October 2018

CATARACT

Presentation spotlight
Compensating for zonular weakness in cataract surgery


by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer


Large zonular defects
Source: Boris Malyugin, MD

Specialist describes his implementation of capsular tension rings in dealing with zonular defects

IOL implantation in eyes with zonular weakness and crystalline lens subluxation are challenging cases for cataract surgeons. Identifying the extent of the zonular defect will allow the surgeon to plan the right strategy to achieve a stable IOL implantation.
According to Boris Malyugin, MD, S. Fyodorov Eye Microsurgery Federal State Institution, Moscow, Russia, capsular tension rings (CTRs) are key elements in cataract surgery to restore the contours and stability of the capsular bag to allow safe and reliable IOL implantation, even in highly complicated cases.
“We all love CTRs because they help us in difficult cases involving the zonules,” Dr. Malyugin said in his presentation at the 22nd ESCRS Winter Meeting. “However, do not use a CTR if capsular bag integrity is in doubt, like when you have a radial tear or posterior capsular rupture, because you might be expanding the defect in the capsule.”

CTR scenarios

The main reason for crystalline lens subluxation is weak zonular fibers. Zonular deficiency has been associated with a number of etiologies, including hereditary causes such as Marfan syndrome, Weill-Marchesani syndrome, homocystinuria, and congenital iris coloboma, as well as acquired causes like trauma, iatrogenic surgical factors, previous eye surgery, ocular comorbidity (pseudoexfoliation syndrome, retinitis pigmentosa, myopia, glaucoma), and certain types of cataract (white, intumescent), among others. According to Dr. Malyugin, CTRs are helpful in even the most complicated scenarios.
Indications for conventional CTR use include generalized zonular weakness (irido-phacodonesis, star-fold formation on the anterior capsule during CCC), local zonular defects not exceeding 90 degrees (3 clock hours), and anterior capsulorhexis ovalization occurring after IOL implantation. “Sometimes I will use a CTR after I implant a three-piece or single-piece IOL and I see that the anterior capsulorhexis opening is starting to be oval,” Dr. Malyugin said. “It means there is not enough support from the zonules, and in these cases, even if I already completed the surgery successfully, I opt for using a CTR at the end of the procedure to redistribute the tension on the zonules along the capsular bag equator.”
Patients with pseudoexfoliation syndrome present their own set of challenges. Despite careful use of phacoemulsification to break down the nucleus in these cases, the procedure can still damage delicate ocular tissues at times. Dr. Malyugin described a cataract surgery he performed in which even meticulous care resulted in capsular damage. “When performing phaco in an eye with pseudoexfoliation syndrome, I prefer vertical chop, augmented sometimes with horizontal chop. In that particular case, when I started to aspirate the cortical material, I was actually inadvertently aspirating the capsule and causing an iatrogenic zonular defect that happened because of my ‘blind’ maneuvers under the iris. I needed to restore the contour of the capsular bag, which I accomplished by injecting viscoelastic into the bag, repositioning its fornix, and using a conventional CTR to restore bag shape and integrity.”

Potential issues

CTRs are either implanted manually by using a toothless forceps, fish tail technique, strand assisted technique, or they can be implanted with the use of an injector. CTR size selection is calculated using the white-to-white plus 1.0 mm. Available sizes are 10 mm, 11 mm, and 12 mm to accommodate different types of eyes, such as myopic eyes, that require a slightly larger CTR.
Even when using the right technique and a correctly sized CTR, positioning issues can occur. Placing the CTR into the anterior chamber angle can happen and is hard to retrieve if the arcus senilis is wide or due to difficulties in grasping the tip of the device, particularly for inexperienced surgeons. Similarly, it can be hard to reposition a CTR placed in the ciliary sulcus. Other difficulties include mixed fixation in the bag/sulcus and capsular rupture during implantation, which although rare, is still possible. Eyes with small pupils, often associated with zonular weakness, present a challenge to implantation, making it difficult to place the CTR correctly. Also, a CTR may not be enough of a support in a situation in which a widespread zonular defect reveals itself at the very end of surgery, necessitating the placement of scleral wall sutures in order to stabilize the capsule.

Modifications

“CTR modifications help us stabilize the capsular bag in complicated situations with profound zonular dialysis exceeding 3 clock hours,” Dr. Malyugin said. “They can be useful not only in restoring the contour of the capsular bag but also in replacing the missing zonules.”
The Malyugin CTR is a modification of the Cionni CTR, which was designed to eliminate the risk of perforating the capsular bag and is specially adapted for severe zonular dehiscence and dialysis when iris retractors and conventional CTRs cannot fully stabilize the bag. The modified CTR uses an injector, and the device’s curved element easily slides along the equator of the capsular bag without damaging the capsule or expanding the zonular defect. It is fixated using scleral sutures.
In the case of a patient with hereditary zonular deficiency, Dr. Malyugin proceeded with extreme caution from the start, as the capsulorhexis can be one of the challenging steps in these kinds of eyes. “I used a special hook here, an iris capsule retractor,” he said. “I allowed the edge of the hook to rest on the equator, not causing much stress on the edge of the capsule. This helped me perform the continuous capsulorhexis. I aspirated part of the cortical material and injected the modified capsular tension ring, making sure that I always inject the device toward the area of the zonular defect. As soon as it was in the bag, I needed to rotate the device to place the fixation element at the very center of the zonular defect, in order to replace the missing zonules. The fixation element was repositioned on top of the anterior capsule. Then the suture was passed through the ciliary sulcus. The residual cortical material was evacuated, and the IOL was implanted into the capsular bag.”
It can be useful to inject triamcinolone into the eye to identify vitreous matter in the anterior chamber. If a vitreous prolapse is identified, vitrectomy is required. Dr. Malyugin proposed the use of a dry vitrectomy to not hydrate the vitreous, and apply viscoelastic to reposition it into the posterior chamber. “I use 9-0 polypropylene to fixate the eyelet of the CTR, which is partially retracted inside the injector tube, then I inject the device toward the zonular defect,” he said. “The reason for this is because when I have relatively healthy zonules in some areas, I take care to preserve the residual zonules and keep them from unzipping. It is also important to not press on the lens while injecting the CTR because in doing so you will induce the prolapse of the vitreous. Even with the modified CTR sutured to the scleral wall, the surgeon has to remember that vitreous can still seep through the zonular defect and excessive hydration of it should be avoided.
“CTRs should be implanted as late as possible and as soon as necessary. The reason for that is because it compresses the cortical material to the equator and you can have a hard time evacuating cortical material during irrigation/aspiration, which then takes much longer,” Dr. Malyugin said. “Insert them at the very beginning of the case, following the anterior CCC, or after capsular bag content evacuation. In eyes with generalized zonular laxity, use a combination of capsular tension segments (CTS) plus CTR, for instance the Malyugin CTR plus Ahmed CTS. In patients with zonular deficiency, be prepared for much longer surgical time and the right anesthesia, and do proper patient counseling. Finally, always have a backup plan because you cannot guarantee that the capsular bag will be intact or will be preserved during the surgery. I always ask my assistant to prepare not only a single-piece but also a three-piece IOL because I may have to change the plan and suture the lens to the iris or fixate it to the sclera.”

Editors’ note: Dr. Malyugin has financial interests with Morcher (Stuttgart, Germany).

Contact information

Malyugin: boris.malyugin@gmail.com

Compensating for zonular weakness in cataract surgery Compensating for zonular weakness in cataract surgery
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