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Up Front | Oct 2008

Modified Cow-Hitch Suture Fixation

A pictorial description of a transclerally sutured posterior chamber IOL.

Sutured posterior chamber IOLs are a safe and effective method for rehabilitation of aphakic eyes where capsular support is inadequate. Recently, we outlined the technique and discussed the safety of this procedure,1 which uses a transcleral suture to fixate the posterior chamber IOL. During this modified cow-hitch suture technique, the suture is tied to the haptic through the eyelet on the haptic, preventing the need for loose-end knots. These types of suture knots are inadvisable because they may come loose, causing IOL dislocation or intraocular irritation of the iris from the sharp ends of the knot. Our transcleral suture fixation technique will be described in the following pictorial essay.

METHOD
We use the Alcon CZ70BD (Alcon Laboratories, Inc., Fort Worth, Texas) posterior chamber IOL, a one-piece PMMA IOL with a 7-mm optic size and mid-loop eyelets in the haptics. Following fashioning of scleral flaps at 180° based at the scleral limbus, 25-gauge needle punctures are performed approximately 1 mm behind the limbus in the bed of the scleral flap. It is important to make sure these scleral perforations are directly 180° from each other; they must be made diagonally through the center of fixation.

Posterior pars plana vitrectomy or anterior vitrectomy is performed to clear vitreous from the site of the scleral fixation.

Initially, the superior corneal incision is small (approximately 3.2 mm), and the 10-0 Prolene suture on a long, curved needle (CIF4; Ethicon Inc., Sommerville, New Jersey) is passed back and through the scleral perforation in the bed of the scleral flap. The loose loop of suture is hooked with a Kuglen hook, and the loop is brought out through the corneal wound (Figures 1A and 2A). This is repeated for the second scleral flap.

Once the loops of the suture are pulled through the corneal wound, the IOL is placed on a drop of ophthalmic viscosurgical device over the central cornea. It is fixated while the sutures are tied to the haptics. The 10-0 Prolene needle is withdrawn prior to placing the IOL on the central cornea, still leaving the loops of the suture within the eye.

The 10-0 Prolene suture is pulled upward, creating a small loop that is passed through the eyelet (Figures 1B and 2B). Tying forceps are the best instrument for this step. Use them to grasp the loop of the suture after it is passed through the eyelet. The tip of the forceps is then passed through the suture loop to grasp the double suture on the opposite side of the eyelet, creating a cow-hitch knot (Figures 1C, 1D, and 2C). The cow-hitch knot enables the forceps to pull the loop of the suture and pass it around the ends of the haptic, over to the optic side of the eyelet on the haptic (Figures 1E, 1F, and 2D). The suture is then tightened, enabling fixation of the cow-hitch knot to the optic side of the haptic's eyelet (Figures 1G, 2E, and 2F).

Any free slack in the suture is pulled tight and the corneal wound is enlarged to 7 mm, which allows the posterior chamber IOL to pass while continuing to pull on the 10-0 Prolene sutures. The IOL is positioned correctly to enable insertion into the posterior chamber (Figure 1H). Once this is performed, the 10-0 Prolene is fixated to the adjacent sclera in the bed of the scleral flap using the CIF4 needle. An adequate bite of sclera to fixate the suture to is required to prevent cheese-wiring (Figure 1I). Once this is performed and the 10-0 Prolene is securely tightened, the free ends of the suture are buried in the bed of the flap. The scleral flap is closed with 7-0 Vicryl sutures.

SUMMARY
The modified cow-hitch technique provides strong scleral suture fixation of posterior chamber IOLs. The fixation technique employed during this manuever prevents knot slippage and iris chafing from free suture ends. Care must be taken in handling the 10-0 Prolene suture to prevent breakage of the suture during the suturing technique.

Skill in this technique enables rapid suturing of IOLs, preventing manipulation of free suture ends when tying the suture to the haptics.

Jennifer Chen, PhD, is Director of the City Eye Centre, Brisbane, Australia. Dr. Chen states that she has no financial interest in the products or companies mentioned. She may be reached at tel: +61 7 38316888; fax: +61 7 3831 6883; e-mail: eye@cityeye.com.au.

Lawrence Lee, MBBS, FRANZCO, FRACS, is the Director, City Eye Centre, and Director and Associate Professor, Department of Ophthalmology, University of Queensland, Royal Brisbane & Women's Hospital, Herston, Australia. Dr. Lee states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +61 7 3636 5230; fax: +61 7 38316883; e-mail: eye@cityeye.com.au.

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