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Capsular tension rings can be used for subluxated cataracts
A capsular tension ring helps to stabilize a loose lens and to place an IOL in the capsular bag.
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Cataract surgery in the presence of zonular weakness or a subluxated lens is a great challenge. In the past, surgical intervention in these cases was difficult, leading to complications. The use of an endocapsular flexible PMMA ring has changed the surgical approach to subluxated cataracts (Figure 1). Implantation of a capsular tension ring, or CTR, stabilizes a loose lens and allows the surgeon to place the IOL in the most beneficial place – the capsular bag. There are numerous other advantages: Vitreous herniation to the anterior chamber is reduced; a taut capsule gives countertraction to all traction maneuvers, making them easier to perform; capsular support for an “in the bag” implant is obtained; and, most important, the capsular bag maintains its shape, avoiding capsular fibrosis syndrome and IOL decentration.
Surgical maneuvers
| Amar Agarwal |
When zonules are deficient, surgical maneuvers become critical and may increase dialysis. The situation gets complicated with herniation of the vitreous into the anterior chamber through the defect in the capsular-zonular barrier. Introduction of a PMMA ring immediately after the rhexis allows safe aspiration of lens material and implantation of the IOL in the bag with ease. It re-establishes the capsule contour and protects the capsular fornix from being aspirated, avoiding consecutive zonular dialysis extension.
During surgery, any existing vitreous herniation should be pushed back or a vitrectomy should be performed at the outset, with low bottle height and low flow rate. After vitrectomy, a dispersive viscoelastic is instilled, first covering the area of the dialysis. Capsular instability makes capsulorrhexis difficult. So it is started in the area of intact zonules, where the capsule offers sufficient resistance. Hydro-maneuvers should be meticulous to free the lens nucleus. The cannula should be inserted in the direction of the dialysis to avoid enlarging it. Viscodissection may also be helpful.
The CTR is implanted with McPherson forceps, MST rhexis forceps (Microsurgical Technology) or special injectors. The injector has a small hook for the eyelet of the CTR. Once the hook locks onto the eyelet, the plunger is released, which loads the CTR. It is then injected into the bag.
Nucleus removal can be performed in the bag when the nucleus is soft. Orienting the incision at a meridian with no dialysis is important to avoid damage to zonular fibers with phaco tip movements. Slow-motion phaco, with low flow rate, low vacuum and low infusion bottle height, is preferred. Emulsification can be done in the bag when the nucleus is soft and in the anterior chamber when the nucleus is hard. During irrigation and aspiration, excessive radial traction should be avoided. Bimanual I&A is helpful for hard-to-reach areas.
The foldable lens is loaded and implanted in the capsular bag with the haptics in the meridian of the dialysis. A larger diameter lens is preferable to minimize symptoms if lens decentration occurs. IOL stability must be confirmed at the end of the surgery, both in the frontal and sagittal planes, in case suturing a haptic to the sulcus is necessary. This is followed by viscoelastic removal. All tractional maneuvers must be avoided or minimized throughout the surgery.
Trypan blue
Preferably, do not use trypan blue in subluxated cataracts, as the trypan blue will go into the vitreous cavity through the zonular dehiscence and make the whole vitreous cavity blue. This makes visualization difficult.
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Image: Agarwal A |
Image: Freitas LL |
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Image: Agarwal A |
Image: Agarwal A |
Cionni ring
If the lens continues to remain decentered after CTR insertion, a flexible nylon iris hook is used to engage the rhexis margin through a paracentesis opposite to the direction of subluxation. This gives capsular support until the end of surgery, at which time transscleral fixation of one haptic of the IOL can be done for centration.
When zonular dehiscence is large in extent (Figure 2) or progressive in nature, capsular bag shrinkage resulting in IOL decentration and pseudophakodonesis may occur even after a successful surgery with a CTR. Complete luxation of the bag and its contents has also been reported. For such cases, Cionni’s modified design with a fixation hook is a good solution (Figure 3). The hook is kept in the area of the dialysis and is pulled peripherally using a transscleral fixation suture to counteract capsular bag decentration and tilt. In severe cases, two such rings or the two-hooked model can be used. An alternative in cases of severe decentration is to make a small equatorial capsulorrhexis through which a standard CTR can be inserted. A scleral suture can then be passed around the exposed CTR, which is used to center the lens before capsulorrhexis. Peribulbar anesthesia is suitable for creation of scleral windows and transscleral suturing of the capsular ring or of the IOL if necessary.
Aniridia rings
CTRs can also be placed to cover sector iris defects or coloboma. These coloboma shields have an integrated 60° to 90° sector shield to protect against glare and monocular diplopia. More than one CTR can be used if more than 90° of defect is present. Multisegmented coloboma rings are available for aniridia as well as for cases with large, permanently dilated pupils secondary to any cause (Figure 4). Insertion of two of these rings so that the spaces of the first ring are covered by the sector shields of the second makes a contiguous artificial iris possible.
Summary
With the fusion of innovative surgical devices and appropriate surgical techniques, difficult situations such as subluxated cataracts can be managed well, giving good postoperative outcomes and creating satisfied patients.
For More Information:
- Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Group of Eye Hospitals. Dr. Agarwal is author of several books published by SLACK, Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery, and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; fax: 91-44-28115871; e-mail: dragarwal@vsnl.com; Web site: www.dragarwal.com.
References:
- Agarwal A, Agarwal A, Agarwal S. Phacoemulsification. 3rd ed. Thorofare, NJ: SLACK Incorporated; 2004.
- Agarwal A. Phaco Nightmares: Conquering Cataract Catastrophes. Thorofare, NJ: SLACK Incorporated; (in press).
- Agarwal A. Handbook of Ophthalmology. Thorofare, NJ: SLACK Incorporated; 2005.