From Vissum Corporation (Alió, Plaza-Puche); the Division of Ophthalmology, Universidad Miguel Hernández (Alió); and Departamento de Óptica, Farmacología y Anatomía, Universidad de Alicante (Piñero), Alicante, Spain.
Dr Alió is a clinical investigator for Oculentis GmbH. The remaining authors have no proprietary or commercial interest in the materials presented herein.
This study was supported in part by a grant from the Spanish Ministry of Health, Instituto Carlos III, Red Temática de Investigación Cooperativa en Salud “Patología ocular del envejecimiento, calidad visual y calidad de vida,” Subproyecto de Calidad Visual (RD07/0062).
Study concept and design (J.L.A., A.B.P.P., D.P.P.); data collection (J.L.A., A.B.P.P., D.P.P.); analysis and interpretation of data (D.P.P.); drafting of the manuscript (A.B.P.P., D.P.P.); critical revision of the manuscript (J.L.A.); obtained funding (J.L.A.); administrative, technical, or material support (J.L.A., A.B.P.P.); supervision (J.L.A., D.P.P.)
Correspondence: Jorge L. Alió, MD, PhD, Avda de Denia s/n, Edificio Vissum, 03016 Alicante, Spain. Tel: 34 90 233 3444; Fax: 34 96 516 0468; E-mail: email@example.com
A new concept of intraocular multifocality has been recently developed and introduced in clinical practice: refractive rotational asymmetry, in which a refractive sector is used for near vision add. Our research group has demonstrated that this type of intraocular lens (IOL) is able to successfully restore uncorrected near, intermediate, and distance visual acuity after cataract surgery.1,2 In a recent study, we found that the intraocular optical quality of eyes implanted with this type of IOL was affected by IOL tilt and decentration.1 A postulated reason for this finding was the IOL stability related to the haptic design. The use of capsular tension rings was proposed as a potential solution for this relative instability of the IOL within the capsular bag.1
Capsular tension rings have been shown to inhibit posterior capsular opacification,3 play a role in the stability and positioning of IOLs,4 and prevent IOL rotation and decentration caused by capsular bag contraction.5–7 Our research group found significantly lower amounts of intraocular optical aberrations in eyes implanted with a diffractive multifocal IOL using a capsular tension ring when compared to eyes implanted without its use.8
The aim of the current study was to ascertain whether the use of a capsular tension ring positively affects the refractive and visual outcomes as well as the intraocular optical quality of eyes implanted with the rotationally asymmetric multifocal Lentis Mplus LS-312 IOL (Oculentis GmbH, Berlin, Germany). In addition, optical factors that decrease retinal image quality, such as intraocular aberrations, and may lead to poorer visual outcomes were evaluated in cases with and without capsular tension ring.
Patients and Methods
This prospective, randomized, clinical trial included 90 eyes from 53 patients aged between 36 and 82 years. All patients underwent cataract surgery with implantation of the Lentis Mplus LS-312. Patients were assigned randomly using a random number sequence to one of the following two groups: no ring group, 43 eyes implanted with the IOL without using a capsular tension ring; or ring group, 47 eyes implanted with the IOL using a capsular tension ring.
Inclusion criteria were patients with visually significant cataract or presbyopic patients suitable for refractive lens exchange with refractive astigmatism ⩽3.00 diopters (D). Exclusion criteria were patients with any other ocular comorbidities, amblyopia, neuro-ophthalmic disease, and previous refractive corneal surgery. All patients were adequately informed and signed a consent form. The study adhered to the tenets of the Declaration of Helsinki and was approved by the local ethics committee.
Intraocular Lens and Capsular Tension Ring
The Lentis Mplus LS-312 is a rotationally asymmetric multifocal IOL containing an aspheric distance-vision zone combined with a 3.00-D posterior sector-shaped near-vision zone, which has been described previously.9
StabilEyes Capsular Tension Rings (Abbott Medical Optics, Santa Ana, California) were used in the current study. They are compression-molded Perspex CQ polymethylmethacrylate rings designed to ensure capsular bag stability and promote IOL centration. The same sizes were used in all cases: expanded diameter of 13 mm and compressed size of 11.0 mm.
All surgeries were performed by the same experienced surgeon (J.L.A.). Topical anesthesia was used in all cases and adequate dilation was obtained with intra-cameral mydriasis. The incision for the IOL implantation was placed on the steepest corneal meridian. Capsular tension ring injection into the capsular bag was performed before IOL implantation by means of a syringe-style micro inserter that was supplied with the capsular tension ring by the manufacturer (StabilEyes system). The Lentis Mplus IOL was then implanted using a specific injector (Viscoject 2.2 Cartridge-Set LP604240M, Oculentis GmbH), which was designed to enlarge the corneal incision (approximately 2.2 mm). The IOL was placed in the capsular bag with the two orientation marks indicating the limit of the segment for near vision at the 3- and 9-o’clock positions.1,10,11
Pre- and Postoperative Examinations
Distance visual acuity was measured with Snellen charts and near visual acuity with Radner Reading Charts (Spanish validated version)12 using a standard illumination of 500 lux; reading distance was 40 cm in all patients. All visual acuity values reported in this study are in monocular vision conditions. Other specific examinations performed included corneal topography (CSO; Costruzione Strumenti Oftalmici, Florence, Italy), ocular aberrometry (COAS; Wavefront Sciences Inc, Albuquerque, New Mexico), biometry (IOLMaster; Carl Zeiss Meditec, Jena, Germany), and contrast sensitivity (CST 1800; Vision Sciences Research Corp, Walnut Creek, California) under photopic (85 cd/m2) and low mesopic (3 cd/m2) conditions. For the IOL power calculation, the Hoffer Q and SRK/T formulae were used in both groups. The Hoffer Q formula was used when the eye axial length was ⩽22 mm, and the SRK/T formula was used when the eye axial length was >22 mm. The A-constant value of 118.5 was introduced for the calculations with the SRK/T formula and the personalized ACD (pACD) constant value of 4.97 was introduced for the calculations with the Hoffer Q formula. Target refraction was emmetropia in all patients.
Postoperatively, patients were evaluated 1 day, 1 month, and 3 months after surgery by an independent certified optometrist following the same investigational protocol. The postoperative examination protocol included the measurement of the ocular optical performance with the OQAS system (Optical Quality Analysis System; Visiometrics SL, Terrassa, Spain) and the calculation of the intraocular optical aberrations and Strehl ratio. Using the OQAS, the ocular point spread function (PSF) and modulation transfer function (MTF) can be obtained. All measurements were taken with a 5-mm pupil using phenylephrine 10% for dilation.
Intraocular optical quality was estimated calculating the intraocular optical aberrations from the total eye and anterior corneal aberration. Intraocular aberrations were calculated using Visual Optics Lab software (version 6.89; Sarver and Associates Inc, Celebration, Florida) by subtracting corneal aberrations from total ocular aberrations 3 months after surgery.
Aberration coefficients and root-mean-square (RMS) values were obtained and analyzed for 5-mm pupil diameters in all cases. Defocus curves were obtained at 3 months postoperatively. To generate defocus curves, the visual acuity was measured using Snellen charts at 4 m. The defocus curve was obtained in monocular vision and distance correction by adding plus lenses in 0.50-D steps and recording the visual acuity achieved by the patient with each type of blur. The same procedure was then repeated with negative lenses. All recorded information was presented in a two-dimensional graph using Cartesian coordinates (x-axis, spherical blur; y-axis, near visual acuity).
Statistical analysis was performed using SPSS statistics software package version 15.0 for Windows (SPSS, Chicago, Illinois). Normality of all data samples was evaluated by means of the Kolmogorov-Smirnov test. When parametric analysis was possible, the Student t test for paired data was performed for all parameter comparisons between pre- and postoperative examinations, and the Student t test for unpaired data was used for comparison between groups. When parametric analysis was not possible, the Wilcoxon Rank Sum test was applied to assess the significance of differences between pre- and postoperative data, whereas the Mann-Whitney test was used to compare the analyzed parameters between groups. For all statistical tests, the same level of significance was used (P<.05).
The main outcome measures of the study were corrected and uncorrected distance and near visual acuity, contrast sensitivity, and intraocular optical quality measured by the Strehl ratio and higher order aberrations.
Table 1 summarizes the preoperative demographics of eyes analyzed in the study. No statistically significant differences were found between groups in age, uncorrected distance visual acuity (UDVA), distance and near refraction, keratometry, axial length, anterior chamber depth, and power of the implanted IOL (unpaired Student t and Mann-Whitney tests, P>.09).
Table 1: Preoperative Demographics of Patients Who Underwent IOL Implantation With and Without Capsular Tension Rings
Visual and Refractive Outcomes
Visual outcomes are summarized in Table 2. A statistically significant improvement in UDVA and uncorrected near visual acuity (UNVA) was observed after surgery in both groups (Wilcoxon test, P<.01). No significant change in corrected distance visual acuity (CDVA) was observed in the ring group (Wilcoxon test, P=.16), whereas this change was statistically significant in the no ring group (Wilcoxon test, P<.01). Corrected near visual acuity (CNVA) did not change significantly in either group (Wilcoxon test, P⩾.12). Manifest cylinder was significantly reduced in both groups (Wilcoxon test, P⩽.03), whereas manifest sphere was only significantly reduced in the ring group (Wilcoxon test, P<.01).
Table 2: 3-month Postoperative Outcomes of Patients Who Underwent IOL Implantation With and Without Capsular Tension Ring
Defocus curves obtained in both groups presented similar configurations (Fig 1), although better mean values of visual acuity were obtained in the ring group in the range of defocus between 0 and −2.50 D, which includes intermediate vision. Furthermore, the difference in visual acuity between groups was statistically significant (Mann-Whitney test, P⩽.05) for defocus levels of −1.50, −1.00, and −0.50 D.
Figure 1. Mean defocus curves of the two groups of eyes analyzed: no ring group (green line), eyes implanted with the Lentis Mplus LS-312 multifocal IOL without a capsular tension ring (CTR); and ring group (gray line), eyes implanted with the Lentis Mplus LS-312 multifocal IOL using a CTR. *Statistically significant differences in visual acuity between groups for these defocus levels.
Contrast Sensitivity Outcomes
A trend toward better contrast sensitivity outcome was observed in the ring group, although differences between groups did not reach statistical significance (Fig 2). A difference between groups within or near the limit of statistical significance was found in photopic contrast sensitivity for the highest spatial frequencies (Mann-Whitney test, 12 cycles/degree [cpd], P=.06; 18 cpd, P=.05). No significant differences were found in photopic contrast sensitivity between groups for the lowest spatial frequencies (Mann-Whitney test, 3 cpd and 6 cpd, P⩾.11, respectively). Under scotopic conditions, no statistically significant differences were detected between groups for any spatial frequency (Mann-Whitney test, P⩾.11)
(see Fig 2).
Figure 2. Mean contrast sensitivity function under photopic (85 cd/m2) and mesopic low conditions (3 cd/m2) in the two groups of eyes analyzed: no ring group (green line), eyes implanted with the Lentis Mplus LS-312 multifocal IOL without a capsular tension ring (CTR), and ring group (gray line), eyes implanted with the Lentis Mplus LS-312 multifocal IOL with a CTR.
Optical Quality Outcomes
The mean ocular Strehl ratio was similar in both groups (no ring group, 0.10±0.05; ring group, 0.11±0.04) (unpaired Student t test, P=.61). No statistically significant differences were found between groups in the mean cut-off spatial frequency for the ocular MTF (unpaired Student t test, P=.65; no ring group, 15.85±8.06; ring group, 15.56±8.05).
No statistically significant differences were found between groups for any aberrometric coefficient (unpaired Student t and Mann Whitney tests, P⩾.09) (Fig 3). No statistically significant differences were found between groups for intraocular Strehl ratio (unpaired Student t test, P=.96; no ring group, 0.30±0.04; ring group, 0.30±0.05). The mean values of intraocular higher order RMS in both groups were consistent with those found by ocular aberrometry (Mann-Whitney test, P=.32; no ring group, 0.89±0.39; ring group, 1.00±0.14).
Figure 3. Postoperative intraocular aberrations calculated by means of the VOL-CT software (no ring group, green bars; ring group, gray bars): root-mean-square (RMS) values and standard deviation of total, higher order (HO), tilt, spherical-like, and coma-like aberrations. In addition, primary spherical aberration (PSA) is reported with its sign. CTR = capsular tension ring, SSA = secondary spherical aberration
Figure A (available as supplemental material in the PDF version of this article) is a comparative diagram of the intraocular optical quality for a 5.0-mm pupil in two cases implanted with the Lentis Mplus IOL, one with and one without a capsular tension ring.
A significant improvement in UDVA was achieved after IOL implantation in both groups. These results meet cataract surgery expectations and confirm the safety of cataract surgery with the evaluated IOL. Regarding subjective preoperative refraction, significant changes were detected. Manifest cylinder was reduced in both groups, but manifest sphere was only significantly reduced in eyes in the ring group. These findings should be considered with caution because the subjective refraction in cataractous patients is not always reliable.13–16 When postoperative refraction was compared between groups, a statistically significant difference was found in manifest sphere, with a trend towards more positive values in the ring group, compared to spherical equivalent refraction near emmetropia in the ring group. This suggests that the behavior of the IOL within the capsular bag with and without a capsular tension ring is different. Regarding contrast sensitivity, differences were noted between groups within or near the limit of statistical significance for photopic contrast sensitivity associated with the spatial frequencies of 12 and 18 cpd, with the best outcome for those patients implanted with a capsular tension ring. This could be a consequence of the different optical behavior of the evaluated IOL when implanted in combination with a capsular tension ring. It should be considered that contrast sensitivity for high spatial frequencies is normally affected when optical defects are present in the eye.17
No significant differences were detected between groups in UNVA. Postoperative distance-corrected and corrected near visual acuity were excellent in both groups, with no significant differences between groups. This indicates the good performance of this type of IOL for near vision. However, significant differences were found in the addition power required for near, with a significantly lower value for those eyes implanted with the capsular tension ring, suggesting that better predictability of near refraction may be obtained by implanting the evaluated IOL in combination with a capsular tension ring.
As shown in the defocus curve, a wide range of good near vision was observed in both groups, including intermediate vision performance (75 cm). This is consistent with our previous findings reported with this IOL.1,18 One additional finding was the significant difference in intermediate visual acuity (measured by the defocus curve profile in the range of defocus between 0 and −2.50 D) between groups (defocus levels of −1.50, −1.00, and −0.50 D), with better outcomes in eyes implanted with the IOL in combination with a capsular tension ring. These better intermediate visual outcomes as well as the better refractive predictability with a capsular tension ring suggest that the use of this device promotes improved IOL stabilization in the capsular bag and hence a better intraocular optical performance of the multifocal IOL.
Mean ocular Strehl ratio and cut-off MTF spatial frequencies obtained in both groups were similar to those values found in young healthy eyes and higher than those found in older patients.14 No significant differences in the parameters obtained with the OQAS were detected between the evaluated groups.
Analysis of the postoperative intraocular optical aberrations revealed the presence of intraocular primary coma in both groups, with a trend toward a higher magnitude of this aberration in eyes without capsular tension rings, although such differences did not reach statistical significance. Pupil-dilating eye drops might be a confounding factor. The geometry of the multifocal IOL evaluated leads to the induction of different levels of primary coma depending of the magnitude of the geometrical asymmetry.19 Nanavaty et al20 demonstrated that the vertical coma present in the eye after implantation of a spherical IOL has a positive effect on the near visual acuity, enhancing the depth of focus. Therefore, this geometry-inducing vertical coma seems to be one of the factors contributing to the great depth of focus obtained with this IOL, as has been demonstrated by the defocus curve. This finding is, however, not new. In a previous study, we reported the positive influence of a capsular tension ring on the visual, refractive, and intraocular optical performance with a plate haptic multifocal diffractive IOL.8 Such positive influence is in concordance with other studies4,5,7 that demonstrated the contribution of a capsular tension ring to IOL stability. It seems reasonable to consider that sophisticated optics such as those of multifocal IOLs have a positive influence on optical, refractive, and visual performance by the improvement in IOL stability provided by the capsular tension ring. The present study contributes to this evidence and further supports the use of capsular tension rings with different models of multifocal IOLs. Regarding the C-loop IOL model studied in this investigation, the Lentis Mplus LS-312, the haptic design is not effective in stabilizing this IOL. No significant differences were detected between groups regarding intraocular tilt, with both groups presenting large amounts of this aberration. This suggests that although the capsular tension ring can prevent IOL instability within the capsular bag in some cases, the evaluated IOL can still become tilted and decentered in a number of cases. A new model of this rotationally asymmetric multifocal IOL has been released recently with a plate design to allow more effective control of IOL tilt.
The rotationally asymmetric multifocal Lentis Mplus LS-312 C-loop IOL provides a wide range of focus in pseudophakic eyes, allowing restoration of near, intermediate, and distance vision. When implanted in combination with a capsular tension ring, significantly better intermediate visual outcomes as well as different refractive predictability are obtained with this IOL, suggesting different intraocular optical behavior related to IOL stability. Despite the use of a capsular tension ring, this IOL can be affected by some degree of tilt, which suggests that a different haptic design may be more adequate to stabilize the IOL within the capsular bag. Future studies are necessary to confirm the better positional stability of this IOL with a new plate haptic design. The present study further supports the use of capsular tension rings in combination with multifocal IOLs to improve and promote more stable refractive and visual outcomes.
- Alió JL, Piñero DP, Plaza-Puche AB, Rodriguez Chan MJ. Visual outcomes and optical performance of a monofocal intraocular lens and a new-generation multifocal intraocular lens. J Cataract Refract Surg. 2011;37(2):241–250. doi:10.1016/j.jcrs.2010.08.043 [CrossRef]
- Alió JL, Plaza-Puche AB, Javaloy J, Ayala MJ, Moreno LJ, Piñero DP. Comparison of a new refractive multifocal intraocular lens with an inferior segmental near add and a diffractive multifocal IOL. Ophthalmology. 2012;119(3):555–563. doi:10.1016/j.ophtha.2011.08.036 [CrossRef]
- Kim JH, Kim H, Joo CK. The effect of capsular tension ring on posterior capsular opacity in cataract surgery. Korean J Ophthalmol. 2005;19(1):23–28. doi:10.3341/kjo.2005.19.1.23 [CrossRef]
- Lee DH, Lee HY, Lee KH, Chung KH, Joo CK. Effect of a capsular tension ring on the shape of the capsular bag and opening and the intraocular lens. J Cataract Refract Surg. 2001;27(3):452–456. doi:10.1016/S0886-3350(00)00610-6 [CrossRef]
- Rohart C, Gatinel D. Influence of a capsular tension ring on ocular aberrations after cataract surgery: a comparative study. J Refract Surg. 2009;25(1 Suppl):S116–S121.
- Sun R. Functions of the capsular tension ring. J Cataract Refract Surg. 2007;33(1):4. doi:10.1016/j.jcrs.2006.08.050 [CrossRef]
- Lee DH, Shin SC, Joo CK. Effect of a capsular tension ring on intraocular lens decentration and tilting after cataract surgery. J Cataract Refract Surg. 2002;28(5):843–846. doi:10.1016/S0886-3350(01)01174-9 [CrossRef]
- Alió JL, ElKady B, Ortiz D, Bernabeu G. Microincision multifocal intraocular lens with and without a capsular tension ring: optical quality and clinical outcomes. J Cataract Refract Surg. 2008;34(9):1468–1475. doi:10.1016/j.jcrs.2008.05.042 [CrossRef]
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- Nanavaty MA, Spalton DJ, Marshall J. Effect of intraocular lens asphericity on vertical coma aberration. J Cataract Refract Surg. 2010;36(2):215–221. doi:10.1016/j.jcrs.2009.08.024 [CrossRef]
Preoperative Demographics of Patients Who Underwent IOL Implantation With and Without Capsular Tension Rings
|No Ring Group
||62.68±12.44 (36 to 82)
||60.59±7.77 (48 to 82)
||0.81±0.41 (0.01 to 2.00)
||0.67±0.53 (0.00 to 2.00)
||+0.50±2.41 (−4.88 to 4.88)
||+1.40±2.87 (−7.25 to 7.00)
||0.12±0.16 (0.00 to 0.70)
||0.05±0.10 (0.00 to 0.44)
||0.67±0.45 (0.00 to 1.22)
||0.82±0.33 (0.22 to 1.40)
|Near addition (D)
||2.33±0.87 (0.00 to 3.00)
||2.53±0.38 (1.75 to 3.00)
||0.15±0.16 (0.00 to 0.70)
||0.08±0.12 (0.00 to 0.40)
3-month Postoperative Outcomes of Patients Who Underwent IOL Implantation With and Without Capsular Tension Ring
||Mean±Standard Deviation (Range)
|No Ring Group
||0.15±0.21 (0.00 to 1.00)
||0.19±0.28 (−0.02 to 1.30)
||−0.01±0.64 (−3.00 to +1.25)
||+0.16±1.01 (−3.25 to +1.25)
||0.45±0.71 (0.00 to 3.25)
||0.53±0.46 (0.00 to 1.75)
||−0.23±0.75 (−3.25 to 0.75)
||−0.10±1.06 (−3.88 to −1.25)
||0.05±0.10 (0.00 to 0.52)
||0.02±0.06 (−0.08 to 0.30)
||0.21±0.17 (0.00 to 0.90)
||0.22±0.16 (0.00 to 0.52)
||0.23±0.21 (0.00 to 0.70)
||0.15±0.12 (0.00 to 0.52)
|Near addition (D)
||0.96±0.73 (0.00 to 2.50)
||0.55±0.62 (0.00 to 2.00)
||0.09±0.13 (0.00 to 0.70)
||0.10±0.10 (0.00 to 0.40)