David F. Chang, MD, reported that he was an investigator for the Morcher capsular tension ring and a consultant for AMO.
He has no financial interest in any product mentioned. E-mail: dceye@earthlink.net
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San Francisco—Weak zonules pose a great deal of concern to cataract surgeons. However, the availability of capsular tension rings (CTRs)
is a real boon in helping surgeons deal with loose zonules.
David F. Chang, MD, provided his practical tips for using CTRs during cataract surgery at the fourth annual San Francisco
Cornea, Cataract, and Refractive Surgery Symposium.
Weak zonules can result from a number of different problems, notably, ocular trauma, aging, pseudoexfoliation, or Marfan's
syndrome; however, weak zonules can also be associated with retinopathy of prematurity, prior trabeculectomy or vitrectomy,
or an ultra-brunescent cataract.
"Weak zonules complicate every step of the surgical procedure as well as the postoperative centration and stability of the
IOL," Dr. Chang said. "Capsular tension rings are designed to redistribute all of the surgical and capsular forces to the
areas of the strongest intact zonules. The ring will increase the tension of the posterior capsule, resist contraction of
the capsulorhexis, and may retard the development of posterior capsule opacification."
The devices do have disadvantages, however, in that their insertion can cause zonular trauma, they impede cortical clean-up,
and they can become dislocated if the posterior chamber ruptures, pointed out Dr. Chang, clinical professor, University of
California, San Francisco, and in private practice in Los Altos, CA.
Insertion of CTRs is contraindicated in the presence of a torn capsulorhexis or posterior capsule, or when one cannot adequately
visualize the capsulorhexis. The device is inserted using either forceps or an injector.
When to insert
Figures 1A and 1B. Capsular tension ring (Ophtec/AMO) is injected into the bag, following use of two Mackool capsule retractors
(FCI) to stabilize the capsular bag during phacoemulsification. (Figures courtesy of David F. Chang, MD)
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"The main surgical decision about capsular tension rings is when during the course of a procedure to insert them. Insertion
can be done before, during, or after phacoemulsification, after cortical irrigation/ aspiration cleanup, or even after the
IOL has been implanted," he said. "The objectives can vary with each situation. In some cases we are primarily worried about
the postoperative stability of the IOL, while in other cases our main concern is with avoiding capsular rupture and vitreous
loss during phaco."
Dr. Chang first demonstrated insertion of the CTR with the injector prior to IOL implantation in a case in which the cataract
had already been extracted. To reduce the risk of perforating a lax posterior capsule with the ring, a generous amount of
viscoelastic should be used to inflate the capsular bag. He uses a Lester hook to help bend the CTR into place as it is injected
into the bag. This, he explained, allows the brunt of the bending forces to be borne by the hook instead of the capsulorhexis
or the bag.
"This is the easiest situation in which to insert a capsular tension ring. It is ideal for surgeons just learning the procedure,
because the capsular bag is empty," he said.
In another video case presentation, a round capsulorhexis became oval following IOL implantation, which indicated the presence
of weak zonules. In this situation, the axial distending force of the haptics exceeded the circumferential zonular tension
90 away, producing an elliptical distortion of the capsulorhexis. To avoid excessive capsular contraction, a CTR was inserted
subsequent to IOL implantation. After the bag was reinflated, the ring was manually inserted with forceps in a counterclockwise
direction, which followed the natural curve of the IOL haptics. This case demonstrated the difficulty of inserting the CTR
without an injector. Injectors compress the ring enough to facilitate their entry through a small capsulorhexis and small
incision while distending the capsulorhexis as little as possible.
"When inserting the CTR manually, the surgeon must not release the trailing eyelet prematurely such that it disappears into
the angle," he advised. After CTR placement in this eye, the oval capsulorhexis became round, confirming the redistribution
of zonular tension.
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Dr. Chang believes that a CTR can improve long-term IOL/capsular bag stability if the zonules are moderately weak, or missing
from just one quadrant. However, in the setting of severe and widespread zonular weakness, ring suturing may be necessary.
Neither the Cionni CTR modification nor the Ahmed capsular tension segments are FDA approved, but both devices allow scleral
suture fixation of the stabilizing element.
Use of capsule retractors
To stabilize the weakened capsular bag during phacoemulsification, the options are using a CTR or capsule retractors (iris
retractors), Mackool capsule retractors, or the Ahmed segment, Dr. Chang explained.
Dr. Chang presented one case of severe and diffuse zonular weakness in a brunescent cataract in which CTR placement did little
to improve the bag stability.
"For such severe zonular weakness, there is a limit to what CTRs can accomplish, because there are not enough healthy zonules
to recruit and redistribute surgical forces to," he stated.
Dr. Chang's next case illustrated what was thought to be a focal zonular dialysis, where a CTR was placed prior to removal
of the cortex. In fact, this eye had more than 6 hours of zonular weakness, and the CTR significantly impeded cortical cleanup
with the irrigation/aspiration handpiece. The video demonstrated that the ring actually transmitted the aspirating forces
to all 12 clock hours of the capsular bag. The ring pinned down the cortex peripherally, and as it was tangentially stripped,
the entire capsular bag moved. The CTR actually caused more stress to the zonules in this eye. Finally, a capsule retractor
was inserted to provide sufficient peripheral counter-traction in the problematic quadrant to remove the cortex. "This illustrates
why I usually try to delay inserting the capsular tension ring until after the cortex is removed," he said.
For cases with large zonular defects, or widespread zonular weakness, Dr. Chang prefers the Mackool cataract support system.
These are specially designed capsular retractors that have a long-enough curve to hook a small-diameter capsulorhexis edge,
and yet have the retractor tip support the peripheral bag equator. The disposable versions are easier for novices to insert,
and are sold by FCI and Impex. A titanium reusable set is available from Duckworth & Kent.
Capsule retractors do several things that CTRs cannot. They firmly anchor the peripheral bag to the eye wall, providing torsional
stability and antero-posterior support. They can also re-center the bag with a large zonular dialysis.
Dr. Chang showed two cases with focal traumatic zonular dialysis in which the Mackool retractors were used along with bimanual
microincisional phaco to remove the nucleus. The latter strategy allowed dissociation of the irrigation and aspiration instruments
in an effort to prevent a fluid misdirection syndrome. Unlike the CTR, the point pressure applied by the two Mackool retractors
did not impede cortical stripping.
Finally, a CTR was implanted prior to IOL insertion to provide postoperative capsular stability.
Acrylic IOLs
With weak zonules, Dr. Chang prefers a hydrophobic acrylic optic.
"There is less anterior capsular fibrosis and contraction with this material," he said.
In addition, Dr. Chang recommends using acrylic IOLs with three-piece haptics, which provide more rigidity than one-piece
haptics. Finally, to prevent capsulophimosis, he feels it is important to enlarge a small-diameter capsulorhexis secondarily
in these eyes once the IOL has been implanted.
In a final case of traumatic mydriasis and large nasal zonular dialysis, there was extensive wrinkling of the anterior capsule
when the capsulorhexis was initiated, indicating severe zonular laxity. Without the anchoring effect of peripheral zonular
tension, the anterior capsule flap becomes very difficult to control as it is torn, and the tear tends to run peripherally.
In these situations, it may be safer to make the capsulorhexis diameter smaller to assure completion. After a dispersive viscoelastic
was used to patch the zonular dialysis, two Mackool capsule retractors were inserted. This provided excellent capsular stability
as bimanual microincisional phaco and bimanual cortical aspiration were performed. Lacking centripetal zonular traction, the
posterior capsule was extremely lax during cortical irrigation/aspiration, and tended to become ensnared in the 0.3-mm aspirating
port.
In order to delay CTR placement, the capsular bag was filled with Viscoat (Alcon Laboratories). A dispersive viscoelastic
agent resists aspiration, expands the capsular bag, and restrains the posterior capsule from trampolining toward the port.
After completion of cortical removal, the CTR was inserted.
However, the bag was still lacking antero-posterior support across one hemisphere. Because of this, Dr. Chang opted to insert
the foldable IOL in the sulcus. A 13.5-mm long foldable IOL (STAAR AQ 2010) had been ordered in advance for this possibility.
"U.S. surgeons and their patients have been reaping the benefits of capsular tension rings for about a year," Dr. Chang concluded.
"There are some tricks to using them and you need to know the limits of what they can accomplish. Capsule retractors may provide
greater capsular stability during phaco, and can allow CTR insertion to be delayed after cortical cleanup."
CTRs have received FDA approval. They presently are available from Morcher (FCI Ophthalmics) in 12-, 13-, and 14-mm sizes,
and from Ophtec (AMO) in 12- and 13-mm sizes.
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