Appropriate use of preoperative eyedrops is essential in providing a well-dilated pupil prior to cataract surgery and in minimizing the risk of endophthalmitis. Residents should develop a consistent approach to their preoperative regimen based on fundamental principles and the specific characteristics of a given procedure.
- Most cases of endophthalmitis following cataract surgery result from inoculation of bacteria into the eye from endogenous lid flora.Maximal reduction of bacteria on the ocular surface and control of blepharitis are therefore essential.
- Blepharitis should be addressed well before the day of surgery with warm compresses, lid hygiene, and systemic treatment with doxycy- cline, azithromycin, or similar medication as necessary.
- The goal is not to sterilize the eye but to reduce bacterial counts to a sufficiently low level so that the anterior chamber is exposed to no more than a small inoculum during insertion of instruments into the eye without development of infection.
II. GENERAL PRINCIPLES
- It is important that eyedrops are instilled in a way that does not dilute their concentration. A common mistake is to rapidly instill a whole series of eyedrops, including antibiotics, cycloplegics, adrenergic agents, and possibly nonsteroidal anti-inflammatory drugs (NSAIDs) immediately after one another. Such a technique may induce reflex tearing from irritation, or simply overfill the fornix so that the drops spill onto the eyelids. In either case, the efficacy is likely to be reduced.
- Patients should be instructed to gently close their eyelids (or apply punctual occlusion) for a minute or more or so after a single drop of each drug is instilled.
- Use of a pledget (eg, 1 cm × 2 mm cellulose sponge), soaked in the combination of drops and placed in the inferior fornix, may be more economical and efficient and provide better dilation than standard eyedrop instillation.
Endophthalmitis is a fortunately rare complication of cataract surgery and for that reason it is unlikely that a randomized controlled clinical trial will ever be done that definitively demonstrates efficacy of a particular prophylactic antibiotic regimen. However, several large studies have shown that povidone-iodine 5% is safe and effective in reducing the risk of endophthalmitis, regardless of other antibiotics used.
- Most cases of postoperative endophthalmitis are due to gram-positive organisms, with increasing resistance among coagulase-negative staphylococci to ciprofloxacin.The fourth-generation fluoroquinolones provide better gram-positive coverage than ciprofloxacin or ofloxacin. Surgeons may need to modify their prophylactic regimen depending on the patterns of resistance in their own population base.
- While povidone-iodine is a broad-spectrum antibiotic, it does have some holes in coverage, such as Serratia. Both moxifloxacin 0.5% and gatifloxacin 0.3% provide broad-spectrum coverage against gram- positive and gram-negative organisms. Both gatifloxacin and moxi- floxacin are well tolerated by the eye.5
- A combination of povidone-iodine and a fourth-generation fluoroquinolone is therefore most commonly used for endophthalmitis prophylaxis. Povidone-iodine should be diluted from the stock 10% solution to 5% with balanced salt solution for the ocular surface because the higher concentration can cause significant corneal epi- theliopathy due to its low pH. The periocular skin can be treated with either concentration.
- Paradoxically, lower concentrations of povidone-iodine (0.05% to 0.5%) are actually more bactericidal than the standard 5% solution because the dilution increases the release of the active free iodine; a much longer contact time is required for the 5% solution to achieve the same kill rate. However, the stock 5% solution is stable for a much longer period of time. The use of intraoperative irrigation with freshly diluted povidone-iodine 0.25% during cataract surgery has been shown to be highly effective at reducing anterior chamber bacterial contamination at the conclusion of surgery without ocular toxicity.
- Never use povidone-iodine scrub around the eyes, as the surfactant is toxic to the corneal epithelium.
- Some investigators believe that a preoperative antibiotic regimen is best started 24 to 72 hours before surgery in order to achieve adequate drug levels in the eye.Others feel that such an approach may be logistically difficult and feel it is sufficient to initiate antibiotic drops 1 to 2 hours before surgery (eg, 1 drop every 10 to 15 minutes for 4 doses), especially if followed by povidone-iodine.
- Studies indicate that moxifloxacin 0.5% achieves higher intraocular levels than gatifloxacin 0.3%, whether started the day before surgery or 1 hour before surgery; however, there are no controlled clinical trials that indicate superior clinical efficacy of moxifloxacin. Both drugs are relatively expensive.
*Dikutip dari Buku Essentials of Cataract Surgery 2nd Ed, halaman 25-27