OD News Articles

3rd January 2020

PXF Syndrome: Truth or Consequences

by Maynard Pohl, OD Bellevue, WA

Pseudoexfoliation (PXF) syndrome is an age-related systemic disease that targets ocular tissues. Over time, flakes of granular amyloid-like protein fibers from the lens and iris pigment epithelium are deposited on the lens capsule—and to a lesser degree, the ciliary body, zonules, corneal endothelium, and iris. Although its cause is unknown, PXF syndrome is more common in women and people over the age of seventy. The condition also affects some population groups more than others. For example, its prevalence in Scandinavia suggests a genetic component.

 
CLINICAL CHARACTERISTICS

The definitive diagnosis of PXF syndrome is based on slit lamp and gonioscopy exams. Findings are:

  • Often bilateral, but asymmetric
  • White flake-like residue on the anterior lens capsule and pupillary margin
  • Pigmentation of the trabecular meshwork
  • Less commonly, iris transillumination defects

In some cases, the granular material is located on the peripheral lens capsule where it is covered by the pupil. A dilated anterior segment exam helps ensure that PXF is not overlooked. But these patients can sometimes be poor dilators.

ASSOCIATED RISKS

PXF is a significant risk factor for secondary glaucoma. Worldwide, this syndrome is the most common cause of secondary glaucoma. As exfoliative material collects in and around the trabecular meshwork, it can slow the outflow of aqueous humor and elevate intraocular pressure—which may damage the optic nerve.

IOP in PXF eyes fluctuates more than average and can reach levels in the 40s to 50s without symptoms. Despite the lack of symptoms, significant optic neuropathy is often noted. Approximately one-third of patients with PXF develop glaucoma.

PXF is also associated with an increased incidence of cataract formation. And it certainly increases the risk for intraoperative and postoperative complications. Primary care optometric physicians and ophthalmic surgeons must be aware of several issues in managing PXF patients considering cataract surgery.

PRE-OPERATIVE CONSIDERATIONS

Before referring patients with PXF for cataract surgery, the presence of PXF glaucoma should be determined. Referral for glaucoma consultation and glaucoma control may be needed. PXF glaucoma management follows the same medical and surgical approach as open-angle glaucoma. However, selective laser trabeculoplasty (SLT) is often more effective due to the presence of trabecular meshwork pigment.

Cataract surgery does not cure PXF. These patients require continued lifetime monitoring of both eyes for glaucoma or potential future development.

Once cataract surgery is indicated, it’s important to determine the presence of zonular weakness through careful slit-lamp biomicroscopy. Subtle subluxation, zonular dialysis, or iridophacodonesis may be detected by having the patient move their eyes while observing lens or iris movement under slit-lamp examination. Interestingly, the amount of visible PXF material in the eye does not always correlate with the degree of zonular weakness. Zonular instability may also be associated with shallow anterior chamber depth (less than 2.5 mm centrally), which is a useful predictor of intraoperative complications.

Gonioscopy offers another clinically useful perspective in PXF patients. Increased trabecular meshwork pigment is typically noted. Zonular dialysis, if present, may be quantified by the number of clock hours involved. And when phacodonesis is present, it can be graded on a scale of 1+ to 4+.

After cataract surgery with PXF, there is a persisting risk for IOL instability. Despite the type of placement (in-the-bag or ciliary sulcus with optic capture), lens implants can become decentered or dislocated. So the use of premium IOLs, including toric, extended focus, and multifocal lenses, must be carefully considered. When PXF patients are planning for cataract surgery, your role in preoperative discussions is vital in helping meet their postoperative expectations.

INTRAOPERATIVE CONSIDERATIONS

When patients with PXF undergo cataract surgery, intraoperative discoveries allow the surgeon to confirm and assess the status of this syndrome accurately. Highly skilled and experienced surgeons have the ability to safely manage the unpredictable surgical course. Small pupils and zonular weakness must be adequately addressed to ensure safety.

When patients have significant zonular instability, placement of a PMMA capsular tension ring (CTR) is often considered. If zonular weakness is mild to moderate, a CTR may be sufficient to support intraoperative maneuvers and stabilize an IOL in the capsular bag with excellent centration. Considering the potential long-term issues of these patients, some surgeons have advocated the routine use of CTR in PXF cases, both as a surgical aid and for long-term stability.

CONCLUSION

PXF syndrome and secondary glaucoma are common anterior segment disorders that we all encounter in our practices. They present challenges that require refined clinical skills in definitive diagnosis and management. And when cataract surgery is indicated, careful planning paves the way for successful outcomes. Solid interprofessional relationships between experienced optometric physicians and skilled cataract surgeons help to ensure a safe and successful surgery. With proper preoperative, intraoperative, and postoperative comanaged care, the risks associated with PXF and cataract surgery can be minimized. It is our firm belief that this model of care provides patients with the greatest benefit.



QUESTIONS

If you have questions, feel free to contact any of our optometric physicians. We’re always happy to help.


 

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