Capsular tension rings (CTRs) are used to stabilize the capsular bag of the crystalline lens during and after cataract surgery. The CTR was conceived in 1991 by Hara et al.,1 who implanted a closed silicone equator ring in rabbit eyes. The concept was further developed by Nagamoto and Bissen-Miyajima,2 and a CTR was implanted in the first human eye during cataract surgery in 1993 by Witschel and Legler (B. Witschel, MD, U.F.C. Legler, MD, “The Capsular Ring,” Video J Cataract Refract Surg 1993; vol IX, issue 4). Capsular tension rings of various designs are now used throughout the world.3–5
The conventional CTR is an open-ended, flexible, horseshoe-shaped poly(methyl methacrylate) (PMMA) filament with an eyelet at each end (Figure 1). Once positioned in the capsular bag, the CTR places centrifugal forces against the capsule equator that support the area of zonular weakness and redistribute tension from existing zonules over the areas of zonulysis. This stress distribution significantly reduces the likelihood of stretching or tearing the ciliary zonules.5 After surgery, a CTR helps maintain the equatorial area of the lens capsule in a fully distended circle of 360 degrees, which minimizes the risk for decentration of the intraocular lens (IOL) and may decrease the risk for dislocation of the capsule–IOL complex.5,6
One challenge in using a CTR is the difficulty of removing nuclear or cortical material once the ring has been implanted. The circular ring compresses residual lenticular/cortical material against the capsular bag and impedes its removal. We describe a modified CTR, the Henderson capsule tension ring (HCTR), type 10C (Morcher), which is currently under review by the U.S. Food and Drug Administration (FDA).
The HCTR is a modification of the original FDA-approved Morcher CTR. It is an open, modified, C-shaped loop made of single-piece rigid PMMA (Figure 2). The HCTR was constructed with the same force parameters as the conventional Morcher type 14 CTR. The spring constants are the same in both types. The new ring is modified from the original CTR design by 8 equally spaced indentations of 0.15 mm. The total external expanded diameter is 12.29 mm; the inner compressed diameter is 11.00 mm. The main advantage of the modification is that it allows easier removal of nuclear and cortical material while maintaining equal expansion of the capsular bag.
The HCTR has been implanted in 6 enucleated porcine eyes: 2 before phacoemulsification, 2 after phacoemulsification and before cortical removal, and 2 after cortical removal before IOL implantation (B.A. Henderson, MD, J.Y. Kim, MD, “Modified Henderson Capsule Tension Ring,” presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, March 2006). The HCTRs were placed in the bag with the Geuder injector (Figure 3) after continuous curvilinear capsulorhexis openings were made. In all 6 eyes, the HCTRs were implanted easily in the capsular bag without capsule rupture. The nuclear and cortical materials were removed without distorting the HCTR or the capsular bag (Figures 4 and 5).
A separate single-blind prospective randomized case control study with the HCTR and conventional CTRs (Morcher 14C and AMO StabilEyes) was performed. The trial found that mean surgical time, effective phacoemulsification time, and mean irrigating balanced salt solution volume were less in the HCTR group (P = .06, P = 0.34, and P = 0.03, respectively; Kruskal-Wallis test) (B.A. Henderson, MD, J.Y. Kim, MD, “Prospective Randomized Blind Study of Lens Material Removal After Placement of Conventional and Henderson Capsule Tension Rings,” presented at the annual meeting of the American Academy of Ophthalmology, Las Vegas, Nevada, USA, November 2006). Since the porcine lens is soft and easily removed by phacoemulsification or aspiration, the division between phacoemulsification time and aspiration time can vary between eyes. Therefore, the mean total phacoemulsification time, which included both lens and cortex removal, was measured rather than the cortical aspiration time alone. In this manner, the differences in time between the 2 study groups could be more accurately measured, avoiding the need to distinguish between lens and cortical material.
Zonular weakness can result from trauma, previous surgery, mature cataracts, high myopia, and pseudoexfoliation. It can occur with congenital, metabolic, and endocrine disorders that influence the ciliary zonules; eg, Marfan's syndrome, Marchesani's syndrome, scleroderma, homocystinuria, spherophakia, porphyria, and hyperlysinemia. A CTR may also be helpful in cases in which exact centration of the IOL is needed after cataract surgery to achieve a satisfactory visual result, as with multifocal IOLs.
Since the introduction of the original CTR, modifications have been made, including the Cionni ring,7 square-edged rings,8 and capsular tension segments (I.I.K. Ahmed, MD, “Capsular Hemi-Ring: Next Step in Effective Management,” presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, April 2003). These modifications are part of a “progressive evolution in the management of zonular weakness.”9
The optimal timing for placement of CTRs has been studied. Bayraktar et al.5 found that in eyes with pseudoexfoliation, placing the ring before phacoemulsification reduced zonular dialysis during surgery and improved IOL fixation. Conversely, Ahmed et al.10 reported that the ideal timing was “after lens extraction and decompression of the capsular bag.” Early ring implantation was found to increase capsular torque and displacement; removing cortical material after placing the CTR could be difficult and tedious.10
We believe the new HCTR modification with indentations provides the surgeon an alternative in cases in which capsular stability is needed before the lens has been fully removed. The HCTR maintains the benefit of distributing stress around the entire equatorial area of the lens capsule; the indentations allow the lens and cortex to be stripped and removed. Once the residual material has been removed, the HCTR can be rotated to change the position of the indentations and allow removal of lens material that was compressed by the nonindented portions of the HCTR.
We acknowledge that capsular bags can vary in size and therefore standard CTR sizes may not provide a consistent amount of bag inflation and zonular support. Without proper sizing, the benefit of these modified indentations may be lost as the compression of the residual lens material may continue even in the indented portions of the ring. Additional studies are needed to investigate the efficacy of the HCTR.
The safety and stability of CTRs have been described in numerous reports.5,11,12 New innovations, driven by advances in technology, will assist us as we strive to improve the safety of ophthalmic surgery.
1. Hara T, Hara T, Yamada Y. “Equator ring” for maintenance of the completely circular contour of the capsular bag equator after cataract removal. Ophthalmic Surg. 1991;22:358-359.
2. Nagamoto T, Bissen-Miyajima H. A ring to support the capsular bag after continuous curvilinear capsulorhexis. J Cataract Refract Surg. 1994;20:417-420.
3. Gimbel HV, Sun R, Heston JP. Management of zonular dialysis in phacoemulsification and IOL implantation using the capsular tension ring. Ophthalmic Surg Lasers. 1997;28:273-281.
4. Menapace R, Findl O, Georgopoulous M, et al., 2000. The capsular tension ring: designs, applications, and techniques [review/update], J Cataract Refract Surg, 26, 898-912.
5. Bayraktar S, Altan T, Küçüksümer Y, Yılmaz Ö.F. Capsular tension ring implantation after capsulorhexis in phacoemulsification of cataracts associated with pseudoexfoliation syndrome; intraoperative complications and early postoperative findings. J Cataract Refract Surg. 2001;27:1620-1628.
6. Jacob S, Agarwal A, Agarwal A, et al. Efficacy of a capsular tension ring for phacoemulsification in eyes with zonular dialysis. J Cataract Refract Surg. 2003;29:315-321.
7. Cionni RJ, Osher RH. Management of profound zonular dialysis or weakness with a new endocapsular ring designed for scleral fixation. J Cataract Refract Surg. 1998;24:1299-1306.
8. Nishi O, Nishi K, Menapace R, Akura J. Capsular bending ring to prevent posterior capsule opacification: 2 year follow-up. J Cataract Refract Surg. 2001;27:1359-1365.
9. Hasanee K, Ahmed IIK. Capsular tension rings: update on endocapsular support devices. Ophthalmol Clin North Am. 2006;19(4):507-519.
10. Ahmed IIK, Cionni RJ, Kranemann C, Crandall AS. Optimal timing of capsular tension ring implantation: Miyake-Apple video analysis. J Cataract Refract Surg. 2005;31:1809-1813.
11. Price FW Jr, Mackool RJ, Miller KM, et al. Interim results of the United States Investigational Device Study of the Optec capsular tension ring. Ophthalmology. 2005;112:460-465.
12. Boomer JA, Jackson DW. Anatomic evaluation of the Morcher capsular tension ring by ultrasound biomicroscopy. J Cataract Refract Surg. 2006;32:846-848.