Ab externo 4-point scleral fixation

Abstract

Scleral fixation of a posterior chamber intraocular lens (IOL) using the Lewis technique1 can involve intraoperative and postoperative difficulties, such as rotating and burying the knots and the risk of the suture eroding transconjunctivally over time.2 Because of concerns about these issues, we have modified our scleral fixation technique. The corneal center is marked using a Sinskey hook. After fornix-based conjunctival flaps are created at the nasal and temporal limbus, radial marks are made at the 3 and 9 o'clock limbus, taking care to center the radial keratotomy marker with the corneal center. After an L-shaped scleral incision is made (Figure 1), partial-thickness scleral flaps are fashioned, centered on the limbal marks. Two marks are made in the scleral bed (Devon skin marker, Graphic Controls) 1.0 mm from the surgical limbus and 1.0 mm superior and inferior to the radial limbal mark. A 7.0 mm corneal incision is made, and the anterior chamber is entered at the ends of the incision. Bimanual anterior vitrectomy is performed to remove vitreous from the anterior chamber. Vitreous and capsule remnants under the 3 and 9 o'clock iris are also removed. Sodium hyaluronate (Healon® 1%) is injected to reform the anterior chamber.Figure 1.: (Rao) Modified technique for scleral fixation of a posterior chamber IOL; scleral flap and surface marking of fixation sutures.A 10-0 polypropylene (Prolene®) suture (Ethicon STC6) is cut into 2 arms. The needle on one arm is passed through the inferior mark in the scleral bed, perpendicular to the sclera (Figure 2). The needle is guided out of the corneal incision with a 27 gauge needle. The polypropylene suture needle is threaded through the eyelet on the inferior haptic of the IOL from below upward. It is then passed into the eye, through the corneal incision, and guided out of the eye by a 27-gauge needle inserted through the superior mark in the scleral bed. The other haptic is treated in a similar fashion (Figure 3), taking care to ensure that the corresponding suture (180 degrees apart) is also passed through the eyelet from below upward.Figure 2.: (Rao) The 10-0 Prolene needle is passed through the scleral bed into the eye and is guided out of the corneal section by a 27 gauge needle.Figure 3.: (Rao) Prolene suture is passed through the superior haptic from above and is guided out of the eye by a 27 gauge needle passed through the scleral bed (not shown). Arrows indicate the direction of Prolene suture passage.The corneal wound is opened to its full extent, and the IOL is inserted in the posterior chamber. The sutures are pulled up and tied in the scleral bed. The knot is rotated into the eye through the superior track made by the 27 gauge needle (as it offers less resistance to passage of the knot). Holding up 1 arm of the suture creates an arrowhead at the knot, enabling easier rotation into the eye. The suture is cut after the knot has passed through the sclera to reduce the risk of the knot unraveling during suture rotation. Further rotation ensures that the cut ends retract into the eye. A single suture at the angle of the scleral flap secures the polypropylene loop under the flap. This procedure enables the surgeon to deal with vitreous and capsule remnants before passing the suture, thus avoiding suture and haptic entanglement in these structures. Sodium hyaluronate restores normal anatomical relationships in the anterior segment. This prevents the erroneous placement of the needle that can occur in a collapsed globe. The limbal and scleral markings ensure that the fixation sutures are placed in a symmetric fashion, 180 degrees opposite each other. Retrieving the needle through the corneal wound allows easy placement through the eyelet of the IOL and avoids the need for prolonged manipulations. Symmetric placement of sutures through the eyelets of both haptics is essential to avoid torque and tilt of the IOL and has been described.3 The scleral flap allows a bailout in the occasional patient in whom knot rotation is difficult. The use of a superior scleral tunnel can also be considered, depending on the surgical situation and pre-existing astigmatism. We have used this standardized approach with good anatomical and functional results in patients with intraoperative posterior capsule rupture, planned secondary IOL placement in aphakia, in conjunction with pars plana vitrectomy for a dislocated crystalline lens, and during penetrating keratoplasty. Srinivas K. Rao DO Lingam Gopal MS Rajesh Fogla DNB, FRCS Dennis S.C. Lam FRCS, FRCOphth Prema Padmanabhan MS aHong Kong, China