The Self-Sealing Temporal Clear Corneal Tunnel Incision

Several studies^1-3 have concluded that the increased frequency of endophthalmitis in cataract surgery is coincident with the development of sutureless clear corneal incisions. Epidemiologically, such coincidence makes the use of this type of incision a risk factor for postoperative endophthalmitis; however, I have the feeling that this conclusion, based on pooled data from the literature, does not represent the experience of many anterior segment surgeons.^2,3

The main problem with review studies that show a correlation between endophthalmitis and the clear corneal incision is that they include various surgeons creating incisions. The integrity of each incision can vary depending on the surgeon's skill and experience.

Surgeons have also contemplated the flexibility of the sutureless clear corneal incision in its ability to modify the surgical procedure under special circumstances, including posterior capsule rupture, conversion to extracapsular cataract extraction (ECCE), posttraumatic zonular instability, pseudoexfoliation syndrome, or poor mydriasis.

STUDY DESIGN
I performed a prospective study of 2,000 consecutive cataract surgeries (all performed by one surgeon) to estimate the safety of the temporal self-sealing clear corneal tunnel incision and the incidence of intra- and early postoperative complications, including posterior capsule rupture, zonulysis, fall of nucleus into the vitreous, endophthalmitis, and need for suture. All surgeries were performed under topical anesthesia; I created a temporal clear corneal three-level tunnel incision using the Clear-Cut slit-angled disposable metal knife (Alcon Laboratories, Inc., Fort Worth, Texas).

In 76 eyes (3.8%), I used iris retractors to treat inadequate mydriasis, and I used trypan blue in 182 eyes (9.1%) that had white cataracts. Of these cataracts, 14 (0.7%) were intumescent lenses. Phacodonesis was present in 15 eyes (0.75%). In all cases, I tested the integrity of the incision by creating a central corneal indentation and an indentation at the pars plana, located 3 to 4 mm from the incision by the end of the surgery. Stromal hydration was used only for the sideport incisions. In patients with dementia, I placed a suture to deter the patient from rubbing his eye.

RESULTS
In this series, 44 (2.2%) posterior capsule ruptures occurred, and 12 eyes (0.6%) required a capsular tension ring (CTR) to compensate for extended zonular instability. In two instances of capsular block syndrome, the nucleus fell into the vitreous cavity. Additionally, three cases required supplementary pars plana vitrectomy for removal of nucleus and lens fragments, and two cases (0.01%) required conversion to ECCE.

I used an anterior chamber IOL in eight cases (0.4%) and a 10-0 nylon suture in 67 cases (3.35%) to insure the integrity of the incision. I did not have to return to the operating room for suture placement in any case. In all 2,000 cases, there was only one case of endophthalmitis and no case of corneal decompensation.

I work in a local hospital were most of my patients are farmers—the majority (57.6%) of whom have a preoperative visual acuity 6/60 or less. Pseudoexfoliation syndrome, associated with poor mydriasis and zonular instability, also occurred in approximately half of the eyes operated.

TECHNIQUE
I always prescribe tobramycin and NSAID drops to be taken preoperatively—tobramycin twice daily at the lid margin for 1 to 7 days before surgery and NSAID drops the day before surgery. In the operating room, after prep and drape, I instill povidone iodine 5% drops in the conjunctival sac.

I fixate the globe with a cotton-tipped applicator and adjust the operating microscope to 7X to 8X magnification of the temporal cornea. I make an initial partial thickness groove in the clear cornea—just in front of the leading edge of the anterior vascular arcade—at the incision site with a 3.2-mm knife. I find that this initial groove (1) offers a more smooth entrance wound and (2) acts as a reference point to start the cornel tunnel.

I use the same knife to enter the cornea at the mid-stromal depth and advance the blade in a slightly upward direction to keep it almost parallel to the corneal surface. Once approximately half of the blade has entered the cornea, I change direction toward the iris plane, entering the anterior chamber. Afterward, I perform the sideport incision; then only do I inject the ophthalmic viscosurgical device (OVD).

At the end of the operation, I pressurize the eye with balanced saline solution to ensure the integrity and endurance of the incision. In event of even a small leak, I place one or two 10-0 nylon sutures. I use stromal hydration for the sideport incision only, and I perform a subconjuctival or peribulbar injection of tobramycin (although recently I have alternatively used netilmicin). I check the eye 2 to 4 hours after the operation, strongly advising my patient not to touch his eye and wear an eye patch while sleeping.

It has been proved that clear corneal wounds of a square or nearly square surface architecture, when meticulously checked for sealing, create a stable postoperative environment. This is demonstrated by the absence of hypotony and wound leakage.⁵ Although clear corneal incisions in vivo may cause minor anatomic imperfections, they can be clinically stable.⁶

SPECIAL CASES
Poor mydriasis (requiring iris retractors). I make the sideport incision at the 12-o'clock position in a right eye or the 6-o'clock position in a left eye so that I can place the four iris retractors in the 1.30-, 4.30-, 7.30-, and 10.30-o'clock positions.

Hard cataracts and zonular instability. Iris retractors offer an additional advantage in cases of hard cataracts and zonular instability. I can use them to stabilize the lens capsule by catching the continuous curvilinear capsulorrhexis.

Enlarging the incision for conversion to ECCE or anterior chamber IOL implantation. I always use the same Clear-Cut slit-angled disposable metal knife, enlarging the incision toward the 12-o'clock position only, for as long as needed. I try to keep the knife in the same plane with the initial incision. I use sutures when I have to extend the initial incision, placing the first suture at the edge of the initial incision and continuing as needed.

CONCLUSION
A sutureless, clear corneal cataract incision has been related to an increased incidence of postoperative endophthalmitis. I prefer using a modified incisional approach during phacoemulsification, the self-sealing temporal clear corneal tunnel incision. This incision is a safe procedure in relation to intra- and postoperative complications⁴ and in special cases requiring the surgeon to modify his standard technique.

Aliki Liaska, MD, FEBO, is a Consultant Ophthalmic Surgeon in the Department of Ophthalmology, General Hospital of Lamia, Lamia, Greece. Dr. Liaska states that she has no financial interest in the products or companies mentioned. She may be reached at tel: +30 69778 36222; fax: +30 22310 38355; or e-mail: allias8@yahoo.gr.

1. Taban M, Behrens A, Newcomb RL, et al. Acute endophthalmitis following cataract surgery: A systematic review of the literature. Arch Ophthalmol. 2005;123:613-620.
2. Lundström M. Endophthalmitis and incision construction. Cur Opin Ophthalmol. 2006;17(1):68-71.
3. Monica ML, Long DA. Nine-Year safety with self-sealing corneal tunnel incision in clear cornea cataract surgery. Ophthalmology. 2005;112:985-986.
4. Jaycock P, Johnston RL, Taylor H, et al. The Cataract National Dataset electronic multi-center audit of 55,567 operations: updating benchmark standards of care in the United Kingdom and internationally. Eye. 2007;Nov 23 [Epub ahead of print].
5. Masket S, Belani S. Proper wound construction to prevent short-term hypotony after clear corneal incision cataract surgery. J Cataract Refract Surg. 2007;33(3):383-386.
6. Torres LF, Saez-Espinola F, Colina JM, et al. In vivo architectural analysis of 3.2-mm clear corneal incisions for phacoemulcification using optical coherence tomography. J Cataract Refract Surg. 2006;32(11):1820-1826.