Intraocular Lens Implantation

39   Intraocular Lens Implantation

Harry B. Grabow and William J. Fishkind

Intraocular lens (IOL) implantation, whether phakic or aphakic, entails complications that can occur before, during, or long after implantation. They can result in damage to the eye, the IOL, or both. Surgeons and manufacturers alike, in an effort to minimize the incidence and severity of IOL-related complications, have been studying implantation techniques and IOL behavior since the late 1970s. The method of insertion of an IOL into the eye, and the IOL design, material, and location are all associated with potential complications.

The effect of the location of an IOL inside the eye has been under continuous scrutiny. IOLs have been fixated in the anterior chamber (AC) angle, the anterior iris stroma, the pupil, the posterior chamber (ciliary sulcus), the lens capsular bag, and the pars plana. IOL materials have proliferated since the first polymethylmethacrylate (PMMA) IOL was implanted by Harold Ridley1 in 1949. Brought on by the success of small-incision phacoemulsification in the 1970s,2 rigid PMMA lenses have been supplanted by foldable lenses of silicone, polyhydroxyethyl-methacrylate (poly-HEMA), acrylic, and biologic collagen.3 Each material behaves differently from the others during and after implantation.

The introduction of any physical object through an incision into the eye can result in damage to the intraocular structures (Box 39.1). If an IOL is forced through an incision that is too small, the incision might enlarge by tearing or stretching, with the possible result of an unstable and leaking wound, requiring suturing to prevent leakage. Wound leakage is thought to be one cause of postoperative infectious endophthalmitis.

In an attempt to pass the insertion device through the tight incision, excessive posterior angulation may cause inadvertent iridodialysis, with associated hyphema, or a torn posterior capsule. This is especially possible if substantial force is used to push the insertion device through the tight incision. The release of the cartridge into the AC can be so forceful that the cartridge passes though the posterior capsule. Similarly, an insertion forceps, or cartridge angled too anteriorly, might cause stripping of Descemet’s membrane. The improper wound and chamber dynamics thus created could result in iris prolapse, chamber collapse, corneal endothelial damage, and subsequent postoperative corneal edema.

Improper attention during implantation may traumatize the capsule, resulting in zonulodialysis, tearing of the anterior capsule, tearing of the posterior capsule, and rupture of the anterior hyaloid face, increasing the incidence of postoperative cystoid macular edema (CME) and retinal detachment.

With proper attention paid to wound size and construction, chamber maintenance, ophthalmic viscosurgical device (OVD), and careful intraocular manipulation, the incidence of traumatic IOL implantation can be greatly minimized.

Just as the ocular tissues may be damaged during IOL implantation, so may the IOL itself (Box 39.2). Damage to an IOL ranges from minor optic surface damage from implant forceps or injectors causing scratches, or scuffing of acrylic or silicone IOLs, to major optic fracture or transection. IOL haptics may also be deformed or fractured.

Three-piece foldable IOLs may sustain damage to the haptics during implantation. When an insertion cartridge or forceps is used, the leading or trailing haptic may be caught by the folder and crimped. A bend in the haptic can be gently straightened and the IOL implanted. To do this, withdraw the damaged haptic through the wound and utilize two instruments to straighten the bend. Then dial the IOL into position. If the haptic fractures or is broken during the straightening process, it must be removed and the IOL replaced.

Box 39.1 Operative Ocular Complications of IOL Implantation

  • Unstable wound/leakage
  • Stripped Descemet’s membrane
  • Corneal endothelial trauma
  • Iris prolapse
  • Iridodialysis
  • Hyphema
  • Zonulodialysis
  • Torn anterior capsule
  • Torn posterior capsule
  • Rupture anterior hyaloid

Box 39.2 Operative IOL Complications

  • Haptic deformation
  • Haptic fracture
  • Haptic avulsion
  • Optic excoriation
  • Optic deformation
  • Optic fracture
  • Asymmetric bag/sulcus implantation
  • Reversed-optic implantation*
  • Off-axis implantation**
  • Posterior IOL dislocation

*Angled haptics, toric, and multifocal IOLs.

**Toric IOL.

Infrequently, when injecting three-piece lenses, if the lens is not positioned properly in the cartridge, the leading or trailing haptic may be torn off during implantation. This IOL also must be removed and replaced. Additionally, improper plunger positioning may crimp the leading or trailing haptic. This can usually be straightened, but if severe, or broken, the IOL must be removed and replaced. Overriding plungers can damage the optic. Minor scratches can be left alone, but if in doubt about the severity of a scratch or scuff, remove the IOL and replace it with an undamaged one. It is far more difficult to go back later if the patient complains of dysphotopsia. Let your conscience be your guide on this issue.

One-piece IOLs have problems with the haptics or optics similar to three-piece IOLs. However, the haptic–optic junction is more robust, so haptic avulsion is more rare and haptic crimping does not occur. The surface of the one-piece acrylics, depending on the manufacturer, may be more prone to scuffing

Silicone three-piece IOLs that are left in the barrel of the injector too long can often stick to the plastic cartridge and tear during insertion. Therefore, it is important not to load the IOL into the cartridge more than 5 minutes prior to insertion, and not to start the IOL down the barrel until the actual time of intended insertion (Box 39.3). Plate haptic silicone 6.0-mm optic lenses were originally designed to go through cartridges large enough for 4.0-mm scleral incisions. However, they are now going through cartridges tapered to fit through sub–3.0-mm clear-corneal incisions. Subsequent compression and occasional piston override can result in either haptic or optic fracture. If the fracture has completely transected the trailing plate haptic, destabilizing the optic centration, the IOL must be removed and replaced (Fig. 39.1). However, if the fracture involved avulsion of only a corner of a plate or is only partially through a haptic, the lens may be left in situ, as the centration of the IOL will not be affected (Fig. 39.2). The general rule regarding optic tears is as follows: A partial fracture of an optic that does not involve the central 3 to 4 mm of the “optical zone” may be left in place; if the tear enters the visual axis, the possibility of dysphotopsias is significant and the IOL should be removed and replaced.

In these cases with small tears, rotation of the peripheral optic fracture to the 12 o’clock position enables the upper eyelid to cover the peripheral optic aberration. In addition, capsulorrhexis contraction and fibrosis may cover the area (Fig. 39.3), as well as the pupil itself.

Phakic Intraocular Lens

Errors of implantation may also occur without damage to the IOL. Although AC IOL implantation is now rarely performed during cataract surgery, it is currently used, although usually not a first choice, for the phakic correction of ametropia. As the pupil is often intentionally miotic for AC implantation, damage to the iris may occur. Iridodialysis with hyphema can occur both on the proximal side, due to dragging of the subincisional iris while moving the leading haptic toward the pupil, and on the distal side, when attempting to force the trailing haptic of an oversized IOL into the proximal angle. Tucking of the distal iris causes an acute ovaling of the pupil (Fig. 39.4). Excessive manipulation of an AC IOL may result in chamber collapse with IOL contact with the corneal endothelium.

The implantable Collamer lens (ICL; Staar Surgical, Monrovia, CA) is an extremely soft and friable Collamer material. It must be loaded carefully and injected slowly. If the lens is damaged in any way, it should be removed and replaced. Lens length and vault are difficult to determine and are directly related to postoperative complications. A full discussion of the ICL is beyond the scope of this chapter.

Phakic and aphakic iris-supported IOL implantation is also currently available in Europe. The Worst-Fechner “lobster-claw” IOL4 (Artisan, Ophtec, Groningen, the Netherlands) is enclaved onto the anterior iris stroma, unlike their first-generation predecessors, such as the Binkhorst iris-clip IOL, the Worst two-loop medallion IOL, the Copeland Maltese cross IOL, the Fyodorov Sputnik IOL, and others, which were pupil-supported. The enclavation process of these newer version iris-supported IOLs, in the event of phakic implantation, can result in pressure damage to the lens in back with subsequent development of cataract, or to endothelial damage in both phakic and aphakic implantation if care is not taken to suture or secure the wound before enclavation to prevent viscoelastic escape and chamber collapse (assuming that proper stabilization of the IOL was maintained).

Posterior Chamber Intraocular Lens

Implantation of the posterior chamber (PC) presumes the presence of an intact or mostly intact zonulocapsular apparatus. The zonule may be complete or incomplete. The capsule may be intact or partially collapsed from sectoral zonulodialysis or torn anteriorly or posteriorly. Just as an AC IOL can tuck the peripheral anterior iris stroma, so can a PC IOL tuck the peripheral posterior iris pigmented layer. The haptic, in this case, may push the iris forward at that location, causing sectoral angle closure and peripheral anterior synechiae formation. Chronic chafing of the pigmented layer can result in a transillumination defect and pigment dispersion syndrome. Vigorous implantation of haptics into the ciliary sulcus can result in traumatic zonulodialysis and inadvertent posterior loop location on the pars plana.5,6 Implantation in the PC in the absence of capsular support requires suturing of loops to the sclera.7,8 Avoiding damage to the ciliary sulcus structures by the blind passage of a needle behind the iris can be facilitated by passing a hollow needle ab externo to guide the intraocular suture needle out through the proper anatomic location911 (see Chapters 27 to 31).

Implantation of the capsular bag entails potential complications. Unintentional asymmetric bag/sulcus implantation, with one haptic in the capsular bag and one in the ciliary sulcus, may occur, particularly in cases of large capsulorrhexis openings where the continuous curvilinear capsulorrhexis (CCC) is larger than the diameter of the optic, in cases of small pupils with impaired visualization of haptic placement, or in cases of anterior radial tears.12,13 This may be recognized by inspection at the time of implantation or may not be recognized until a postoperative dilated slit-lamp examination. Careful IOL rotation before removal of the OVD can verify the haptic position in the capsular bag. Early repositioning of the optic into the capsular bag may be performed in the operating room. However, if not recognized until later, when capsular fibrosis has caused decentration or anterior subluxation of the IOL, then loop-haptic and plate-haptic IOLs must be treated differently.

A three-piece rounded optic loop-haptic IOL may simply be dialed out of the fibrosed capsular bag into the ciliary sulcus, provided that significant loop deformity has not occurred. This is usually possible with a three-piece foldable lens with extruded PMMA haptics.

A one-piece IOL with a square edge cannot be placed in the ciliary sulcus (Fig. 39.5). The square edge and lack of angulation will invariably cause recurrent iris chafe, with subsequent pigmentary dispersion and glaucoma, and iris atrophy. Therefore, the capsular bag must be viscodissected and opened and the IOL repositioned into the capsular bag. Viscodissection of the capsular bag can be performed years after the original surgery and is more successful when the anterior capsulotomy is smaller than the IOL optic, preventing fibrosis of the anterior capsule to the posterior capsule. To do this, OVD should be gently injected through the opening in the bag created at the haptic–optic junction. If successful, the capsule will distend, enabling gentle visco-separation of the anterior from the posterior capsule. The plane of separation is then performed for 360 degrees. The IOL can then be dialed out of the capsular bag and inspected. It then can be repositioned with both haptics within the capsular bag, or, if the haptics are significantly distorted, replaced. If it is impossible to separate the anterior capsule from the posterior capsule due to capsular fibrosis, further attempts should be curtailed rather than risk tearing the capsular bag or disinserting the zonule. The IOL can nevertheless be dialed out of the bag, but the new IOL must be placed in the ciliary sulcus.

May 13, 2018 | Posted by in OPHTHALMOLOGY | Comments Off on Intraocular Lens Implantation
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