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Guidelines help ophthalmologists in battle against endophthalmitis
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 Richard L. Lindstrom |
Every surgical procedure, including the in-office intraocular injection of medication, carries the risk of inducing endophthalmitis. We all practice evidence-based medicine as much as possible, but some devastating complications, such as postoperative endophthalmitis, are so rare that the ideal prospective, randomized clinical trials that represent level 1 evidence are nearly impossible to perform. We are then left with retrospective studies and extrapolation from the universe of infection prevention literature obtained from the experience of surgeons in every field. There are some general guidelines that appear again and again, whether it be in ophthalmology, orthopedics or neurosurgery.
First, some patients are at higher risk than others. In ophthalmology, risk is increased by age, immunosuppression, diabetes mellitus, concomitant use of steroids or immunosuppressive drugs, structural lid abnormalities, nasolacrimal duct obstruction, contralateral ocular prosthesis, or history of endophthalmitis, contact lens wear and ocular surface disease, including conjunctivitis, blepharitis and even dry eye. Treatment of these conditions before surgery can be expected to reduce the risk of infection.
Second, the pathogens causing endophthalmitis in the majority of cases reside on the surface of the patient, primarily the conjunctiva, lids and periocular skin. Therefore, prepping the periocular skin, lid margins and conjunctiva with an antiseptic, in most cases povidone-iodine, is appropriate. The povidone-iodine needs to be dripped onto the ocular surface to achieve maximum benefit, not just applied to the periocular skin. Because this application burns, a topical anesthetic before povidone-iodine application enhances patient comfort, and the benzalkonium preservative in the drops may also be beneficial, so I use preserved, not non-preserved, drops. In addition, the anesthetic application reduces the barrier effect of the corneal epithelium, allowing increased penetration of the topical antibiotics to be applied later. Irrigation of the conjunctival fornices is counterproductive, as a significant nidus of bacteria resides in the conjunctival fornices loculated in mucus, and irrigation just increases colony count more anterior, where the eye will be entered. While careful draping and sterile attire for the surgeon, including gloves, caps, mask and gown, are routine in the operating room, for an office-based intraocular injection, the use of a sterile solid-bladed speculum to isolate lids and lashes and careful hand washing or application of alcohol gel or foam combined with a no-touch technique are my preference.
Third, it is important to know what bacteria are most likely to cause infection, and we have good data here from several studies. It is the patient’s normal flora, dominated by gram-positive bacteria, primarily Staphylococcus epidermidis, Staphylococcus aureus and the particularly virulent streptococci. On the gram-negative side, Pseudomonas and Moraxella cause rarer but devastating infections. It is important to remember that more patients every year harbor methicillin- and fluoroquinolone-resistant staph species. Some patients will know they carry these MRSA and MRSE infections, and if so, antibiotic selection should be modified.
Fourth, all specialties, including ophthalmology, have strong evidence that the use of prophylactic antibiotics in the perioperative period reduces the incidence of infection. To be most effective, the antibiotic needs to be applied before and immediately after the operative procedure. For me, topical antibiotic drops just before and just after the procedure are logical. Most of us use a current-generation fluoroquinolone, but in cases of known MRSA or MRSE, I favor the readily available Polytrim (polymyxin B/trimethoprim, Allergan) drops that continue to show nearly 100% efficacy against these pathogens. In a cataract operation, I give three to four doses of topical antibiotic preop and a dose at the end of surgery, upon arrival in the recovery area and just before leaving, followed by four times a day for 2 weeks. This is likely overkill for an office-based intraocular injection, and drops just before and after the procedure are my approach. However, in very high-risk cases, I will use a regimen similar to that employed in cataract surgery.
Finally, it is important to instruct the patient and those who answer our telephones regarding the signs and symptoms associated with a sight-threatening complication such as endophthalmitis. I use the mnemonic RSVP, which means return to the clinic or emergency room immediately and be examined by one of our doctors. R stands for significant new red eye, S for significant new light sensitivity, V for significant new vision loss and P for significant new pain.
I find that pain and lid edema are early hallmarks of infectious endophthalmitis, being unusual in the patient with sterile inflammation. A few cells in the vitreous with no red eye, no lid edema, no photophobia, no vision loss and no pain are deserving of good counseling and a repeat check in a day or two. A few cells in the vitreous with a red eye, photophobia, vision loss and pain are, to me, an infection until proven otherwise.
Practicing in an urban environment, I rely on my vitreoretinal colleagues when endophthalmitis is suspected, as they are in many cases just across the hall. The rural ophthalmologist needs to be prepared to do vitreous taps followed by injection of appropriate intravitreal antibiotic and institution of adjunct systemic and topical therapy. Some will institute this therapy and then refer to a consultant ophthalmologist, while others will treat endophthalmitis themselves. Either is appropriate with proper training.