Pedro Tañá- Rivero
To assess refractive and visual outcomes following phacoemulsification with femtosecond laser-assisted cataract surgery (FLACS) using intra- operative aberrometry and implantation of a toric intraocular lens (IOL) in eyes with different degrees of astigmatism.
One hundred two eyes of 70 patients who underwent implantation of the transitional toric 565 Precizon IOL (Ophtec BV) were enrolled. FLACS, capsular tension ring insertion, and intraoperative aberrometry were performed. Main outcome measures were refractive error, uncorrected- and corrected distance snellen decimal visual acuity values (UDVA and CDVA, respectively), and IOL rotation. Specif- ically, a vector analysis was carried out with J0 and J45 evaluation. Eyes were evaluated 1-year after surgery.
Overall, 94.12% (96 eyes) and 100% (102 eyes) of the eyes showed a spherical equivalent (SE) within ± 0.50D and ± 1.00D, respectively. The mean SE and refractive cylinder were – 0.06 ± 0.29D and – 0.23 ± 0.37D, respectively.
Vector analysis revealed that 100% of the eyes were within ± 0.50D for the J0 and J45 cylindrical com- ponents. The mean toric axis rotation was 1.10 ± 1.71° (from 0° to 5°), 77% (79 eyes), and 100% (102 eyes) of the eyes showed UDVA and CDVA of 20/25, respectively. The postoperative mean values of monocular UDVA and CDVA were 0.88 ± 0.17 and 0.96 ± 0.07 (about 20/20), respec- tively. No patient required IOL realignment during the postoperative follow-up.
The present study suggests that the use of the Precizon IOL after FLACS, using intraoperative aberrometry in patients with different amounts of astigmatism, provides good visual acuity, accurate refractive outcomes, and excellent rotational stability.
Toric – Astigmatism – Intraocular lens – Phacoemulsification – Cataract
Refractive error correction after cataract surgery needs to be minimized or removed to provide our patients the best quality of vision. Accurate preoperative biometry with precise intraocular lens (IOL) power calculation is mandatory for optimum refractive outcomes. Obvi- ously, this necessarily includes also the correction of corneal astigmatism. It has been found that about one third of eyes have 1.00D or more and would benefit from its correction at the time of the surgery [1, 2]. Uncorrected astigmatism affects the quality of vision drastically . A recent systematic review and meta- analysis concluded that toric IOLs provided better uncorrected distance visual acuity (UDVA), greater spectacle independence, and lower amounts of resid- ual astigmatism than non-toric IOLs . This study considers different toric IOL models, preoperative astigmatism (0.75–3.00D), and follow-ups (3–6 months). The benefit of using toric IOLs has also been reported in eyes with high corneal astigma- tism during cataract  and refractive lens exchange  surgeries.
To correct astigmatism properly, the toric IOL should be placed accurately at the required axis and must remain stable during the postoperative period. Deviation of the axis position may occur either intraoperatively (malposition due to incorrect target or marking the axis) or after implantation (rotation of the lens). The use of intraoperative aberrometry systems helps minimize the incidence of intraopera- tive alignment errors [7, 8]. Previous literature about different toric IOLs usually reports rotational stability of three to six months [4-6] based on the premise that IOLs do not rotate significantly after anterior and posterior capsules fuse. The majority of IOL rotation occurs within the initial days after the surgery . However, the success of a toric IOL needs to be analyzed, considering that it should allow a stable po- sition in the capsular bag over time. Capsular bag shrinkage due to fibrosis is the most frequent cause of IOL rotation and frequently occurs during the first three months after IOL implantation [10-11]. Capsu- lorhexis size, IOL design, and its material may influence the capsule fusion and, hence, IOL rotational stability ; in fact, IOL rotation has been associated with increasing capsular bag diameter . Inappro- priate capsulorhexis size for IOL coverage also may contribute to postoperative rotation. Accurate capsu- lotomy with femtosecond laser-assisted cataract surgery (FLACS) may help to create well-centered circular continuous capsulorhexis, providing adequate IOL coverage essential to ensure IOL stability. Despite some authors finding no clinically significant differences (i.e., visual acuity and residual refraction) in eyes treated with standard phacoemulsification and FLACS with toric IOL implantation, some have reported that total ocular higher-order aberrations were slightly lower . In fact, internal vertical was significantly lower in femtosecond eyes [14, 15]. Other authors concluded that FLACS appears to provide improved refractive outcomes in toric IOLs . We should take into account that visual quality may be improved by lower IOL tilt (related to vertical coma) as previously suggested . Then, we consider that accurate capsulotomy with FLACS and the use of an image-guided system may contribute to the success of toric IOL implantation during the early but also late postoperative period.
The objective of our study was to analyze the visual and refractive outcomes of one toric IOL (Precizon), using FLACS and intraoperative aberrometry in cataract patients with a one-year follow-up. This lens has been previously evaluated in vitro  and after cataract surgery [18–22]. The clinical studies carried out showed good short-term results, but as far as we know, ours is the first study that showed a longer analysis of the Precizon IOL past one year and used FLACS with intraoperative aberrometry.
We retrospectively examined 102 eyes of 70 patients at the Oftalvist Clinic, Spain. The study was carried out in accordance with the tenets of the Declaration of Helsinki and approved by the Institutional Review Board. Informed consent was obtained from all patients after the nature, and possible consequences of the study were explained. Inclusion criteria included significant cataracts, preexisting corneal astigmatism between 0.75 and 8 D, age between 50 and 90 years. Exclusion criteria consisted of history of glaucoma, macular degeneration or retinopathy; corneal disease; irregular astigmatism; abnormal iris; pupil deformation; and history of prior ocular inflammation.
All eyes were implanted with the PrecizonÒ toric IOL Model 565 (Ophtec BV, Groningen, the Netherlands). This IOL is a biconvex, single-piece, aspheric (spher- ical aberration-free design) toric with a transitional conic toric surface. The IOL has a closed-loop haptic design to reduce rotation and a 360-degree square edge (0 degrees angulation). The lens is composed of 25% hydrophilic acrylic (ultraviolet cut-off wavelength at 360 nm) and has an optic body diameter of 6 mm and an overall diameter of 12.5 mm (refractive index of 1.46). A constant for ultrasound is 118.0 and 118.5 for optical biometry. Spherical powers range from + 10.00 to + 30.00 D (0.5D increments) and cylinder powers from 1.00 to 10.00 D (0.5D increments).
Before surgery, a 0°–180° axis was marked with all patients sitting upright at a slit-lamp using a horizontal slit beam. Intraoperatively, the intended implantation axis was marked on the limbus after correctly aligning a Mendez ring to the primary marks to ascertain the intended angle of placement according to the preop- erative plan. All surgical procedures were performed under topical anesthesia by FPP, using the LDV Z8 (Ziemer Ophthalmic Systems AG, Port, Switzerland) femtosecond laser platform through a 2.2-mm tempo- rally located clear corneal incision. With the laser system, a standardized 5 mm diameter, laser-assisted capsulotomy centered on the pupil, as well as a ring lens fragmentation pattern, was performed. After cataract removal and posterior capsule polishing, the capsular bag was filled with sodium hyaluronate 10 mg/ml 1%. The toric and spherical IOL powers were determined using the ORA system with Ver- ifEye + (Alcon, Fort Worth, TX, USA). This system (based on Talbot-Moire interferometry) performs real- time calculation of IOL power as well as of the axis under aphakic condition. It allows axis refinement by providing the direction and the magnitude of ration necessary to achieve a minimum residual astigmatism. A capsular tension ring (CTR) was inserted into the capsular bag. The CTR was implanted to improve the stability of the capsular bag, to improve the centration of the IOL, and to facilitate a possible future exchange of the IOL if necessary. The IOL was implanted using a disposable DualTec IOL injector (Ophtec BV, Groningen, the Netherlands). After complete aspira- tion of the viscosurgical device, intraoperative aber- rometry was used to refine the position of the toric IOL axis refinement with the chosen IOL until the ‘‘no recommended rotating’’ instruction appeared.
Preoperative and postoperative assessment
All patients were evaluated previously and the following examinations were carried out: Snellen decimal monocular UDVA and corrected distance visual acuity (CDVA), refraction, corneal topography (Pentacam, Oculus Optikgera ̈te GmbH, Wetzlar, Ger- many), and optical biometry (IOLMaster 700, Carl Zeiss Meditec AG, Jena, Germany). In addition, slit- lamp examination, Goldmann tonometry for intraoc- ular pressure (IOP) measurement, and dilated fun- doscopy were performed. IOL power calculation was based on IOLMaster measurements, considering a historical level of surgically induced astigmatism by the incision of 0.25 D. IOL power was calculated using the Hoffer Q formula if the axial length was shorter than 22 mm, or using the SRK/T formula if the axial length was 22 mm or longer. IOL cylinder power and target IOL axis were calculated using the online Precizon Toric Calculator (Ophtec, Toric IOL Calcu- lator, https://calculator.ophtec.com/). The targeted refraction was emmetropia.
Postoperative examinations were performed at the standard visits post-surgery in our center, and the analysis of the outcomes was carried out one year after surgery. A standard ophthalmologic examination, including refraction (sphere, cylinder and axis), IOP measurement, and slit-lamp biomicroscopy, was per- formed. UDVA and CDVA were measured. Rotation of the IOL was assessed after full mydriasis through analysis of the IOL marks. The postoperative IOL mark at one year was compared with the IOL mark at one day after surgery. Clockwise rotation was consid- ered positive rotation and counter clockwise negative rotation. The difference between postoperative day one and postoperative year one was considered IOL rotation.Manifest refractions in conventional script notation (S [sphere], C [cylinder], a [axis]) were converted to power vector coordinates by the following formula:
where SE is the spherical equivalent and J0 and J45 are the two Jackson crossed-cylinders equivalent to the conventional cylinder.
Our study considered the outcomes of 102 eyes of 79 consecutive patients (39 eyes from males and 63 eyes from females) who underwent FLACS with Precizon toric IOL implantation. Patients’ demographics and preoperative data of our sample are shown in Table 1. Mean patient age was 68.29 ± 8.31 years (ranging from 51 to 89 years). All surgeries were uneventful, and there were no complications in any of the cases during the surgery and follow-up. No patient required IOL repositioning due to misalignment, and no posterior capsule opacification was observed during the postoperative follow-up.
CDVA distance corrected visual acuity,
IOL intraocular lens power
Standard graphs for reporting refractive and visual acuity outcomes were constructed. Figure 1 shows the distribution of SE refraction after the surgery (accu- racy). The highest percentage of eyes, 65.69% (67 eyes), was for the range ± 0.13D, followed by about 18.63% (19 eyes) for the – 0.50 to + 0.14D range; 94.12% (96 eyes) and 100% of eyes were within ± 0.50D and ± 1.00D, respectively. The mean postop- erative SE was – 0.06 ± 0.29D (ranging from 0.63 to – 1.00D). Figure 2 shows the distribution of the refractive cylinder before and after the surgery. Note from this figure the change of distribution after the surgery to low values of astigmatism. Specifically, its analysis after surgery revealed that all eyes showed a value of B 1.00D, 83.34% (85 eyes) B 0.50D, and 69.61% (71 eyes) B 0.25D (see Figure 2). Mean postoperative refractive cylinder (- 0.23 ± 0.37 D, ranging from 0 to – 1.00 D) was significantly reduced compared to preoperative values (see Table 1, p \ 0.05). The power vector analysis is plotted in Figure 3, showing the attempted versus achieved SE (top) and for both components of astigmatism: J0 (middle) and J45 (bottom). Solid lines represent the best-fit line for each graph (regression equations and values were also included), and dotted lines consider intervals of ± 1.00D for SE and ± 0.50D for J0 and J45. As previously indicated, all eyes showed an SE within ± 1.00D and J0 and J45 within ± 0.50D. The power vectors, SE, J0, and J45 refractive components,
decreased significantly after one year of follow-up (p \ 0.05); the SE component dropped from – 1.64 ± 3.72D preoperatively to – 0.06 ± 0.29D one year after surgery; J0 and J45 decreased from – 0.10 ± 1.11D and 0.09 ± 0.67D preoperatively to – 0.02 ± 0.14D and 0.01 ± 0.11D at one year post- operatively, respectively. To visualize the change in refractive cylinder due to the toric IOL implantation better, Figure 4 shows the astigmatic component of the power vector as represented by the two-dimen- sional vector (J0, J45) for refractive astigmatism before and one year after the surgery. The origin in this graph (0, 0) represents an eye free of astigmatism. Inrelation to the rotational stability of the toric IOL, we found at postoperative one year a mean toric axis rotation of 1.10° ± 1.71°, with a range varying from 0° to 5°.
Figure 5 shows the percentage of eyes with cumu- lative preoperative Snellen CDVA and postoperative Snellen UDVA and CDVA (20/x or better). After surgery, 58% of eyes (n = 59) showed a UDVA of 20/20 and improved to 77% (n = 79) for CDVA postoperatively; 77% (n = 79) and 100% (n = 102) of eyes showed UDVA and CDVA of 20/25 or better after the surgery, respectively. Compared to the preoperative CDVA, the percentages of cumulative UDVA and CDVA increased after the surgery. The postoperative mean values of monocular distance Snellen decimal UDVA and CDVA were 0.88 ± 0.17 and 0.96 ± 0.07, respectively.
As introduced, the use of toric IOLs to correct corneal astigmatism at the time of cataract surgery improved our patients’ quality of vision. These lenses increased the percentage of satisfaction, resulting in spectacle independence [4, 23]. In the present study, we analyzed the outcomes at the one-year follow-up, reported after implanting the Precizon toric IOL in a large population. For comparative purposes, we have included in Table 2 those previous clinical studies published about this lens. Five clinical studies reported data with several samples, follow-ups, ages, and corneal astigmatism to be corrected, among other parameters. Specifically, Table 3 shows the mean values and ranges, when available, for visual acuity and refractive outcomes. Rotational stability of the lens for each study was also included.
As we have reported, the use of intraoperative aberrometry minimizes the incidence of intraoperative alignment errors [7, 8], allowing realization of the most adequate IOL power and position and reducing postoperative astigmatism . Intraoperative aber- rometry enables intraoperative measurement of resid- ual refraction, allowing the surgeon to position the lens accurately, based on live residual refractive cylinder results. Hatch et al.  found that patients after cataract surgery with IOL toric implantation using intraoperative aberrometry were 2.4 times more likely to have \ 0.50D of postoperative astigmatism. Woodcock et al. , in a sample of 242 eyes, found that intraoperative aberrometry increased the percent- age of eyes with postoperative refractive astigma- tism B 0.50D and reduced the mean postoperative refractive astigmatism at one month. In contrast, Solomon and Salas , in a comparative study with 104 eyes, concluded that intraoperative markerless, computer-assisted registration, and biometric guid- ance summarily yielded less remaining refractive cylinder than toric IOL placement guided by intraop- erative aberrometry. In our series, we have found intraoperative aberrometry to be an excellent system to control IOL alignment during the surgery.
The outcomes of our clinical study show that the implantation of the Precizon toric IOL, using intraop- erative aberrometry with FLACS, provided good visual and refractive outcomes. Predictability both for SE and astigmatism and excellent rotational stability support the use of this lens in patients with different degrees of corneal astigmatism
Author contributions – FPP conception of work, data analysis and interpretation, writing of manuscript. RPP data acquisition, data analysis and interpretation. RRM; data analysis and interpretation, writing of manuscript, RRM data analysis and interpretation, PTR data analysis and interpretation. All authors read and approved the final manuscript.
Conflict of interest – The authors declare that there is no conflict of interest.
Consent to publish – Patients signed informed consent.
Human and animal rights – All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent – Informed consent was obtained from all individual participants included in the study.
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