The incision as a risk factor for endophthalmitis

ByJohn D. Hunkeler, MD

Effective wound management is mandatory to reduce the likelihood of infectious endophthalmitis after cataract surgery. When performing cataract surgery in the normal adult eye, the surgeon must be concerned about three elements of wound management: construction, protection and inspection.

Wound construction

Proper wound construction requires a good incision design, executed perfectly with a sharp blade, regardless of the type of incision.

Studies have identified wound leak as the most important risk factor for the development of bacterial endophthalmitis after cataract surgery.¹ In a retrospective review of the records of 27 cataract surgery patients who developed endophthalmitis and compared to a randomly selected group of control patients, incision leak had the highest odds ratio (OR 44.4; P = .005) of the surgical factors found to increase the risk for endophthalmitis. Other risk factors included surgical complications (OR 1.72; P = .001) and not patching the eye (OR 7.1; P = .015).¹

In addition, starting topical antibiotics on the day after surgery, as was done in the study conducted by the European Society of Cataract and Refractive Surgeons on endophthalmitis prophylaxis,² increased the risk of endophthalmitis 13-fold over starting the antibiotics the day of surgery.¹ In contrast, in the European study, the use of intracameral cefuroxime reduced the risk of endophthalmitis by fivefold.

Studies in cadaveric eyes and rabbit eyes have shown that india ink placed on the surface of the eye can reflux into the anterior chamber through unsutured clear corneal incisions.^3,4

Incision designs for clear corneal cataract surgery include stepped incisions, beveled incisions and grooved incisions; any and all of these can be self-sealing when properly designed. The self-sealing properties of incisions can be documented using optical coherence tomography (OCT) in the immediate postoperative period. ⁵ Fine and colleagues found that an incision in the corneal plane with a cord length of at least 2 mm provided architecture for self-sealing.⁵ Proper construction of clear corneal incisions resulted in increased stability and added safety; the authors contended that the safety of these wound characteristics contributed to a series of 9,000 cases over 10 years without one incident of endophthalmitis.

Anterior segment OCT might allow physicians in the future to examine the effectiveness of different instruments for making incisions into the anterior chamber.

Wound protection

Protection of the wound is vital in clear corneal cataract surgery. Intraoperative manipulations resulting in an irregular cut, such as a “smile” incision that is not rectangular, can increase the risk of wound leak. A square or rectangular incision design is important for wound strength.^6,7

The incision must be protected from damage by the phacoemulsification instrument during the surgi]cal procedure, not only from tearing the wound edges,but also from the effects of intraoperative heat. Modern phacoemulsification equipment is designed to reduce the heat generated in the incision, but prolonged phacoemulsification procedures with high levels of energy can result in a loss of epithelium on the front surface of the clear corneal incision due to heat transfer. Such external wound damage indicates internal wound damage and may increase the risk of incision leak.

Enlarging the incision rather than traumatizing the incision during IOL insertion should be performed to cprevent damage to the wound at the end of the procedure.

In addition to the primary incision, the paracentesis or sideport incision also must be well constructed and protected from damage during surgery. Inserting oversized instruments or performing excessive manipulation through these auxiliary incisions can set the stage for wound leak. In cases in which the primary incision is verified to be watertight, the fact that the paracentesis is leaking may be overlooked.

Wound inspection

The final element in wound management is inspection at the end of surgery. Incision hydration with balanced salt solution should be performed to prevent leakage. The surgeon should then directly inspect the wound for evidence of fluid egress; if leakage is seen, then more hydration can be performed or a suture can be placed, if necessary.

Establishing proper IOP at the end of surgery is important. If IOP exceeds central retinal arterial pressure during hydration of the primary or paracentesis incisions, then patients may lose fixation on the microscope light. If this occurs, then decompressing the anterior chamber at the end of surgery is vital.

Proper incision construction, leading to proper wound architecture, is of primary importance.
— John D. Hunkeler, MD

A 10-minute postoperative examination is helpful to check for wound leaks. After performing surgery on one patient, a surgeon can then examine the patient from the previous case in the discharge room with a portable slit lamp. If a shallow chamber is seen, then the surgeon can insert a suture. The 10-minute postoperative examination can be performed quickly, and it provides an extra level of reassurance that the eye still looks like it did on the operating table.

Conclusion

Paying attention to these three elements of wound management — construction, protection and inspection — helps a surgeon to guard against wound leakage and to reduce the risk of inoculation from endophthalmitis-causing organisms into the anterior chamber after surgery. Proper incision construction, leading to proper wound architecture, is of primary importance among the variables that contribute to endophthalmitis prophylaxis. The surgical wound should be protected from damage intraoperatively and postoperatively, and the wound should be examined for leakage so that proper steps can be taken to correct any complications that may arise.

References

Wallin T, Parker J, Jin Y, et al. Cohort study of 27 cases of endophthalmitis at a single institution. J Cataract Refract Surg. 2005;31:735-741.

Barry P, Seal DV, Gettinby G, et al; ESCRS Endophthalmitis Study Group. ESCRS study of prophylaxis of postoperative endophthalmitis after cataract surgery: Preliminary report of principal results from a European multicenter study. J Cataract Refract Surg. 2006;32:407-410.

McDonnell PJ, Taban M, Sarayba M, et al. Dynamic morphology of clear corneal cataract incisions. Ophthalmology. 2003;110:2342-2348.

Taban M, Rao B, Reznik J, Zhang, et al. Dynamic morphology of sutureless cataract wounds – effect of incision angle and location. Surv Ophthalmol. 2004;49(suppl 2):S62-S72.

Fine IH, Hoffman RS, Packer M. Profile of clear corneal cataract incisions demonstrated by ocular coherence tomography. J Cataract Refract Surg. 2007;33:94-97.

Ernest PH, Lavery KT, Kiessling LA. Relative strength of scleral corneal and clear corneal incisions constructed in cadaver eyes. J Cataract Refract Surg. 1994;20:626-629.

Ernest PH, Fenzl R, Lavery KT, Sensoli A. Relative stability of clear corneal incisions in a cadaver eye model. J Cataract Refract Surg. 1995;21:39-42.

Wound construction and endophthalmitis

Wound construction

Olson: Meticulous wound construction and, when in doubt, putting a suture in the wound is important. In a clear corneal incision, with every blink, tears are going in and out of the anterior chamber. In surgery with sutures, the leak results from positive pressure against zero pressure, a net flow from inside the anterior chamber to outside the eye. If a wound leak occurs, it should be a mini leak, not a gross leak.

Wittpenn: When I see patients 4 or 5 days postoperatively, I like to see sealed conjunctiva over the external opening. My goal in wound construction is to cover every wound with conjunctiva, and I use sutures if a question of leakage exists. Subsequently, I make my incision in the superior limbus, because the conjunctiva covers a superior wound in most patients. I do not want the patient to feel something temporally and induce iris prolapse by rubbing his/her eyes. When I have to create a clear cornea or temporal incision, I suture 100% of the time.

Olson: In the early days of sutureless clear corneal surgery, when incisions ranged from 3.5 mm to 5 mm, a rash of endophthalmitis occurred as a result of the eyelid opening superior incisions. A temporal incision in clear corneal surgery seemed to decrease that incidence.

Chang: The temporal location has advantages in terms of being astigmatically neutral. It gives better surgical exposure for the surgeon; the eye does not have to be rotated downward with a bridle suture, which in turn can cause ptosis. However, temporal incisions have a greater risk of becoming deformed by eye rubbing. Should we be putting a shield on to protect against transient leaks?

McDonald: We use a shield the day of surgery to prevent the patient from touching the eye.

O’Brien: Because of the lingering effects of topical anesthesia, I apply a patch and shield after a loading dose of topical antibiotics at the conclusion of the case that remains for 1 to 2 hours until the patient is home safely. Then the patch and shield are removed, and the frequent application of topical antibiotic eyedrops is initiated (six to eight times daily for 48 hours).

Hunkeler: The patient is slightly more comfortable with a clear corneal incision.