This article focuses on the consequences of zonular pathology in patients with pseudoexfoliation syndrome (PXF) and how this pathology influences cataract surgical technique and prognosis. PXF is an age-related condition associated with a LOXL1 genetic defect in which fibrillar extracellular material builds up throughout the body wherever the relevant enzyme is missing. Strangely, its only known manifestation occurs in the eye despite the enzyme's presence in many other organs. The ONE Media Library also has a video from Dr. Arbisser in which she demonstrates her surgical technique in PXF patients.
We all recognize PXF's classic signs of the bull's eye pattern of dandruff-like flakes on the lens and other structures, the increased trabecular meshwork pigment and increased incidence of cataract, with the propensity for poor mydriasis and zonular fragility. The Framingham Eye Study found the overall prevalence of PXF to be 0.6 percent in patients between 52 and 64 years old and 5 percent in those between 75 and 85 years old. PXF is the most common cause of open-angle glaucoma worldwide, with glaucoma occurring in 15 to 20 percent of those with PXF.
First described in the mid-1980s, capsulorhexis has been responsible for many of the greatest advances in eye surgery. However, for patients with progressive zonular pathology, it may be less beneficial.
Preparing before surgery
PXF cataract patients should be evaluated preoperatively for the presence of glaucoma and its preoperative control and told about the ongoing risk of its future development. I inform patients about zonular anatomy and the potential for pathology leading to complications during surgery, the possible need for a capsular tension ring (CTR) and the possibility of needing future early laser intervention or even further surgery for a subluxed bag-lens.
Your preoperative exam should note phakodonesis, decentration of the nucleus and asymmetry of anterior chamber depth monocularly by slit-lamp exam or between the two eyes by IOL M measurement. Asymmetry should alert you to possible zonular weakness which may manifest intraoperatively. Also a shallow anterior chamber (2.5 mm or less without the presence of a thick lens) is suspicious. The degree of pseudoexfoliative material is not proportional to the likelihood of zonular instability. Since this is a systemic disease, the fellow eye, even lacking typical signs, should be considered at risk.
Consider applying scopolamine, along with tropicamide and epinephrine, in poorly dilating eyes. Keep iris hooks or Malyugin rings available. It is necessary to have CTRs, segments, capsule support hooks and backup three-piece IOLs at hand. Consider booking extra time for suspect cases.
Intraoperative signs of zonular laxity or lysis include spidering or dimpling of the anterior capsule upon initiating the capsulorhexis and difficulty propagating the rhexis with movement of the peripheral capsule. Hydrodissection often precludes easy rotation of the lens. Bounce-back to the original position on movement is an ominous sign that the loose zonules are allowing rotation of the bag and not sustaining its position to allow nuclear rotation. During phaco, downward pressure may reveal bared vitreous face around the lens equator, or the bag equator may waft centrally as the lens material is removed and no longer serve the purpose of a "shoe tree" in the "shoe." During cortex removal, the bag lacks tension and tends to follow the cortex to the aspiration port, causing inefficient stripping. The lens may prove challenging to position within the bag and may cause ovalization of a previously round rhexis in the meridian of haptic pressure. Pseudophakodonesis ominously portends instability. Leaving a small rhexis, especially with intact lens epithelial cells on the anterior flap, increases the likelihood of postoperative phimosis promoting ongoing centripetal forces postoperatively.
With early identification, steps can be taken to minimize forces on the zonules intraoperatively. Lax zonules can be weakened by allowing large shifts in anterior chamber depth, rotational forces and downward and nasal pressure during nuclear sculpting and lens insertion. Broken zonules can behave like a zipper whose teeth are misaligned, unzipping with minimal force. The capsule will be more flaccid and easier to damage during phaco or aspiration. Vitreous easily presents around zonules, and fluid may misdirect around them, increasing posterior pressure. CTR insertion can also be traumatic.
Tools and techniques may mitigate these concerns. Establish adequate dilation to allow a 5 mm rhexis. Control the lens dome with viscous viscoelastic (OVD). Initiate the rhexis with a sharp instrument, such as a cystotome, rather than pinching with forceps. Forceps propagation of the rhexis controls the vector better than needles can. The size of the rhexis is critical to intraoperative and postoperative success. A small or asymmetric rhexis may result in phimosis or decentration, and one too big challenges our ability to optic capture the IOL.
In severe cases, a two handed technique using a hook to provide counter pressure is helpful. If multidirectional hydrodissection does not result in free lens rotation, consider supporting the bag. Iris or capsule hooks or segments (I prefer those without one-point fixation) are used to suspend the bag and offer "artificial zonular" support. Although I aim to use a CTR as late as possible, it can be inserted with lens material still in situ once the bag is suspended after visco-cortical cleaving. This makes a plane under the capsule, trapping as little cortex as possible. This increases the tension on the posterior capsule, reducing the risk of its aspiration into the phaco port. The case can now proceed in a normal fashion until the bag is cleansed of all lens material.
If laxity is judged to be less severe or the nucleus rotates, we can proceed rather than opt for bag support. I recommend entering the chamber with the phaco hand-piece, with the balanced salt solution (BSS) bottle low and avoiding iris retropulsion by lifting the iris off of the capsule. This prevents undue chamber deepening. Raising the bottle to its normal height before initiating phaco facilitates a stable chamber throughout the rest of nuclear removal. A chop technique without sculpting is most zonule friendly. The nucleus can be removed without rotation if it is hydrodelineated. Supporting the chamber with BSS through the side-port by exchanging the chopper for a syringe and cannula prior to removing the phaco tip will prevent collapse while exchanging the phaco for the irrigation and aspiration (I&A).
Cortical removal may be best accomplished with more tangential than centripetal vector. In the presence of extreme laxity, removal can be done "dry," manually under cohesive OVD support to reduce trauma. If there is still no CTR in place and the bag is suspended, it should be placed while the hooks are present. If the bag is not suspended but signs of laxity indicate the need for a CTR, the bag should be well expanded with cohesive OVD and the CTR positioned to limit translation of rotational forces to the bag. Some surgeons prefer manual placement. Others, including me, prefer using an inserter, which prevents the device from touching the external eye and allows a smooth gentle insertion. If it won't go around the bend easily, a suture can be placed through the leading eyelet, creating a tether to be pulled during insertion. This eliminates all force on the bag and is removed after complete insertion.
Unfortunately, the FDA hasn't approved any device that locks together or maintains its diameter; these modified CTRs are available outside the U.S. Ring size seems unimportant because contractile forces of the bag shrink the CTR diameter over time, regardless of initial dimensions.
Once the bag is clean, assess the degree of zonular pathology, which may predict what happens to the patient's eye in a decade. When signs of zonular pathology are evident, the surgeon must judge when and if to change from the routine technique and plan. The degree of zonular pathology and the patient's age should be considered when determining the need for a standard or modified CTR, the best choice of lens and optimal lens placement.
We have seen an increasing number of cases with postoperative bag-lens subluxation and dislocation. Although the incidence isn't known, referral centers are counting them in the hundreds. It's a rare ophthalmologist who hasn't recognized more than one.
These eyes have several things in common. They have undergone capsulorhexis with a lens in the bag, the single thing that has allowed uncomplicated phacoemulsification to flourish with all its advantages and has driven implant (IOL) design and stability. No IOL models or materials seem immune. Some cases have been reported with CTRs in situ. The average time from surgery to subluxation is 8.5 years. Many manifest shallow anterior chambers preoperatively. Most lack historical trauma. Some are bilateral. Vitreoretinal surgery preceded many cases of subluxation. Uveitis and high axial length have been implicated. YAG laser posterior capsulotomy may exacerbate an already loose bag. Most characteristic is the presence of pseudoexfoliation syndrome.
Eyes with subluxated bag-lens are challenging to restore to full integrity. We can sulcus suture the bag, try to sew it to the iris or explant it in favor of an iris-sutured PC IOL or an anterior chamber lens. These eyes often have inflammation and pressure rises from old lens material that seeps from the bag periphery when punctured, higher order aberrations from tilt or decentration, cystoid macular edema from violating reactive tissues like iris and blood vessels and breached anterior hyaloid. Fashioning larger incisions, with the subsequent wound healing issues or bleeding from scleral punctures, along with early or late endophthalmitis from erosion of sutures, adds to the morbidity. Retinal integrity is not threatened by leaving a dislocated bag-lens in the posterior segment. Simply adding a secondary IOL may be the least traumatic option if the patient doesn't notice a floating foreign body.
Given these facts, what changes should we make in our technique for patients at risk? Although some surgeons have advocated placing CTRs in all PXF patients, many prefer their selective use. The younger the patient at the time of cataract surgery and the more obvious any sign of zonular weakness, the more benefit. If nothing else, CTRs provide an anchor for a future suture if the bag-lens subluxates and requires fixation (especially with a one-piece IOL, which doesn't present an easy haptic to lasso). Most ophthalmologists will recommend a modified Cionni ring or sutured Ahmed segment only if the bag is not centered at the end of the case.
The rhexis must not be smaller than 5 mm or significantly asymmetric. It can be modified to perfection, just overlapping the optic edge, after IOL placement. Some surgeons advocate forgoing the many known benefits of optic edge coverage entirely and secondarily tearing the rhexis beyond the optic edge after implantation. Consider polishing anterior capsules free of lens epithelial cells, which can transform and lead to anterior capsule fibrosis. Do not vacuum but rather polish the posterior capsule. Acrylic materials are known to be more capsule biocompatible than silicone.
I typically implant a one-piece IOL in the bag. For PXF patients with clear evidence of significant zonular pathology, I now prefer sulcus implantation with optic capturing of three-piece IOLs after CTR placement in the bag. I presented this technique in 2007 at ASCRS. I, and now others, have seen a marked reduction in pseudophakodonesis and iridodonesis and no phimosis of capsules in these eyes. My theory is that the lens supports the bag, and the bag, which remains on stretch because of the CTR, supports the lens. The lens remains centered by the rhexis and is therefore unable to find its way through any zonular defect, thus preventing lens decentration. There is no centripetal force to challenge zonular integrity since the IOL optic fills the rhexis opening.
I use Howard Gimbel's well-known technique for optic capture. The sulcus is defined with OVD, leaving the bag uninflated. The three-piece lens is injected with the leading haptic clearly placed in the sulcus. The trailing haptic is pronated into place with a two-handed technique (not dialed), minimizing displacement of the optic and stress on the zonules. Mild pressure is placed on the optic 90 degrees away from the haptic optic junction in order to dunk the edge under the rhexis on one side and then the other, allowing the rhexis to become ovoid. With very loose zonules this may require a two-handed technique, lifting the bag gently with a sweep under the rhexis edge while applying downward pressure on the optic. The end result is that the haptics are secured in the sulcus and the optic is in the bag. I hope this maneuver can prevent bag-lens subluxation.
It may be that a planned posterior capsulorhexis with a buttonhole technique (bag implantation of a three-piece IOL with optic capture through the posterior rhexis into Berger's space) is the very best solution. With the exception of the immediate haptic optic junction, this avoids touching of the lens epithelial cells to the IOL, which can initiate fibrotic transformation. This lesser known and more challenging technique is well described by Rupert Menapace on the Academy's ONE network.
Naturally, if all zonules give way over time, no strategy avoids bag dislocation. However, spontaneous dislocation of the crystalline lens is extremely rare, even in PXF patients. In the days before rhexis, can-opener capsulotomy bags or those with sulcus-implanted lenses failed to dislocate. This suggests that total spontaneous dissolution of zonules without phimotic provocation is unlikely.
Some cataract surgeons advocate using relaxing incisions in the anterior rhexis edge at the time of surgery. However, this can lead to instability of the IOL itself and is not recommended. We must watch these patients more carefully in the early postoperative period for phimosis and anterior capsule fibrosis and perform YAG laser relaxing incisions in the anterior rhexis edge early and often as needed. A recent novel paper advocates performing these incisions prophylacticly in all PXF patients during the first postoperative month.
As ophthalmic surgeons' techniques and experience improve over time, we are able to save more eyes from intraoperative complications. As our complication rate falls, we perform surgery in ever-younger patients with routine in-the-bag results. This may come back to haunt us in PXF eyes. We have only been at risk since the wide adaptation of capsulorhexis for this condition, whose natural history is to present in eight to 10 years. I fear that we are now seeing the tip of what may turn out to be a disturbingly large iceberg if we continue using our current technique with these patients.
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