Comparison of clinical outcomes of toric intraocular lens, Precizon vs Tecnis: a single center randomized controlled trial

This prospective randomized comparative study included 40 eyes of 40 patients who were scheduled for cataract surgery with implantation of toric IOL from April 2016 at Samsung Medical Center, Seoul, Korea. Written informed consents were obtained from 40 consecutive patients before performing the study. These patients were randomly allocated into two groups to receive either Precizon toric IOL or Tecnis toric IOL during the cataract surgery. Inclusion criteria were visually significant cataract and regular corneal astigmatism measured with Scheimpflug imaging (Pentacam HR, Oculus, Wetzlar, Germany) between 0.50 diopter (D) and 2.50 D considering both anterior and posterior corneal surface. The surgically induced astigmatism (SIA) of the operating surgeon was found as 0.50 D for temporal clear corneal incision, so patients were included if their requiring corneal astigmatism correction considering surgically induced astigmatism was more than 1 D considering their steep axis. Each patients had a complete ophthalmological examination. Exclusion criteria were amblyopia, irregular astigmatism, corneal opacity, glaucoma, retinal disease, history of ocular inflammation, history of ocular trauma, and previous other intraocular surgery. Also patients were excluded if they take medications such as a-blocker. This study was approved by Institutional Review Board of Samsung Medical Center(Permission number: SMC 2016–04-147). It was carried out in accordance with the Declaration of Helsinki. The manuscript reporting adheres to the CONSORT guidelines for the reporting of randomized trials. In South Korea, clinical trial registration is not mandatorily required for these randomized comparative study. However we registered the trial in 2017 when we submit the paper to meet the international guidelines. The authors confirm that all ongoing and related trials for this drug/intervention are registered. The enrolled eyes were randomized into two groups using a computer generated random number table with a 1:1 ratio at screening visit. One investigator (N.Y.J.) generated and implemented the randomization allocation process.

Preoperatively, all patients underwent complete ophthalmic evaluation including uncorrected distant visual acuity (UCDVA), best corrected distant visual acuity (BCDVA), refractive errors, and corneal topography using Scheimpflug imaging (Pentacam HR, Oculus, Wetzlar, Germany).

Biometry measurements (axial length and anterior chamber depth) used for IOL power calculation were obtained with optical coherence biometry (IOLMaster, software version 5.02, Carl Zeiss Meditec AG, Jena, Germany). The spherical power of the IOL was calculated using SRK-T formula. Emmetropia was target postoperative spherical equivalent (SE). Surgeon used his typical surgical induced astigmatism magnitude, and all main wound incision was planned to be at temporal side of the cornea. Total corneal astigmatism was calculated considering both anterior and posterior corneal surface measured with Pentacam HR using vector summation according to Alpins’ method [8]. From these data, calculations of the cylindrical power and axis placement were performed using each IOL manufacturer’s online calculator. For Precizon toric IOL, PRECIZON Online Calculator (available from: http://​calculator.​ophtec.​com/​) was used with A-constant of 118.5. For Tecnis toric IOL, Tecnis toric express calculator (available from: http://​www.​amoeasy.​com/​calc/​) was used with A-constant of 119.3. Surgically induced astigmatism of 0.50 D was assumed for all cases.

Characteristics of both IOLs are shown in Additional file 1: Table S1. The Precizon toric IOL Model 565 (Ophtec BV) is a piece of hydrophilic acrylic, monofocal, and aspheric IOL with a transitional conic toric surface (patent pending). It has consistent power from the center to the periphery, yielding a broader toric meridian. It is more resistant of IOL misalignment [9]. It has a closed-loop haptic design. This lens is also aberration free. Tecnis toric IOL has anterior toric surface with a proprietary wavefront-designed toric aspheric optic, resulting in negative spherical aberration [10]. It has open-loop C-haptics. Both toric IOL have two reference marks on the axis of the cylinder of their surface.

Before surgery, 0° - 180° axis was marked with all patient seating upright at slit-lamp using a horizontal slit beam. Intraopertively, 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 preoperative plan. One experienced surgeon (T.Y.C.) performed all surgeries under topical anesthesia (proparacaine hydrochloride 0.5%, Alcaine; Alcon Laboratories, Fort Worth, TX, USA). Phacoemulsification was performed through a 2.75 mm temporal clear corneal incision. After performing continuous curvilinear capsulorrhexis with an intended diameter 5.0 mm and hydrodissection, phacoemulsification of the nucleus and bimanual aspiration of the residual cortex were conducted using Centurion Vision System (Alcon, Laboratories, Fort Worth, TX, USA). Toric IOL was implanted in the capsular bag using injector and disposable cartridge system before removing ophthalmic viscosurgical device (OVD). After removing the OVD, the IOL was rotated to its final targeted position by exactly aligning the toric reference marks on the IOL surface with limbal axis marks. Finally, a balanced salt solution was injected into the incision site to close the corneal incision, causing edema. Before finishing the surgery, intraoperative photographs were taken for all cases. After the surgery, postoperative eye drops of antibiotics (gatifloxacin 0.3%, Gatiflo; Handok, Seoul, Korea) and corticosteroid (lotepredrol etabonate, lotemax; Bausch + Lomb, Tampa, FL, USA) were used 4 times a day. They were tapered over a month. For all patients, non-steroidal anti-inflammatory drugs (NSAIDs) (ketorolac tromethamine 0.45%, Ocuveil; Allergan, Inc., Irvine, CA, USA) were used for 2 weeks.

Postoperative examinations were performed at 1 day, 1 week, 1 month, and 3 months after the surgery. All patients underwent measurement of UCDVA, BCDVA, uncorrected intermediate (80 cm) visual acuity (UCIVA), manifest refraction, and slit-lamp examination with IOP measurement. At 1-month and 3-month postoperatively, ocular wavefront aberrometry was performed using WASCA (Carl Zeiss Meditec AG, Jena, Germany). Parameters analyzed for a 5.0 mm pupil included vertical and horizontal coma, vertical and horizontal trefoil, spherical aberration, and root mean square (RMS) values of total aberrations and high order aberrations. The WASCA abberometer provided Zernike coefficients in Malacara notation. However, results are presented in standard notation of Optical Society of America(OSA).

Vector analysis was performed using the Alpins method, facilitated by the ASSORT program version 5.04 (Assort Pty., Ltd., Victoria, Australia). Target induced astigmatism (TIA) was defined as the astigmatic change in the magnitude and axis the surgery was intended to correct. Therefore, actual measured preoperative corneal topographic astigmatism was used. Surgically induced astigmatism (SIA) was defined as the amount and axis of the astigmatism the surgery actually induced. Difference vector was defined as the induced astigmatic change by the magnitude and axis that would enable the initial surgery to achieve its intended astigmatic target. That means the difference vector is the actual measured postoperative refraction remaining after the surgery. Correction index calculated by determining ratio of SIA to TIA (correction index is preferably 1.0; if correction index > 1.0 overcorrection occurred and if correction index < 1.0 undercorrection occurred). Magnitude of error is the arithmetic difference between magnitudes of SIA and TIA (magnitude of error > 0 indicates overcorrection and magnitude of error < 0 undercorrection). Angle of error is the angle described by the vectors of SIA versus TIA (angle of error > 0: achieved correction index is counterclockwise to where it was intended; angle of error < 0: achieved correction is clockwise to its intended axis). Index of success is calculated by dividing the difference vector by TIA, representing a relative measure of success (index of success is preferably 0).

Rotations of the IOL were assessed by analyzing digital photographs in retro-illumination of the IOL with full mydriasis. Conjunctival vessels, iris patterns, or conjunctival pigmented lesions were selected as a reference point to compare the axis between photographs. Postoperative rotation was defined as the difference between intraoperative axis and the achieved axis at 3 months postoperatively. The absolute rotation amount was analyzed by calculating differences between the angle of the IOL reference marks of intraoperative photographs and 3 months postoperative photographs using ImageJ program. One independent investigator performed the measurement.

The study population was calculated according to previous conducted studies, Vale et al. [5] and Sheppard AL et al. [10] assuming 1:1 randomization with a significance level of 5% and a power of 80%. Based on previous data, the sample size was calculated to be 40 eyes were required, corresponding to 20 eyes in each group.

After cataract surgery, UCDVA, BCDVA, and cylindrical errors were significantly (P < 0.05) improved in both groups (Table 2). In the Precizon group, UCDVA was significantly (P < 0.05) increased from 0.50 ± 0.17 (range, 0.30 to 0.82) logMAR preoperatively to 0.09 ± 0.09 (range, 0 to 0.30) logMAR after 3 months postoperatively. In the Tecnis group, UCDVA was also significantly (P < 0.05) improved from 0.38 ± 0.13 (range, 0.22 to 0.52) logMAR preoperatively to 0.08 ± 0.12 (range, 0 to 0.30) logMAR at 3 months postoperatively. The percentage of UCDVA that was 0.1 logMAR or better (Snellen chart 20/25 or better) was 91% in the Precizon group and 83% in the Tecnis group.

In the Precizon group, BCDVA was significantly (P < 0.05) increased from 0.30 ± 0.18 (range, 0 to 0.70) logMAR preoperatively to 0.02 ± 0.02 (range, 0 to 0.05) logMAR at 3 months postoperatively. In the Tecnis group, BCDVA was also significantly (P < 0.05) improved from 0.21 ± 0.13 (range: 0 to 0.50) logMAR preoperatively to 0.01 ± 0.02 (range, 0 to 0.05) logMAR at 3 months postoperatively (Table 2). The final BCDVA of all eyes in both groups achieved 0.05 logMAR (Snellen chart 20/25 or better).

The refractive cylinder was decreased from − 1.06 ± 0.94 D preoperatively to − 0.31 ± 0.29 D (70% decrease) at 3 months postoperatively in the Precizon group. It was decreased from − 1.83 ± 1.29 D preoperatively to − 0.41 ± 0.33 D (77% decrease) at 3 months postoperatively in the Tecnis group (Table 2). At the last follow-up, residual refractive cylinder which was less than 0.50 D occurred in 16 (80%) eyes in the Precizon group and in 14 (70%) eyes in the Tecnis group.

Results of postoperative visual acuity and refraction in both groups are shown in Table 2. No statistically significant difference in UCDVA or BCDVA (P = 0.562, P = 0.368, respectively) was found between the two groups. UCIVA in the Precizon group tended to be better compared to that of the Tecnis group. However, the difference was not statistically significant (P = 0.147). No significant difference in refractive outcomes (sphere, cylinder, and spherical equivalent, P = 0.423, P = 0.604, and P = 0.400, respectively) was found between the two groups.

Vector anlysis was pereformed at 3 months postoperatively (Table 3). The TIA vector means were 1.41 ± 0.49 D in the Precizon group and 1.41 ± 0.43 D in the Tecnis group.

No statistically significant difference in average TIA vector nor average SIA vector (P = 0.982, P = 0.468, respectively) was found between the two groups. The average DV for the Precizon and Tecnis groups were 0.31 ± 0.23 versus 0.42 ± 0.24, respectively, and these were not significantly different (P = 0.343). The mean correction index (ratio SIA to TIA; preferably 1), were 0.97 ± 0.25 versus 1.08 ± 0.27, respectively, reflecting slight undercorrection in the Precizon group and slight overcorrection in the Tecnis group(P = 0.377). Other vector analysis parameters show no statistically significant difference beween groups(P > 0.05).

The mean amount of toric IOL axis rotation was 1.50° ± 0.84° (range, 0.18° to 3.02°) in the Precizon group, which was significantly (P = 0.01) lower than that (2.56° ± 0.68°; range, 1.50° to 3.50°) in the Tecnis group (Table 2). No eye had IOL rotation for more than 4°. No eye required a second surgery to correct the IOL axis during the 3 months of follow-up period.

Ocular wavefront aberrometry values at 3 months postoperatively are shown in Table 4. Spherical aberration was significantly (P = 0.004) lower in the Tecnis group compared to that in the Precizon group. Other ocular wavefront aberrametry parameters showed no statistically significant (P > 0.05) difference between the two groups.