• Features
Pseudoexfoliation and Cataract Surgery
How to detect this potential complication of cataract surgery and tailor your surgical approach.
Michael
E. Snyder, MD
Cincinnati
Patients with pseudoexfoliation syndrome have a significantly greater risk for a variety of complications related to cataract surgery. Pseudoexfoliation syndrome, or PXS, is characterized by distribution of fibrillar material throughout the anterior segment. PXS was once thought to be a strictly ocular condition, but the distribution of this material throughout the systemic vasculature is well-established.1
The origin of the pseudoexfoliative material remains elusive. The dust-like particles are best seen on the anterior surface of the crystalline lens, but they are distributed initially across the surface of the lens. They are redistributed as the pupil expands and contracts, creating the familiar central and peripheral pattern of deposits with mid-peripheral clearing. The condition is implicated as a risk factor for a higher incidence of cataract.2
The fibrillar deposits can also be seen along the pupil margin, Schwalbe's line, and on the endothelial surface of the cornea, where they are sometimes confused with keratic precipitates.3 Dissemination of the material into the interstices of the trabecular meshwork may be the origin of pseudoexfoliation glaucoma. Fibrillogranular deposition can also be seen on the zonules and along the vitreous in aphakic or pseudophakic patients (See Figure 1).
|
| Figure 1. Prominent white fibrillar deposits (yellow arrow) are visible along the vitreous strands in this pseudophakic patient with an open posterior capsulotomy. White arrowheads indicate one arcuate vitreous fibril has pseudoexfoliation deposits, which appear similar to a string of pearls. Note that there are no deposits on the pupillary margin. These findings indicate pseudoexfoliation and may alter your approach to cataract surgery on the fellow eye. |
This article reviews
the risks when performing cataract surgery in the presence of pseudoexfoliation,
their implications and how to minimize them.
Making the Diagnosis
While the classic distribution of pseudoexfoliation material on the anterior lens capsule should never create a diagnostic dilemma, limited pharmacologic mydriasis can adversely affect the ability to make the diagnosis. Flaky deposits on the corneal endothelium is one clue in assessing the condition. You can differentiate this material from true keratic precipitates by their bright white color and fluffy appearance. When differentiation is difficult, a one-to-two week trial of topical steroids can be diagnostic, because KP changes in appearance or location, while pseudexfoliative material does not.
Poor pupillary dilation itself may be a sign of PXS. Careful scrutiny of the pupil margin may reveal the tiny white flakes rubbed from the lens surface. Extensive, patchy iris transillumination defects are also common. Some investigators speculate that these thinned irides have an ischemic origin.
An unusually shallow anterior chamber depth from zonular laxity can indicate pseudoexfoliation, especially if it is asymmetrical.4 Even though a patient's cataract and symptomatic complaints are monocular, the contralateral eye may have subtle findings of pseudoexfoliation which are not seen in the planned surgical eye. Though pseudoexfoliation syndrome can be markedly asymmetric, it is bilateral.5
In patients with coexisting glaucoma and cataract, gonioscopy is indicated and may reveal the pigmented Sampaolesi line along the posterior terminus of Descemet's membrane (Schwalbe's line). True exfoliation is rare. In these cases, the lens capsule is split into two layers with an evanescent sheet attached to the anterior lens capsule floating in the aqueous.6,7
Once you've diagnosed pseudoexfoliation, you can prepare for the case by modifying your usual technique and planning for both short- and long-term potential complications.
Pseudoexfoliation and the Cornea
Even if exfoliative material is not clinically visible on the corneal endothelium, the cell count may be significantly reduced and the cells that remain may not function well.8,9 With this in mind, you may opt to use additional endothelial protection including a "soft shell" viscoelastic technique or a "pseudoplastic" viscoelastic such as Healon5. If the lens is dense or the case requires longer than average ultrasound time, I insert more viscoelastic for added protection. If pseudoexfoliative endothelial deposits are present, I don't aspirate or irrigate them. These efforts are futile, because many deposits are covered by the endothelial cells. Attempts to remove these deposits would likely damage the already compromised endothelium.
Pseudoexfoliation and the Pupil
Poor pupillary mydriasis, a well-known feature of exfoliation syndrome, can seriously hamper the surgeon's view. Some investigators suggest its etiology is hypoxic damage to the dilator muscle.10 It is crucial to achieve a reasonably sized continuous curvilinear capsulorhexis in pseudoexfoliation patients, since they have a significantly higher incidence of anterior capsular contraction. Additional pupillary dilation may also be necessary.
For surgeons experienced in small pupil phacoemulsification, a Kuglen hook or similar iris retractor can temporarily decenter the pupil during capsulorhexis to achieve an appropriately sized CCC opening. "Viscomydriasis" with a highly retentive agent such as Healon5 usually provides an adequate hole for capsulorhexis. Excessive viscomydriasis, however, is contraindicated since the zonules may be weakened and posterior luxation of the crystalline lens can result.11
Several mechanical means can temporarily dilate the pupil during surgery. These include flexible iris retractors (Grieshaber, Surgidev, and others), titanium iris retractors designed by Richard MacKool, MD, flexible pupil dilating rings (Graether expander), and rigid dilating rings (Morcher).
Pupil stretching maneuvers,
while effective, are not indicated for all pseudoexfoliation cases. The blood/
aqueous barrier is compromised in these eyes and excessive inflammatory responses
are well-documented. The same is true for sphincterotomies. Further, the iris
is more flaccid in PXS and more likely to be inadvertently aspirated. Mechanical
means to augment mydriasis also keep the floppy iris margin away from the phaco
aspiration port.
PXS and Capsular Integrity
Pseudoexfoliation patients have altered lens capsules that are structurally compromised compared with unaffected eyes.12 Reduced capsular integrity translates into an increased risk of intraoperative complications, including posterior capsular tears. The anterior capsule may be more friable and requires even more delicate handling to prevent a meridional extension and possible resultant posterior capsular tear during capsulorhexis.
Because capsulorhexis creation
is more difficult in these challenging cases, I find that staining the capsule
with indocyanine green (IC Green, Akorn) or trypan blue (Vision Blue, D.O.R.C.)
is useful. The exfoliated material has a higher affinity for ICG stain than
unaffected capsule (See Figure 2). An excessive amount
of material may prevent staining of the underlying capsule. Since the fibrillar
material is not cohesive, it may flake off. This can look like an extension
of the capsulorhexis. I find that reapplication of ICG stains the true capsule,
and confirms an intact capsulorhexis margin.
 |
| Figure 2. (A) In this cataract stained with indocyanine green dye, the mid-peripheral “clear” zone of pseudoexfoliation material between the arrowheads stains only faintly compared with the surrounding fibrillar material, making the PXS pattern easily distinguishable. (B) At higher magnification with retroillumination, the normal staining capsule (white asterisk) appears adjacent to the heavier staining pseudoexfoliation material (light green asterisk). The fibrillar material has flaked away, giving an appearance similar to a capsulorhexis break with a meridional extension (light green arrowheads). |
Dislocation of the nucleus into the vitreous cavity may occur even during routine hydrodissection in pseudoexfoliation cases.13 I am extremely careful to avoid a posterior capsular tear during the phacoemulsification.
Capsulorhexis in True Exfoliation
While true exfoliation is
an entirely different entity, you may run across a case from time to time. The
issues and visual challenges of capsulorhexis may be similar to those of the
PXS patient, especially when capsular dyes are used. I apply more stain when
I suspect that an exfoliated capsule or a pseudoexfoliative membrane has adsorbed
the stain and is masking the underlying capsule. This allows me to differentiate
these thin, clear layers more easily. Once you've confirmed a pseudoexfoliative
membrane or exfoliated capsule, gently peeling the anterior layer centripetally
away from the area of intended capsulorhexis aids in creating the capsulorhexis
(See Figure 3).
 |
| Figure 3. (A) In true exfoliation, the loose anterior layer can be gently peeled centrally, out of the path of the intended capsulorhexis. (B) Capsulorhexis of the posterior, intact layer can be undertaken under direct visualization. Note that the anterior layer partially masked the staining of the posterior layer, even when the anterior chamber was freely irrigated with the ICG solution. The apparent peripheral masking was from the iris margin which dilated more upon instillation of viscoelastic material (viscomydriasis). |
Zonular Integrity
Weak zonules is one of the most notorious, common and perilous problems facing the cataract surgeon in pseudoexfoliation cases. The degree of weakening, though highly variable, appears to increase with increasingly apparent amounts of deposits.
Capsular contraction is more likely since there is reduced zonular countertraction against the centripetal forces of the remaining lens epithelial cells.14 I prefer capsulorhexis of 5 mm or greater, and use a capsular tension ring (Morcher, Ophtec) to reduce the risk of this complication. Because capsular contraction is more common with silicone IOLs, I prefer another material in PXS cases.15
Early on, you may sense
diffuse zonular weakness or laxity, even during CCC creation. Once this weakness
is apparent, the risk of creating zonular dialysis looms. In such a case, flexible
"iris' retractors can engage the capsulorhexis margin and stabilize the loosened
capsular bag16 (See Figure 4). Phacoemulsification
can be completed more safely, reducing the risk of frank zonular dialysis and
vitreous loss or posterior dislocation of nuclear fragments.
 |
| Figure 4. Flexible nylon ”iris“ retractors (Surgidev) used here as capsule retractors, engage the capsulorhexis margin to stabilize a loosened capsular bag. Any number of retractors can be placed depending on the degree of capsular instability. |
If a small or moderate zonular dialysis occurs, a standard capsular tension ring can re-expand the capsular bag and redistribute the mechanical stresses evenly across the remaining zonules. The CTR can be manually implanted into the fornix of the capsular bag or injected with the inserter device manufactured by Gueder. For a larger zonular dialysis, a suture-fixated, modified Cionni ring (M-CTR, Morcher) with one or two fixation eyelets will re-expand the capsular bag and secure the capsular bag/IOL complex to the scleral wall (See Figure 5).
 |
| Figure 5. (A) The design of the single fixation hook modified endocapsular tension ring (M-CTR) shows the fixation element coursing 0.25 mm anteriorly so that it rests anterior to the capsulorhexis. (B) A double-fixated M-CTR in situ. The white arrows indicate the fixation eyelets on the end of the fixation hook elements. The sutures have not yet been placed. The faint yellow shadows estimate the approximate position of the portions of the M-CTR that are not visible. |
Since zonular instability in pseudoexfoliation syndrome is a progressive condition, redistribution of the mechanical forces to the remaining zonules may be an inadequate long-term solution.
In one case from early 1997,
a two to three clock-hour zonular dialysis was detected intraoperatively during
a small pupil phacoemulsification in a PXS patient. A standard CTR was placed
and the case was completed safely with a favorable result. The PC-IOL was placed
in the capsular bag and was well-centered ... for two years. The patient then
presented with a sudden decrease in vision and the capsular bag/IOL complex
was markedly subluxated (See Figure 6). Before her
arrival in the operating room for refixation, the lens dislocated posteriorly,
requiring a very challenging repositioning and refixation. Had a modified ring
(M-CTR) been used, the implant would likely have stayed anteriorly. Even if
the M-CTR were placed without suturing it for fixation, then the intraocular
manipulations for IOL repositioning from the posterior segment would have been
significantly easier. Posterior luxation of the capsular complex is not an isolated
case.11,14,17 Indications for prophylactic placement or placement
with fixation of an M-CTR in PXS patients are under investigation.
 |
| Figure 6. The intact PCIOL/capsular bag/ capsular tension ring complex has subluxated two years after cataract surgery. The white arrows indicate pseudoexfoliation material on the frayed anterior zonular insertion to the capsular bag. The (standard) endocapsular tension ring can be seen in situ in the fornix of the capsular bag (yellow asterisk). |
IOL Choice
There is increased risk of capsular contracture after silicone lens implantation relative to other IOL materials. Other features of lens design come into play in PXS patients, as well. Research shows these patients have an increased incidence of posterior capsular opacification.18 I prefer an intraocular lens with a sharp posterior edge to reduce LEC migration and subsequent PCO.
Coexisting Cataract and Glaucoma
Glaucoma and cataract commonly coexist in patients with PXS. When cataract surgery is indicated, implications for management of the glaucoma should be considered. Most commonly, if the glaucoma is well-controlled preoperatively, cataract surgery alone is sufficient. Indeed, some reports indicate that intraocular pressure falls in PXS patients with glaucoma following phacoemulsification alone.19
The threshold for performing a combined trabeculectomy and phacoemulsification with IOL placement in PXS glaucoma patients varies widely among practitioners and is beyond the scope of this article. Similarly, the indications and threshold for combined cataract surgery and non-penetrating filtering surgery (viscocanalostomy) have not been well-established.
An
investigational technique called trabecular aspiration raises some relevant
and interesting issues. Trabecular aspiration uses a soft-tipped cannula attached
to an aspiration line that is swept across the trabecular meshwork of the pseudophakic
eye, theoretically "vacuuming" exfoliation material from the meshwork. Some
early studies show impressive results, while others have shown only a short-term
benefit.20,21 Further studies and longer-term data will be helpful.
Pseudoexfoliation syndrome adds to the challenges of cataract surgery. Although some of these challenges are significant, with the use of dyes, capsule retractors and implant rings, and meticulous attention to surgical technique, even extreme PXS cataract cases may be safely completed. We can hope for approval of standard and Cionni modified (fixable) capsular tension rings and of the intraocular uses of ICG and trypan blue capsular stains. With regulatory approval, widespread access to these important tools in the ophthalmic armamentarium will help surgeons in these difficult cases.
Dr. Snyder is an anterior segment surgeon and practices at the Cincinnati Eye Institute.
|