Cataract Surgery | Nov 2005
Conditions and Capsular Tension Rings
When to use these devices in clinical practice.
David M. Dillman, MD
The FDA approved the use of capsular tension rings (CTRs) more than 1 year ago. Surgeons can choose from a variety of these devices, including the Stabileyes CTR (Ophtec BV; Groningen, the Netherlands; distributed in the US by Advanced Medical Optics, Inc., Santa Ana, CA), the CTR (Morcher GmbH, Stuttgart, Germany; distributed by FCI Ophthalmics, Inc.; Marshfield Hills, MA), and the Cionni Morcher CTRs (Morcher GmbH; distributed by FCI Ophthalmics, Inc.). CTRs facilitate cataract surgery performed in the presence of weakened zonules. This article shares what I learned from my first full year of using the Stabileyes CTR.
INDICATIONS FOR USE
It is important to bear in mind that CTRs are appropriate in eyes with a complete anterior capsulorhexis, an otherwise fully intact capsular bag, and weakened zonules. They provide structural support, not surgical miracles. CTRs are actually contraindicated in the presence of an unwanted opening in either the anterior or posterior capsule as well as in the presence of extremely compromised zonules such as those that have lost more than four clock hours of integrity. This article does not discuss devices for cases of extreme zonular deterioration, including the Cionni Morcher CTRs and the Ahmed capsular tension segments (Morcher GmbH; not FDA approved).
SYSTEMIC INDICATIONS FOR CTRs
Compromised zonular strength results from several congenital, endocrinic, and metabolic conditions, including Marfan's syndrome, Marchesani's syndrome, scleroderma, homocystinuria, spherophakia, porphyria, hyperlysinemia, hyperlipoproteinemia, and sulfite oxidase deficiency. I have trouble spelling these, let alone recognizing them. Although I try to be aware of their existence, I do not often see these conditions in Danville, Illinois.
OCULAR CONDITIONS FOR CTRs
It is well known that eyes with pseudoexfoliation (PXF) often have weakened zonules and therefore a lax capsular bag. In such eyes, cataract surgery is more challenging, and the risk for intraoperative complications is higher than in healthy eyes. Even if the surgery itself is free of complications, eyes with PXF are at a higher risk for developing postoperative complications such as a decentered IOL and capsular phimosis.
Will every eye with PXF have weakened zonules and a compromised capsular bag? Should every eye with PXF receive a CTR as a matter of routine? I have heard arguments on both sides. At present, I routinely place a CTR in an eye with PXF. If I detect even a hint of weakness in the zonule/bag complex, I place the CTR early, before performing phacoemulsification. Otherwise, I place the device before I insert the IOL.
Previous Ocular Trauma
Surgeons all know to carefully examine preoperatively an eye with a known history of trauma. Even without obvious compromise of the zonule/capsular bag at the time of the slit-lamp evaluation, this complication occurs intraoperatively.
A history of previous ocular surgery is a subset of the category of previous ocular trauma. I am particularly vigilant for eyes that have (1) undergone a vitrectomy (stretched zonules due to a lack of posterior support), (2) had successful filtration surgery for glaucoma (stretched zonules because of a shallow anterior chamber), and (3) undergone “aggressive” RK (ie, with incisions made via the Russian technique that extend all the way to the limbus and/or number more than eight). These eyes may well have endured a micro- or macroperforation with subsequent shallowing of the anterior chamber and stretching of the zonules.The good news is that CTRs can provide needed support in these cases.
Future Eye Surgery
If it makes good sense to place a CTR in an eye that has undergone a vitrectomy, then perhaps surgeons should consider placing the device in an eye that is going to have a vitrectomy. The most obvious patient group, of course, would be diabetics who are referred for cataract surgery prior to undergoing a vitrectomy as part of the treatment for their diabetic retinopathy. A second group would be patients referred for cataract surgery prior to macular surgery for the treatment of macular holes, epiretinal membranes, etc.
It may be appropriate to consult a retinal surgeon before prophylactically placing a CTR. The retinal specialists with whom I work like having a CTR in place.
Long Axial Length
The amount of a patient's refractive myopia does not always correlate well with his axial length. Steep corneas and nuclear sclerosis can cause myopia in the presence of fairly average axial lengths. I therefore home in on the axial myope. Unusually long eyes have a greater propensity for stretched zonules both intra- and postoperatively. Also, these eyes are perhaps more susceptible to movement of the zonule/capsular bag complex postoperatively and the subsequent influence on the vitreous base. I do not have an absolute number, but I always place a CTR in eyes with an axial length of 26mm or longer. I individually consider eyes with an axial length of between 25 and 26mm.
Using CTRs has made me a better observer of intraocular events. Weak zonules can make the capsulorhexis more difficult to start and to complete. They can impede hydrodissection by resisting efforts to spin the lens. They can also hinder the maneuvering of nuclear fragments within the confines of the capsular bag.
In some cases, the zonules are normal at the beginning of the case but weaken as it proceeds. I most expect this problem when I deal with an extremely dense cataract that requires considerable manipulation for its safe removal, and I will often place a CTR into these eyes if I sense that their zonular status has changed.
TIMING THE PLACEMENT OF CTRs
Surgeons new to CTRs often want to know the best time during surgery to place the device. It is easiest to place a CTR into a capsular bag that is nicely distended with a viscoelastic after performing both phacoemulsification and cortical cleanup. The device can only help intraoperatively with these surgical steps, however, when it is located within the capsular bag and not sitting on the stand. I generally place the CTR upon my first inkling that the device may be necessary.
David M. Dillman, MD, is Medical Director of Dillman Eye Care Associates in Danville, Illinois. He has been paid by Advanced Medical Optics, Inc., for conducting seminars for the company. Dr. Dillman may be reached at (217) 443-2020; email@example.com.