Figure 1. The endocapsular equator ring is a closed silicone ring with a square edge, an outer diameter of 9.5 mm, and width and thickness of 1.0 mm. A groove on the inner surface facilitates intraocular lens loop fixation.
Figure 2. The endocapsular equator ring is inserted into the capsular bag using the intraocular lens injector.
Figure 3. Observation of case 14 of group 1 two years and 6 months postoperatively. A, Endocapsular equator ring (E-ring) eye. B, Control eye. Top, retroillumination photograph. Middle, Scheimpflug slit image. Bottom, anterior optical coherence tomography image. In the E-ring eye, the entire posterior capsule is clear. The posterior capsular opacification (PCO) value of the central area is 1.5. There is no contact between the intraocular lens optic and the posterior capsule. The E-ring has not caused elevation of the iris root. In the control eye, prominent PCO is observed. The PCO value of the central area is 20.5.
Figure 4. Comparison of posterior capsular opacification (PCO) values between eyes with and without the endocapsular equator ring (E-ring) in group 1. *Significant difference.
Figure 5. Comparison of the rates of Nd:YAG posterior capsulotomy. *Significant difference at P < .01 (Fisher exact test). E-ring indicates endocapsular equator ring.
Hara T, Hara T, Narita M, Hashimoto T, Motoyama Y, Hara T. Long-term Study of Posterior Capsular Opacification Prevention With Endocapsular Equator Rings in Humans. Arch Ophthalmol. 2011;129(7):855-863. doi:10.1001/archophthalmol.2011.38
Author Affiliations: Hara Eye Hospital, Utsunomiya, Japan.
Objective To confirm the effect of a square-edged, closed endocapsular equator ring (E-ring) for preventing posterior capsular opacification (PCO) after cataract extraction.
Methods Fifty-one eyes underwent cataract surgery associated with E-ring implantation between October 2002 and March 2008. Group 1 included 14 patients (14 eyes) who received an E-ring and intraocular lens (IOL) in 1 eye before March 2006. Their fellow eyes received only an IOL as controls. Group 2 included 23 patients (37 eyes) who received an E-ring and IOL in 1 or both eyes after March 2006 and another 37 age-matched control eyes with only IOL implants. After cataract removal, the E-ring (1.0 mm wide and thick and 9.0 or 9.5 mm long) was implanted in the capsule and an IOL was fixed in the ring. In the control eyes, only an IOL was implanted. The follow-up periods were 2 to 7 years. The PCO value was determined using the Hayashi method.
Results Two years postoperatively in group 1, the PCO value in the central area of the eyes with an E-ring was significantly lower than in the controls (4.4 vs 11.4, respectively; P = .005). No eyes with an E-ring required Nd:YAG laser posterior capsulotomy postoperatively compared with 23 of 51 control eyes (45%). The posterior capsule in the eyes with an E-ring remained transparent without touching the IOL optic. The 9.5-mm ring fit all eyes.
Conclusion The 9.5-mm E-ring, which fit all eyes, prevented PCO in human eyes 2 to 7 years postoperatively.
Schaumberg et al1 reported that the rate of postoperative posterior capsular opacification (PCO) was 20.7% at 2 years and 28.5% 5 years after cataract surgery. Lundqvist and Mönestam2 reported that 40% of patients younger than 65 years needed Nd:YAG laser capsulotomy compared with 20% of the older patients 10 years postoperatively. Many trials have been performed to prevent PCO3,4; however, the high rate of Nd:YAG laser capsulotomy indicates that preventing PCO is still problematic.
In 1991, we introduced a closed silicone ring (endocapsular equator ring [E-ring]).5 We proved the validity of our hypothesis that the square-edged E-ring preserves posterior capsular transparency by preventing posterior movement of the activated lens epithelial cells (LECs) at the equator in rabbit eyes in 19956 and monkey eyes in 1998.7 In 2007, we published the first case report on a 22-year-old atopic eye.3 We now report further proof of the efficacy of E-rings for preventing PCO in a larger number of patients who have been followed up for a longer period.
All patients had undergone cataract surgery. Patients with general disorders also were included if their diseases did not affect the results of the cataract surgery. The patients were selected based on the standards of the ethics committee of Hara Eye Hospital. After the patients received a full verbal and written explanation of this procedure, all provided informed consent.
Group 1 included 14 patients (14 eyes) (mean [SD] age, 69.9 [14.90] years; range, 22-80 years). Each patient received an E-ring and an intraocular lens (IOL) in 1 eye and only an IOL in the control eye. All surgeries were performed between September 20, 2002, and February 22, 2006. The follow-up periods ranged from a minimum of 2 years to a maximum of 7 years.
Because the E-ring was effective in group 1, we evaluated a larger number of patients in group 2 (37 eyes of 23 patients) who received an E-ring and IOL between March 8, 2006, and March 26, 2008, to determine the incidence of Nd:YAG laser posterior capsulotomy. During the same period, 37 age-matched eyes that underwent only IOL implantation served as controls. The follow-up period was at least 2 years. The mean (SD) age of the patients who received an E-ring was 49.7 (12.92) years (range, 19-64 years); the mean (SD) age of the patients who did not receive an E-ring was 50.6 (13.56) years (range, 21-69 years).
The E-ring used in the current study was almost the same design as that reported previously3 except for the size (Figure 1). The solid, flexible, silicone, closed ring has an outer diameter of 9.5 mm, a width and thickness of 1.0 mm, and a square edge. In the previous report, the 9.0-mm ring prevented PCO but caused slight iritis. The 9.0-mm rings were used in the first 8 eyes of the current group 1 with uneventful signs except for slight flare. However, in eye 8, severe iritis developed probably because of slight endocapsular ring rotation. The size then was increased to 9.5 mm beginning with eye 9 and for all subsequent eyes in groups 1 and 2. The weight of the 9.5-mm ring was 23.6 mg in air and water. The ring can be put into a conventional IOL injector for a Morcher soft IOL (Morcher GmbH, Stuttgart, Germany) and injected into the capsular bag in the same way as for IOL implantation (Figure 2).
For the eyes that received an E-ring, specially designed 9.5-mm-long IOLs with a 5.0-mm acryl optic were used (Figure 1). In the 51 control eyes that did not receive an E-ring, soft or hard IOLs were used: 6 Alcon MA 30BA IOLs (soft, acryl + polymethylmethacrylate [PMMA], 3 piece; Alcon, Fort Worth, Texas), 1 Menicon ES23 IOL (hard, PMMA, 1 piece; Menicon, Nagoya, Japan), 32 Hoya VA55CB IOLs (soft, acryl + PMMA, 1 piece; Hoya Corporation, Tokyo, Japan), and 12 Hoya UV60SB IOLs (hard, PMMA, 1 piece; Hoya Corporation). All IOLs were implanted in the bag.
The principle of the surgical method was the same as reported previously.3 Anesthesia was achieved with instillation of several drops of oxybuprocaine hydrochloride, 0.4%. The cataract was removed by phacoemulsification through a 3.2-mm limbal incision. After meticulous removal of the cortex and polishing of the posterior capsule, the anterior chamber was filled with viscoelastic material and the E-ring was injected into the capsule through the injector. A soft IOL then was implanted into the capsular bag. Using forceps, the IOL loops were fixed into the inner groove of the E-ring under direct observation through an operating microscope. Finally, the viscoelastic material was removed. No sutures were placed. The eye patch was removed the next day. One of us, Tsutomu Hara, performed the procedure in the first 5 cases in group 1 and one of us, Takeshi Hara, performed the procedure in the rest of the cases. The mean (SD) surgical time (including positioning of the lid speculum) in group 1 was 22.4 (5.62) minutes (range, 14-34 minutes) in the E-ring eyes and 8.4 (2.59) minutes (range, 6-16 minutes) in the control eyes. In group 2, after the surgeon became adept at performing the procedure, the surgical time decreased to 13.7 (4.78) minutes (range, 7-21 minutes) in the E-ring eyes and increased to 11.5 (4.26) minutes (range, 7-21 minutes) in the control eyes. All surgeries were transmitted simultaneously to the patients' families in the observation room accompanied by a real-time explanation provided by the surgeon.8 The postoperative care was the same as reported previously.3 The eyes with an E-ring were treated with steroid uptake (methylprednisolone, 4 mg/tablet), 4 tablets/d for 2 days starting 1 day preoperatively, 6 tablets/d for the following 2 days, 4 tablets/d for 3 days, 2 tablets/d for 3 days, 1 tablet/d for 3 days, and then treatment was stopped. A total of 164 mg over 13 days was administered. During the preliminary trial, eye drops and oral nonsteroidal anti-inflammatory drugs were used, but the effect was less than that of a steroid.
The preoperative and postoperative examinations were the same as described previously.3 The PCO values, based on the Hayashi et al method9 (recorded in the central 1 mm and peripheral 2 to 3 mm from the pupillary center), were recorded preoperatively and 1 week, 1 month, and 1 and 2 years postoperatively. The PCO values were expressed on a scale ranging from 0 (clear) to 255 (cloudy).
The results from group 1 are shown in Table 1 and Table 2. The E-ring prevented PCO in most cases in this study. A typical case is shown in Figure 3.
Severe iritis developed postoperatively in 1 eye in group 1 that received a 9.0-mm ring, and the PCO value in the temporal area was 53.3. When this case was eliminated by the Smirnov-Grubbs test, the mean (SD) PCO values in the eyes with an E-ring centrally, nasally, and temporally were 4.4 (2.47), 2.0 (0.95), and 3.3 (5.75), respectively. The values in the control eyes were 11.4 (5.42), 25.5 (13.31), and 20.0 (10.11), respectively. The eyes with an E-ring had significantly lower values (P = .005; P = .001; and P = .001) (Figure 4).
No eye with an E-ring required Nd:YAG laser posterior capsulotomy throughout the follow-up period. In the group 1 control eyes, although Nd:YAG laser posterior capsulotomy was not required until 2 years postoperatively, 43% (6 of 14 eyes) required it by the end of the follow-up period. In the control eyes in group 2, 38% (14 of 37 eyes) required Nd:YAG laser posterior capsulotomy by 2 years postoperatively; a total of 45% (23 of 51 eyes) required it by 3 years postoperatively.
Figure 5 shows the rates of Nd:YAG laser posterior capsulotomy, which was performed when patients complained of visual disturbances and considerable PCO was observed during the slitlamp microscopy examination. Of the 23 control eyes that underwent Nd:YAG laser posterior capsulotomy, the mean (SD) postoperative best-corrected visual acuity was 1.2 (0.10), the mean (SD) value before capsulotomy was 0.6 (0.30), and that after capsulotomy was 1.1 (0.24), indicating that unnecessary capsulotomies were not performed.
The mean final VA in eyes with an E-ring was 1.1 (range, 0.3-1.2). Except for 1 eye, the VA was stable from 1 week to 2 years postoperatively.
As described previously, eye 8 in group 1 that received the 9.0-mm ring developed severe postoperative iritis with massive fibrin formation. The patient was a 69-year-old woman with mild diabetes mellitus (fasting blood glucose level, 143 mg/dL [to convert to millimoles per liter, multiply by 0.0555]). The iritis resolved with treatment with 30 mg/d of oral prednisolone by 1 month postoperatively and the prednisolone was stopped. Despite this complication, the posterior capsule remained clear and the final VA was 1.2. Besides this case, the eyes with an E-ring generally had a higher laser flare value than the control eyes 1 week to 1 month postoperatively. This difference disappeared at 1 year and did not affect the VA, intraocular pressure, or corneal endothelial cell density.
The current study proved that the E-ring almost completely prevented PCO. If the E-rings are used in all cataract surgeries, logically no posterior capsulotomy is required in all eyes. However, E-rings cannot be used for all cases. Thus, the indications and contraindications are described. One year after our first report on the closed E-ring,5 a slim open ring (as slim as conventional IOL loops) was reported to preserve the round shape of the capsular bag,10,11 and it is now widely used as a capsular tension ring. The E-ring, a square-edged, closed ring, prevents PCO but is Quiz Ref IDcontraindicated for eyes with disorders in the posterior capsule or Zinn ligaments because of its weight, which may cause dislocation of the ring or capsule with the ring inside. In contrast, the capsular tension ring preserves the integrity of capsules with disrupted posterior capsule or Zinn ligaments but has less ability to prevent PCO.12,13
Why is the E-ring so effective for preventing PCO? To analyze the mechanism and its significance, it is important to look back on the history of studies of PCO prevention. Posterior capsular opacification begins with the metamorphosed LECs under the anterior capsule, and PCO is only a result of the process. Many trials have been performed to remove the LECs intraoperatively.4,14 Because Kleinmann et al15 reported that the capsular bag can survive anatomically without the LECs, this seems to be a rational approach, but all trials failed. During actual clinical surgery, it is almost impossible to remove all LECs superiorly, and if any LECs remain, they transform into fibroblastlike cells,16 anterior capsular opacification occurs, and the subsequent PCO cannot be prevented. In addition, there is no chemical procedure to remove all LECs completely and safely. In 2010, Mamalis et al17 reported a method to remove most LECs using Nd:YAG laser. Further results are expected.
Trials were performed to prevent transformation of the LECs. The aqueous humor contains some inhibitory growth factors to prevent the transformation and subsequent proliferation of the LECs.18 A study was performed to maintain contact between fresh aqueous humor and the LECs and to maintain an ample endocapsular aqueous humor exchange.19 Nagamoto et al20 designed a special ring for this purpose.
In a study of lens refilling21,22 to restore accommodation, in which a flexible material was injected into the almost completely retained capsular bag after the cataract was removed through a 1.5-mm anterior capsular opening, PCO was a serious problem. Therefore, many trials to prevent capsular opacification were done during the study. When we observed the postoperative central anterior capsule in vivo by specular microscopy after removal of the cataract by the method mentioned previously, the LECs were preserved in a more normal shape and the capsules remained clear at the area where the anterior capsule was in close contact with the posterior capsule. However, when the PMMA IOL was inserted between these capsules, the LECs became mobile and both capsules were opacified.16 When the dual-optic accommodative IOL was placed in the almost retained capsular bag and the anterior and posterior capsules were pressed tightly from inside using PMMA optics, both capsules maintained their transparency but could not prevent massive proliferation from the compression-free equatorial area.23
To obtain more ideal compression from inside over a wide area, a silicone endocapsular balloon was inserted into the almost completely retained capsular bag and inflated. However, capsular opacification in the anterior and posterior capsules could not be prevented.24 In like manner, all trials failed.
To prevent PCO at the posterior capsule, many trials have been performed to test the IOL materials.25,26 The theory that the shape of the square edge is more important than the IOL materials has gained popularity, and the theory has gained acceptance with the current IOLs.12,18,27 Low PCO and Nd:YAG capsulotomy rates from 1.4% to 2.1% have been reported.27- 29 However, the results are not yet definitive; some studies also have reported that a sharp posterior optic edge is the main factor in preventing PCO.30 Several recent reports have stated that the fundamental difference in the effect of many square-edged IOLs is not due to the material but the grade of deviation from a perfect square.31,32 However, if the optic edge is perfectly square, it causes light scattering.33
Quiz Ref IDThe crucial point is that the E-ring is placed at the equator. If the same grade of the square is used, it has a greater effect in a narrow equator than in wide and flat posterior capsules. Without considering the optical disturbance, we can pursue the perfect square at the equator. In addition, in the E-ring, both the anterior and posterior square edges function evenly. However, if the ring is slim like the capsular tension ring, PCO cannot be prevented.6 Therefore, the current size of the E-ring seems optimum. Galand et al34 reported that the mean (SD) size of the capsular bag in 49 human cadaver eyes was 10.32 (0.42) mm (range, 9.37-11.12 mm). Nishi et al12 and Menapace et al13 designed an open endocapsular ring with a square edge to adjust for the different capsular sizes. Those investigators also confirmed the efficacy of the square-edged ring. In practice, the closed E-ring with the 9.5-mm diameter could be applied for all patients aged 19 to 80 years.
In eyes with an E-ring, the anterior and posterior capsules are separate and ample space is retained in the capsule. Therefore, sufficient endocapsular flow of the aqueous humor may be preserved. Consideration of capsulorrhexis size and IOL materials then becomes unnecessary. Because the posterior capsule remained transparent without touching the IOL optic in eyes with an E-ring, most IOL trials mentioned previously become unnecessary. Although the results of all previous trials of the anterior capsule, posterior capsule, and IOL structure are still far from satisfactory, the E-ring has resolved the final problem of preventing PCO almost completely.
Quiz Ref IDThe most frequent complication associated with the E-ring is increased anterior chamber flare. During the current study, we focused on clearing the posterior capsule by any means. Thus, the doses and the period of steroid uptake increased more than after standard cataract surgery. Mechanical irritation resulting from endocapsular ring rotation due to the smaller ring size (9.0 mm) was thought to be the cause. The 9.5-mm E-ring did not rotate, and although the increased flare was not suppressed completely, no iritis was seen during slitlamp examinations. The weight does not seem problematic, because the total weight of the 9.5-mm E-ring (23.6 mg) and IOL (10.6 mg) is 34.2 mg, which is much lighter than the 230 mg of the senile crystalline lens.35Quiz Ref IDThe results obtained with the 9.5-mm ring are better than those with the 9.0-mm ring.
In the current study, a steroid was used for 13 days, which, retrospectively, did not cause further complications. In patients with diabetes mellitus, no further general deterioration followed. In the future, while maintaining the 9.5-mm diameter, we will reduce the height and width of the ring. After that, there is a possibility to minimize the increased flare and subsequently the steroid dose. In a preliminary study, the 10.0-mm ring was tested; however, it was too large for practical use.
In eye 8, in which severe iritis developed, the final VA remained 1.2, which indicated that the ring independently prevented PCO regardless of inflammation. In 1980, Tano et al36 reported that steroid administration inhibited intravitreal growth of the fibroblasts. However, in the current case, steroid administration might not prevent PCO. In rabbit eyes, in which extensive postoperative capsular opacification usually occurs, the E-ring prohibited PCO without preoperative and postoperative local or general medication.6 In electron microscopic14,16,37 and immunohistochemical observations, including the in situ hybridization technique, the postoperative changes under the anterior capsule and equator were the same as during normal wound healing.38 Fagerholm et al39 reported the same concept earlier. If it is confirmed, postoperative PCO is not affected fundamentally by steroids.
In the future, a large disc lens with an ample square edge will be developed.40,41 However, implantation of such a disc lens through a small opening will be difficult. In addition, there will be attempts to combine the IOL and the E-ring. However, the benefits of separate E-rings and IOLs must be emphasized. If they are separate, postoperative IOL exchange becomes easy, which will promote its application for pediatric cataracts, cataract for high myopia in which the exact preoperative IOL power calculation is difficult, patient dissatisfaction with an implanted accommodative IOL, and the exact angle setting of the toric IOL.
Quiz Ref IDAlthough PCO currently is treated routinely by Nd:YAG laser posterior capsulotomy, complications, such as increased IOP, uveitis, cystoid macular edema,42 and reopening of a macular hole,43 have been reported. In addition, the overall expense for treating PCO is considerable.44 In any event, PCO could be prevented almost completely. Although reducing the steroid dose is a problem, the current study provides useful suggestions.
In 1979, Hoffer45 first introduced the idea of positioning a barrier at the posterior optic. After we began the current study, we found that Thomas Neuhan, MD, had patented the same idea. However, he had no plan to perform further experiments, and he encouraged us to go forward. We pay tribute to the foresight of these investigators.
Correspondence: Tsutomu Hara, MD, Nishi 1-1-11, Utsunomiya 320-0861, Japan (firstname.lastname@example.org).
Submitted for Publication: October 9, 2010; final revision received December 21, 2010; accepted December 21, 2010.
Published Online: March 14, 2011. doi:10.1001/archophthalmol.2011.38
Author Contributions: Tsutomu Hara had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Financial Disclosure: None reported.