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Up Front | Feb 2005

Clear Corneal Incisions and Endophthalmitis

An attention to detail can avert this complication.

There is no doubt that the incidence of infectious endophthalmitis after cataract surgery has increased. Most frequently quoted are the retrospective study by Cooper et al1 and the prospective study by Nagaki et al.2 Another certainty is that the use of clear corneal incisions has risen recently. The transition from scleral tunnel to clear corneal incisions involves a learning curve, during which time the surgeon may experience an increased rate of complications. The question to be addressed, therefore, is whether the rising use of clear corneal incisions is causing the increase in cases of endophthalmitis following cataract surgery.


It is important to take into account the change in bacterial resistance to antibiotics (Figure 1). Gram-positive organisms are overwhelmingly responsible for postoperative endophthalmitis: 69% of patients with bacterial endophthalmitis were culture positive, and 94% of the infectious agents were gram-positive organisms.3 In 1997 and 1998, 100% of the organisms associated with postcataract surgery endophthalmitis were sensitive to the fluoroquinolones then available (Figure 2). By 1999, only 20% remained sensitive, and 100% of those organisms were resistant to the existing fluoroquinolones by 2001.4 The growing resistance of microorganisms to antibiotics certainly has some bearing on the increased rate of endophthalmitis.

Two Swedish reports5,6 in 2002 cited the lowest level of endophthalmitis ever despite an increased use of clear corneal incisions. The findings are probably a result of the use of prophylactic intracameral cefuroxime at the close of surgery. These reports provide further evidence of the significant role that antibiotics play in the prevention of bacterial endophthalmitis.


Although we use only clear corneal incisions, we have not encountered a single case of infectious endophthalmitis in more than 9 years and 8,000 cases. Rather than good luck, we believe our experience is due to our attention to detail.

A recent dye study by McDonnell et al7 in cadaver eyes demonstrated that, in the presence of hypotony, clear corneal incisions tend to draw India ink into the incision. Shingleton et al8 reported that 20% of the patients examined 2 hours postoperatively had IOPs of less than 10mmHg. Dr. Fine found a 15% similar incidence in his own practice (unpublished data). Of extreme importance is the fact that neither Shingleton et al nor Dr. Fine have experienced an increased incidence of endophthalmitis in spite of immediate postoperative hypotony, which McDonnell et al7 hypothesized was the cause of an increased incidence of endophthalmitis.

Preparing the Eye

We apply 5% povidone-iodine (Betadine; Purdue Frederick, Stamford, CT) to the ocular area, and we use Steristrips to evert the eyelashes so that they are flush against the skin and the meibomian gland's orifices are exposed. After draping the eye, we place a wick in the lateral canthus to disallow the pooling of fluid.

Creating the Incision

Rather than incising the steep axis, we create incisions at the temporal corneal periphery in order to address astigmatism and postoperatively neutralize the pressure effects of blinking and gravity. When indicated, limbal relaxing incisions address preoperative astigmatism.

Replacing aqueous with viscoelastic stabilizes the eye and firms the anterior chamber. This technique also permits us to construct incisions reproducibly, because the eye does not become unpredictably distorted due to hypotony.

To create the incision, we applanate the trapezoidal knife against the surface of the globe with the point just anterior to the conjunctival insertion. The knife is advanced in the plane of the cornea for 2mm and then directed through Descemet's membrane, into the anterior chamber. We then advance the knife until the internal incision's width is the appropriate size, usually indicated by the width of the shoulders of the tip.

We prefer single-plane incisions, which create better architecture for valve structure than do grooved incisions and maximize endothelial pumping, because there is no opening in the corneal-epithelial fluid barrier. We use trapezoidal incisions, which we can enlarge for IOL implantation by advancing the trapezoidal knife farther into the eye without compromising the architecture of the incision. We avoid side-cutting knives, which can alter the incision's architecture and are frequently inaccurate with respect to the final width of the incision. All cataract incisions should be at least 2mm long and no more than 2.5 to 3.5mm wide.

Surgical technique is crucial to the incision's integrity. We never grasp the superior lip with a forceps, because this instrument can abrade the epithelium and cause a loss of the fluid barrier. Instead, we lift the roof of the incision from its floor with a cannula in order to insert an instrument such as a pupil dilator or an injector for a capsular tension ring. We prefer beveled phaco tips, which we insert bevel down by pushing against the floor of the incision and insinuate into the eye. During phacoemulsification, power modulations protect the eye against thermal injuries, which can compromise the integrity and sealing of the incision.

Implanting the IOL

IOL implantation should occur through adequately and precisely enlarged incisions. Stretching the incision aggressively can negatively affect its ability to seal. When stabilizing the eye with a fixation ring, injection systems are far superior to folding forceps, which require a larger incision and distort the wound further.

Sealing the Incision

We perform stromal hydration of the main and sideport incisions by filling the eye to physiologic pressures or slightly higher without ever overpressurizing the eye. The patient wears a soft contact lens if the epithelium located over the incision is abraded. We suture the incision whenever necessary and always test for leakage. It is important to recognize the importance of endothelial pumping and proper architectural features that allow for mechanical stability. To test for leakage, we place fluorescein stain on the eye and press the posterior lip of the incision with a finger (Figure 3). Many of the studies showing an incision's inability to seal are based on pinpoint pressure.9,10 This technique is completely nonphysiologic and irrelevant; a patient would have to press on his eye with something the size of a pencil's point. Moreover, pinpoint pressure can cause a paracentesis, although hypersquare, to leak, but no one questions the safety of this type of incision.

Using Antibiotics

Our patients receive a fourth-generation fluoroquinolone q.i.d. for 3 days preoperatively, at least q.i.d. on the surgical day, and q.i.d. for 10 days postoperatively. We believe it would not be unreasonable to administer this antibiotic q2h on the day of surgery and perhaps even on the first postoperative day.


Clear corneal incisions offer many benefits, including safety and efficacy, but successful outcomes require a surgeon's attention to detail, as described herein. That stated, ophthalmologists should use the incision that they can perform with the most reproducibly safe results.

I. Howard Fine, MD, is Clinical Professor of Ophthalmology at the Casey Eye Institute, Oregon Health & Science University, and he is in private practice at Drs. Fine, Hoffman, & Packer in Eugene, Oregon. He is a paid consultant for Advanced Medical Optics, Inc., and he receives research and travel support from Alcon Laboratories, Inc. Dr. Fine may be reached at (541) 687-2110; hfine@finemd.com.
Richard S. Hoffman, MD, is Clinical Associate Professor of Ophthalmology at the Casey Eye Institute, Oregon Health & Science University, and he is in private practice at Drs. Fine, Hoffman, & Packer in Eugene, Oregon. He states that he holds no financial interest in the products or companies mentioned herein. Dr. Hoffman may be reached at (541) 687-2110; rshoffman@finemd.com.
Mark Packer, MD, FACS, is Clinical Assistant Professor of Ophthalmology at the Casey Eye Institute, Oregon Health & Science University, and he is in private practice at Drs. Fine, Hoffman, & Packer in Eugene, Oregon. He is a paid consultant for Advanced Medical Optics, Inc., and he has received travel support and honoraria from Alcon Laboratories, Inc. Dr. Packer may be reached at (541) 687-2110; mpacker@finemd.com.
1. Cooper BA, Holekamp NM, Bohigian G, Thompson PA. Case-control study of endophthalmitis after cataract surgery comparing scleral tunnel and clear corneal wounds. Am J Ophthalmol. 2003;136:300-305.
2. Nagaki Y, Hayasaka S, Kadoi C, et al. Bacterial endophthalmitis after small-incision cataract surgery: effect of incision placement and intraocular type. J Cataract Refract Surg. 2003;29:20-26.
3. Han DP, Wisniewski SR, Wilson LA, et al. Spectrum and susceptibilities of microbiologic isolates in the Endophthalmitis Vitrectomy Study. Am J Ophthalmol. 1996;122:1-17.
4. Kowalski RP, Karenchak LM, Romanowski EG. Infectious disease: changing antibiotic susceptibility. Ophthalmol Clin North Am. 2003;16:1-9.
5. Montan PG, Wejde G, Setterquist H, et al. Prophylactic intracameral cefuroxime: evaluation of safety and kinetics in cataract surgery. J Cataract Refract Surg. 2002;28:982-987.
6. Montan PG, Wejde G, Koranyi G, Rylander M. Prophylactic intracameral cefuroxime: efficacy in preventing endophthalmitis after cataract surgery. J Cataract Refract Surg. 2002;28:977-981.
7. McDonnell PJ, Taban M, Sarayba M, et al. Dynamic morphology of clear corneal incisions. Ophthalmology. 2003;110:2342-2348.
8. Shingleton BJ, Wadhwani RA, O'Donoghue MW, et al. Evaluation of intraocular pressure in the immediate period after phacoemulsification. J Cataract Refract Surg. 2001;27:524-527.
9. 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.
10. 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.
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