After a perfectly performed cataract procedure with excellent results on the first postoperative day, it is disheartening when the patient returns with signs of increased inflammation likely to be endophthalmitis (Figure 1). Although cataract surgeons have come a long way in treating endophthalmitis, severe organisms such as Streptococcus and Pseudomonas species still routinely devastate final visual acuity. Even more benign bacteria will often negatively affect results.
As clear corneal surgery became common practice, the incidence of endophthalmitis increased. Because new approaches or technology are so often greeted by pessimism, it is easy to dismiss critics' complaints as a normal reaction to change. My colleagues and I adopted clear corneal surgery with great enthusiasm, and it became our predominant technique by mid-1996. Clear corneal surgery in combination with topical anesthesia allows for a prompt return of vision without sutures.
Our experience with endophthalmitis is no different than others' in that the complication is rare but often occurs in clusters, making it nearly impossible to gauge the actual incidence. As a result, we began a prospective, quality-control study on endophthalmitis in 1997.
In early 2001, we concluded that our incidence of endophthalmitis was increasing dramatically from a historical rate that we calculated as less than 1 in 1,000 cataract surgeries. We had enough data to know this increase was not simply a cluster of events. Furthermore, we had no cases of endophthalmitis in patients who had corneal-scleral incisions. All of the incidents of endophthalmitis occurred in patients with clear corneal incisions. Nevertheless, we know many ophthalmologists across the country, myself included (I have not had a single case of endophthalmitis after cataract surgery), who state that they have not had a problem with clear corneal surgery during their career. How to make sense of the seeming conflict of data and personal reports was a major and important research step that we decided we must undertake.CAUSES OF ENDOPHTHALMITIS
Choice of Surgery and Lens
Many studies have suggested an increase in endophthalmitis with clear corneal incisions. Nagaki et al1 conducted a prospective, randomized, clinical trial comparing the difference between clear corneal and corneal-scleral incisions, the difference between using silicone and acrylic lenses, and the relation of incision and lens type to the incidence of endophthalmitis. This study, which included more than 12,000 surgeries, is definitive in addressing both surgical and lens choices. The results showed a statistically significant increase in the incidence of endophthalmitis in association with clear corneal surgeries (0.29% vs 0.05%; P=.037), but the investigators did not find a difference between silicone and acrylic lenses. It is virtually impossible to refute their study, and the only conclusion that I can make is that clear corneal surgery can dramatically increase the incidence of endophthalmitis. The operative word is can, not will.Cataract Surgery Incisions
In their landmark work, Taban et al2 studied how wounds behave under pressure using eye-banked eye preparations. They demonstrated that a long incision, which my colleagues and I have always considered the strongest, is very resistant to elevated IOP. However, long incisions can sometimes gape and leak with a low IOP compared with incisions that are more perpendicular to the surface of the eye. The latter type of incision, or short incisions, will leak with an elevated IOP, but they actually seal better with a low IOP. Taban et al2 studied further and used India ink as a bacterial model because its particle size is similar to that of bacteria. They found that, as the IOP increased, even long incisions resistant to leakage gaped externally and allowed the India ink to enter the wound. Additionally, as the IOP dropped, there was the potential for an internal gape that theoretically could result in bacteria's entering the anterior chamber, although the IOP never dropped to zero and there was never obvious leakage (Table 1). One criticism of this study is that the investigators used dead tissue without living endothelial cells; certainly, if the endothelial pump had been intact, it would have secondarily sealed the wound and possibly avoided some of the leakage associated with their findings.Clear Corneal Surgery
The study by Taban et al2 combined with our own results as well as those of Nagaki et al1 point to the fact that microleaks after cataract surgery are more common in patients who undergo clear corneal surgery, at least some of the time. In addition, the increased risk of leakage with attendant contamination is why some ophthalmologists are seeing more cases of endophthalmitis. A definitive study to prove that thesis would be extremely difficult to create, but the circumstantial evidence seems sufficient.
It is important for ophthalmologists to understand that the risk of endophthalmitis is not guaranteed to be higher with clear corneal surgery but that the incisions themselves are very unforgiving. I believe the reasons why some ophthalmologists have not encountered a rise in their rates of endophthalmitis are their careful attention to detail and their suturing of any marginal wounds, which are more likely to leak than those that are well constructed.Wounds
Marginal wounds require careful scrutiny. In my experience, they are generally related to a small tear in Descemet's membrane, overstretching and internal tearing, or an external tear, all of which dramatically decrease the IOP/leakage curve.
A small tear in Descemet's membrane can occur at any time during cataract surgery and usually starts at the wound internally and runs back toward the limbus. The tear will leave a portion of Descemet's membrane and endothelium that can flap back and forth during irrigation, but, because it is located under the wound, the tear can often go unnoticed (Figure 2). I always irrigate through the stab incision, because I can often see the torn flap moving as the irrigation passes. Irrigation can frequently bring the torn flap into apposition with the cornea. I believe that all such cases require a suture.
Although some cataract surgeons may consider it overkill, I feel that the closure of the wound requires both a mechanically correct incision and the secondary sealing action of the endothelial pump. As outlined by Taban et al,2 relying on the mechanical nature of the wound alone is risky. Even though ophthalmologists worry about early elevated postoperative IOP, Shingleton et al3 clearly showed that significant hypotony (frequently 5mmHg) often occurs after surgery. Low pressure is as much a concern as high pressure. A well-constructed wound without an active endothelial pump is a risk I am not willing to take.
Internal tearing or stretching of the wound typically occurs when cataract surgeons force instruments or a lens through a wound that is too small. At the conclusion of surgery, some of the structures may be torn, and the wound may not come together nicely. I do not believe that these indications necessarily require the placement of a suture. If I can easily cause leakage with a little stromal hydration, inflation of the eye, and pressure applied directly behind the wound as well as 180º away, then I will place a suture.
A third problem is an external tear on either side of the incision. This is easily done during the creation of the incision with a diamond blade, either due to torquing or lifting one side of the keratome such that one edge is much shorter than the desired 2.0- to 2.5-mm length. I am convinced that the wound is only as strong as its weakest part. If one side is torn due to surgical maneuvers inside the eye or cut at the beginning of the procedure, then a suture is necessary. As mentioned earlier, if this wound does not automatically and easily seal, I recommend placing a suture.
Stromal hydration can be used to seal the incision. For the wound to seal and the endothelial pump to work, everything must remain in apposition for a period of time. Otherwise, the profound leakage through the wound will overwhelm the endothelial pump, and the wound will continue to leak. Still, surgeons cannot rely too much on stromal hydration, which forces otherwise marginal wounds to close that can leak later. Stromal hydration is a temporary fix.STUDY
In another study, my colleagues and I randomly analyzed 10% of more than 15,000 consecutive cataract surgeries and compared these with 27 cases of endophthalmitis after cataract surgery during the same timeframe.4 We found that, if the wound were frankly leaking on the first postoperative day, the risk of endophthalmitis increased more than fortyfold. In fact, with sutureless, clear corneal incisions that leak on the day after surgery (often as a patient blinks), we can see the tears moving in and out of the anterior chamber. I consider such leakage a mandatory reason to put in a suture. These patients need frequent dosing of topical fourth-generation fluoroquinolones and require close observation for the earliest sign of increased inflammation, which should be considered a presumptive diagnosis of endophthalmitis (Table 2).
Eyes with torn capsules or zonules were about 15 times more likely to develop endophthalmitis. This incidence was four times higher than described in the classic study by Javitt et al,5 who showed that vitreous loss increased endophthalmitis fourfold back when it was standard to suture the incision. Torn capsules and zonules, therefore, warrant a sutured incision and increased surveillance.
The other statistically significant findings of our study relate to the type of antibiotic, when antibiotics were used, and the use of a collagen shield. We switched to fluoroquinolones from aminoglycosides and used only Ciloxan (Alcon Laboratories, Inc., Fort Worth, Texas) and Ocuflox (Allergan Inc., Irvine, CA.). We found that the use of Ciloxan increased the risk of endophthalmitis three- to fivefold, which may be related to the inability of ciprofloxacin to penetrate into the anterior chamber. Fortunately, such is not the case for ofloxacin, levofloxacin (Quixin; Santen, Inc., Napa, CA), or any of the new fourth-generation fluoroquinolones. This is the first study of which I am aware to give strong, presumptive evidence that antibiotics are important in the prevention of endophthalmitis. It is important to remember that culturing the anterior chamber after cataract surgery will result in a positive endophthalmitis culture 20% to 60% of the time, statistics that have been shown in many studies. Most notable is that the anterior chamber can clear a fairly good sized bacterial inoculum, but the vitreous cannot. Our study results strongly suggest that, if there is enough antibiotic in the eye to eliminate the bacterial inoculum, endophthalmitis can be prevented.
Starting antibiotics on the day of surgery versus waiting until the next day also decreased the risk of endophthalmitis by a factor of three to five. The use of a collagen shield decreased the risk of endophthalmitis three- to fivefold.
All of our findings stood up to the rigor of a multivariate regression analysis and were independently important. In addition to facilitating the delivery of antibiotics to the eye, a collagen shield may provide some support to the wound, much like a bandage contact lens, and may help prevent early leakage. My colleagues and I performed a series of studies, which have been submitted for publication, looking at the use of fourth-generation fluoroquinolones with a collagen shield for the prophylaxis of endophthalmitis. With this approach, gatifloxacin and moxifloxacin demonstrated excellent penetration into the anterior chamber.CONCLUSION
Clearly, antibiotic prophylaxis as well as the integrity of the cataract incision are important to the prevention of endophthalmitis. Marshall6 found that the new Atomic Edge silicon chip blade (BD Ophthalmic Systems, Franklin Lakes, NJ) creates a wound with much greater bursting strength than that created by a diamond. The silicon blade is an example of innovative technology to strengthen sutureless wounds. Other ophthalmologists argue we simply need to go back to using sutures. What is needed are good dialogue and solid studies so we can make progress and minimize this scourge. At the least, we should suture all questionable wounds and frequently use antibiotics that can achieve therapeutic levels in the eye starting right after surgery.
Randall J. Olson, MD, is Professor and Chair of the Department of Ophthalmology, John A. Moran Eye Center of Ophthalmology and Visual Sciences in Salt Lake City. He states that he holds no financial interest in any of the products or companies mentioned herein. Dr. Olson may be reached at (801) 585-6622; firstname.lastname@example.org. Nagaki Y, Hayasuku, Kodoi C, et al. Bacterial endophthalmitis after small-incision cataract surgery. Effects of incision placement and intraocular lens types. J Cataract Refract Surg. 2003;29;20-26.
2. Taban M, Rao B, Reznik J, et al. Dynamic morphology of sutureless cataract wounds–effect of incision angle and location. Surv Ophthalmol. 2004;48:562-572.
3. Shingleton, BJ, Heltzer J, O'Donoghue MW. Outcomes of phacoemulsification in patients with and without pseudoexfoliation syndrome. J Cataract Refract Surg. 2003;29:1080-1085.
4. Wallin T, Parker J, Jin Y, et al. A cohort study of 27 cases of endophthalmitis at a single institution. J Cataract Refract Surg. In Press.
5. Javitt JC, Vitale S, Canner JK, et al. National outcomes of cataract extraction: endophthalmitis following inpatient surgery. Arch Ophthal. 1991;109:1085-1089.
6. Marshall, J. The 2004 Charles D. Kelman innovator's lecture, Developments, Debate and Dilemma: wavefronts and biomechanics. Paper presented at: The ASCRS/ASOA Symposium on Cataract, IOL, and Refractive Surgery; May 3, 2004; San Diego, CA.