September 2019

IN FOCUS

Challenging Cataract Cases
Be prepared for loose zonules


by Stefanie Petrou Binder, MD EyeWorld Contributing Writer


Diffuse zonular laxity, as seen in this retroillumination slit lamp photograph, can make cataract surgery challenging.

Sectoral zonulopathy of a few clock hours
Source (all): Kevin M. Miller, MD

 

Zonulopathy is encountered in a wide spectrum of clinical situations. Synonymous with zonular dehiscence or zonular dialysis, it describes a weakened state of zonular support that affects the integrity of the lens capsule unit and plays an important role in the approach a surgeon takes to cataract surgery. EyeWorld interviewed Uday Devgan, MD, and Kevin M. Miller, MD, to gain insight into this frequently encountered clinical entity and learn how to best deal with it.

Identify zonulopathy

Identifying zonulopathy will allow the surgeon to plan cataract surgery for the patient, select the appropriate devices, and prepare for the management of potential zonulopathy-related complications. Zonulopathy can be segmental, which is most commonly traumatic or iatrogenic, or diffuse, as seen in eyes with pseudoexfoliation syndrome, retinitis pigmentosa, retinopathy of prematurity, extreme age, extreme myopia, multiple previous pars plana vitrectomies, or with silicone oil tamponade. Additionally, systemic conditions associated with diffuse zonulopathy include Marfan syndrome, homocystinuria, Weill-Marchesani syndrome, Ehlers-Danlos syndrome, Rieger syndrome, sulfite oxidase deficiency, and Crouzon syndrome.
The preoperative evaluation is important to differentiate acquired zonulopathy from chronic issues, according to Dr. Devgan. “Patients with a history of recent trauma can have zonular compromise, usually for just a few clock hours, and this is not expected to worsen in the future as long as additional trauma can be avoided. However, patients with chronic ocular issues such as pseudoexfoliation and retinitis pigmentosa will likely see progression of the zonulopathy in the future. Even systemic conditions such as Marfan syndrome, homocystinuria, and other diseases can cause a progressive deterioration of zonular strength with age,” Dr. Devgan said.
The manner in which zonulopathy presents itself is highly varied and necessitates a sharp eye on the part of the surgeon. “At the slit lamp, we can often see areas of zonular loss with good dilation,” Dr. Devgan said. “Other times, the extent of the zonular loss is so significant that there is phacodonesis with movement of the entire crystalline lens with eye movement. In extreme cases, the entire lens can become dislocated and can sunset out of the visual axis and even into the mid-vitreous. Placing the patient in a supine position in the examination room can help to highlight this issue,” he said.

Preserve the zonules

Preserving the integrity of the zonular fibers is vital. The zonular attachments to the lens capsule not only provide stability during cataract surgery, they also directly affect the long-term visual outcome of the procedure. When the zonules are compromised, surgery is adapted to preserve the remaining zonules as best as possible and to ensure stability of the intraocular lens implant.
According to Dr. Miller, the extent of zonular laxity or dehiscence can at times be obvious. More often, however, the pathology is subtle, and therefore knowing the indicators of zonular weakness is paramount. “Look for iridodonesis and phacodonesis. Often, the lens will be deep to the iris and you may see vitreous in the anterior chamber. In these cases, the vitreous needs to be removed completely from the anterior chamber, the capsular bag stabilized, and the cataract gently removed. In all cases, I will use a capsular tension ring to reduce further damage to the zonular fibers,” he said.
Missing zonules of one or two clock hours do not present a dire situation, however, Dr. Miller always places a capsular tension ring (CTR) to support the capsule in that area and keep it from folding in on itself. As a general rule, he places CTRs in all eyes that have obvious zonular problems, whether sectoral or diffuse. In addition to a CTR, depending on capsule centration, he uses capsule tension segments or modified Cionni tension rings to secure the capsule bag to the sclera when necessary.
“It will help those eyes with sectoral zonular loss, like from trauma,” Dr. Miller said. “There is also the trauma of the surgery itself and what that does to the zonules, but there is the postoperative effect of the capsule shrink wrapping around the implant. If it shrinks aggressively, it will tear the zonules, so I insert a CTR to reduce additional stress on the zonules. But more importantly, the CTR offers advantages for iris or scleral fixation in the months and years that follow, if the lens implant decides to decenter or dislocate,” he said.
Dr. Miller implements an injector for capsular tension ring implantation. In the absence of a capsule retractor to stabilize the capsular bag, he injects toward the area of zonular dehiscence, laying the ring out for the first 180 degrees and injecting it for the rest.
A CTR will stretch the bag in cases of focal zonular dialysis, stretch the equator of the capsule bag to resist the centripetal contraction that typically follows surgery, potentially reduce the event of late decentrations and dislocations, and allow easier management of late capsular problems, he noted.
When zonular support is lost and the eye is essentially aphakic, the surgeon is constrained to abandon the capsule and look for other solutions. Dr. Miller thinks that anticipating this situation lets the surgeon prepare for a more complicated surgery, including selection of a three-piece or anterior chamber IOL, as well as an appropriate choice of anesthesia. These surgeries take longer, such as for scleral tunnel procedures, and are associated with increased stress in older patients. Oftentimes, a vitrectomy and the use of an anterior chamber lens serves an older patient best without overly prolonging surgery.

Intraoperative pearls

Zonular weakness may not always be obvious. Knowing what to look for intraoperatively can make all the difference, according to Dr. Devgan. “During cataract surgery, if the zonular structures are intact and normal, the anterior lens capsule should be taut, like the head of a drum, especially after instillation of viscoelastic. When we poke into the anterior lens capsule with our forceps or a cystotome for the creation of the capsulorhexis, it should puncture easily. But if we see radial wrinkles from our attempted puncture and the anterior capsule is not tightly stretched, this indicates zonular laxity. This is difficult to puncture and is an important warning sign that zonular weakness may pose challenges and induce complications during cataract surgery,” he said.
Dr. Devgan makes a generous capsulorhexis between 5 and 5.5 mm in diameter and avoids placing stress on the capsular bag during nucleus division. He recommended caution during cortex removal to avoid further zonular compromise and careful IOL selection and placement to offer the best long-term results. Dr. Devgan recommended hydrodissection in which he tilts the nucleus on its side then begins to chop and use phacoemulsification.
Sometimes signs of zonular weakness appear intraoperatively. “Using phaco chop, we can bring each nuclear half out of the capsular bag and into the iris plane for aspiration. If the shape of the capsulorhexis morphs from round to D-shaped, for example, during cortex removal using irrigation/aspiration, it indicates zonular loss along the flat surface. The ideal next step is to implant a capsular tension ring or a Cionni ring to bolster the weak area and to provide stability for IOL implantation,” Dr. Devgan said.
In the absence of the appropriate devices, the surgeon can use the IOL’s haptics to provide support. Dr. Devgan suggested implanting the IOL so that one haptic is placed along the area of zonular weakness. This haptic will exert an outward force supporting the capsular bag equator, resulting in a well-centered optic.

Femto advantage

Dr. Miller relies on a femtosecond laser when zonular weakness threatens to complicate cataract surgery. “Capsulorhexis is often very difficult in these eyes because the lens wants to follow you when you’re doing a manual capsulorhexis. It is also stressful on the remaining zonules. If I can use a femto laser when a lens is not too far displaced, I prefer that. A lens capsule that is less than 2–3 mm off axis that I can visualize enough of to put down the treatment pattern is a great candidate for a femtosecond laser capsulorhexis,” Dr. Miller said.

At a glance

• The cataract surgeon needs to adapt his or her approach to cataract surgery based on the degree of zonulopathy present in the eye.
• Zonulopathy caused by trauma is generally segmental while diffuse zonulopathy is associated with a variety disease states.
• The surgeon’s main goal is to preserve the integrity of the remaining zonular fibers, which stabilize the lens capsule and affect the long-term visual outcomes.

About the doctors

Uday Devgan, MD
Devgan Eye Surgery
Los Angeles

Kevin M. Miller, MD
Kolokotrones Chair in Ophthalmology
David Geffen School of
Medicine at University of
California, Los Angeles

Relevant financial interests

Miller
: None
Devgan: CataractCoach.com

Contact information

Miller: miller@jsei.ucla.edu
Devgan: devgan@gmail.com

Be prepared for loose zonules Be prepared for loose zonules
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