Emmetropia is the objective of modern cataract surgery. Spherical refractive errors should be managed by accurate biometry. In addition, astigmatism correction should be a target of the surgery, providing independence from spectacles.
The prevalence of preoperative corneal astigmatism ⩾1.00 diopters (D) in patients undergoing cataract surgery is estimated to be between 30% and 37%.1–3 Several techniques exist to correct corneal astigmatism, including limbal relaxing incisions,4 opposite clear corneal incisions,5 excimer laser refractive procedures,6,7 femtosecond laser–assisted astigmatic keratotomy,8 and toric intraocular lens (IOL) implantation.9 Several studies have shown that toric IOL implantation is more effective and predictable than incisional corneal refractive techniques, although a recent study found this to be true only for higher degress of astigmatism.10,11
Several toric IOL models are available. The purpose of this study was to perform a comparative evaluation of the visual and refractive outcomes after phacoemulsification with implantation of two types of toric IOLs in patients with low to moderate corneal astigmatism.
Patients and Methods
This prospective clinical study was performed at the Egas Moniz Hospital, Lisbon, Portugal. Patients undergoing phacoemulsification between August 2011 and December 2011 were randomly assigned to receive one of two types of toric IOLs. In one group, patients received the Tecnis toric ZCT150-400 (Abbott Medical Optics Inc [AMO], Santa Ana, California) (Tecnis group), and in the other group, patients received the Acrysof IQ Toric SN6AT3-6 (Alcon Laboratories Inc, Ft Worth, Texas) (Acrysof group). The characteristics of both IOLs are shown in Table A (available as data material in the PDF version of this article). The study was performed in accordance with the principles of the Declaration of Helsinki. All patients provided written informed consent.
Inclusion criteria were senile cataract and regular corneal astigmatism between 1.00 and 3.00 D. Exclusion criteria were irregular astigmatism, corneal dystrophy, tear-film or pupillary abnormalities, history of glaucoma or intraocular inflammation, macular disease or retinopathy, or neuro-ophthalmic disease. Patients were excluded from final analysis if they had any intra- or postoperative complications other than IOL rotation.
Preoperatively, all patients had a full ophthalmologic examination, including Snellen distance (4 m) UDVA and CDVA, subjective refraction, slit-lamp examination, Goldmann applanation tonometry, and dilated funduscopy in mydriasis.
Intraocular lens power was calculated using the Hoffer Q and SRK/T formulas. The goal was emmetropia. Hoffer Q was used for axial length <22 mm, and SRK/T was used for axial length ⩾22 mm. Axial length values were obtained using the IOLMaster partial coherence interferometer (Carl Zeiss Meditec, Jena, Germany). Keratometry values were obtained using the Pentacam rotating Scheimpflug imaging device (Oculus Optikgeräte GmbH, Wetzlar, Germany).
Intraocular lens cylinder power and axis placement were calculated using the online calculator for each IOL. For the Acrysof toric IOL, the Acrysof toric calculator ( http://www.acrysoftoriccalculator.com) was used with an A-constant of 119.2; for the Tecnis toric IOL, the Tecnis toric express calculator was used ( http://www.amoeasy.com/calc%28bD1lbiZjPTA1MA==%29/Default.htm) with an A-constant of 119.3. Surgically induced astigmatism of 0.50 D was assumed in all cases.
With the patient seated to prevent cyclorotation, the 0 to 180° meridian was marked using an Elies pendulum marker (E.Janach srl, Como, Italy). Intraoperatively, the implantation axis was marked using a Mendez degree gauge (Duckworth & Kent Ltd, Hertfordshire, United Kingdom) and an axis marker (Duckworth & Kent Ltd) based on the axis obtained from the toric calculator program.
One experienced surgeon (T.F.) performed all surgeries under topical anesthesia using a standard bi-manual microincision phacoemulsification technique. The IOLs were implanted with an injector (Monarch III [Alcon] for the Acrysof and DK7786 syringe-style inserter [Duckworth & Kent Ltd] for the Tecnis) through an enlarged corneal incision (2.4 mm at 120°). After implantation of the IOL and complete aspiration of the viscosurgical device (Healon, AMO), the IOL was rotated to its final position by aligning the corneal axis marks with the reference marks on the IOL.
Postoperatively, patients were prescribed moxifloxacin 0.5% (Vigamox, Alcon Laboratories Inc), prednisolone acetate 1% (Frisolona forte; Allergan, Irvine, California), and ketorolac 0.5% (Acular, Allergan).
Postoperative examinations were performed at 1 day, 1 week, and 1 and 2 months after surgery using the same tests as for the preoperative examination. At 2-month follow-up, ocular aberrometry was performed with the Optical Path Difference (OPD)-III scan refractive power/corneal analyzer system (NIDEK Co Ltd, Gamagori, Japan). The system is a combination autorefractometer, Placido disk topographer, and wavefront aberrometer. It performs aberrometry with dynamic skiascopy with an acquisition of 1440 data points to produce a map of the optics of the entire eye. After subtracting corneal aberrations from total eye aberrations, internal aberrations are also determined.12 The OPD-Scan automatically performs 3 measurements and yields the mean of these 3 measurements as an output. The parameters analyzed for a 4.0-mm pupil included the root-mean-square (RMS) of higher order aberrations, RMS of the total spherical aberration, RMS of the total coma, and RMS of the total trefoil, and point spread function (PSF), expressed as the Strehl ratio. The PSF expresses the effect of the aberrations on the retinal image and consequently the quality of the image. The Strehl ratio is a measure of optical quality and represents the ratio between the intensity of the real PSF and the intensity of the diffraction-limited PSF.
The IOL alignment axis was calculated from the OPD-Scan (toric IOL summary map) after pupillary mydriasis of at least 6.0 mm using tropicamide 1%.
All data were collected in an Excel database (Microsoft Office 2010; Microsoft Inc, Redmond, Washington). All statistical analyses were performed using SPSS for Windows (version 16.0; SPSS Inc, Chicago, Illinois). The Mann-Whitney U test was used for between-group comparisons. The results are expressed as the mean±standard deviation. P<.05 was considered statistically significant.
This study included 40 eyes from 26 patients aged between 54 and 80 years. The Tecnis group included 20 eyes from 14 patients, and the Acrysof group included 20 eyes from 12 patients. No eyes were excluded from analysis due to intra- or postoperative complications. Table 1 shows the patients’ demographics and IOL models used in both groups. Preoperatively, no relevant significant between-group differences were noted. All patients completed 2-month follow-up.
Table 1: Patient Demographics and Clinical Information
Visual Acuity and Refraction
Table 2 shows the postoperative visual acuity and refraction in both groups at 2-month follow-up. No statistically significant between-group differences were noted in any primary acuity or refractive outcome (P=.834 and P=.178, respectively). Uncorrected distance visual acuity was 0.3 logMAR or better (Snellen equivalent 20/40 or better) in 100% of eyes in the Tecnis group and 95% of eyes in the Acrysof group. All eyes in both groups achieved 0.10 logMAR or better (Snellen equivalent 20/25 or better) CDVA. Eleven (55%) eyes in the Tecnis group and 13 (65%) eyes in the Acrysof group were within ±0.50 D of the attempted spherical correction, and 19 (95%) eyes in the Tecnis group and 18 (90%) eyes in the Acrysof group were within ±1.00 D. Refractive cylinder was <0.50 D in 15 (75%) eyes in the Tecnis group and 17 (85%) eyes in the Acrysof group and <1.00 D in 20 (100%) eyes in the Tecnis group and 19 (95%) eyes in the Acrysof group. Postoperative spherical equivalent refraction was within ±0.50 D of the attempted correction in 14 (70%) eyes in the Tecnis group and 15 (75%) eyes in the Acrysof group and within ±1.00 D in 15 (75%) eyes in the Tecnis group and 18 (90%) eyes in the Acrysof group.
Table 2: Visual Acuity and Refractive Results at 2 Months Postoperatively
No eye required a second surgery to align the IOL axis during the 2-month follow-up period. No eye had IOL rotation >10°. Mean toric IOL axis rotation was 3.15°±2.62° in the Tecnis group (range: 0 to 10°) and 3.25°±2.04° in the Acrysof group (range: 0 to 8°) (P=.265).
Visual and Optical Quality
Table 3 shows the optical quality and ocular aberrometry values at 2 months postoperatively. No statistically significant between-group differences were noted for all ocular aberrometry values, except for spherical aberration, which was lower in the Tecnis group (P=.029).
Table 3: Ocular Aberrometry Analysis at 2 Months Postoperatively
Toric IOLs are becoming an increasingly used method to correct corneal astigmatism during cataract surgery. We compared the implantation of the Tecnis toric IOL with the Acrysof IQ toric IOL after phacoemulsification. To the best of our knowledge, this is the first study to directly compare these two types of IOLs.
In addition to the US Food and Drug Administration Clinical Investigation trials,13,14 the Acrysof toric IOL has been tested in several randomized trials that confirmed its safety, efficacy, rotational stability, optical quality, and subjective patient satisfaction.15–20 More recently, an aspheric version of this IOL (Acrysof IQ) was launched. The Tecnis toric IOL was recently launched in Europe, providing the cataract surgeon with another choice for the correction of astigmatism. Several communications in congresses attested its safety, efficacy, rotational stability, and subjective satisfaction.21
In our study, both IOLs provided excellent and comparable visual outcomes, with 100% of eyes in the Tecnis group and 95% of eyes in the Acrysof group achieving 0.3 logMAR or better (Snellen equivalent 20/40 or better) UDVA. The refractive outcomes were also comparable between the two IOLs. Rotational stability was evaluated with the OPD-III scanning system using the toric IOL summary map. This method is both fast and reliable for analyzing toric IOL alignment.22 The postoperative rotational stability was excellent and similar for both IOLs.
Higher order aberrations were also evaluated using the OPD-III scanning system. This system has good repeatability for the wavefront measurement of total, corneal, and internal optical aberrations.23–26 In our study, there were no statistically significant between-group differences for ocular higher order aberration RMS, coma, trefoil, and the Strehl ratio. Postoperative spherical aberration was lower in the Tecnis group (P=.029). Both the Tecnis toric and Acrysof IQ toric IOLs have aspheric anterior surfaces. Aspheric IOLs have been designed to compensate for the positive spherical aberration of the cornea. The benefits of using aspheric IOLs in cataract surgery have been extensively described in the literature. These IOLs provide higher vision quality than spherical IOLs in terms of retinal image quality, high-contrast visual acuity, and contrast sensitivity.27–30 Although we did not perform preoperative aberrometry with the OPD-III scanning system, given the difference found postoperatively in spherical aberration, we retrospectively studied preoperative corneal aberration values from the Pentacam wavefront aberration map (Oculus Optikgeräte GmbH, Wetzlar, Germany). We are aware that both this retrospective approach and using different devices for pre- and postoperative aberration evaulation may be a potential limitation of our study. Nevertheless, preoperative corneal spherical aberration in our patients was similar in both groups (Tecnis group 0.41±0.13, AcrySof group 0.45±0.12; P=.190). These values are comparable to those found in other studies that measured spherical aberration in cataract patients.31 We hypothesize that the total postoperative spherical aberration was lower in the Tecnis group because of the higher compensation of corneal spherical aberration with this IOL than with the Acrysof IQ (−0.27 μm for the Tecnis vs −0.20 μm for the Acrysof). However, this small difference did not seem to affect the overall postoperative optical quality, with total higher order aberrations and PSF being comparable between the two groups.
The results of our study show that the Tecnis toric and Acrysof IQ toric IOLs appear equally effective alternatives for the cataract surgeon in the correction of preexisting corneal astigmatism from 1.00 to 3.00 D during phacoemulsification.
- Khan MI, Muhtaseb M. Prevalence of corneal astigmatism in patients having routine cataract surgery at a teaching hospital in the United Kingdom. J Cataract Refract Surg. 2011;37(10):1751–1755. doi:10.1016/j.jcrs.2011.04.026 [CrossRef]
- Hoffmann PC, Hütz WW. Analysis of biometry and prevalence data for corneal astigmatism in 23,239 eyes. J Cataract Refract Surg. 2010;36(9):1479–1485. doi:10.1016/j.jcrs.2010.02.025 [CrossRef]
- Ferrer-Blasco T, Montés-Micó R, Peixoto-de-Matos SC, González-Méijome JM, Cerviño A. Prevalence of corneal astigmatism before cataract surgery. J Cataract Refract Surg. 2009;35(1):70–75. doi:10.1016/j.jcrs.2008.09.027 [CrossRef]
- Ouchi M, Kinoshita S. AcrySof IQ toric IOL implantation combined with limbal relaxing incision during cataract surgery for eyes with astigmatism >2.50 D. J Refract Surg. 2011;27(9):643–647. doi:10.3928/1081597X-20110317-03 [CrossRef]
- Qammar A, Mullaney P. Paired opposite clear corneal incisions to correct preexisting astigmatism in cataract patients. J Cataract Refract Surg. 2005;31(6):1167–1170. doi:10.1016/j.jcrs.2004.11.053 [CrossRef]
- Norouzi H, Rahmati-Kamel M. Laser in situ keratomileusis for correction of induced astigmatism from cataract surgery. J Refract Surg. 2003;19(4):416–424.
- Gunvant P, Ablamowicz A, Gollamudi S. Predicting the necessity of LASIK enhancement after cataract surgery in patients with multifocal IOL implantation. Clin Ophthalmol. 2011;5:1281–1285. doi:10.2147/OPTH.S23345 [CrossRef]
- Kim P, Sutton GL, Rootman DS. Applications of the femtosecond laser in corneal refractive surgery. Curr Opin Ophthalmol. 2011;22(4):238–244. doi:10.1097/ICU.0b013e3283477c9c [CrossRef]
- Mendicute J, Irigoyen C, Ruiz M, Illarramendi I, Ferrer-Blasco T, Montés-Micó R. Toric intraocular lens versus opposite clear corneal incisions to correct astigmatism in eyes having cataract surgery. J Cataract Refract Surg. 2009;35(3):451–458. doi:10.1016/j.jcrs.2008.11.043 [CrossRef]
- Mingo-Botín D, Muñoz-Negrete FJ, Won Kim HR, Morcillo-Laiz R, 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(10):1700–1708. doi:10.1016/j.jcrs.2010.04.043 [CrossRef]
- Poll JT, Wang L, Koch DD, Weikert MP. Correction of astigmatism during cataract surgery: toric intraocular lens compared to peripheral corneal relaxing incisions. J Refract Surg. 2011;27(3):165–171.
- Solomon KD, Fernández de Castro LE, Sandoval HP, Vroman DT. Comparison of wavefront sensing devices. Ophthalmol Clin North Am. 2004;17(2):119–127. doi:10.1016/j.ohc.2004.02.003 [CrossRef]
- Summary of Safety and Effectiveness Data. US Food and Drug Administration Web site. www.accessdata.fda.gov/cdrh_docs/pdf/P930014S015b.pdf. Accessed March 7, 2012.
- Summary of Safety and Effectiveness Data. US Food and Drug Administration Web site. http://www.accessdata.fda.gov/cdrh_docs/pdf/P930014S045b.pdf. Accessed March 7, 2012.
- Mendicute J, Irigoyen C, Aramberri J, Ondarra A, Montés-Micó R. Foldable toric intraocular lens for astigmatism correction in cataract patients. J Cataract Refract Surg. 2008;34(4):601–607. doi:10.1016/j.jcrs.2007.11.033 [CrossRef]
- Hoffmann PC, Auel S, Hütz WW. Results of higher power toric intraocular lens implantation. J Cataract Refract Surg. 2011;37(8):1411–1418. doi:10.1016/j.jcrs.2011.02.028 [CrossRef]
- 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(1):54–59. doi:10.1016/j.jcrs.2011.08.028 [CrossRef]
- Koshy JJ, Nishi Y, Hirnschall N, Crnej A, Gangwani V, Maurino V, Findl O. Rotational stability of a single-piece toric acrylic intraocular lens. J Cataract Refract Surg. 2010;36(10):1665–1670. doi:10.1016/j.jcrs.2010.05.018 [CrossRef]
- Scialdone A, Raimondi G, Monaco G. In vivo assessment of higher-order aberrations after Acrysof Toric intraocular lens implantation: a comparative study [published online ahead of print December 1, 2011]. Eur J Ophthalmol. doi:10.5301/ejo.5000090 [CrossRef] .
- Ahmed II, Rocha G, Slomovic AR, et al. Canadian Toric Study Group. Visual function and patient experience after bilateral implantation of toric intraocular lenses. J Cataract Refract Surg. 2010;36(4):609–616. doi:10.1016/j.jcrs.2009.10.044 [CrossRef]
- Shah S, Sheppard A, Bhatt U, Wolffsohn J. Visual outcomes and patient satisfaction with a new toric monofocal intraocular lens. Presented at: XXIX Congress of the European Society of Cataract and Refractive Surgeons. ; September 17–21, 2011. ; Vienna, Austria. .
- Carey PJ, Leccisotti A, McGilligan VE, Goodall EA, Moore CB. Assessment of toric intraocular lens alignment by a refractive power/corneal analyzer system and slitlamp observation. J Cataract Refract Surg. 2010;36(2):222–229. doi:10.1016/j.jcrs.2009.08.033 [CrossRef]
- Holzer MP, Goebels S, Auffarth GU. Precision of NIDEK OPD-scan measurements. J Refract Surg. 2006;22(9 Suppl):S1021–S1023.
- Burakgazi AZ, Tinio B, Bababyan A, Niksarli KK, Asbell P. Higher order aberrations in normal eyes measured with three different aberrometers. J Refract Surg. 2006;22(9):898–903.
- Rozema JJ, Van Dyck DE, Tassignon MJ. Clinical comparison of 6 aberrometers. Part 2: statistical comparison in a test group. J Cataract Refract Surg. 2006;32(1):33–44. doi:10.1016/j.jcrs.2004.11.052 [CrossRef]
- Kohnen T, Klaproth OK, Bühren J. Effect of intraocular lens asphericity on quality of vision after cataract removal: an intraindividual comparison. Ophthalmology. 2009;116(9):1697–1706. doi:10.1016/j.ophtha.2009.03.052 [CrossRef]
- Cui H, Hu R, Zhang Y, Lou D. Comparison of pseudophakic visual quality in spherical and aspherical intraocular lenses. Can J Ophthalmol. 2009;44(3):274–278. doi:10.3129/i08-121 [CrossRef]
- Packer M, Fine IH, Hoffman RS. Aspheric intraocular lens selection: the evolution of refractive cataract surgery. Curr Opin Ophthalmol. 2008;19(1):1–4. doi:10.1097/ICU.0b013e3282f2d791 [CrossRef]
- Montés-Micó R, Ferrer-Blasco T, Cerviño A. Analysis of the possible benefits of aspheric intraocular lenses: review of the literature. J Cataract Refract Surg. 2009;35(1):172–181. doi:10.1016/j.jcrs.2008.09.017 [CrossRef]
- Amano S, Amano Y, Yamagami S, et al. Age-related changes in corneal and ocular higher-order wavefront aberrations. Am J Ophthalmol. 2004;137(6):988–992. doi:10.1016/j.ajo.2004.01.005 [CrossRef]
- Kuroda T, Fujikado T, Maeda N, Oshika T, Hirohara Y, Mihashi T. Wavefront analysis in eyes with nuclear or cortical cataract. Am J Ophthalmol. 2002;134(1):1–9. doi:10.1016/S0002-9394(02)01402-2 [CrossRef]
Patient Demographics and Clinical Information
||Tecnis ZCT Group
||Acrysof SN6AT Group
||65.85±4.16 (63 to 76)
||67.4±11.9 (54 to 80)
|Male sex, n (%)
|Right eyes, n (%)
||0.49±0.10 (0.7 to 0.20)
||0.58±0.19 (0.88 to 0.30)
|Corneal astigmatism (D)
||1.96±0.45 (1.02 to 2.64)
||2.07±0.37 (1.14 to 2.91)
|IOL type (n)
|IOL power (D)
||23.75±2.82 (17.50 to 24.00)
||21.62±2.08 (15.00 to 24.50)
Visual Acuity and Refractive Results at 2 Months Postoperatively
||0.12±0.06 (0 to 0.2)
||0.13±0.10 (0 to 0.4)
||0.02±0.04 (0 to 0.1)
||0.04±0.05 (0 to 0.05)
||−0.11±0.72 (−1.25 to +1.00)
||0.06±0.64 (−1.25 to +0.75)
||−0.56±0.35 (−1.00 to 0)
||−0.41±0.32 (−1.25 to 0)
||−0.19±0.74 (−1.38 to +0.88)
||−0.14±0.64 (−1.62 to +1.50)
Ocular Aberrometry Analysis at 2 Months Postoperatively
||0.66±0.39 (0.15 to 1.22)
||0.52±0.14 (0.346 to 0.766)
||0.08±0.07 (0 to 0.153)
||0.12±0.07 (0.02 to 0.187)
||0.27±0.25 (0.06 to 0.672)
||0.18±0.09 (0.09 to 0.29)
||0.52±0.26 (0.13 to 0.85)
||0.34±0.22 (0.14 to 0.72)
||0.05±0.07 (0 to 0.18)
||0.02±0.01 (0 to 0.04)