ARTICLE
Clinical outcomes and rotational stability of a 4-haptic toric intraocular lens in myopic eyes Rita Mencucci, MD, Eleonora Favuzza, MD, Francesca Guerra, MD, Giovanni Giacomelli, MD, Ugo Menchini, MD
PURPOSE: To evaluate the refractive outcomes and rotational stability of a 4-haptic toric intraocular lens (IOL) in myopic eyes and the correlations between IOL rotation and refractive sphere, axial length (AL), and white-to-white (WTW) diameter. SETTING: Eye Clinic, Careggi Hospital, Florence, Italy. DESIGN: Prospective case series. METHODS: Phacoemulsification cataract extraction and implantation of an AT Torbi 709M IOL were performed. Corneal astigmatism was 1.50 diopters (D) or greater and the AL between 25.0 mm and 27.0 mm in all eyes. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, and IOL axis were evaluated preoperatively and postoperatively up to 6 months. RESULTS: The study enrolled 20 eyes (20 patients). The UDVA and CDVA improved significantly postoperatively (P < .001). The mean refractive spherical equivalent decreased significantly from 7.10 D G 1.78 (SD) preoperatively to 0.55 G 0.25 D 1 day postoperatively (P < .001) and remained stable thereafter. Vector analysis showed that 90% and 85% of the eyes were within G0.25 D for J0 and J45, respectively. At 3 months and 6 months, the mean IOL rotation was 2.66 G 1.53 degrees and 3.00 G 1.69 degrees, respectively (P < .001), with 95% of eyes and 90% of eyes, respectively, within G5 degrees. A positive correlation was found between IOL rotation and preoperative sphere; none was found with AL and WTW. CONCLUSIONS: Implantation of the 4-haptic toric IOL in myopic eyes was effective and safe. The IOL showed no significant rotation over the 6-month follow-up. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2014; 40:1479–1487 Q 2014 ASCRS and ESCRS
Today, cataract surgery aims not only to replace the opacified crystalline lens with an intraocular lens (IOL) but also to improve the patient's refractive status. Refractive errors are extremely common, with approximately 40% of the population older than 20 years having myopia and 35% having astigmatism.1 Various toric IOLs that correct both sphere and cylinder have been developed and are available to surgeons to reduce patients' spectacle dependence and improve their quality of life.2 A common complication of toric IOLs is postoperative rotation.3,4 Intraocular lens stability and the absence of rotation are essential for the effectiveness of toric IOLs. It has been shown that every degree of off-axis rotation results in a loss of up to 3.3% of the
Q 2014 ASCRS and ESCRS Published by Elsevier Inc.
IOL's cylindrical power. If the IOL rotates by more than 30 degrees, the cylinder correction from the IOL is completely lost.3 During the first few days after surgery, and before the natural healing of the capsular bag occurs, there is an increased risk for IOL rotation. Parameters affecting the risk primarily include an IOL surface with a low coefficient of friction,5 the design of the IOL,6 an overall length of the IOL that is too small for the capsular bag,3 and instability of the anterior chamber. As with any type of bag-fixated IOL, late postoperative rotation can also occur; however, the mechanism is different. Late IOL rotation (that occurring after 3 months) is principally associated with the compressive forces of delayed capsule fibrosis.7
0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2013.12.024
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Myopic eyes, which are commonly longer than average,8 tend to have a bigger capsular bag than emmetropic eyes.9 Thus, these eyes could be at greater risk for early IOL rotation. The capsular bag diameter varies from 10.3 mm to 10.8 mm10,11 and is difficult to directly measure preoperatively. However, the axial length (AL) and white-to-white (WTW) corneal diameter are routinely measured preoperatively during standard biometry examinations. The AL has been shown to be a good indicator of postoperative capsular bag diameter.12 In addition, the WTW distance has been found to be positively correlated to the anterior chamber depth (ACD) in myopic eyes.13 There is still, however, opposing evidence regarding the possible correlation between the AL and IOL rotation. Results in some studies support this correlation,14,15 while others fail to establish a link.16,17 Also, little is known about a possible relationship between the WTW distance and IOL rotation. The purpose of this prospective study was to evaluate the overall refractive correction and rotational stability of the AT Torbi 709M toric IOL (Carl Zeiss Meditec AG) in a series of myopic eyes with cataract and a corneal astigmatism greater than 1.50 diopters (D). In addition, the study analyzed the potential correlations between IOL rotation and preoperative sphere, AL, and WTW distance. PATIENTS AND METHODS This prospective noncomparative study included eyes that had phacoemulsification and implantation of a toric IOL at Careggi Hospital, Florence, Italy, and were consecutively enrolled between April 2011 and January 2012. The study followed the tenets of the Declaration of Helsinki. Before being enrolled, patients satisfying the inclusion criteria were given a thorough explanation of the procedure, the risks, and the potential complications. All patients provided written informed consent. Institutional review board or ethics committee approval was not required for the study. The inclusion criteria were clinically significant cataract (minimum grade II on the Lens Opacities Classification System III18), an AL between 25.0 mm and 27.0 mm, and astigmatism on corneal topography of 1.50 D or greater. Exclusion criteria were previous ocular surgery, systemic and ocular anomalies or pathologies that could reduce visual function or postoperative IOL stability (eg, pathologic
Submitted: September 10, 2013. Final revision submitted: November 28, 2013. Accepted: December 8, 2013. From the Eye Clinic, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy. Corresponding author: Rita Mencucci, MD, Department of Surgery and Translational Medicine, Eye Clinic, Largo Brambilla 3, 50134 Florence, Italy. E-mail: [email protected].
myopia, amblyopia, glaucoma, macular degeneration, corneal edema, corneal dystrophy, irregular astigmatism, pseudoexfoliation syndrome), and unsuitable for adequate follow-up.
Surgical Technique The same experienced surgeon (R.M.) performed all surgeries using topical corneal anesthesia, a standard clear corneal incision, and phacoemulsification. Before surgery, with the patient seated, the cornea was marked by placing 2 limbal points along the principal meridian (0 to 180 degrees) with a Nuijts toric reference marker (American Surgical Instruments Corp.). Intraoperatively, a second marking was performed before phacoemulsification with a Mendez ring combined with the Bores intraoperative axial marker (American Surgical Instruments Corp.) to confirm the optimum axis for the toric IOL. Phacoemulsification was performed through a 2.2 mm single-plane sutureless temporal microincision. After a continuous curvilinear capsulorhexis of approximately 5.5 mm was created and hydrodissection performed, the cataract was removed by phacoemulsification using a stop-and-chop technique (Infiniti, Alcon Laboratories Inc.). The toric IOL was subsequently implanted in the capsular bag using a Viscoject injector (Medicel AG) and sodium hyaluronate 3.0%–chondroitin sulfate 4.0% with sodium hyaluronate 1.0% (Duovisc). Calculations of the IOL sphere and cylinder powers were determined before surgery using the IOL manufacturer's online calculator.A The IOL was rotated into a position approximately 10 degrees short of the marked axis before the residual ophthalmic viscosurgical device was removed from behind the IOL and from the anterior chamber. Last, the IOL was rotated to align the axis lines on the IOL with the marked corneal steep meridian. In all cases, the postoperative treatment comprised a topical antibiotic, corticosteroid eyedrops, and nonsteroidal antiinflammatory drug eyedrops.
Intraocular Lens The IOL used in this study, the AT Torbi 709M, is 1 piece, hydrophilic acrylic, monofocal, aspheric, and bitoric. It is foldable and has a 25% water content and hydrophobic surface properties. The IOL has a supporting 4-haptic design with no angulation, a biconvex 6.0 mm optic, and an overall diameter of 11.0 mm.
Preoperative and Postoperative Examinations All preoperative and postoperative assessments were performed by 2 experienced ophthalmologists (R.M., E.F.). Preoperatively, all patients had a full ophthalmologic examination including biometry measurements (eg, AL, ACD, WTW) using partial coherence interferometry (IOLMaster, Carl Zeiss Meditec AG), assessment of monocular logMAR uncorrected (UDVA) and corrected (CDVA) distance visual acuities (Early Treatment of Diabetic Retinopathy Study chart), and manifest refractive evaluation of sphere and cylinder. In addition to the preoperative IOL calculation, the predicted postoperative refraction was estimated with a factor for surgically induced astigmatism (SIA) of 0.50 D at the incision axis. Postoperative examinations were performed at 1 day, 3 months, and 6 months. The UDVA and CDVA were recorded at 3 months and 6 months. Postoperative refraction, residual cylinder, and toric IOL axis alignment were
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measured at each follow-up visit. The toric IOL axis was measured postoperatively using a superimposed protractor and digital image-analysis software (Photoshop 7.0, Adobe Systems, Inc.) and a modification of Shah et al.’s method.19 At the 1-day examination, a slitlamp image of the IOL was taken after pupil dilation, a prominent episcleral vessel was identified, and the axis between the vessel and the center of the IOL was drawn. In the 3-month and 6-month images, this axis was used to determine the horizontal axis. To obtain reproducibility, care was taken to minimize the effect of head movements by keeping the same angle between the episcleral vessel and the horizontal axis in all the subsequent postoperative images. All measurements were performed in triplicate.
Astigmatism Analysis Astigmatism analysis was performed using the power vector analysis method described by Thibos and Horner.20 The analysis included the calculation of M, J0, J45, and B. The M value is the spherical equivalent (SE) of the refractive error, and J0 and J45 are 2 Jackson cross cylinders equivalent to the conventional cylinder at an axis of 0 degree and 45 degrees, respectively. The M, J0, and J45 values represent the coordinates of a point in a 3-dimensional space, and B is the length from that point to the origin. It thus represents a power vector defined as the geometric representation of the spherocylindrical refractive errors in 3 orthogonal independent dioptric components (M, J0, and J45). The B value is the length of the vector and a measure of the overall blurring strength of the spherocylindrical refractive error. Manifest refractions were converted to power vector coordinates and overall blurring strength according to the following formulas: M Z S þ C=2 J0 Z ðC=2Þcosð2aÞ J45 Z ðC=2Þsinð2aÞ BZ
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi M2 þ J02 þ J452
where S is the spherical power, C is the cylindrical power, and a is the cylinder axis.
Statistical Analysis Statistical analysis was performed using Excel software (Microsoft Corp.) and Minitab software (version 15, Minitab, Inc.). The results are presented as the mean, standard deviation (SD), and range (minimum, maximum). Normality of all data samples was first checked using the Anderson-Darling
test. The significance of the difference between the preoperative data and postoperative data was then assessed. When parametric analysis was appropriate, the Student t test for paired data was performed. When parametric analysis was not possible, a 1-sample Wilcoxon signed-rank test was applied. A P value lower than 0.05 was considered statistically significant. Correlation coefficients (Spearman test) were used to determine the correlation between variables.
RESULTS The study included 20 eyes of 20 patients. The mean age of the 5 men (25%) and 15 women (75%) was 67.45 G 5.65 years (range 60 to 76 years). The IOL was implanted in the right eye in 13 patients (65%) and in the left eye in 7 patients (35%). Table 1 shows the baseline AL, WTW, and ACD as well as the spherical and cylindrical powers of the IOL. Figure 1 shows the AL distribution. Visual Acuity and Refraction Table 2 shows the visual acuity and refractive results over time. The UDVA and CDVA improved significantly after surgery (P ! .001). After 3 months, the UDVA and CDVA remained stable (Figure 2). At the last follow-up visit, all eyes had a CDVA of better than 0.10 logMAR. The UDVA was better than 0.15 logMAR in all eyes and 0.10 logMAR or better in 15 eyes (75%). The decrease in SE was statistically significant between preoperatively and 1 day postoperatively and between preoperatively and 6 months postoperatively (P ! .001). The changes between 1 day and 6 months were not statistically significant. The mean predicted SE was 0.44 G 0.16 D (range 0.78 to 0.17 D). The mean difference between the predicted and measured postoperative SE after 1 day was 0.11 D and the difference was within G0.50 D in all eyes. After 6 months, 17 eyes (85%) had an SE within G1.00 D and 6 (30%) were within G 0.50 D. Table 3 shows the vector analysis results. The vector components J0 and J45 decreased immediately after the surgery, although the changes did not reach statistical significance (P Z .654 and P Z .541, respectively). The results were close to the optimum value of zero throughout the study. Six months postoperatively, the vector values were within G0.25 D in 18 eyes
Table 1. Baseline characteristics (N Z 20). IOL Power (D) Value Mean G SD Range
AL (mm)
WTW (mm)
ACD (mm)
Spherical
Cylindrical
26.11 G 0.68 25.03, 27.00
11.84 G 0.18 11.50, 12.10
3.40 G 0.26 3.00, 3.80
11.88 G 2.22 8.50, 16.00
2.65 G 0.83 1.50, 5.00
ACD Z anterior chamber depth; AL Z axial length; IOL Z intraocular lens; WTW Z white-to-white diameter
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surgery and 18 (90%) were within G5 degrees after 6 months. All eyes were within G10 degrees throughout the follow-up. The mean absolute rotation 3 months and 6 months postoperatively was 2.66 G 1.53 degrees (range 0.70 to 6.00 degrees) and 3.00 G 1.69 degrees (range 0.90 to 6.50 degrees), respectively. This difference was statistically significant (P ! .001). The rotation at 6 months was counterclockwise in 11 patients (55%) and clockwise in 9 patients (45%). No correlation was found between the IOL rotation at 3 or 6 months and the AL (r Z 0.268, P Z .254 and r Z 0.226, P Z .337, respectively) or the WTW diameter (r Z 0.286, P Z .221 and r Z 0.302, P Z 0.195, respectively). There was, however, a statistically significant correlation between the IOL rotation at 3 months and 6 months and the preoperative sphere value (r Z 0.532, P Z .016 and r Z 0.557, P Z .011, respectively) (Figure 4). The negative Spearman coefficient value indicated a negative correlation between the spherical power and IOL rotation.
Figure 1. Axial length distribution. The 3 zones represent the definition commonly accepted for normal (up to 24.5 mm), long (from 24.5 to 26.0 mm), and very long (from 26.0 mm) eyes.24,25
(90%) for J0 and in 17 eyes (85%) for J45. Figure 3 shows the change in SIA using a 2-dimensional vector (J0, J45). The origin of the graphs represents an eye free of astigmatism. Postoperatively up to 6 months, the cluster of points is consistently concentrated around the origin, showing that the astigmatism was corrected in most cases. There was a statistically significant decrease in the B value immediately after surgery (between preoperatively and 1 day postoperatively) (P ! .001). The increase in the B value between 1 day and 3 months postoperatively was statistically significant (P Z .011).
Complications No eye-threatening complication was observed during the follow-up. No patient required IOL repositioning due to misalignment. In addition, no posterior capsule opacification was observed, and no eye required a neodymium:YAG capsulotomy.
DISCUSSION Intraocular Lens Rotation
Astigmatism and myopia are among the most common refractive errors of patients with cataract. Achieving emmetropia in these patients has become
Of the 20 eyes included in the study, 19 (95%) were within G5 degrees of the operative axis 3 months after
Table 2. Visual acuity and preoperative and postoperative manifest refractions (N Z 20). Postoperative Parameter UDVA (logMAR) Mean G SD Range CDVA (logMAR) Mean G SD Range Sphere (D) Mean G SD Range Cylinder (D) Mean G SD Range
Preoperative
1 Day
3 Months
6 Months
1.31 G 0.23 1.70, 1.00
d d
0.09 G 0.04* 0.02, 0.15
0.09 G 0.04 0.02, 0.15
0.61 G 0.20 1.00, 0.35
d d
0.04 G 0.03* 0.00, 0.10
0.04 G 0.03 0.00, 0.07
5.93 G 1.67 10.00, 3.50
0.41 G 0.26* 0.75, 0.25
0.43 G 0.22 0.75, 0.00
0.43 G 0.22 0.75, 0.00
2.35 G 0.59 3.50, 1.50
0.28 G 0.14* 0.50, 0.00
0.61 G 0.31* 1.25, 0.00
0.53 G 0.32† 1.25, 0.00
CDVA Z corrected distance visual acuity; UDVA Z uncorrected distance visual acuity *P ! .005 compared with the previous visit † P ! .05 compared with the previous visit
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Figure 2. The UDVA and CDVA over time (*** Z P ! .005; CDVA Z corrected distance visual acuity; UDVA Z uncorrected distance visual acuity).
possible since the development and regular use of toric IOLs and the evolution of astigmatically neutral corneal incisions. The performance of toric IOLs is nonetheless extremely dependent on correct alignment in the eye at the time of the surgery and in particular on the absence of rotation in the early postoperative period. The capsular bag healing process takes place progressively after removal of the crystalline lens. It is normally complete within 1 month after surgery.21 During this time, the IOL is loosely supported by the haptics and is at higher risk for rotation. Depending on the design of the IOL,21 the formation of capsule fibrosis, and other biomechanical changes,22 closure of the bag can occur asymmetrically, creating a risk for IOL decentration and rotation.
There is still an open debate about the ideal design for a toric IOL. Patel et al.17 found that plate-haptic IOLs had a tendency to be less stable than open-loop haptic IOLs in the early postoperative period (within 2 weeks after surgery), whereas the plate-haptic platform tended to rotate less than the loop haptic in the late postoperative period (between 2 weeks and 3 months). Prinz et al.23 found that the greatest rotation occurred within the first week postoperatively with both IOL types, with a slightly higher tendency toward rotation for the plate-haptic IOL than for the loop-haptic IOL. However, they found very good rotational stability for both IOL types within 1 year postoperatively, with no significant difference. Myopic eyes with large capsular bags require extra attention because the risk for early rotation of the IOL is greater. It is generally considered that eyes with an AL between 24.5 mm and 26.0 mm are long (ie, have moderate myopia) and that eyes with an AL greater than 26.0 mm are very long (ie, have high myopia).24,25 According to this classification, 60% of eyes in our study had high myopia and 40% had moderate myopia. To our knowledge, this study is the first to evaluate the effectiveness and the safety of a toric IOL in long to very long eyes (corresponding to moderate to high axial myopia). In this series, the CDVA and UDVA improved significantly after surgery. The UDVA was better than 0.30 logMAR in all eyes and 0.10 logMAR or better in 75% of eyes at the last follow-up. These results were similar to or better than most values published in studies of the same IOL or equivalent IOLs. In a study by Bascaran et al.,14 88.1% of eyes had a UDVA of better than 0.30 logMAR and 61.9% of better than 0.10. Scialdone et al.26 report a UDVA of 0.30 logMAR or better in all eyes and of 0.10 logMAR or better in 61.1% of eyes. In a study by Ali o et al.,27 the UDVA was 0.30 logMAR or better in 76.1% of eyes. The
Table 3. Refractive characteristics (N Z 20). Mean G SD (D) Postoperative Parameter
Preoperative
1 Day
3 Months
6 Months
M J0 J45 B
7.10 G 1.78 0.08 G 0.89 0.13 G 0.85 7.20 G 1.78
0.55 G 0.25* 0.01 G 0.10 0.01 G 0.12 0.58 G 0.22*
0.73 G 0.28 0.03 G 0.25 0.01 G 0.24 0.80 G 0.30†
0.69 G 0.28 0.03 G 0.22 0.02 C 0.22 0.75 G 0.30
B Z blur; J0 Z Jackson cross-cylinder equivalent to the conventional cylinder at axis 0 degree; J45 Z Jackson cross-cylinder equivalent to the conventional cylinder at axis 45 degrees; M Z spherical equivalent *P ! .005 compared with the previous visit † P ! .05 compared with the previous visit
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Figure 3. Refractive astigmatism preoperatively (A) and postoperatively at 1 day (B), 3 months (C), and 6 months (D). The origin of the graph represents an eye free of astigmatism (J0 and J45 Z Jackson cross cylinders equivalent to the conventional cylinder at axis at 0 degree and at 45 degrees, respectively).
CDVA in our study was better than 0.10 logMAR in all eyes. Again, the results are consistent with those published by Bascaran et al.14 and Ali o et al.27 These authors report a CDVA of better than 0.10 logMAR in 90.2% of eyes and of 0.18 logMAR or better in 85.7% of eyes, respectively. As expected, this significant improvement in CDVA and UDVA was accompanied by a significant reduction in sphere and cylinder; the mean correction was 92.28% and 77.28%, respectively, of the preoperative values. The reduction in cylinder was comparable to that in other studies of eyes with low or no myopia as follows: 80% in Bascaran et al.14 with the same IOL and 67.7% in Mango-Botín et al.28 with the Acrysof toric IOL (Alcon Laboratories, Inc.). In our study, J0 and J45 decreased, reaching values close to zero immediately after surgery; both values remained stable in all eyes and for the duration of the study. Six months after surgery, all eyes had a J0 value within G0.50 D and 95% had a J45 value within G0.50 D. All eyes had a J45 value within G1.00 D. These results are similar to those reported by Bascaran et al.14 with the same IOL in a population of eyes without myopia.
The B value in our study was slightly higher than that reported by Mingo-Botín et al.28 (0.42 G 0.25 D) in eyes without myopia in which a toric IOL was implanted. This difference, however, is not likely clinically significant.29 Most IOL rotation occurred during the first 3 months after surgery. At the last follow-up, the mean cylinder power was 0.53 G 0.32 D. Given that 1 degree of misalignment of the IOL corresponds to a loss of 3.3% of its cylinder and taking into account IOL rotation and cylinder, we were able to estimate the loss of cylinder power of the IOL caused by misalignment. We found that the IOL had lost, on average, 0.27 D (9.90%) of its initial power due to a mean rotation of 3.0 degrees after 6 months. Previous studies report a slightly higher loss of cylinder ranging from 12.15%28 to 16%14 in eyes with low or no myopia. Three months postoperatively, the mean IOL rotation was very low (2.66 G 1.53 degrees), with 95% of the IOLs within G5 degrees of rotation and 100% within G10 degrees. These values are in accordance with previously reported rotational shift measured in nonmyopic eyes.14,27 Between 3 months and 6 months,
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Figure 4. Axial length, WTW distance, and preoperative sphere versus the mean IOL absolute rotation 3 months and 6 months after surgery (IOL Z intraocular lens).
the mean IOL rotation (0.34 G 0.24 degrees) was negligible and clinically insignificant, leading to a cylindrical power shift of 0.03 D. This result might confirm that by 3 months after surgery, the capsular bag had fused. Overall, the rotational stability of the IOL was very satisfactory in the myopic population included in our analysis. There was a slightly higher incidence of counterclockwise rotation (55%) than clockwise rotation (45%) at 6 months. Results of the rotational behavior of loop-haptic and plate-haptic IOLs in the literature are contradictory17,23 and could also depend on the different time of postoperative evaluation and the different grades of capsular bag shrinkage.23 Scialdone et al.26 found predominantly counterclockwise IOL rotation (73%) 3 months after surgery with AT Torbi 709M IOLs and Acrysof IQ SN6AT IOLs (Alcon Laboratories, Inc.). A higher number of patients and a longer follow-up would be useful to further analyze rotational behavior of IOLs. Myopic eyes require special attention in terms of toric IOL implantation. Some authors have found
that the AL is a good indicator of the postoperative capsular bag diameter.12 However, the evidence of a correlation between the AL and the amount of IOL rotation is weak, with some studies reporting a relationship14,15 and some the lack of a correlation.16,17 In our study, we found no correlation between IOL rotation at 3 months and the AL (r Z 0.268, P Z .254) or the WTW diameter (r Z 0.268, P Z .254). The only variable that had a statistically significant correlation with IOL rotation at 3 months was the preoperative sphere (r Z 0.532, P Z .016). However, the preoperative sphere can be influenced by the grade of nuclear cataract, which can cause an increase in myopic error.30 We failed to establish a correlation between IOL rotation and the AL or between IOL rotation and the WTW diameter. A limitation of our study was the small range of ALs included (25.0 to 27.0 mm). We believe a correlation between AL and IOL rotation might be found by analyzing a wider AL range. In conclusion, in this study the implantation of the AT Torbi 709M toric IOL to replace the cataractous
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human crystalline lens in myopic eyes with AL between 25.0 mm and 27.0 mm was effective and safe. The IOL showed no significant rotation over the 6-month follow-up. The AL and the WTW diameter were not good indicators of IOL rotation. Further studies with larger patient cohorts are desirable to confirm these results. WHAT WAS KNOWN Considering that myopic eyes tend to have a longer AL and a bigger capsular bag than normal eyes and that IOL rotation is a common complication of cataract surgery, eyes with astigmatism and moderate or high myopia are presumably at greater risk for early postoperative IOL rotation. WHAT THIS PAPER ADDS A 4-haptic toric IOL implanted in moderate myopic eyes was effective and stable over a 6-month period.
REFERENCES 1. Vitale S, Ellwein L, Cotch MF, Ferris FL III, Sperduto R. Prevalence of refractive error in the United States, 1999-2004. Arch Ophthalmol 2008; 126:1111–1119. Available at: http:// archopht.jamanetwork.com/data/Journals/OPHTH/6892/eeb 80002_1111_1119.pdf. Accessed April 29, 2014 2. Mencucci R, Giordano C, Favuzza E, Gicquel J-J, Spadea L, Menchini U. Astigmatism correction with toric intraocular lenses: wavefront aberrometry and quality of life. Br J Ophthalmol 2013; 97:578–582 3. Novis C. Astigmatism and toric intraocular lenses. Curr Opin Ophthalmol 2000; 11:47–50 4. Tsinopoulos IT, Tsaousis KT, Tsakpinis D, Ziakas NG, Dimitrakos SA. Acrylic toric intraocular lens implantation: a single center experience concerning clinical outcomes and postoperative rotation. Clin Ophthalmol 2010; 4:137–142. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850825/pdf/opth4-137.pdf. Accessed April 29, 2014 5. Oshika T, Nagata T, Ishii Y. Adhesion of lens capsule to intraocular lenses of polymethylmethacrylate, silicone, and acrylic foldable materials: an experimental study. Br J Ophthalmol 1998; 82:549–553. Available at: http://www.pubmedcentral.nih.gov/ picrender.fcgi?artidZ1722579&blobtypeZpdf. Accessed April 29, 2014 6. Chang DF. Comparative rotational stability of single-piece openloop acrylic and plate-haptic silicone toric intraocular lenses. J Cataract Refract Surg 2008; 34:1842–1847 7. Chang DF. Early rotational stability of the longer Staar toric intraocular lens; fifty consecutive cases. J Cataract Refract Surg 2003; 29:935–940 8. Atchison DA, Jones CE, Schmid KL, Pritchard N, Pope JM, Strugnell WE, Riley RA. Eye shape in emmetropia and myopia. Invest Ophthalmol Vis Sci 2004; 45:3380–3386. Available at: http://www.iovs.org/content/45/10/3380.full.pdf. Accessed April 29, 2014
9. Vass C, Menapace R, Schmetterer K, Findl O, Rainer G, Steineck I. Prediction of pseudophakic capsular bag diameter based on biometric variables. J Cataract Refract Surg 1999; 25:1376–1381 e M. Direct measurement of the 10. Galand A, Bonhomme L, Colle capsular bag. Am Intra-Ocular Implant Soc J 1984; 10:475–476 11. Richburg FA, Sun HS. Size of the crushed cataractous capsule bag. Am Intra-Ocular Implant Soc J 1983; 9:333–335 12. Kim J-H, Lee D, Cha Y-D, Oh S-H, Mah K-C, Lee M-S. The analysis of predicted capsular bag diameter using modified model of capsule measuring ring in Asians. Clin Exp Ophthalmol 2008; 36:238–244 lez-Me ijome JM, Garcıa13. Alfonso JF, Ferrer-Blasco T, Gonza s-Mico R. Pupil Manjarres M, Peixoto-de-Matos SC, Monte size, white-to-white corneal diameter, and anterior chamber depth in patients with myopia. J Refract Surg 2010; 26:891–898 14. Bascaran L, Mendicute J, Macias-Murelaga B, Arbelaitz N, Martinez-Soroa I. Efficacy and Stability of AT TORBI 709M toric IOL. J Refract Surg 2013; 29:194–199 15. Shah GD, Praveen MR, Vasavada AR, Vasavada VA, Rampal G, Shastry LR. Rotational stability of a toric intraocular lens: influence of axial length and alignment in the capsular bag. J Cataract Refract Surg 2012; 38:54–59 16. Zuberbuhler B, Signer T, Gale R, Haefliger E. Rotational stability of the AcrySof SA60TT toric intraocular lenses: a cohort study. BMC Ophthalmol 2008; 8:8. Available at: http://www. biomedcentral.com/content/pdf/1471-2415-8-8.pdf. Accessed April 29, 2014 17. Patel CK, Ormonde S, Rosen PH, Bron AJ. Postoperative intraocular lens rotation; a randomized comparison of plate and loop haptic implants. Ophthalmology 1999; 106:2190–2195; discussion by DJ Apple, 2196 18. Chylack LT Jr, Wolfe JK, Singer DM, Leske MC, Bullimore MA, Bailey IL, Friend J, McCarthy D, Wu S-Y; for the Longitudinal Study of Cataract Study Group. The Lens Opacities Classification System III. Arch Ophthalmol 1993; 111:831–836. Available at: http://www.chylackinc.com/LOCS_III/LOCS_III_Certification_ files/LOCS_III_Reprint_pdf.pdf. Accessed April 28, 2014 19. Shah GD, Praveen MR, Vasavada AR, Rampal NV, Vasavada VA, Asnani PK, Pandita D. Software-based assessment of postoperative rotation of toric intraocular lens. J Cataract Refract Surg 2009; 35:413–418 20. Thibos LN, Horner D. Power vector analysis of the optical outcome of refractive surgery. J Cataract Refract Surg 2001; 27:80–85 21. Sacu S, Findl O, Linnola RJ. Optical coherence tomography assessment of capsule closure after cataract surgery. J Cataract Refract Surg 2005; 31:330–336 -Mico R, Cervin ~o A, Ferrer-Blasco T. Intraocular lens cen22. Monte tration and stability: efficacy of current technique and technology. Curr Opin Ophthalmol 2009; 20:33–36 23. Prinz A, Neumayer T, Buehl W, Vock L, Menapace R, Findl O, Georgopoulos M. Rotational stability and posterior capsule opacification of a plate-haptic and an open-loop-haptic intraocular lens. J Cataract Refract Surg 2011; 37:251–257 24. Lee KM, Lee EJ, Wee WR, Han YK, Kim MK, Hyon JY. Myopic shift of foldable acrylic intraocular lenses after sulcus fixation. Br J Ophthalmol 2012; 96:1316–1319 25. Flores-Moreno I, Lugo F, Duker JS, Ruiz-Moreno JM. The relationship between axial length and choroidal thickness in eyes with high myopia. Am J Ophthalmol 2013; 155:314–319 26. Scialdone A, De Gaetano F, Monaco G. Visual performance of 2 aspheric toric intraocular lenses: comparative study. J Cataract Refract Surg 2013; 39:906–914
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JL, Agdeppa MCC, Pongo VC, El Kady B. Microincision 27. Alio cataract surgery with toric intraocular lens implantation for correcting moderate and high astigmatism: pilot study. J Cataract Refract Surg 2010; 36:44–52 ~oz-Negrete FJ, Kim HRW, Morcillo-Laiz R, 28. Mingo-Botın D, Mun Rebolleda G, Oblanca N. Comparison of toric intraocular lenses and peripheral corneal relaxing incisions to treat astigmatism during cataract surgery. J Cataract Refract Surg 2010; 36:1700–1708 29. Chung STL, Jarvis SH, Cheung S-H. The effect of dioptric blur on reading performance. Vision Res 2007; 47:1584–1594 30. Pesudovs K, Elliott DB. Refractive error changes in cortical, nuclear, and posterior subcapsular cataracts. Br J Ophthalmol 2003; 87:964–967. Available at: http://www.ncbi.nlm.nih.gov/ pmc/articles/PMC1771794/pdf/bjo08700964.pdf. Accessed April 29, 2014
OTHER CITED MATERIAL A. Carl Zeiss Meditec AG. [Online calculator]. Available at: https:// zcalc.meditec.zeiss.com/zcalc/. Accessed April 29, 2014
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First author: Rita Mencucci, MD Eye Clinic, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy
Clinical outcomes and rotational stability of a 4-haptic toric intraocular lens in myopic eyes Rita Mencucci, MD, Eleonora Favuzza, MD, Francesca Guerra, MD, Giovanni Giacomelli, MD, Ugo Menchini, MD
PURPOSE: To evaluate the refractive outcomes and rotational stability of a 4-haptic toric intraocular lens (IOL) in myopic eyes and the correlations between IOL rotation and refractive sphere, axial length (AL), and white-to-white (WTW) diameter. SETTING: Eye Clinic, Careggi Hospital, Florence, Italy. DESIGN: Prospective case series. METHODS: Phacoemulsification cataract extraction and implantation of an AT Torbi 709M IOL were performed. Corneal astigmatism was 1.50 diopters (D) or greater and the AL between 25.0 mm and 27.0 mm in all eyes. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, and IOL axis were evaluated preoperatively and postoperatively up to 6 months. RESULTS: The study enrolled 20 eyes (20 patients). The UDVA and CDVA improved significantly postoperatively (P < .001). The mean refractive spherical equivalent decreased significantly from 7.10 D G 1.78 (SD) preoperatively to 0.55 G 0.25 D 1 day postoperatively (P < .001) and remained stable thereafter. Vector analysis showed that 90% and 85% of the eyes were within G0.25 D for J0 and J45, respectively. At 3 months and 6 months, the mean IOL rotation was 2.66 G 1.53 degrees and 3.00 G 1.69 degrees, respectively (P < .001), with 95% of eyes and 90% of eyes, respectively, within G5 degrees. A positive correlation was found between IOL rotation and preoperative sphere; none was found with AL and WTW. CONCLUSIONS: Implantation of the 4-haptic toric IOL in myopic eyes was effective and safe. The IOL showed no significant rotation over the 6-month follow-up. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. J Cataract Refract Surg 2014; 40:1479–1487 Q 2014 ASCRS and ESCRS
Today, cataract surgery aims not only to replace the opacified crystalline lens with an intraocular lens (IOL) but also to improve the patient's refractive status. Refractive errors are extremely common, with approximately 40% of the population older than 20 years having myopia and 35% having astigmatism.1 Various toric IOLs that correct both sphere and cylinder have been developed and are available to surgeons to reduce patients' spectacle dependence and improve their quality of life.2 A common complication of toric IOLs is postoperative rotation.3,4 Intraocular lens stability and the absence of rotation are essential for the effectiveness of toric IOLs. It has been shown that every degree of off-axis rotation results in a loss of up to 3.3% of the
Q 2014 ASCRS and ESCRS Published by Elsevier Inc.
IOL's cylindrical power. If the IOL rotates by more than 30 degrees, the cylinder correction from the IOL is completely lost.3 During the first few days after surgery, and before the natural healing of the capsular bag occurs, there is an increased risk for IOL rotation. Parameters affecting the risk primarily include an IOL surface with a low coefficient of friction,5 the design of the IOL,6 an overall length of the IOL that is too small for the capsular bag,3 and instability of the anterior chamber. As with any type of bag-fixated IOL, late postoperative rotation can also occur; however, the mechanism is different. Late IOL rotation (that occurring after 3 months) is principally associated with the compressive forces of delayed capsule fibrosis.7
0886-3350/$ - see front matter http://dx.doi.org/10.1016/j.jcrs.2013.12.024
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Myopic eyes, which are commonly longer than average,8 tend to have a bigger capsular bag than emmetropic eyes.9 Thus, these eyes could be at greater risk for early IOL rotation. The capsular bag diameter varies from 10.3 mm to 10.8 mm10,11 and is difficult to directly measure preoperatively. However, the axial length (AL) and white-to-white (WTW) corneal diameter are routinely measured preoperatively during standard biometry examinations. The AL has been shown to be a good indicator of postoperative capsular bag diameter.12 In addition, the WTW distance has been found to be positively correlated to the anterior chamber depth (ACD) in myopic eyes.13 There is still, however, opposing evidence regarding the possible correlation between the AL and IOL rotation. Results in some studies support this correlation,14,15 while others fail to establish a link.16,17 Also, little is known about a possible relationship between the WTW distance and IOL rotation. The purpose of this prospective study was to evaluate the overall refractive correction and rotational stability of the AT Torbi 709M toric IOL (Carl Zeiss Meditec AG) in a series of myopic eyes with cataract and a corneal astigmatism greater than 1.50 diopters (D). In addition, the study analyzed the potential correlations between IOL rotation and preoperative sphere, AL, and WTW distance. PATIENTS AND METHODS This prospective noncomparative study included eyes that had phacoemulsification and implantation of a toric IOL at Careggi Hospital, Florence, Italy, and were consecutively enrolled between April 2011 and January 2012. The study followed the tenets of the Declaration of Helsinki. Before being enrolled, patients satisfying the inclusion criteria were given a thorough explanation of the procedure, the risks, and the potential complications. All patients provided written informed consent. Institutional review board or ethics committee approval was not required for the study. The inclusion criteria were clinically significant cataract (minimum grade II on the Lens Opacities Classification System III18), an AL between 25.0 mm and 27.0 mm, and astigmatism on corneal topography of 1.50 D or greater. Exclusion criteria were previous ocular surgery, systemic and ocular anomalies or pathologies that could reduce visual function or postoperative IOL stability (eg, pathologic
Submitted: September 10, 2013. Final revision submitted: November 28, 2013. Accepted: December 8, 2013. From the Eye Clinic, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy. Corresponding author: Rita Mencucci, MD, Department of Surgery and Translational Medicine, Eye Clinic, Largo Brambilla 3, 50134 Florence, Italy. E-mail: [email protected].
myopia, amblyopia, glaucoma, macular degeneration, corneal edema, corneal dystrophy, irregular astigmatism, pseudoexfoliation syndrome), and unsuitable for adequate follow-up.
Surgical Technique The same experienced surgeon (R.M.) performed all surgeries using topical corneal anesthesia, a standard clear corneal incision, and phacoemulsification. Before surgery, with the patient seated, the cornea was marked by placing 2 limbal points along the principal meridian (0 to 180 degrees) with a Nuijts toric reference marker (American Surgical Instruments Corp.). Intraoperatively, a second marking was performed before phacoemulsification with a Mendez ring combined with the Bores intraoperative axial marker (American Surgical Instruments Corp.) to confirm the optimum axis for the toric IOL. Phacoemulsification was performed through a 2.2 mm single-plane sutureless temporal microincision. After a continuous curvilinear capsulorhexis of approximately 5.5 mm was created and hydrodissection performed, the cataract was removed by phacoemulsification using a stop-and-chop technique (Infiniti, Alcon Laboratories Inc.). The toric IOL was subsequently implanted in the capsular bag using a Viscoject injector (Medicel AG) and sodium hyaluronate 3.0%–chondroitin sulfate 4.0% with sodium hyaluronate 1.0% (Duovisc). Calculations of the IOL sphere and cylinder powers were determined before surgery using the IOL manufacturer's online calculator.A The IOL was rotated into a position approximately 10 degrees short of the marked axis before the residual ophthalmic viscosurgical device was removed from behind the IOL and from the anterior chamber. Last, the IOL was rotated to align the axis lines on the IOL with the marked corneal steep meridian. In all cases, the postoperative treatment comprised a topical antibiotic, corticosteroid eyedrops, and nonsteroidal antiinflammatory drug eyedrops.
Intraocular Lens The IOL used in this study, the AT Torbi 709M, is 1 piece, hydrophilic acrylic, monofocal, aspheric, and bitoric. It is foldable and has a 25% water content and hydrophobic surface properties. The IOL has a supporting 4-haptic design with no angulation, a biconvex 6.0 mm optic, and an overall diameter of 11.0 mm.
Preoperative and Postoperative Examinations All preoperative and postoperative assessments were performed by 2 experienced ophthalmologists (R.M., E.F.). Preoperatively, all patients had a full ophthalmologic examination including biometry measurements (eg, AL, ACD, WTW) using partial coherence interferometry (IOLMaster, Carl Zeiss Meditec AG), assessment of monocular logMAR uncorrected (UDVA) and corrected (CDVA) distance visual acuities (Early Treatment of Diabetic Retinopathy Study chart), and manifest refractive evaluation of sphere and cylinder. In addition to the preoperative IOL calculation, the predicted postoperative refraction was estimated with a factor for surgically induced astigmatism (SIA) of 0.50 D at the incision axis. Postoperative examinations were performed at 1 day, 3 months, and 6 months. The UDVA and CDVA were recorded at 3 months and 6 months. Postoperative refraction, residual cylinder, and toric IOL axis alignment were
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measured at each follow-up visit. The toric IOL axis was measured postoperatively using a superimposed protractor and digital image-analysis software (Photoshop 7.0, Adobe Systems, Inc.) and a modification of Shah et al.’s method.19 At the 1-day examination, a slitlamp image of the IOL was taken after pupil dilation, a prominent episcleral vessel was identified, and the axis between the vessel and the center of the IOL was drawn. In the 3-month and 6-month images, this axis was used to determine the horizontal axis. To obtain reproducibility, care was taken to minimize the effect of head movements by keeping the same angle between the episcleral vessel and the horizontal axis in all the subsequent postoperative images. All measurements were performed in triplicate.
Astigmatism Analysis Astigmatism analysis was performed using the power vector analysis method described by Thibos and Horner.20 The analysis included the calculation of M, J0, J45, and B. The M value is the spherical equivalent (SE) of the refractive error, and J0 and J45 are 2 Jackson cross cylinders equivalent to the conventional cylinder at an axis of 0 degree and 45 degrees, respectively. The M, J0, and J45 values represent the coordinates of a point in a 3-dimensional space, and B is the length from that point to the origin. It thus represents a power vector defined as the geometric representation of the spherocylindrical refractive errors in 3 orthogonal independent dioptric components (M, J0, and J45). The B value is the length of the vector and a measure of the overall blurring strength of the spherocylindrical refractive error. Manifest refractions were converted to power vector coordinates and overall blurring strength according to the following formulas: M Z S þ C=2 J0 Z ðC=2Þcosð2aÞ J45 Z ðC=2Þsinð2aÞ BZ
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi M2 þ J02 þ J452
where S is the spherical power, C is the cylindrical power, and a is the cylinder axis.
Statistical Analysis Statistical analysis was performed using Excel software (Microsoft Corp.) and Minitab software (version 15, Minitab, Inc.). The results are presented as the mean, standard deviation (SD), and range (minimum, maximum). Normality of all data samples was first checked using the Anderson-Darling
test. The significance of the difference between the preoperative data and postoperative data was then assessed. When parametric analysis was appropriate, the Student t test for paired data was performed. When parametric analysis was not possible, a 1-sample Wilcoxon signed-rank test was applied. A P value lower than 0.05 was considered statistically significant. Correlation coefficients (Spearman test) were used to determine the correlation between variables.
RESULTS The study included 20 eyes of 20 patients. The mean age of the 5 men (25%) and 15 women (75%) was 67.45 G 5.65 years (range 60 to 76 years). The IOL was implanted in the right eye in 13 patients (65%) and in the left eye in 7 patients (35%). Table 1 shows the baseline AL, WTW, and ACD as well as the spherical and cylindrical powers of the IOL. Figure 1 shows the AL distribution. Visual Acuity and Refraction Table 2 shows the visual acuity and refractive results over time. The UDVA and CDVA improved significantly after surgery (P ! .001). After 3 months, the UDVA and CDVA remained stable (Figure 2). At the last follow-up visit, all eyes had a CDVA of better than 0.10 logMAR. The UDVA was better than 0.15 logMAR in all eyes and 0.10 logMAR or better in 15 eyes (75%). The decrease in SE was statistically significant between preoperatively and 1 day postoperatively and between preoperatively and 6 months postoperatively (P ! .001). The changes between 1 day and 6 months were not statistically significant. The mean predicted SE was 0.44 G 0.16 D (range 0.78 to 0.17 D). The mean difference between the predicted and measured postoperative SE after 1 day was 0.11 D and the difference was within G0.50 D in all eyes. After 6 months, 17 eyes (85%) had an SE within G1.00 D and 6 (30%) were within G 0.50 D. Table 3 shows the vector analysis results. The vector components J0 and J45 decreased immediately after the surgery, although the changes did not reach statistical significance (P Z .654 and P Z .541, respectively). The results were close to the optimum value of zero throughout the study. Six months postoperatively, the vector values were within G0.25 D in 18 eyes
Table 1. Baseline characteristics (N Z 20). IOL Power (D) Value Mean G SD Range
AL (mm)
WTW (mm)
ACD (mm)
Spherical
Cylindrical
26.11 G 0.68 25.03, 27.00
11.84 G 0.18 11.50, 12.10
3.40 G 0.26 3.00, 3.80
11.88 G 2.22 8.50, 16.00
2.65 G 0.83 1.50, 5.00
ACD Z anterior chamber depth; AL Z axial length; IOL Z intraocular lens; WTW Z white-to-white diameter
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surgery and 18 (90%) were within G5 degrees after 6 months. All eyes were within G10 degrees throughout the follow-up. The mean absolute rotation 3 months and 6 months postoperatively was 2.66 G 1.53 degrees (range 0.70 to 6.00 degrees) and 3.00 G 1.69 degrees (range 0.90 to 6.50 degrees), respectively. This difference was statistically significant (P ! .001). The rotation at 6 months was counterclockwise in 11 patients (55%) and clockwise in 9 patients (45%). No correlation was found between the IOL rotation at 3 or 6 months and the AL (r Z 0.268, P Z .254 and r Z 0.226, P Z .337, respectively) or the WTW diameter (r Z 0.286, P Z .221 and r Z 0.302, P Z 0.195, respectively). There was, however, a statistically significant correlation between the IOL rotation at 3 months and 6 months and the preoperative sphere value (r Z 0.532, P Z .016 and r Z 0.557, P Z .011, respectively) (Figure 4). The negative Spearman coefficient value indicated a negative correlation between the spherical power and IOL rotation.
Figure 1. Axial length distribution. The 3 zones represent the definition commonly accepted for normal (up to 24.5 mm), long (from 24.5 to 26.0 mm), and very long (from 26.0 mm) eyes.24,25
(90%) for J0 and in 17 eyes (85%) for J45. Figure 3 shows the change in SIA using a 2-dimensional vector (J0, J45). The origin of the graphs represents an eye free of astigmatism. Postoperatively up to 6 months, the cluster of points is consistently concentrated around the origin, showing that the astigmatism was corrected in most cases. There was a statistically significant decrease in the B value immediately after surgery (between preoperatively and 1 day postoperatively) (P ! .001). The increase in the B value between 1 day and 3 months postoperatively was statistically significant (P Z .011).
Complications No eye-threatening complication was observed during the follow-up. No patient required IOL repositioning due to misalignment. In addition, no posterior capsule opacification was observed, and no eye required a neodymium:YAG capsulotomy.
DISCUSSION Intraocular Lens Rotation
Astigmatism and myopia are among the most common refractive errors of patients with cataract. Achieving emmetropia in these patients has become
Of the 20 eyes included in the study, 19 (95%) were within G5 degrees of the operative axis 3 months after
Table 2. Visual acuity and preoperative and postoperative manifest refractions (N Z 20). Postoperative Parameter UDVA (logMAR) Mean G SD Range CDVA (logMAR) Mean G SD Range Sphere (D) Mean G SD Range Cylinder (D) Mean G SD Range
Preoperative
1 Day
3 Months
6 Months
1.31 G 0.23 1.70, 1.00
d d
0.09 G 0.04* 0.02, 0.15
0.09 G 0.04 0.02, 0.15
0.61 G 0.20 1.00, 0.35
d d
0.04 G 0.03* 0.00, 0.10
0.04 G 0.03 0.00, 0.07
5.93 G 1.67 10.00, 3.50
0.41 G 0.26* 0.75, 0.25
0.43 G 0.22 0.75, 0.00
0.43 G 0.22 0.75, 0.00
2.35 G 0.59 3.50, 1.50
0.28 G 0.14* 0.50, 0.00
0.61 G 0.31* 1.25, 0.00
0.53 G 0.32† 1.25, 0.00
CDVA Z corrected distance visual acuity; UDVA Z uncorrected distance visual acuity *P ! .005 compared with the previous visit † P ! .05 compared with the previous visit
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Figure 2. The UDVA and CDVA over time (*** Z P ! .005; CDVA Z corrected distance visual acuity; UDVA Z uncorrected distance visual acuity).
possible since the development and regular use of toric IOLs and the evolution of astigmatically neutral corneal incisions. The performance of toric IOLs is nonetheless extremely dependent on correct alignment in the eye at the time of the surgery and in particular on the absence of rotation in the early postoperative period. The capsular bag healing process takes place progressively after removal of the crystalline lens. It is normally complete within 1 month after surgery.21 During this time, the IOL is loosely supported by the haptics and is at higher risk for rotation. Depending on the design of the IOL,21 the formation of capsule fibrosis, and other biomechanical changes,22 closure of the bag can occur asymmetrically, creating a risk for IOL decentration and rotation.
There is still an open debate about the ideal design for a toric IOL. Patel et al.17 found that plate-haptic IOLs had a tendency to be less stable than open-loop haptic IOLs in the early postoperative period (within 2 weeks after surgery), whereas the plate-haptic platform tended to rotate less than the loop haptic in the late postoperative period (between 2 weeks and 3 months). Prinz et al.23 found that the greatest rotation occurred within the first week postoperatively with both IOL types, with a slightly higher tendency toward rotation for the plate-haptic IOL than for the loop-haptic IOL. However, they found very good rotational stability for both IOL types within 1 year postoperatively, with no significant difference. Myopic eyes with large capsular bags require extra attention because the risk for early rotation of the IOL is greater. It is generally considered that eyes with an AL between 24.5 mm and 26.0 mm are long (ie, have moderate myopia) and that eyes with an AL greater than 26.0 mm are very long (ie, have high myopia).24,25 According to this classification, 60% of eyes in our study had high myopia and 40% had moderate myopia. To our knowledge, this study is the first to evaluate the effectiveness and the safety of a toric IOL in long to very long eyes (corresponding to moderate to high axial myopia). In this series, the CDVA and UDVA improved significantly after surgery. The UDVA was better than 0.30 logMAR in all eyes and 0.10 logMAR or better in 75% of eyes at the last follow-up. These results were similar to or better than most values published in studies of the same IOL or equivalent IOLs. In a study by Bascaran et al.,14 88.1% of eyes had a UDVA of better than 0.30 logMAR and 61.9% of better than 0.10. Scialdone et al.26 report a UDVA of 0.30 logMAR or better in all eyes and of 0.10 logMAR or better in 61.1% of eyes. In a study by Ali o et al.,27 the UDVA was 0.30 logMAR or better in 76.1% of eyes. The
Table 3. Refractive characteristics (N Z 20). Mean G SD (D) Postoperative Parameter
Preoperative
1 Day
3 Months
6 Months
M J0 J45 B
7.10 G 1.78 0.08 G 0.89 0.13 G 0.85 7.20 G 1.78
0.55 G 0.25* 0.01 G 0.10 0.01 G 0.12 0.58 G 0.22*
0.73 G 0.28 0.03 G 0.25 0.01 G 0.24 0.80 G 0.30†
0.69 G 0.28 0.03 G 0.22 0.02 C 0.22 0.75 G 0.30
B Z blur; J0 Z Jackson cross-cylinder equivalent to the conventional cylinder at axis 0 degree; J45 Z Jackson cross-cylinder equivalent to the conventional cylinder at axis 45 degrees; M Z spherical equivalent *P ! .005 compared with the previous visit † P ! .05 compared with the previous visit
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Figure 3. Refractive astigmatism preoperatively (A) and postoperatively at 1 day (B), 3 months (C), and 6 months (D). The origin of the graph represents an eye free of astigmatism (J0 and J45 Z Jackson cross cylinders equivalent to the conventional cylinder at axis at 0 degree and at 45 degrees, respectively).
CDVA in our study was better than 0.10 logMAR in all eyes. Again, the results are consistent with those published by Bascaran et al.14 and Ali o et al.27 These authors report a CDVA of better than 0.10 logMAR in 90.2% of eyes and of 0.18 logMAR or better in 85.7% of eyes, respectively. As expected, this significant improvement in CDVA and UDVA was accompanied by a significant reduction in sphere and cylinder; the mean correction was 92.28% and 77.28%, respectively, of the preoperative values. The reduction in cylinder was comparable to that in other studies of eyes with low or no myopia as follows: 80% in Bascaran et al.14 with the same IOL and 67.7% in Mango-Botín et al.28 with the Acrysof toric IOL (Alcon Laboratories, Inc.). In our study, J0 and J45 decreased, reaching values close to zero immediately after surgery; both values remained stable in all eyes and for the duration of the study. Six months after surgery, all eyes had a J0 value within G0.50 D and 95% had a J45 value within G0.50 D. All eyes had a J45 value within G1.00 D. These results are similar to those reported by Bascaran et al.14 with the same IOL in a population of eyes without myopia.
The B value in our study was slightly higher than that reported by Mingo-Botín et al.28 (0.42 G 0.25 D) in eyes without myopia in which a toric IOL was implanted. This difference, however, is not likely clinically significant.29 Most IOL rotation occurred during the first 3 months after surgery. At the last follow-up, the mean cylinder power was 0.53 G 0.32 D. Given that 1 degree of misalignment of the IOL corresponds to a loss of 3.3% of its cylinder and taking into account IOL rotation and cylinder, we were able to estimate the loss of cylinder power of the IOL caused by misalignment. We found that the IOL had lost, on average, 0.27 D (9.90%) of its initial power due to a mean rotation of 3.0 degrees after 6 months. Previous studies report a slightly higher loss of cylinder ranging from 12.15%28 to 16%14 in eyes with low or no myopia. Three months postoperatively, the mean IOL rotation was very low (2.66 G 1.53 degrees), with 95% of the IOLs within G5 degrees of rotation and 100% within G10 degrees. These values are in accordance with previously reported rotational shift measured in nonmyopic eyes.14,27 Between 3 months and 6 months,
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Figure 4. Axial length, WTW distance, and preoperative sphere versus the mean IOL absolute rotation 3 months and 6 months after surgery (IOL Z intraocular lens).
the mean IOL rotation (0.34 G 0.24 degrees) was negligible and clinically insignificant, leading to a cylindrical power shift of 0.03 D. This result might confirm that by 3 months after surgery, the capsular bag had fused. Overall, the rotational stability of the IOL was very satisfactory in the myopic population included in our analysis. There was a slightly higher incidence of counterclockwise rotation (55%) than clockwise rotation (45%) at 6 months. Results of the rotational behavior of loop-haptic and plate-haptic IOLs in the literature are contradictory17,23 and could also depend on the different time of postoperative evaluation and the different grades of capsular bag shrinkage.23 Scialdone et al.26 found predominantly counterclockwise IOL rotation (73%) 3 months after surgery with AT Torbi 709M IOLs and Acrysof IQ SN6AT IOLs (Alcon Laboratories, Inc.). A higher number of patients and a longer follow-up would be useful to further analyze rotational behavior of IOLs. Myopic eyes require special attention in terms of toric IOL implantation. Some authors have found
that the AL is a good indicator of the postoperative capsular bag diameter.12 However, the evidence of a correlation between the AL and the amount of IOL rotation is weak, with some studies reporting a relationship14,15 and some the lack of a correlation.16,17 In our study, we found no correlation between IOL rotation at 3 months and the AL (r Z 0.268, P Z .254) or the WTW diameter (r Z 0.268, P Z .254). The only variable that had a statistically significant correlation with IOL rotation at 3 months was the preoperative sphere (r Z 0.532, P Z .016). However, the preoperative sphere can be influenced by the grade of nuclear cataract, which can cause an increase in myopic error.30 We failed to establish a correlation between IOL rotation and the AL or between IOL rotation and the WTW diameter. A limitation of our study was the small range of ALs included (25.0 to 27.0 mm). We believe a correlation between AL and IOL rotation might be found by analyzing a wider AL range. In conclusion, in this study the implantation of the AT Torbi 709M toric IOL to replace the cataractous
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human crystalline lens in myopic eyes with AL between 25.0 mm and 27.0 mm was effective and safe. The IOL showed no significant rotation over the 6-month follow-up. The AL and the WTW diameter were not good indicators of IOL rotation. Further studies with larger patient cohorts are desirable to confirm these results. WHAT WAS KNOWN Considering that myopic eyes tend to have a longer AL and a bigger capsular bag than normal eyes and that IOL rotation is a common complication of cataract surgery, eyes with astigmatism and moderate or high myopia are presumably at greater risk for early postoperative IOL rotation. WHAT THIS PAPER ADDS A 4-haptic toric IOL implanted in moderate myopic eyes was effective and stable over a 6-month period.
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First author: Rita Mencucci, MD Eye Clinic, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy
