3 Wound Construction and Complications As incisions in cataract surgery have evolved alongside improvements in intraocular lens (IOL) design, phacoemulsification systems, and surgical instrumentation, the incisions have become smaller. Both scleral tunnel incisions and clear corneal incisions are widely used today and have varying advantages and disadvantages. Ideal incisions minimize surgically induced astigmatism and are self-sealing to reduce the risks of hypotony and endophthalmitis. As technology continues to advance, femtosecond lasers have aided surgeons in creating more reproducible and customizable incisions while tissue adhesives provide alternative means for creating watertight closure with ease of use. Vision outcomes in cataract surgery rely on wound size and architecture. Problems in wound construction are not uncommon, but the creation of proper wounds is crucial in wound healing and avoidance of potential complications. Surgeons should be able to quickly recognize inaccuracy in wound construction and be prepared to manage complications that may stem from the changes in surgical technique needed to adapt to poorly constructed incisions. Proper design and construction of incisions used in cataract surgery are crucial in achieving successful surgical results. Cataract surgical incisions have evolved greatly overtime. With innovations in IOL design, phacoemulsification, and instrumentation, incision size has been reduced and has enabled improved outcomes in cataract surgery. The most common incision types include scleral tunnels, clear cornea, and femtosecond laser–assisted cornea; each type has advantages, disadvantages, and keys to success. Understanding the anterior segment architecture and structural relationships (Fig. 3.1) can aid in the successful creation of surgical incisions. The scleral tunnel incision was introduced in 1977 by Richard Kratz. Incisions are created 2 mm posterior to the limbus. A scleral partial-thickness incision is made, tunneled through sclera into clear cornea parallel to the corneal surface, and Descemet’s membrane is incised to enter the anterior chamber (Figs. 3.2 and 3.3). These incisions are up to 7 mm in length to enable the insertion of large, nonfoldable polymethylmethacrylate (PMMA) IOLs and require closure with multiple sutures. In 1989, the Food and Drug Administration (FDA) approved the first foldable IOL (AMO PhacoFlex model SI-18, Allergan Medical Optics, Santa Ana, CA), which enabled making smaller incisions of 4 mm in width. These incisions could be closed with a single interrupted suture, providing greater wound stability, more astigmatic neutrality, and faster vision rehabilitation. Another innovation in scleral tunnel design is the sclerocorneal frown incision, which is oriented with the curvature away from the limbus. The more anterior portion of the incision is 2 mm posterior to the limbus, and the incision varies in width depending on the size of IOL to be inserted. The internal lip of the incision is parallel to and positioned 1 mm anterior to the limbus. The external portion of the incision enables greater stretch for implantation of the IOL optic. As with tangential scleral tunnels, sutures are generally used to ensure watertight closure. In all incisions, sutures should be trimmed short and rotated to bury the knot and avoid postoperative patient discomfort. Scleral tunnel incisions have the advantages of increased wound strength and a self-sealing nature (Table 3.1). To achieve watertight closure, the tunneled portion of the scleral and corneal stroma must be in a consistent plane aligned with the most posterior portion of the incision. Due to their greater distance from the visual axis, scleral tunnels induce minimal astigmatism. Potential disadvantages of scleral tunnel incisions include wound leaks, inadvertent creation of filtering blebs, tunnel hemorrhages leading to hyphema, and difficulty with manipulation of the phacoemulsification handpiece and instruments within the incision. Fig. 3.1 Anatomic relationships. This cross-sectional image of the anterior segment shows the relationship between the peripheral cornea, corneoscleral junction, and anterior chamber angle in a phakic eye. Fig. 3.2 Scleral tunnel incision. The external incision is curved away from the limbus. The internal incision is 1 mm anterior to the limbus. Fig. 3.3 Clear corneal, near-clear corneal, and sclera-corneal incisions. This diagram illustrates the locations of the different corneal and corneoscleral incisions, and their three-dimensional relationship to the anterior segment anatomy. Table 3.1 Scleral Tunnel Incisions
Incisions in Cataract Surgery
Scleral Tunnel Incisions
Advantages | Disadvantages |
More resistant to stretch and mechanical trauma | Time-consuming |
Less surgically induced astigmatism | Often require sutures for closure |
Self-sealing over longer lengths | Inadvertent creation of filtering blebs |
Clear Corneal Incisions
Multiple surgical innovations led to the development of sutureless clear corneal incisions. First introduced by Howard Fine1 in 1991, these incisions were initially 1.75 mm in length and 4 mm in width to enable IOL insertion. Watertight construction was difficult, leading to potential bacterial contamination and endophthalmitis. As IOL technology advanced, incision size decreased, and Fine later introduced stromal hydration to aid in wound sealing. These incisions were 2.8 to 3.2 mm in width at the limbus and 1.75 mm in length. The incision size has continued to decrease to 2.2 mm in width or even less. Smaller incisions have led to less surgically induced astigmatism and improved sealing.
The most posterior portion of the clear corneal incision is constructed just anterior to limbal arcades of conjunctival blood vessels (Figs. 3.3 and 3.4). A hinge of variable depth is created to provide a more watertight closure. Multiplanar incisions, incorporating both vertical and horizontal elements, provide stability at a wide range of intraocular pressure ranges. Although longer incisions may be more resistant to wound leakage, this benefit must be weighed against potential induction of corneal striae and poor visualization caused by the increased length.
The temporal clear corneal incision has become the most predominant incision used in cataract surgery.2 The advantages include efficiency of wound creation, self-sealing nature, minimal astigmatism induction, rapid visual recovery, wound stability, and lack of conjunctival manipulation and trauma (Table 3.2). The temporal location has the advantage of accessibility, and due to the greater horizontal diameter of the cornea, temporal incisions are less likely to invade the visual axis. Additionally, temporal incisions may partially neutralize the against-the-rule astigmatism present in many patients undergoing cataract surgery. Disadvantages of clear corneal incisions include potential thermal damage or mechanical trauma during surgery, as well as the potential for bacterial contamination and subsequent endophthalmitis.
Femtosecond Laser Clear Corneal Incisions
Femtosecond laser technology is commonly used in laserassisted in situ keratomileusis (LASIK) flap creation and has certain advantages over traditional microkeratomes for flap creation, including safety and reproducibility. More recently, it has been used in cataract surgery for clear corneal incisions as well as paracenteses. This new technology enables customization of the length, angles, and shape of incisions with excellent reproducibility. Grewal and Basti3 used spectral-domain anteriorsegment optical coherence tomography (AS-OCT) to evaluate the morphology of clear corneal incisions created by a femtosecond laser and compared them with those made by traditional steel keratomes. They found that femtosecond laser incisions had less endothelial wound gape and misalignment, as well as fewer Descemet’s membrane detachments.
Fig. 3.4 Clear corneal incision. The external incision is just inside the conjunctival arcade. The internal incision is no wider than the tunnel length. (a) No hinge. (b) Small hinge. (c) Deep hinge.
Table 3.2 Clear Corneal Incisions
Advantages | Disadvantages |
Ease of creation | Possible increased risk of endophthalmitis |
Minimal astigmatic effect | Less wound strength |
Sutureless watertight closure | |
Lack of conjunctival manipulation and trauma | |
Rapid visual recovery |
It is expected that laser-created incisions will improve in reliability with further technological advances in lasers and OCT. Although the clinical advantages over traditional incision construction remain to be proven, technological advances may enable improved refractive outcomes in the future.
Tissue Adhesives
Liquid adhesive ocular bandages, including OcuSeal (Beaver-Visitec, Waltham, MA) and ReSure sealant (Ocular Therapeutix, Inc., Bedford, MA) have been created for topical application to seal cataract wounds. These transparent polymerizing hydrogels may be applied topically and polymerize on the ocular surface to form an adhesive coating (Fig. 3.5). Although OcuSeal is not yet available in the United States, the ReSure sealant is an available hydrogel composed of polyethylene glycol, trilysine, buffering salts, and 90% water.4 Recent studies have demonstrated less surgically induced astigmatism with tissue adhesives in comparison with sutured wounds, and similar astigmatism in comparison with controls.5 Although common side effects include foreign-body sensation and hyperemia, a study reported less foreign-body sensation in comparison with both sutured wounds and patients without any sutures.5 Hydrogel sealants have been shown to be both safe and effective in preventing wound leakage after cataract surgery.6
