Multifocal intraocular lens (IOL) technology has undergone significant developments in the past decade. Initially, most multifocal IOLs were bifocal; that is, they provided a near focus and a far focus.1 Several studies analyzed the intermediate vision provided by bifocal IOLs with different near additions. Although results improved with a lower addition, patients were not completely comfortable performing activities requiring a sharp intermediate focus.2,3 Trifocal IOLs were designed to overcome these limitations. These IOLs distribute incoming light to 3 foci, with the goal of improving intermediate vision and achieving higher spectacle independence.4,5 Clinical studies that compared different bifocal IOLs and trifocal IOLs6,7 found that trifocal IOLs provided better intermediate vision with no deterioration in near vision, thus decreasing the number of patients requiring spectacle correction.
Postoperative astigmatism can interfere with the performance of multifocal IOLs,8 and approximately 30% of patients having cataract surgery have preoperative astigmatism of at least 1.00 diopter (D).9 Astigmatism can be corrected with corneal relaxing incisions,10 corneal laser excimer procedures,11 or astigmatic keratotomy performed with a femtosecond laser.12 However, toric IOLs have been shown to be the most predictable method of astigmatism correction.13,14 Thus, toric versions of trifocal IOL designs were developed to improve spectacle independence in patients with astigmatism who are candidates for trifocal IOL implantation. Studies15–17 have shown that patients with astigmatism who had implantation of trifocal toric IOLs achieved good subjective outcomes after surgery. However, to our knowledge, few studies have directly compared the performance of trifocal toric IOLs with that of their spherical counterparts.18
The purpose of this study was to evaluate the visual performance and subjectively reported outcomes of patients with bilateral implantation of the spherical version or toric version of the AcrySof IQ PanOptix trifocal IOL (Alcon Laboratories, Inc.).
Patients and methods
This prospective case series study was performed at Clínica Rementería, Madrid, Spain, and followed the tenets of the Declaration of Helsinki. An ethics committee reviewed and approved the study, and all patients provided informed consent after receiving an explanation of the nature of the study had been explained.
The study included cataract patients who were seeking spectacle independence and were scheduled for bilateral implantation of 1 of 2 diffractive trifocal IOLs, the AcrySof IQ PanOptix spherical or AcrySof IQ PanOptix toric; the 2 IOLs have the same platform. Toric IOLs were implanted in patients with 1.00 D or more of preoperative corneal astigmatism. Patients having surgery between September 2016 and September 2018 were evaluated for inclusion.
Exclusion criteria included amblyopia, a history of ocular surgery or ocular pathology, an abnormal iris, and intraoperative or postoperative complications. Patients without cataract who were scheduled for IOL implantation for refractive purposes alone were also excluded.
All patients had an extensive ophthalmologic examination that included refraction, screening for ocular conditions and systemic disease, slitlamp biomicroscopy, and fundus evaluation. The following were performed: uncorrected (UDVA) corrected (CDVA) distance visual acuity measurements, slitlamp evaluation of the anterior segment, intraocular pressure measurement, corneal topography (Pentacam HR, model 70,900, Oculus Optikgeräte GmbH), specular biomicroscopy (CEM-530, Nidek Co, Ltd.), dilated fundus examination, optical coherence tomography (OCT) examination of the macula and optic nerve (Cirrus HD-OCT 5000, Carl Zeiss Meditec AG), and IOL calculation with swept-source OCT (SS-OCT) (IOLMaster 700, Carl Zeiss Meditec AG).
The target refraction was emmetropia in all cases. Candidates for toric IOL implantation were also examined with an image-guided surgery system (VERION, Alcon Laboratories, Inc.). The power of the toric IOLs and their implantation axis were calculated using the Alcon AcrySof toric calculator.A The spherical power was taken from the SS-OCT data (ie, the first IOL with the lowest negative spherical equivalent; the corneal values from the SS-OCT device were used. The Barrett formulaB was used, with centroid surgically induced astigmatism of 0.10 D for right eyes and 0.15 D for left eyes. For eyes with oblique astigmatism, the Holladay 1 formula19 was selected.
The AcrySof IQ PanOptix is a single-piece spherical IOL of hydrophobic acrylic material with ultraviolet-light and blue-light filtration and a refractive index of 1.55 at a wavelength of 550 nm. It has modified L-haptics with a 0-degree angle, a 13.0 mm total diameter, and a 6.0 mm optic zone. The anterior surface has a negative spherical aberration (−0.1 μm) to compensate for the positive spherical aberration of the cornea. The IOL is available from +6.00 D to +30.00 D in 0.50 D increments and from +31.0 D to +34.00 D in 1.00 D increments.
The optical zone of the IOL is diffractive in the central 4.5 mm of the anterior surface with 15 diffractive annuli. It has an outer refractive annulus (from 4.5 to 6.0 mm). This IOL is commercially available as a panfocal lens with quadrifocal IOL technology. The diffractive design of the IOL distributes the incoming light into the following 4 foci: distance focus from the base curve, 120 cm, 60 cm, and 40 cm. The optical design of the diffractive zone is modified to redistribute the energy of the intermediate focus at 120 cm to the distance focus. Therefore, the quadrifocal design offers a trifocal function at far, intermediate (60 cm/+2.17 D add), and near (40 cm/+3.25 D), and it is referred to as a trifocal IOL in this paper.21
The AcrySof IQ PanOptix toric IOL has the same design and material as the spherical version. However, the posterior surface of the IOL is biconical, creating a toricity to correct corneal astigmatism. The toric IOL is available in 5 dioptric (model T2 to T6) to correct from 1.00 to 3.75 D of astigmatism. The IOL has indentations at the margin near the base of each haptic that serve as marks for correct orientation of the IOL in the capsular bag.
All cataract surgeries were performed by 1 or 2 experienced surgeons (L.A.R, J.G.P); each surgeon performed procedures in both groups (ie, spherical IOL and toric IOL). The following standard protocol was used in all cases: topical and intracameral anesthesia, 2.2 mm clear corneal incision at 135 degrees, and stop-and-chop phacoemulsification. Surgery was performed first in the eye with the worst visual acuity; contralateral surgery took place between 2 days and 7 days later. Toric IOL implantation was performed with the help of the image-guided surgery system.
All patients were evaluated 1 day after each procedure and 1 week, 1 month, and 3 months after the second-eye surgery. This paper reports the 3-month postoperative results. The following tests were performed: monocular and binocular UDVA and CDVA, monocular and binocular uncorrected (UIVA) and distance-corrected (DCIVA) intermediate visual acuity, monocular and binocular distance-corrected (DCNVA), uncorrected (UNVA) near visual acuity, binocular defocus curves, and binocular contrast sensitivity.
Photopic conditions for all measurements were 85 candelas/m2. Distance visual acuity was measured using a 22-inch light-emitting diode liquid crystal display system (CC-100 HW 5.0 series, Topcon Corp.) displaying Early Treatment Diabetic Retinopathy Study (ETDRS) charts at 4 m. Intermediate acuities and near visual acuities were measured using the 2000 New ETDRS logarithmic visual acuity chart (Precision Vision) at 60 cm and 33 cm, respectively. Subjective refraction was performed with the ETDRS chart at 4 m. Then, the patients observed the ETDRS chart through lenses from ranging from −5.00 D to +3.00 D in 0.50 D steps. The best visual acuity at each step was recorded and used to create the binocular defocus curves.
The binocular contrast sensitivity function (CSF) was measured at spatial frequencies of 3, 6, 12, and 18 cycles per degree using the Functional Acuity Contrast Test (Test SV-1000) of the CC-100 HW 5.0 series system (Topcon). The CSF values were obtained as absolute logarithm of contrast sensitivity 10.
Three months after surgery, patients completed the Catquest 9SF questionnaire, which was recently validated in a Spanish population both monofocal IOLs and trifocal IOLs.20 The Catquest-9SF consists of 3 sets of items (9 items in total) as follows: a global daily life difficulty item (item 1), a global vision satisfaction item (item 2), and a group of 7 items referring to difficulties in performing day-to-day activities, such as reading text, recognizing people’s face, or the ability to walk on uneven surfaces (items 3 to 9). A lower score translates to a worse patient-perceived outcome. The response of “cannot decide” was treated as missing data in the analysis.
The calculation of the required sample size was based on the monocular CDVA. A difference of 0.2 logarithm of the minimum angle of resolution (logMAR) units (standard deviation 0.05) was assumed to be clinically significant.7 Based on this assumption, an α of 0.05, and a power of 0.8, it was calculated that 25 eyes were required in each group. At least 40 eyes were included to assume a normal distribution.
Statistical analysis was performed using SPSS for Windows software (version 20.0, IBM Corp.). The Kolmogorov-Smirnov test was used to evaluate the normality of the data distributions. Because the data were found to be normal, the 2 study groups were compared using the Student t test. Differences were considered statistically significant when the P value was less than 0.05 (ie, at the 5% level).
The study comprised 250 eyes of 125 patients. The spherical IOL group included 83 patients with a mean age of 65.73 years ± 8.59 (SD). The toric IOL group included 42 patients with a mean age of 65.07 ± 8.14 years (P = .34). Table 1 shows the preoperative characteristics in both groups. There were no statistically significant in any characteristic differences between the groups.
Table 2 shows the 3-month postoperative monocular visual distance, intermediate, and near vision outcomes. No statistically significant between-group differences were detected. All surgeries were uneventful, were no intraoperative or postoperative complications.
Three months after surgery, the mean sphere in the spherical IOL group was 0.05 ± 0.21 D (range −0.50 to +1.00 D), the mean cylinder was −0.15 ± 0.35 D (range −1.75 to 0.00 D), and the mean manifest refraction spherical equivalent was −0.03 ± 0.14 D (range −0.75 to 0.38 D). The values in the toric group were 0.08 ± 0.24 D (range −0.50 to +1.0 D), −0.11 ± 0.28 D (range −1.25 to 0.00 D), and 0.01 ± 0.14 D (range −0.50 to 0.50 D), respectively.
Figure 1 shows the bifocal defocus curves for IOL designs. Both curves are almost overlapping; no statistically significant differences were found at any vergence between the spherical IOL and the toric IOL. Similarly, there were no statistically significant between-group differences in contrast sensitivity performance (Figure 2).
Figure 3 shows the Catquest 9SF questionnaire results for item 1 and item 2 (global daily life difficulty and satisfaction with current vision, respectively). There were no statistically significant differences between the 2 IOLs (item 1, P = .15; item 2, P = .45).
Figure 4 show the questionnaire results for the 7 items referring to difficulties in performing day-to-day activities. Again, there was no statistically significant difference in any item between the 2 IOLs (item 3, P = .4; item 4, P = .49; item 5, P = .27; item 6, P = .47; item 7, P = .39; item 8, P = .26; item 9, P = .08).
The aim of trifocal IOLs is to provide good vision not only at far and near but also at intermediate distances, thus reducing spectacle dependence. Today, good intermediate vision is important for performing daily tasks (ie, using laptop computers and smartphones). Previous studies4,5 found that trifocal IOLs can provide a useful third focus for intermediate vision.
Toric IOLs have shown good results in astigmatic patients, preventing the visual disturbances resulting from residual astigmatism after surgery.13,14 Therefore, toric versions of several trifocal spherical designs are now available with the goal of offering spectacle independence to astigmatic patients who have cataract surgery; thus far, the reported results have been good.15–17 In the current study, we analyzed and compared the visual performance and the subjective satisfaction of patients who had bilateral implantation of the spherical or toric version of the AcrySof IQ PanOptix trifocal IOL (PanOptix); the 2 versions have the same platform.
Defocus curves aim to simulate the visual performance of IOLs in daily life, in which patients need to see objects at different distances. The defocus curves of the 2 IOL groups in our study were almost overlapping, showing that the visual function did not deteriorate with astigmatic correction. As expected, the defocus curves did not show the 2 peaks typical of bifocal IOL but rather a peak for distance vision that decreased slightly up to the near vision focus. Both groups achieved a visual acuity of 0.1 logMAR or better between +0.50 D and −2.50 D, which is similar to the defocus curve described for the FineVision toric trifocal IOL (PhysIOL SA) (visual acuity 0.13 logMAR or better between +1.00 D and −3.00 D)18 and slightly better than reported for the AT LISA tri toric 939MP IOP IOL (Carl Zeiss Meditec) (visual acuity 0.2 logMAR or better between +1.00 D and −2.50 D).15
However, defocus curves are not fully representative of reading visual acuity because the effects of convergence, pupil constriction, and the illumination level are not taken into consideration. Thus, visual acuity was also measured at intermediate and near distances. Studies of intermediate and near visual acuities22,23 performed using a reading desk reported that the preferred intermediate distance is between 61.5 cm and 64.2 cm and the near distance between 34.6 cm and 38.7 cm. Thus, we used distances of 60 cm and 33 cm, respectively, as in previous reports.17,24
Visual acuity values for all distances were similar in the 2 IOL groups in our study, with no statistically significant differences. Previous studies of the visual performance with the PanOptix IOL21,24,25 reported similar results, with UDVA values ranging from −0.05 logMAR to 0.04 logMAR, UIVA from 0.20 to 0.06 logMAR, and UNVA from 0.08 logMAR to 0.05 logMAR.
However, to our knowledge, no published study has directly compared the spherical AcrySof IQ PanOptix IOL with its toric version. Our results suggest that the visual outcomes are equivalent between the 2 versions. Poyales and Garzon18 reported the same similarity between the spherical version and toric version of the FineVision trifocal IOL. They found excellent self-reported outcomes, with patients gaining functional uncorrected visual acuity across all distances. However, in contrast to our study, in which both designs performed almost identically, eyes with the FineVision toric IOL had worse binocular CDVA, mean monocular DCIVA at 66 cm, and DCNVA than eyes with the spherical version, although the difference of 1 to 2 letters was not clinically relevant.
In our study, we also analyzed the potential impact of the particular distribution of light of the IOL versions on contrast sensitivity. The toric version of IOL not only distributes incoming light to 3 foci, it also simultaneously seeks to compensate for the flattest and the steepest meridians of the cornea in these 3 foci. Previous studies evaluated whether the creation of 3 foci would lead to a worse visual quality than the creation of 2 foci. Most studies found no differences in CSF outcomes between trifocal IOLs and bifocal IOLs.26,27 The only other paper comparing the CSF of a spherical trifocal IOL and toric trifocal IOL of the same model found a trend toward reduced contrast sensitivity with the spherical IOL. However, these differences were not statistically significant and the authors concluded that the CSF values with the spherical IOL and the toric IOL were similar.18 We found no statistically significant difference at any spatial frequency between the toric IOL and spherical IOL. Thus, toricity does not seem to cause worse visual quality with the PanOptix platform. The CSF was not measured under mesopic conditions; further studies should be performed to determine whether toric trifocal IOLs affect visual quality under low illumination.
In addition, assessing vision for real-life tasks is not the same as assessing reading optotypes. In this study, we tried to determine the patients’ perceived outcomes using the Catquest-9SF questionnaire. The Catquest-9SF has been found to be highly responsive in assessing the results of cataract surgery.20 There was no significant between-group difference in the item assessing global daily-life difficulty; patients in both groups said they had little difficulty in their everyday life. Overall satisfaction with postoperative vision was also good in both groups. Furthermore, patients in both groups reported having little difficulty performing day-to-day activities. Similar to the global items, there were no between-group differences in specific tasks. Thus, the toric trifocal IOL achieved good subjective satisfaction scores that were comparable to those obtained with the spherical IOL.
The overall results in our study showed very similar results between the 2 IOL versions of the same platform. However, to provide effective refractive compensation for both meridians, correct intraoperative positioning of the toric IOL is mandatory. Previous studies evaluating the impact of toric IOL misalignment28,29 found that 1 degree of misalignment causes a loss of approximately 3% of the effective cylinder power and that the entire toric effect is lost with 30 degrees of misalignment. Furthermore, a previous study assessing visual outcomes with multifocal toric and monofocal toric IOLs30 reported that misalignment had a greater impact on vision with multifocal IOL designs. Hence, correct positioning of the toric IOL is crucial for achieving satisfactory results. Finally, centration and stability of multifocal toric IOLs are key to avoiding dysphotic symptoms. In our study, implantation of the toric IOL was guided by a digital marker. We believe this step is required to achieve accurate centration.
Although our study found good and comparable results between the 2 IOL versions, it has limitations. First, we considered cataract patients only; studies of aspheric trifocal IOL and trifocal toric IOL implantation for refractive correction only might yield different results or results in which the differences between designs are more evident. Moreover, our study was performed 3 months after surgery. A longer follow-up, for example 12 months, might show changes in the IOL or capsular bag that could affect the visual and the refractive outcomes.
In conclusion, the current study found good and similar results with the spherical version and toric version of a trifocal IOL with the same platform. With a correct alignment of the toric IOL, the visual quality and patient satisfaction are comparable between the 2 versions of the IOL.
What Was Known
- Trifocal intraocular lenses (IOLs) can provide a useful third focus for intermediate vision.
- Monofocal and bifocal toric IOLs correct the steepest and the flattest meridians in astigmatic eyes.
What This Paper Adds
- After correct implantation and alignment, the visual quality and patient satisfaction with the toric trifocal IOL studied were excellent and can be considered directly comparable with those of the nontoric version of the same platform design.
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None of the authors has a financial or proprietary interest in any material or method mentioned.
Other Cited Material
A. Alcon Laboratories, Inc. The ALCON® online toric IOL calculator with the Barrett toric algorithm. Available at: http://www.acrysoftoriccalculator.com/
B. American Society of Cataract and Refractive Surgery. Barrett toric calculator. Available at: http://www.ascrs.org/barrett-toric-calculator