-730
doi: 10.1016/S0886-3350(02)01350-0
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Postoperative endophthalmitis is one of the most serious complications of cataract surgery. It may result in devastating complications with severe vision loss. Fortunately, the incidence of infectious endophthalmitis after modern cataract surgery has decreased to the range of 0.7% to 0.12%.1–4 Several factors may be related to the risks of postoperative endophthalmitis including the introduction of a large inoculum of bacteria into the anterior chamber as well as factors that may affect the adequacy of the patient's ocular immune response.

The primary source of bacteria in culture-positive cases of endophthalmitis is thought to be the ocular surface and adnexa of the patient. Speaker et al.5 found an association between the external bacterial flora and the bacteria isolated from vitrectomy specimens in 82% of patients with postoperative endophthalmitis. Similarly, the Endophthalmitis Vitrectomy Study6 found that the intraocular isolates were indistinguishable from conjunctival and lid specimens in 67.7% of cases with bacterial postoperative endophthalmitis when analysis was possible. Thus, the likely source of postoperative endophthalmitis is bacterial contamination of the anterior chamber by the patient's own bacterial flora at the time of surgery.

In this issue, Leong et al. report results of a study evaluating bacterial contamination of the anterior chamber in a group of patients who had cataract removal by phacoemulsification. Ninety-eight eyes of 96 patients were evaluated in a prospective manner. The patients' tarsal and bulbar conjunctiva as well as eyelid margin were cultured with swabs before the use of antibiotic or antiseptic drops. Sixty-five percent of the preoperative conjunctival swabs were positive for growth with the expected gram-positive organisms, corynebacteria, coagulase-negative staphylococci, and Propionibacterium acnes. The patients then received drops of povidone-iodine 10% solution as well as standard periocular preparation for cataract surgery. The anterior chamber was then entered, and a sample of aqueous fluid was removed for culturing. At the conclusion of the surgery, a second anterior chamber aspirate was collected and conjunctival smears were taken in a similar manner to the smears obtained before the application of topical antibiotics. The incidence of bacterial growth in the postoperative conjunctival swabs dropped to 16%, with corynebacteria and coagulase-negative staphylococci being the most commonly found.

The most interesting finding in this study was that all the intraoperative anterior chamber samples were culture negative. The patients were a relatively heterogeneous group, with clear corneal wounds in 68% and scleral tunnels in 32%. Ninety-five percent of the patients received a silicone foldable intraocular lens (IOL) and 5%, a poly(methyl methacrylate) IOL. Eighteen percent of patients required wound suturing for watertight closure. Intraoperative complications occurred in 4 patients, with iris prolapse in 1 and a ruptured posterior capsule in 3, 2 of whom had associated vitreous loss.

Surprisingly, 1 patient with negative anterior chamber cultures developed postoperative endophthalmitis 5 days after surgery. The patient had an evidently uneventful “routine” surgery with a nonsutured superior corneal wound and insertion of a foldable silicone IOL. At the 1 day postoperative examination, the eye did not show undue inflammation or signs of infection or wound leakage. The vitreous culture grew Staphylococcus epidermidis, which was indistinguishable from the S epidermidis isolate found on the preoperative conjunctival swab. In addition, this patient had a previous renal transplant and was concomitantly receiving a number of immunosuppressive agents including prednisone. Thus, the patient's immunosuppression may have been an independent risk factor for postoperative endophthalmitis even though the anterior chamber cultures were negative.

Intraocular contamination appears to be relatively common after uneventful cataract surgery. The rate of culture positivity in anterior chamber aspirates after uneventful cataract surgery ranges from 13.7% to 43%.7,8 However, no patient in either of these 2 studies developed postoperative endophthalmitis, which implies that there must be other factors involved, including small size of the bacterial inoculum, bacterial clearance, and other inherent patient factors that may have a bearing on the development of postoperative endophthalmitis. Certainly, intraoperative risk factors may be associated with an increased incidence of postoperative endophthalmitis. These include inadequate disinfection of the eyelid or conjunctiva, surgery longer than 30 minutes, vitreous loss, the use of polypropylene-haptic IOLs, and unplanned or unapparent ocular penetration.9

One factor that may be involved in the decreased incidence of postoperative endophthalmitis over the past several decades is improvement in surgical techniques, which is summarized nicely in the paper by Leong et al. Advances from earlier intracapsular cataract extraction techniques to extracapsular cataract extraction and finally to phacoemulsification resulted in overall smaller incisions and better control of the anterior chamber during cataract surgery. Theoretically, phacoemulsification through a smaller wound with a closed, maintained anterior chamber may result in less bacterial contamination during surgery. This was certainly shown by Leong et al. to decrease the rate of positive cultures in the anterior chamber effectively to zero. Thus, an extremely low contamination rate is possible using modern closed-system phacoemulsification techniques. However, other factors are involved in postoperative endophthalmitis aside from the contamination of the anterior chamber as evidenced by the patient in this study with postoperative endophthalmitis despite negative anterior chamber cultures at the conclusion of surgery.

Cataract surgeons can take many steps that may decrease the incidence of postoperative endophthalmitis. Meticulous prepping and draping of the patient before surgery is important to isolate the eyelids and lashes from the surgical field. Steps to decrease the conjunctival bacterial flora, such as application of topical povidone-iodine, are essential as they are likely the source of most cases of postoperative endophthalmitis. In addition, steps to decrease any possible contamination of the anterior chamber during or after cataract surgery using a small, watertight wound with a closed system during surgery are critical. Finally, all attempts should be made to decrease any preoperative patient risk factors such as immunosuppression or systemic disorders that may affect wound healing and the ability of the eye to ward off any inoculum of bacteria during cataract surgery.

References

1. Aaberg TM Jr, Flynn HW Jr, Schiffman J, Newton J. Nosocomial acute-onset postoperative endophthalmitis survey. Ophthalmology 1998; 105:1004-1010
2. Javitt JC, Vitale S, Canner JK, et al. National outcomes of cataract extraction. Endophthalmitis following inpatient surgery. Arch Ophthalmol 1991; 109:1085-1089
3. Ormerod LD, Ho DD, Becker LE, et al. Endophthalmitis caused by coagulase-negative staphylococci. 1. Disease spectrum and outcome. Ophthalmology 1993; 100:715-723
4. Powe NR, Shein OD, Gieser SC, et al. Synthesis of the literature on visual acuity and complications following cataract extraction with intraocular lens implantation. Arch Ophthalmol 1994; 112:239-252
5. Speaker MG, Milch FA, Shaf MK, et al. Role of external bacterial flora in the pathogenesis of acute postoperative endophthalmitis. Ophthalmology 1991; 98:639-649
6. Bannerman TL, Rhoden DL, McAllister SK, et al. The source of coagulase-negative staphylococci in the Endophthalmitis Vitrectomy Study; a comparison of eyelid and intraocular isolates using pulsed-field gel electrophoresis. Arch Ophthalmol 1997; 115:357-361
7. Dickey JB, Thompson KD, Jay WM. Anterior chamber aspirate cultures after uncomplicated cataract surgery. Am J Ophthalmol 1991; 112:278-282
8. Mistlberger A, Ruckhofer J, Raithel E, et al. Anterior chamber contamination during cataract surgery with intraocular lens implantation. J Cataract Refract Surg 1997; 23:1064-1069
9. Meinkoff JA, Speaker MG, Marmor M, Raskin EM. A case-control study of risk factors for postoperative endophthalmitis. Ophthalmology 1991; 98:1761-1768
© 2002 by Lippincott Williams & Wilkins, Inc.