Insertion of the Intraocular Lens
For discussion of the history of IOL design and development, see the Appendix in this volume. IOLs are also discussed in BCSC Section 3, Clinical Optics, and Section 13, Refractive Surgery. For a more detailed discussion of currently available IOLs, see Chapter 9.
In uncomplicated cataract surgery, the surgeon’s goal is generally to place an IOL into the capsular bag. The surgeon must determine whether the support structures within the eye are adequate to maintain IOL centration and stability. With posterior capsule rupture, sufficient anterior capsule support may allow a 3-piece PCIOL to be safely placed in the ciliary sulcus. Complete lack of capsular support warrants placement of an anterior chamber lens (ACIOL) or a scleral-or iris-fixated posterior chamber lens.
In all cases, an OVD is used to fill the capsular bag or expand the ciliary sulcus, stabilize the anterior chamber during IOL insertion, and protect the corneal endothelium from contact with the IOL. The phacoemulsification incision must be large enough to accommodate the IOL and inserter; if necessary, the incision may be enlarged after removal of the cataract.
Foldable single-piece IOLs
Foldable single-piece and 3-piece IOLs are the most commonly used IOL styles. A foldable single-piece IOL (Fig 8-14) is loaded into an injector cartridge that has been prefilled with OVD. The cartridge is then inserted into a handpiece, which is operated using a manual plunger or screw mechanism. Preloaded IOL injector systems and automated inserters are also available. The tip of the injector is then introduced into the corneal wound and the IOL inserted, with the first haptic placed carefully into the capsular bag under direct visualization. The trailing haptic is flexed and placed into position, or “dialed in,” by rotating it clockwise with slight posterior pressure utilizing either the tip of the injector or a second instrument, such as a hook, so that the second haptic slides under the anterior capsule (Video 8-7). A foldable single-piece IOL should never be placed in the ciliary sulcus or anterior chamber because of the risk of iris chafing and uveitis-glaucoma-hyphema (UGH) syndrome (see Chapter 11).
Figure 8-14 An illustration of a modern foldable single-piece posterior chamber intraocular lens (IOL).
(Illustration courtesy of Mark Miller.)
Injection of a single-piece intraocular lens. Courtesy of Lisa Park, MD.
Foldable 3-piece IOLs
Foldable 3-piece IOLs are generally made of either an acrylic or a silicone optic with polypropylene haptics (Fig 8-15). These lenses can be placed into either the capsular bag or the ciliary sulcus using an injector, or they can be folded in half and placed through the incision using implant forceps. The optic and trailing haptic are positioned using forceps or by dialing in the lens, as described in the preceding section.
Polymethyl methacrylate IOLs
Polymethyl methacrylate (PMMA) IOLs are not foldable and may be safely inserted with standard, fine-tip, smooth forceps. The phacoemulsification incision must be widened to accommodate the size of the lens, and the IOL is advanced by first placing the leading haptic into position and then rotating the optic and trailing haptic into place.
Scleral- or iris-fixated posterior chamber IOLs
Several techniques have been described for securing a PCIOL behind the iris when capsular support is inadequate. If the lens is to be sutured to the sclera, polypropylene sutures or Gore-Tex sutures (W. L. Gore & Associates) are typically used instead of nylon sutures, because nylon degrades over time and lens dislocation may result. Transscleral polypropylene or Gore-Tex sutures may be used to secure the IOL haptics in the ciliary sulcus, or the haptics may be sutured to the overlying iris with polypropylene sutures. Note that the Gore-Tex suture packaging explicitly states that the product is not for ophthalmic use. Alternative techniques have been described whereby the PCIOL haptics are secured via a scleral tunnel, with or without the use of surgical glue.
A scleral-fixated PCIOL is a valuable alternative to an ACIOL in situations when an angle-supported lens may be problematic, such as when peripheral anterior synechiae are present or there is significant corneal endothelial compromise. Scleral-fixation techniques are more difficult than those used in standard implantation and are associated with a greater risk of complications such as vitreous hemorrhage, lens dislocation, lens tilt, or late endophthalmitis (see Chapters 10 and 11).
Figure 8-15 An illustration of a modern foldable 3-piece posterior chamber IOL.
(Illustration courtesy of Mark Miller.)
Agarwal A, Jacob S, Kumar DA, Agarwal A, Narasimhan S, Agarwal A. Handshake technique for glued intrascleral haptic fixation of a posterior chamber intraocular lens. J Cataract Refract Surg. 2013;39(3):317–322.
Yamane S, Sato S, Maruyama-Inoue M, Kadonosono K. Flanged intrascleral intraocular lens fixation with double-needle technique. Ophthalmology. 2017;124(8):1136–1142.
Anterior chamber IOLs
Modern, flexible, open-loop ACIOLs with 4-point fixation are supported by the anterior chamber angle and considered acceptable for use when implantation in the posterior chamber is not feasible (Fig 8-16). The appropriate length of the ACIOL is commonly determined using 1 mm plus the horizontal diameter of the limbus, as measured externally with a caliper (“white to white”).
If an ACIOL is being implanted during the initial phacoemulsification procedure, it is generally advisable that the primary clear corneal phacoemulsification incision be sutured and abandoned in favor of a wider scleral tunnel incision at a secondary site. Otherwise, the corneal phacoemulsification incision will have to be enlarged with the keratome or with corneal scissors to enable insertion of an ACIOL, and this could lead to inadequate wound integrity. The pupil is generally constricted pharmacologically before IOL implantation, and any vitreous is removed from the anterior chamber. At least one peripheral iridectomy is performed to avoid pupillary block. The anterior chamber depth is stabilized, and the corneal endothelium is protected with an OVD. A lens glide may be inserted across the anterior chamber into the distal angle to isolate the iris from the advancing IOL haptic. The IOL is then inserted, with its leading haptic placed into the angle while the iris is observed for any indication of distortion. If a glide has been used, it is removed as the IOL is stabilized with forceps. The posterior lip of the incision is gently retracted to allow placement of the trailing haptic in the angle (Video 8-8).
Placement of an anterior chamber intraocular lens. Courtesy of Lisa Park, MD.
Figure 8-16 Kelman-style open-loop anterior chamber IOL with flexible 4-point fixation.
(Courtesy of Robert C. Drews, MD.)
Careful inspection confirms the proper insertion. The pupil will peak toward any area of iris “tuck,” in which case the IOL can be repositioned until the pupil is round and the optic is centered. The surgeon can adjust the position of the ACIOL by using a hook to flex the optic toward either angle.
Donaldson KE, Gorscak JJ, Budenz DL, Feuer WJ, Benz MS, Forster RK. Anterior chamber and sutured posterior chamber intraocular lenses in eyes with poor capsular support. J Cataract Refract Surg. 2005;31(5):903–909.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.