Tutorial
Introduction
Damaged IOLs
IOL Malpositions
Undesirable IOL Power
Undesirable IOL Performance
IOL Explantation Techniques
Slides
Indications for IOL Explantation
Harry B. Grabow, MD
An indication for explanting an intraocular lens (IOL) can occur either at the time of primary implantation or months to years later. An explantation is indicated when an IOL becomes damaged or malpositioned, or when the power or performance of the IOL is undesirable.
Damage to polymethylmethacrylate (PMMA) or foldable acrylic IOLs rarely occurs during implantation, but it is not uncommon for damage to occur when implanting a silicone IOL, particularly when injecting it through ever diminishing incisions. Optics can be fractured, either partially or totally, plate haptics can be fractured either partially or totally, and loop haptics can be bent or avulsed. In such cases, the damage must be assessed to determine whether the IOL can remain in position or should be removed. If either optic function or haptic’s ability to produce adequate centration and proper and stable location are determined to be inadequate, the damaged IOL must be removed.
Potential IOL malpositions include decentration, subluxation, dislocation, and, in the case
of toric IOLs, off-axis rotation. An IOL may decenter when placed in the bag if it is too short
in diameter, as in the case of some plate-haptic IOLs, or if an IOL is moved off center by the
forces of capsular fibrosis. When one haptic is placed in the capsular bag and one haptic is
placed in the sulcus, the IOL may decenter because of the asymmetric force of capsular contraction.
If the IOL was placed vertically through a superior incision, with only the inferior loop in the
capsular bag, the capsule may contract and force the optic to decenter superiorly, which is known
as “sunrise syndrome”
(Slide 1). An IOL placed into the sulcus may also decenter if its overall
diameter is too short, resulting in “sunset syndrome”
(Slide 2). Likewise, if an IOL is placed
into a capsule with an unstable opening posteriorly, equatorially, or anteriorly, capsular fibrosis
may cause true lateral subluxation (Slide 3),
total posterior dislocation (Slide 4), or partial
anterior dislocation. In cases of decentration or subluxation, pupil-splitting optic edge symptoms,
such as glare or monocular diplopia, are indications for IOL exchange (that is, IOL removal and
replacement). Total posterior dislocation into the vitreous may, in cases of syneresis, produce
undesirable symptoms due to excessive IOL motility. This would be an indication for IOL exchange.
Anterior chamber IOLs that are angle-fixated and implanted with one or more peripheral iridectomies may rotate and decenter in such a way that a haptic passes through and becomes incarcerated in the iridectomy. This form of IOL malposition may result in chronic iritis, pigment dispersion, corneal endothelial touch, as well as visual symptoms related to optic decentration and tilting.
Trauma can cause an IOL’s malpositioning that will require explantation. An indication observed more recently and one that will become commonplace in the future includes the removal of phakic anterior and posterior chamber IOLs from eyes that develop cataracts.
Undesirable IOL power can occur acutely at the time of uncomplicated primary implantation when the “wrong IOL,” or an IOL intended for another patient, is implanted. Immediate IOL exchange for the correct IOL is the best management. A significant undesired ametropia that is detected at the 1-day postoperative follow-up refraction examination usually indicates an error in power calculation, or, more rarely, a manufacturer’s error in labeling or packaging. IOL exchange is more easily and safely performed before capsular contraction begins. Late symptomatic anisometropia or ametropia may be an indication for IOL exchange. However, if removing the primary IOL may risk capsular or zonular integrity due to excessive fibrosis, then IOL exchange may be contraindicated. In this case, either secondary piggyback implantation or a keratorefractive procedure may be required.
Although an IOL may be correct in power and properly positioned, it may cause undesirable effects that necessitate IOL removal in some patients. With certain designs of IOL optics, particularly 5 x 6 oval PMMA IOLs and square-edge acrylic IOLs, patients have had significant complaints regarding edge glare. Some patients implanted with silicone concentric-ring multifocal IOLs have had these IOLs removed because of intolerable nocturnal glare — particularly rings or halos around automobile headlights. Some patients with acrylic IOLs — both square-edge and round-edge — have complained of seeing temporally a crescent-shaped shadow that is dark and vertical. These unwanted optical images, including glare, halos, and shadows, have been collectively called “dysphotopsia” by Samuel Masket, MD.
The biocompatibility of an IOL depends on the IOL's design, material, and location
inside the eye. Although intracapsular sequestration from uveal and corneal tissue is believed to be the most
biocompatible location for implantation, designs and materials perform differently. For example,
PMMA and silicone IOLs cause more anterior capsular fibrosis than acrylic and hydrogel IOLs
(Slide 5 and Slide 6).
Some investigators believe that PMMA and silicone IOLs may be related to
higher rates of uveitis and cystoid macular edema than acrylic and hydrogel IOLs. Persistent
anterior chamber cell or flare reaction, keratoprecipitates on the IOL surface, posterior
synechiae, secondary ocular hypertension, and persistent cystoid macular edema may be indications
for IOL explantation. An IOL in the ciliary sulcus may cause chronic iridocyclitis and ocular
tenderness, especially if it is too large for the space, as may be seen with 14-mm one-piece PMMA
IOLs. Square-edge optics in the ciliary sulcus may cause pigment dispersion from the back of the
iris. Angle-fixated PMMA IOLs, if too long in diameter, may fixate posteriorly to the scleral
spur, resulting in progressive ovalization of the pupil in the long axis of the IOL. This effect
may also be associated with intolerable ocular pain and tenderness. Conversely, a vertically
placed angle-fixated PMMA anterior chamber IOL that is too short in diameter may move from
side-to-side with ocular saccades, which is the so-called “windshield wiper syndrome” form of
pseudophakodonesis. Chronic rubbing on the corneal endothelium will cause a marked reduction in
endothelial cells potentially leading to corneal decompensation. Early recognition and diminishing
serial endothelial cell counts may necessitate IOL removal.
IOL material incompatibility may occur in two situations. The first situation is when a posterior segment procedure using silicone oil is performed on a patient implanted with a silicone IOL. In this case, the silicone IOL should be exchanged to avoid the loss of visual clarity that may occur when IOL silicone and silicone oil bond. The second material incompatibility has been demonstrated when two acrylic-optic IOLs are placed in contact with one another in one capsular bag, piggyback style, with an anterior capsulorrhexis opening that is smaller than the diameter of the anterior IOL optic. Lens epithelial cells may migrate between these particular optics and undergo fibrous metaplasia forming not only symptomatic opacification, but also a physicochemical-biologic bond between the two IOLs, rendering them chemically and mechanically inseparable. In such cases, simultaneous explantation of both optics and the entire IOL-capsular complex may be required.
The technique of IOL removal and the size of the incision will vary depending on the IOL material, IOL to be removed and the IOL to replace the original IOL. Removal (or implantation) of a PMMA IOL requires an incision long enough to accommodate the width of the rigid optic. Usually the incision ranges from 5 mm to 7 mm. If near the cornea, an incision of this size may require suturing and may have astigmatic consequences. Conversely, removal of foldable lenses can be accomplished through smaller incisions ranging from 3 mm to 4 mm. This incision size may heal without sutures and will have much less effect on corneal curvature. As with all anterior segment procedures, the corneal endothelium, iris, capsule, and zonule must be protected and preserved whenever possible. Carefully planned and executed maneuvers, and judicious use of viscoelastics, facilitate these goals. Dispersive viscoelastics usually maintain space better than cohesive viscoelastics, but overinflation of the anterior segment with a dispersive agent can also rupture zonular fibers and extend unstable capsular tears.
Angle-fixated anterior chamber IOLs that have been implanted for longer than a few months may have developed “fibrotic cocoons” around the haptics. Attempting simple linear extraction in such cases may result in avulsion of the iris root, iridodialysis, hemorrhage, and even total iridectomy, rendering the eye aniridic. Therefore, one should test the implant mobility in these cases by gently attempting to rotate the IOL clockwise on plane will indicate if the IOL haptics are free and able to be safely dialed out of their fibrotic tunnels. Alternatively, significant resistance to rotation may necessitate haptic amputation with scissors, removal of the optic, and reverse dialing of the amputated haptics out of their fibrotic tunnels; or, the haptics may be left safely in situ. This procedure applies to removal of posterior chamber IOLs with haptics in the ciliary sulcus. IOLs that can be rotated and fully mobilized in plane allow easy and safe removal, thereby avoiding uveal hemorrhage.
Foldable silicone posterior chamber IOLs have different degrees of capsular fixation,
depending on the haptic design. Three-piece loop-haptic posterior chamber IOLs can usually be
rotated clockwise in the capsule after first separating the anterior and posterior capsules and
expanding the bag with either balanced salt solution or viscoelastic. If the anterior continuous
curvilinear capsulorrhexis (CCC) has phimosed significantly, it can be enlarged by performing a
secondary CCC. Alternatively, it may be preferable to make two relaxing radial capsulotomies, 180° apart,
to allow explantation of the IOL out of the bag without damaging the zonules. Once the IOL is out of the
bag and in the anterior chamber, removal through a 3- to 4-mm incision can be achieved by either of two
methods — partial optic transsection (hemisection) or complete optic bisection. The former
technique is accomplished by hooking and exteriorizing a haptic through the incision, securing
the optic by grasping the exteriorized haptic with forceps and then cutting the optic halfway
across its diameter with scissors. Therefore, a 6-mm optic has been reduced to 3-mm in the
meridian of the hemisection. By pulling one half of the optic through the incision, the second
half will flex and follow the first half out of the eye. In the alternative technique, the hemisection will allow complete
bisection of the optic by fracture of the remaining hemi-optic. The second hemi-optic can then
be removed by rotating the optic until its haptic can be hooked and grasped for removal or by
grasping the optic with toothed forceps and then removing.
Instruments have been designed specifically for foldable IOL bisection. The Mackool instruments
facilitate intraocular hemisection or bisection with scissors. The Utrata Foldable Lens Cutter
(Rhein Medical, Inc., Tampa, Fla.) can be used for bisection of both three-piece and plate-haptic
silicone IOLs (Slide 7).
The Chu Foldable Lens Cutter (Rhein) is a heavy-bladed scissors used to
bisect both silicone and acrylic optics in one maneuver (Slide 8).
The Koo Foldable IOL Cutter
(ASICO, Westmont, Ill.), one blade of which is actually a serrated platform, is used for cutting
silicone (and possibly acrylic) IOLs (Slide 9).
However, foldable acrylic IOLs may also be refolded in
the anterior chamber and removed in one piece. This maneuver requires care and ample viscoelastic.
An instrument that is used as the central fulcrum may be introduced parallel to folding forceps
through the primary incision or through a small paracentesis 180° away. The fulcrum instrument is
placed completely across and under the optic and is held firmly while the folding forceps
symmetrically depress each half of the optic periphery posteriorly. The fulcrum instrument is
slowly removed before the optic is completely folded and the IOL may then be withdrawn from the
eye in the folding forceps. This maneuver can be easily performed to remove acrylic IOLs, but
removing silicone IOLs in this way is difficult.
Posted April 2001