- Email: [email protected]
Scleral fixation technique using a hydrophobic foldable intraocular lens with ring-shaped connecting bridges
TECHNIQUE
Scleral fixation technique using a hydrophobic foldable intraocular lens with ring-shaped connecting bridges Seungsoo Rho, MD, Won Kyung Song, MD, PhD, Youngje Sung, MD, Hee Jung Kwon, MD, Helen Lew, MD, PhD
We introduce a new method of scleral fixation using a hydrophobic foldable intraocular lens (IOL) with ring-shaped connecting bridges. A double-armed 10-0 polypropylene suturing needle is inserted using the routine ab externo technique. The midportion of the thread is pulled out through a main wound and cut. Using another 10-0 polypropylene needle, the IOL is sutured at both inner ring-shaped connecting bridges (inner shorter rim). The ring-shaped connecting-bridges IOL was carefully injected using the IOL cartridge with gentle pulling out of the thread. The externalized sutures were tied at the corresponding sites. All ties between 2 cut threads were performed using a European death knot. A scleral fixation outcome with the ring-shaped connecting-bridges IOL was similar to a poly(methyl methacrylate) IOL outcome; however, the surgeon should consider the possibility of a postoperative myopic shift. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2015; 41:262–267 Q 2015 ASCRS and ESCRS Online Video
The scleral fixation technique is an essential method for all intraocular surgeons. Scleral fixation is usually performed for complicated cataract operations, aphakia, intraocular lens (IOL) decentration, or severe ocular trauma. Since Malbran et al.1 first reported using an IOL transscleral fixation technique in an aphakic patient, the technique has been modified to reduce complications and improve outcomes.2–4 Previous reports using hydrophilic foldable IOLs show outcomes comparable to those using poly-
(methyl methacrylate) (PMMA) IOLs.5 However, foldable IOLs may present difficulties in IOL centration6 or develop glistenings and undergo opacification.7–12 In 2012, a hydrophobic foldable IOL with ring-shaped connecting bridges (Figure 1, A) between the haptic and the optic (enVista MX60, Bausch & Lomb) became available. Its design allows the surgeon to use the ringshaped connecting bridges for new fixation suture sites. We introduce a new scleral fixation technique with a ring-shaped connecting-bridge IOL and compare the early clinical efficacy and safety with those of a PMMA IOL after a mathematical evaluation of the suture site.
Submitted: June 11, 2014. Final revision submitted: August 19, 2014. Accepted: August 22, 2014.
SURGICAL TECHNIQUE
From the Department of Ophthalmology, CHA Bundang Medical Center, CHA University, Seongnam, South Korea. Corresponding author: Seungsoo Rho, MD, Department of Ophthalmology, CHA Bundang Medical Center, CHA University, 59 Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-712, South Korea. E-mail: [email protected].
262
Q 2015 ASCRS and ESCRS Published by Elsevier Inc.
Before IOL transscleral fixation, an anterior vitrectomy is performed. Triangle-shaped scleral flaps are made at the 8 o'clock and 2 o'clock positions in a right eye or at the 4 o'clock and 10 o'clock positions in a left eye (Video 1, available at: http://jcrsjournal.org). A double-armed 10-0 polypropylene suturing needle is inserted into the globe through the 8 o'clock sclera and anchored by a 24-gauge needle that is passed http://dx.doi.org/10.1016/j.jcrs.2014.12.034 0886-3350
TECHNIQUE: SCLERAL FIXATION OF IOLS WITH RING-SHAPED CONNECTING BRIDGES
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Figure 1. Three possible suture sites on the IOL with ring-shaped connecting bridges. A: Each ring-shaped connecting bridge (black asterisks) has 2 connecting rims (inner and outer). B: Site 1 is 2.0 mm proximal to the haptic tip. C: Site 2 is at the outer rim of the ring-shaped connecting bridge. D: Site 3 is at the inner rim of the ring-shaped connecting bridge.
through the 2 o'clock sclera using the routine ab externo technique (insertion site 2.0 mm ventral to the limbus anterior margin). The mid-portion of the thread is pulled out through a main wound at the 11 o'clock position and then cut. Using another double-armed 10-0 polypropylene needle, the ringshaped connecting-bridge IOL is sutured at both inner ring-shaped connecting bridges (inner shorter rim, Figure 1, D). This suture site is selected to conform to the mathematical calculations of the center-of-mass
concept described below (Figure 2). A thread at the leading ring-shaped connecting bridge is passed through the IOL cartridge and the injector and then tied with the cut thread originating from the 8 o'clock sclera. The ring-shaped connecting-bridge IOL is carefully injected with gentle pulling of the thread at the 8 o'clock position. The thread at the following ring-shaped connecting bridge should remain outside the globe until it is tied to the other fixation thread from the 2 o'clock site (Figure 3, A). The externalized
Figure 2. Monochromatic illustrations of an IOL with ring-shaped connecting bridges and available suture sites. A: Half an IOL with ring-shaped connecting bridges. B: Center of mass within a haptic (black asterisk). C: Center of mass within half an optic (white asterisk). D: Center of mass within a half ring-shaped connecting-bridge IOL (white ring). Note that position 3 (➂) is the closest potential suture site to the center of mass of half a ring-shaped connecting-bridge IOL, among the 3 possible suture sites (➀, ➁, and ➂).
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TECHNIQUE: SCLERAL FIXATION OF IOLS WITH RING-SHAPED CONNECTING BRIDGES
sutures are tied at the corresponding sites. All ties between 2 cut threads are made using a European death knot (Figure 3, B). This is done by laying the 2 ends of the threads together, pointing in the same direction. The overhand knot is made in both threads at the same time. The knot is pulled tight, leaving long tails. The main corneal wounds are 2.8 mm and 6.0 mm, respectively, when using the ring-shaped connectingbridge IOL and a PMMA IOL (CZ70BD, Alcon Laboratories, Inc.). Results This technique was performed in 25 eyes of 25 patients. All patients were followed for at least 3 postoperative months. Transscleral fixation of PMMA IOLs were performed between January 2011 and December 2012; ring-shaped connecting-bridge IOL surgeries were performed after December 2012. In patients with complicated cataract surgery, including posterior capsule rupture or zonular weakness, conversion to extracapsular cataract extraction with anterior vitrectomy was performed before the transscleral fixation. In aphakic patients, anterior vitrectomy was performed before the fixation. In patients with subluxated lenses or IOLs, lensectomy or IOL removal was performed with concomitant anterior vitrectomy. In all cases, additional pars plana vitrectomy was performed, if necessary, at the surgeon's discretion. The total patient population and subgroup preoperative demographics are shown in Table 1 and the preoperative and postoperative values in Table 2. Evaluation of the Optimum Suture Site The ring-shaped connecting-bridge IOL has 2 connecting bridges, 1 on each side between the haptic
and the optic, and there are 3 possible suture sites for fixation (Figure 1; Video 2, available at: http:// jcrsjournal.org). The first is at the haptic that is 2.0 mm proximal from the haptic tip (site 1, Figure 1, B). The second and third suture sites are located, respectively, on the inner (position 2, Figure 1, C) and outer (position 3, Figure 1, D) sides of the ring-shaped connecting bridges. Position 1 is similar to the traditional suture site; it is closest to the scleral fixation site anatomically. However, a lot of pressure is transmitted to the optic, haptic, and ring-shaped connecting bridges so the IOL can easily be tilted even under moderate strain. Although using position 2 produces good results under low-level strain, the IOL is rotated by relatively large pressures because the threadpulling vector is slightly outside the midline of the center of mass, causing counterclockwise rotation. Using position 3, which is along the midline of the center of mass, results in a stable IOL even under large strain levels. The center of mass is the unique site at which the weighted relative position of the distributed mass sums equals zero. To identify the center of mass, the half portion of the ring-shaped connectingbridge IOL is divided into 2 regions; ie, a half optic and a haptic (Figure 2, A to C). Using ImageJ software (National Institutes of Health), the relative weight of each piece was calculated with a random multiple (a half optic Z 4.402; a haptic Z 1.199). The centroid of the haptic (a curved line) can be calculated by the equation below: yZ
ð r sin a Þ Z 0:90r a
where r is the radius, a is the angle of the curved line, and y is the distance from the center of curvature (Figure 2, B [black asterisk]).
Figure 3. A: An external view of thread positioning during surgery. Note that the following thread of the IOL (➀) should be outside the globe until the second knot has been completed with the thread from the 2 o'clock position (➁). B: The European death knot. C: Comparison of suture attachment sites and pathways for implanting PMMA IOLs (orange dotted line) versus IOLs with ring-shaped connecting bridges (yellow line). The red arrow indicates the scleral fixation site that is 2.0 mm ventral to the limbus anterior margin. J CATARACT REFRACT SURG - VOL 41, FEBRUARY 2015
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TECHNIQUE: SCLERAL FIXATION OF IOLS WITH RING-SHAPED CONNECTING BRIDGES
Table 1. Patient demographics. Demographic
PMMA IOL (n Z 11)
RCB IOL (n Z 14)
P Value*
Total (N Z 25)
55.45 G 8.87 91 0.33 G 0.43 18.10 G 4.63 1.27 G 4.69
61.86 G 13.37 79 0.12 G 0.20 17.00 G 6.47 4.30 G 7.51
.134 .609 .727 .709 .505
59.04 G 11.84 84 0.21 G 0.33 17.46 G 5.69 2.78 G 6.35
5 (46) 3 (27) 1 (9) 2 (18)
4 (29) 4 (29) 2 (14) 4 (29)
NA NA NA NA
9 (36) 7 (28) 3 (12) 6 (24)
5 (46) 2 (18) 3 (27) 1 (9) 0 0
8 (57) 2 (14) 2 (14) 0 1 (7) 1 (7)
NA NA NA NA NA NA
13 (52) 4 (16) 5 (20) 1 (4) 1 (4) 1 (4)
7 (64) 0 4 (36) 0
7 (50) 1 (7) 5 (36) 1 (7)
NA NA NA NA
14 (56) 1 (4) 9 (36) 1 (4)
Mean age (y) G SD Male sex (%) Mean preop CDVA (Snellen) G SD Mean preop IOP (mm Hg) G SD Mean preop SE (D) G SD Cause, n (%) Aphakic Lens dislocation IOL dislocation Complicated cataract Accompanying disease, n (%) None Glaucoma Retinal detachment (RD) Corneal laceration Glaucoma C RD Cyclodialysis cleft Concomitant surgery, n (%) None Ahmed valve implant Total vitrectomy Cyclopexy
CDVA Z corrected distance visual acuity; ECC Z endothelial cell count; IOL Z intraocular lens; IOP Z intraocular pressure; NA Z not applicable; PMMA Z poly(methyl methacrylate); RCB Z ring-shaped connecting bridge; SE Z spherical equivalent of the refractive errors *Mann-Whitney test and Wilcoxon signed-rank test (between PMMA and RCB IOL groups)
The centroid of the half optic (a half circle) can be calculated by yZ
4r Z 0:42441r 3p
DISCUSSION
where r is the radius and y is the distance from the center of curvature) (Figure 2, C [white asterisk]). The center of mass in each half of the ring-shaped connecting-bridge IOL can be computed using measures of weight and distance and presuming that the IOL has an even thickness. The center of mass (Xc) for any number of bodies of mass (eg, m1, m2) having distances 1, 2 is found by the formula Xc Z
half IOL, so it was used as the suture site in the surgeries evaluated in this study.
m1 1 þ m2 2þ m1 þ m2 þ
As a result, the center of mass in each half piece of the IOL is proximally a quarter of the distance from the center of mass of the half optic on the straight line connecting the center of mass in a haptic and in a half optic (Xc j 2.58, Figure 2, D [white ring]). These calculations showed that position 3 was the nearest of the 3 potential suture sites to the center of mass of a
We can summarize modern secondary IOL implantation methods by 4 critical factors: The IOLs used must be foldable so the surgeon does not have to widen the wound for implantation, the technique can be easily performed, the technique results in good IOL centration, and IOLs should be made of a suitable material that resists opacification and clinically important glistenings.7–12 The ring-shaped connecting-bridge IOL fulfills these requirements. The mean refractory difference after scleral fixation with the ring-shaped connecting-bridge IOL was approximately 0.68 D; however, the refractory difference after scleral fixation with the PMMA IOL was smaller (0.01 D). We believe the myopic shift associated with using a ring-shaped connectingbridge IOL is primarily due to the fixation site at the sclera (ie, 2.0 mm ventral to the limbus anterior margin). Although the fixation distances of the 2 groups are similar, the anterior pulling vector is slightly more prominent with the ring-shaped
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Table 2. Preoperative and 1-month postoperative data in PMMA group and RCB IOL group. Measurement UDVA (Snellen) CDVA (Snellen) Preop Postop PostopPreop ECC (cells/mm2) Preop Postop PostopPreop IOP (mm Hg) Preop Postop PostopPreop SE (D) Preop GD Postop SE Postop SEPreop GD Complications, n (%) None Vitreous hemorrhage
PMMA IOL (n Z 11)
RCB IOL (n Z 14)
P Value*
Total (N Z 25)
0.36 G 0.31
0.42 G 0.27
.519
0.39 G 0.29
0.33 G 0.43 0.61 G 0.11 0.28 G 0.42
0.12 G 0.20 0.51 G 0.09 0.39 G 0.31
.727 .536 .373
0.21 G 0.33 0.55 G 0.36 0.34 G 0.36
2536.4 G 724.6 1876.3 G 279.0 382.5 G 209.5
2570.4 G 843.2 1927.7 G 886.5 183.0 G 22.27
.186 .857 .114
2556.6 G 778.9 1898.3 G 549.2 297.0 G 69.2
18.10 G 4.63 17.36 G 5.01 0.91 G 9.16
17.00 G 6.47 13.14 G 5.10 3.86 G 9.30
.709 .038 .434
17.46 G 5.69 15.00 G 5.42 1.76 G 9.36
0.33 G 0.05 0.34 G 0.72 0.01 G 0.65
0.17 G 0.06 0.90 G 0.88 0.68 G 0.95
.029 .180 .059
0.24 G 0.21 0.65 G 0.84 0.37 G 0.88
10 (91) 1 (9)
13 (93) 1 (7)
NA NA
23 (92) 2 (8)
CDVA Z corrected distance visual acuity; ECC Z endothelial cell count; GD Z goal diopter; IOL Z intraocular lens; IOP Z intraocular pressure; NA Z not applicable; PMMA Z poly(methyl methacrylate); RCB Z ring-shaped connecting bridge; SE Z spherical equivalent of the refractive errors; UDVA Z uncorrected distance visual acuity Data shown as means G SD except for complications. *Mann-Whitney test (between PMMA and RCB IOL groups)
connecting-bridge IOL (Figure 3, C). The PMMA IOL is also harder and more resistant to the pulling vector, and the hydrophobic acrylic ring-shaped connecting-bridge IOL may be less resistant to the same amount of force. On the contrary, Park and Lee6 suggest that long and rigid PMMA haptics might compress the ciliary tissue, the IOL might tilt, and eventually the distal portion of the haptics might be posteriorly displaced. However, the outcome of scleral fixation using PMMA IOLs in our patients was excellent and the diopter goal and preoperative SE was minimal. Throughout the entire procedure, we used only 1 type of knotting technique, the European death knot, to attach the threads together. The European death knot is well known for canyoneering and is very secure when the 2 threads are of the same material. This knot was tight enough to pass through a scleral tunnel as well as the pathway from the sulcus to the scleral flap site. In all the cases, we thought that other knot types, such as the Fisherman's knot or double figure-8 knot, were unnecessary and that the European death knot was a sufficient and especially simple knot for our purpose.
The greatest advantage of the hydrophobic ringshaped connecting-bridge IOL for scleral fixation is that it eliminates issues of IOL positioning, such as postoperative IOL rotation and decentration. Suturing at the haptic midpoint is vulnerable to rotating forces for 2 reasons: (1) Of the 3 possible suture sites, the haptic suture site is positioned farthest from its center of mass. This makes the IOL susceptible to tilting by any kind of external force; eg, gravity or tension from the thread (Video 2, available at: http://jcrs journal.org). This is similar to having less control of a baseball bat when it is held long versus the increased stability gained by holding it short. (2) We cannot be absolutely sure of the relative positions of the 2 corresponding haptics. Discordance between the 2 positions might cause IOL tilting or decentration due to IOL deformity.13 The conventional method (suturing at the haptic) is usually promising but could produce a gap between the haptic and the sulcus area, leading to IOL tilting in a rare case of ciliary body atrophy. Using hydrophobic ring-shaped connecting-bridge IOLs for scleral fixation is very safe, and outcomes are comparable to the outcomes using PMMA IOLs. However, one should consider the possibility of
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myopic shift, and it is necessary to adjust the preoperative diopter goal. WHAT WAS KNOWN Modern scleral fixation requires 4 critical elements: a foldable IOL, easy technique, good IOL position, and suitable IOL material. Most previously used foldable IOLs were made of hydrophilic material, which can be vulnerable to IOL opacification or to IOL tilting in terms of material and shape. WHAT THIS PAPER ADDS The hydrophobic foldable IOL with ring-shaped connecting bridges allowed surgeons to fixate the IOL more firmly without IOL tilting and to be free of IOL opacification issues. The suture site at the IOL (inner rim of the ring-shaped connecting bridges) was determined using a theory of physics. This method meets the 4 critical conditions of a modern scleral fixation technique. Surgeons should be aware of a possible myopic shift.
REFERENCES 1. Malbran ES, Malbran E Jr, Negri I. Lens guide suture for transport and fixation in secondary IOL implantation after intracapsular extraction. Int Ophthalmol 1986; 9:151–160 2. Kokame GT, Yamamoto I, Mandel H. Scleral fixation of dislocated posterior chamber intraocular lenses; temporary haptic externalization through a clear corneal incision. J Cataract Refract Surg 2004; 30:1049–1056 3. Gabor SGB, Pavlidis MM. Sutureless intrascleral posterior chamber intraocular lens fixation. J Cataract Refract Surg 2007; 33:1851–1854
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4. Taskapili M, Gulkilik G, Engin G, Kocabora MS, Yilmazli C, Ozsutcu M, Kucukasahin H. Transscleral fixation of a single-piece hydrophilic foldable acrylic intraocular lens. Can J Ophthalmol 2007; 42:256–261 5. Taskapili M, Gulkilik G, Kocabora MS, Ozsutcu M, Yilmazli C, Kaya G, Kucuksahin H. Comparison of sulcus implantation of single-piece hydrophilic foldable acrylic and polymethylmethacrylate intraocular lenses in eyes with posterior capsule tear during phacoemulsification surgery. Eur J Ophthalmol 2007; 17:595–600. Available at: http://medlib.yu.ac.kr/eur_j_oph/ejo_ pdf/2007_17_595-600.pdf. Accessed September 23, 2014 6. Park CH, Lee SJ. Suture fixation technique for a single-piece foldable closed-loop intraocular lens. Korean J Ophthalmol 2008; 22:205–209. Available at: http://www.ncbi.nlm.nih.gov/ pmc/articles/PMC2629918/pdf/kjo-22-205.pdf. Accessed September 23, 2014 7. Lim AKE, Goh PP, Azura R, Mariam I. Opacification of AcriFlex 50CSE hydrophilic acrylic intraocular lenses. J Cataract Refract Surg 2011; 37:655–659 8. Park CY, Chuck RS. Reversible opacification of hydrophilic acrylic intraocular lens. J Cataract Refract Surg 2012; 38:166–169 9. Neuhann IM, Neuhann TF, Szurman P, Koemer S, Rohrback JM, Bartz-Schimidt K-U. Clinicopathological correlation of 3 patterns of calcification in a hydrophilic acrylic intraocular lens. J Cataract Refract Surg 2009; 35:593–597 10. Lee SJ, Choi JH, Sun HJ, Choi KS, Jung GY. Surface calcification of hydrophilic acrylic intraocular lens related to inflammatory membrane formation after combined vitrectomy and cataract surgery. J Cataract Refract Surg 2010; 36:676–681 11. Werner L, Apple DJ, Kaskaloglu M, Pandey SK. Dense opacification of the optical component of a hydrophilic acrylic intraocular lens; a clinicopathological analysis of 9 explanted lenses. J Cataract Refract Surg 2001; 27:1485–1492 12. Park DI, Ha SW, Park SB, Lew H. Hydrophilic acrylic intraocular lens optic opacification in a diabetic patient. Jpn J Ophthalmol 2011; 55:595–599 13. Oshika T, Sugita G, Miyata K, Tokunaga T, Samejima T, Okamoto C, Ishii Y. Influence of tilt and decentration of scleralsutured intraocular lens on ocular higher-order wavefront aberration. Br J Ophthalmol 2007; 91:185–188. Available at: http:// www.ncbi.nlm.nih.gov/pmc/articles/PMC1857623/pdf/185.pdf. Accessed September 23, 2014
J CATARACT REFRACT SURG - VOL 41, FEBRUARY 2015
Scleral fixation technique using a hydrophobic foldable intraocular lens with ring-shaped connecting bridges Seungsoo Rho, MD, Won Kyung Song, MD, PhD, Youngje Sung, MD, Hee Jung Kwon, MD, Helen Lew, MD, PhD
We introduce a new method of scleral fixation using a hydrophobic foldable intraocular lens (IOL) with ring-shaped connecting bridges. A double-armed 10-0 polypropylene suturing needle is inserted using the routine ab externo technique. The midportion of the thread is pulled out through a main wound and cut. Using another 10-0 polypropylene needle, the IOL is sutured at both inner ring-shaped connecting bridges (inner shorter rim). The ring-shaped connecting-bridges IOL was carefully injected using the IOL cartridge with gentle pulling out of the thread. The externalized sutures were tied at the corresponding sites. All ties between 2 cut threads were performed using a European death knot. A scleral fixation outcome with the ring-shaped connecting-bridges IOL was similar to a poly(methyl methacrylate) IOL outcome; however, the surgeon should consider the possibility of a postoperative myopic shift. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2015; 41:262–267 Q 2015 ASCRS and ESCRS Online Video
The scleral fixation technique is an essential method for all intraocular surgeons. Scleral fixation is usually performed for complicated cataract operations, aphakia, intraocular lens (IOL) decentration, or severe ocular trauma. Since Malbran et al.1 first reported using an IOL transscleral fixation technique in an aphakic patient, the technique has been modified to reduce complications and improve outcomes.2–4 Previous reports using hydrophilic foldable IOLs show outcomes comparable to those using poly-
(methyl methacrylate) (PMMA) IOLs.5 However, foldable IOLs may present difficulties in IOL centration6 or develop glistenings and undergo opacification.7–12 In 2012, a hydrophobic foldable IOL with ring-shaped connecting bridges (Figure 1, A) between the haptic and the optic (enVista MX60, Bausch & Lomb) became available. Its design allows the surgeon to use the ringshaped connecting bridges for new fixation suture sites. We introduce a new scleral fixation technique with a ring-shaped connecting-bridge IOL and compare the early clinical efficacy and safety with those of a PMMA IOL after a mathematical evaluation of the suture site.
Submitted: June 11, 2014. Final revision submitted: August 19, 2014. Accepted: August 22, 2014.
SURGICAL TECHNIQUE
From the Department of Ophthalmology, CHA Bundang Medical Center, CHA University, Seongnam, South Korea. Corresponding author: Seungsoo Rho, MD, Department of Ophthalmology, CHA Bundang Medical Center, CHA University, 59 Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-712, South Korea. E-mail: [email protected].
262
Q 2015 ASCRS and ESCRS Published by Elsevier Inc.
Before IOL transscleral fixation, an anterior vitrectomy is performed. Triangle-shaped scleral flaps are made at the 8 o'clock and 2 o'clock positions in a right eye or at the 4 o'clock and 10 o'clock positions in a left eye (Video 1, available at: http://jcrsjournal.org). A double-armed 10-0 polypropylene suturing needle is inserted into the globe through the 8 o'clock sclera and anchored by a 24-gauge needle that is passed http://dx.doi.org/10.1016/j.jcrs.2014.12.034 0886-3350
TECHNIQUE: SCLERAL FIXATION OF IOLS WITH RING-SHAPED CONNECTING BRIDGES
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Figure 1. Three possible suture sites on the IOL with ring-shaped connecting bridges. A: Each ring-shaped connecting bridge (black asterisks) has 2 connecting rims (inner and outer). B: Site 1 is 2.0 mm proximal to the haptic tip. C: Site 2 is at the outer rim of the ring-shaped connecting bridge. D: Site 3 is at the inner rim of the ring-shaped connecting bridge.
through the 2 o'clock sclera using the routine ab externo technique (insertion site 2.0 mm ventral to the limbus anterior margin). The mid-portion of the thread is pulled out through a main wound at the 11 o'clock position and then cut. Using another double-armed 10-0 polypropylene needle, the ringshaped connecting-bridge IOL is sutured at both inner ring-shaped connecting bridges (inner shorter rim, Figure 1, D). This suture site is selected to conform to the mathematical calculations of the center-of-mass
concept described below (Figure 2). A thread at the leading ring-shaped connecting bridge is passed through the IOL cartridge and the injector and then tied with the cut thread originating from the 8 o'clock sclera. The ring-shaped connecting-bridge IOL is carefully injected with gentle pulling of the thread at the 8 o'clock position. The thread at the following ring-shaped connecting bridge should remain outside the globe until it is tied to the other fixation thread from the 2 o'clock site (Figure 3, A). The externalized
Figure 2. Monochromatic illustrations of an IOL with ring-shaped connecting bridges and available suture sites. A: Half an IOL with ring-shaped connecting bridges. B: Center of mass within a haptic (black asterisk). C: Center of mass within half an optic (white asterisk). D: Center of mass within a half ring-shaped connecting-bridge IOL (white ring). Note that position 3 (➂) is the closest potential suture site to the center of mass of half a ring-shaped connecting-bridge IOL, among the 3 possible suture sites (➀, ➁, and ➂).
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sutures are tied at the corresponding sites. All ties between 2 cut threads are made using a European death knot (Figure 3, B). This is done by laying the 2 ends of the threads together, pointing in the same direction. The overhand knot is made in both threads at the same time. The knot is pulled tight, leaving long tails. The main corneal wounds are 2.8 mm and 6.0 mm, respectively, when using the ring-shaped connectingbridge IOL and a PMMA IOL (CZ70BD, Alcon Laboratories, Inc.). Results This technique was performed in 25 eyes of 25 patients. All patients were followed for at least 3 postoperative months. Transscleral fixation of PMMA IOLs were performed between January 2011 and December 2012; ring-shaped connecting-bridge IOL surgeries were performed after December 2012. In patients with complicated cataract surgery, including posterior capsule rupture or zonular weakness, conversion to extracapsular cataract extraction with anterior vitrectomy was performed before the transscleral fixation. In aphakic patients, anterior vitrectomy was performed before the fixation. In patients with subluxated lenses or IOLs, lensectomy or IOL removal was performed with concomitant anterior vitrectomy. In all cases, additional pars plana vitrectomy was performed, if necessary, at the surgeon's discretion. The total patient population and subgroup preoperative demographics are shown in Table 1 and the preoperative and postoperative values in Table 2. Evaluation of the Optimum Suture Site The ring-shaped connecting-bridge IOL has 2 connecting bridges, 1 on each side between the haptic
and the optic, and there are 3 possible suture sites for fixation (Figure 1; Video 2, available at: http:// jcrsjournal.org). The first is at the haptic that is 2.0 mm proximal from the haptic tip (site 1, Figure 1, B). The second and third suture sites are located, respectively, on the inner (position 2, Figure 1, C) and outer (position 3, Figure 1, D) sides of the ring-shaped connecting bridges. Position 1 is similar to the traditional suture site; it is closest to the scleral fixation site anatomically. However, a lot of pressure is transmitted to the optic, haptic, and ring-shaped connecting bridges so the IOL can easily be tilted even under moderate strain. Although using position 2 produces good results under low-level strain, the IOL is rotated by relatively large pressures because the threadpulling vector is slightly outside the midline of the center of mass, causing counterclockwise rotation. Using position 3, which is along the midline of the center of mass, results in a stable IOL even under large strain levels. The center of mass is the unique site at which the weighted relative position of the distributed mass sums equals zero. To identify the center of mass, the half portion of the ring-shaped connectingbridge IOL is divided into 2 regions; ie, a half optic and a haptic (Figure 2, A to C). Using ImageJ software (National Institutes of Health), the relative weight of each piece was calculated with a random multiple (a half optic Z 4.402; a haptic Z 1.199). The centroid of the haptic (a curved line) can be calculated by the equation below: yZ
ð r sin a Þ Z 0:90r a
where r is the radius, a is the angle of the curved line, and y is the distance from the center of curvature (Figure 2, B [black asterisk]).
Figure 3. A: An external view of thread positioning during surgery. Note that the following thread of the IOL (➀) should be outside the globe until the second knot has been completed with the thread from the 2 o'clock position (➁). B: The European death knot. C: Comparison of suture attachment sites and pathways for implanting PMMA IOLs (orange dotted line) versus IOLs with ring-shaped connecting bridges (yellow line). The red arrow indicates the scleral fixation site that is 2.0 mm ventral to the limbus anterior margin. J CATARACT REFRACT SURG - VOL 41, FEBRUARY 2015
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TECHNIQUE: SCLERAL FIXATION OF IOLS WITH RING-SHAPED CONNECTING BRIDGES
Table 1. Patient demographics. Demographic
PMMA IOL (n Z 11)
RCB IOL (n Z 14)
P Value*
Total (N Z 25)
55.45 G 8.87 91 0.33 G 0.43 18.10 G 4.63 1.27 G 4.69
61.86 G 13.37 79 0.12 G 0.20 17.00 G 6.47 4.30 G 7.51
.134 .609 .727 .709 .505
59.04 G 11.84 84 0.21 G 0.33 17.46 G 5.69 2.78 G 6.35
5 (46) 3 (27) 1 (9) 2 (18)
4 (29) 4 (29) 2 (14) 4 (29)
NA NA NA NA
9 (36) 7 (28) 3 (12) 6 (24)
5 (46) 2 (18) 3 (27) 1 (9) 0 0
8 (57) 2 (14) 2 (14) 0 1 (7) 1 (7)
NA NA NA NA NA NA
13 (52) 4 (16) 5 (20) 1 (4) 1 (4) 1 (4)
7 (64) 0 4 (36) 0
7 (50) 1 (7) 5 (36) 1 (7)
NA NA NA NA
14 (56) 1 (4) 9 (36) 1 (4)
Mean age (y) G SD Male sex (%) Mean preop CDVA (Snellen) G SD Mean preop IOP (mm Hg) G SD Mean preop SE (D) G SD Cause, n (%) Aphakic Lens dislocation IOL dislocation Complicated cataract Accompanying disease, n (%) None Glaucoma Retinal detachment (RD) Corneal laceration Glaucoma C RD Cyclodialysis cleft Concomitant surgery, n (%) None Ahmed valve implant Total vitrectomy Cyclopexy
CDVA Z corrected distance visual acuity; ECC Z endothelial cell count; IOL Z intraocular lens; IOP Z intraocular pressure; NA Z not applicable; PMMA Z poly(methyl methacrylate); RCB Z ring-shaped connecting bridge; SE Z spherical equivalent of the refractive errors *Mann-Whitney test and Wilcoxon signed-rank test (between PMMA and RCB IOL groups)
The centroid of the half optic (a half circle) can be calculated by yZ
4r Z 0:42441r 3p
DISCUSSION
where r is the radius and y is the distance from the center of curvature) (Figure 2, C [white asterisk]). The center of mass in each half of the ring-shaped connecting-bridge IOL can be computed using measures of weight and distance and presuming that the IOL has an even thickness. The center of mass (Xc) for any number of bodies of mass (eg, m1, m2) having distances 1, 2 is found by the formula Xc Z
half IOL, so it was used as the suture site in the surgeries evaluated in this study.
m1 1 þ m2 2þ m1 þ m2 þ
As a result, the center of mass in each half piece of the IOL is proximally a quarter of the distance from the center of mass of the half optic on the straight line connecting the center of mass in a haptic and in a half optic (Xc j 2.58, Figure 2, D [white ring]). These calculations showed that position 3 was the nearest of the 3 potential suture sites to the center of mass of a
We can summarize modern secondary IOL implantation methods by 4 critical factors: The IOLs used must be foldable so the surgeon does not have to widen the wound for implantation, the technique can be easily performed, the technique results in good IOL centration, and IOLs should be made of a suitable material that resists opacification and clinically important glistenings.7–12 The ring-shaped connecting-bridge IOL fulfills these requirements. The mean refractory difference after scleral fixation with the ring-shaped connecting-bridge IOL was approximately 0.68 D; however, the refractory difference after scleral fixation with the PMMA IOL was smaller (0.01 D). We believe the myopic shift associated with using a ring-shaped connectingbridge IOL is primarily due to the fixation site at the sclera (ie, 2.0 mm ventral to the limbus anterior margin). Although the fixation distances of the 2 groups are similar, the anterior pulling vector is slightly more prominent with the ring-shaped
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Table 2. Preoperative and 1-month postoperative data in PMMA group and RCB IOL group. Measurement UDVA (Snellen) CDVA (Snellen) Preop Postop PostopPreop ECC (cells/mm2) Preop Postop PostopPreop IOP (mm Hg) Preop Postop PostopPreop SE (D) Preop GD Postop SE Postop SEPreop GD Complications, n (%) None Vitreous hemorrhage
PMMA IOL (n Z 11)
RCB IOL (n Z 14)
P Value*
Total (N Z 25)
0.36 G 0.31
0.42 G 0.27
.519
0.39 G 0.29
0.33 G 0.43 0.61 G 0.11 0.28 G 0.42
0.12 G 0.20 0.51 G 0.09 0.39 G 0.31
.727 .536 .373
0.21 G 0.33 0.55 G 0.36 0.34 G 0.36
2536.4 G 724.6 1876.3 G 279.0 382.5 G 209.5
2570.4 G 843.2 1927.7 G 886.5 183.0 G 22.27
.186 .857 .114
2556.6 G 778.9 1898.3 G 549.2 297.0 G 69.2
18.10 G 4.63 17.36 G 5.01 0.91 G 9.16
17.00 G 6.47 13.14 G 5.10 3.86 G 9.30
.709 .038 .434
17.46 G 5.69 15.00 G 5.42 1.76 G 9.36
0.33 G 0.05 0.34 G 0.72 0.01 G 0.65
0.17 G 0.06 0.90 G 0.88 0.68 G 0.95
.029 .180 .059
0.24 G 0.21 0.65 G 0.84 0.37 G 0.88
10 (91) 1 (9)
13 (93) 1 (7)
NA NA
23 (92) 2 (8)
CDVA Z corrected distance visual acuity; ECC Z endothelial cell count; GD Z goal diopter; IOL Z intraocular lens; IOP Z intraocular pressure; NA Z not applicable; PMMA Z poly(methyl methacrylate); RCB Z ring-shaped connecting bridge; SE Z spherical equivalent of the refractive errors; UDVA Z uncorrected distance visual acuity Data shown as means G SD except for complications. *Mann-Whitney test (between PMMA and RCB IOL groups)
connecting-bridge IOL (Figure 3, C). The PMMA IOL is also harder and more resistant to the pulling vector, and the hydrophobic acrylic ring-shaped connecting-bridge IOL may be less resistant to the same amount of force. On the contrary, Park and Lee6 suggest that long and rigid PMMA haptics might compress the ciliary tissue, the IOL might tilt, and eventually the distal portion of the haptics might be posteriorly displaced. However, the outcome of scleral fixation using PMMA IOLs in our patients was excellent and the diopter goal and preoperative SE was minimal. Throughout the entire procedure, we used only 1 type of knotting technique, the European death knot, to attach the threads together. The European death knot is well known for canyoneering and is very secure when the 2 threads are of the same material. This knot was tight enough to pass through a scleral tunnel as well as the pathway from the sulcus to the scleral flap site. In all the cases, we thought that other knot types, such as the Fisherman's knot or double figure-8 knot, were unnecessary and that the European death knot was a sufficient and especially simple knot for our purpose.
The greatest advantage of the hydrophobic ringshaped connecting-bridge IOL for scleral fixation is that it eliminates issues of IOL positioning, such as postoperative IOL rotation and decentration. Suturing at the haptic midpoint is vulnerable to rotating forces for 2 reasons: (1) Of the 3 possible suture sites, the haptic suture site is positioned farthest from its center of mass. This makes the IOL susceptible to tilting by any kind of external force; eg, gravity or tension from the thread (Video 2, available at: http://jcrs journal.org). This is similar to having less control of a baseball bat when it is held long versus the increased stability gained by holding it short. (2) We cannot be absolutely sure of the relative positions of the 2 corresponding haptics. Discordance between the 2 positions might cause IOL tilting or decentration due to IOL deformity.13 The conventional method (suturing at the haptic) is usually promising but could produce a gap between the haptic and the sulcus area, leading to IOL tilting in a rare case of ciliary body atrophy. Using hydrophobic ring-shaped connecting-bridge IOLs for scleral fixation is very safe, and outcomes are comparable to the outcomes using PMMA IOLs. However, one should consider the possibility of
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myopic shift, and it is necessary to adjust the preoperative diopter goal. WHAT WAS KNOWN Modern scleral fixation requires 4 critical elements: a foldable IOL, easy technique, good IOL position, and suitable IOL material. Most previously used foldable IOLs were made of hydrophilic material, which can be vulnerable to IOL opacification or to IOL tilting in terms of material and shape. WHAT THIS PAPER ADDS The hydrophobic foldable IOL with ring-shaped connecting bridges allowed surgeons to fixate the IOL more firmly without IOL tilting and to be free of IOL opacification issues. The suture site at the IOL (inner rim of the ring-shaped connecting bridges) was determined using a theory of physics. This method meets the 4 critical conditions of a modern scleral fixation technique. Surgeons should be aware of a possible myopic shift.
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