·Clinical Research·
Comparative
clinical outcomes of Tecnis toric IOL implantation in femtosecond
laser-assisted cataract surgery and conventional phacoemulsification surgery
Kai-Ran
Lai, Xiao-Bo Zhang, Yin-Hui Yu, Ke Yao
Eye Center, the Second Affiliated
Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, Zhejiang
Province, China
Correspondence to: Ke Yao. Eye Center, the Second
Affiliated Hospital, School of Medicine, Zhejiang University, No.88 Jiefang Rd,
Hangzhou 310009, Zhejiang Province, China. xlren@zju.edu.cn
Received:
Abstract
AIM: To compare the
short-term visual outcomes, residual refractive cylinder, and rotation
stability after Tecnis toric intraocular lens (IOL) implantation during
femtosecond laser-assisted cataract surgery (Femto phaco) and conventional
phacoemulsification surgery (Conventional phaco).
METHODS: In a prospective
cohort study, Conventional phaco and Femto phaco (anterior capsulotomy and lens
fragmentation by a femtosecond laser) with Tecnis toric IOL implantation were
performed in 40 eyes from 36 patients and 37 eyes from 33 patients,
respectively. The uncorrected distance visual acuity (UDVA), corrected distance
visual acuity (CDVA), and manifest refraction were assessed during 1d, 1wk, and
1mo follow-ups. The orientation of the Tecnis Toric IOL was evaluated during
1wk and 1mo follow-ups.
RESULTS: There were no
significant differences in UDCA or CDVA between two groups at 1mo
postoperatively, though relatively more subjects had UDVA values of 20/25 or
better in Femto phaco group than in the Conventional group (P>0.05).
A lower but not significantly lower rate of having more than 5° of IOL rotation
was observed in Femto phaco group at the 1-month follow-up, while a significant
lower rate of residual astigmatism of ≤1 D was observed in Femto phaco group.
CONCLUSION: The Femto phaco group
has significantly more subjects with the residual astigmatism of ≤1 D, but
there are no significant differences in rotation stability and visual outcomes
as compared with the Conventional phaco group after the application of the
Tecnis toric IOL in this cohort.
KEYWORDS: toric intraocular
lens; femtosecond laser-assisted cataract surgery; visual outcomes; rotation
stability
DOI:10.18240/ijo.2020.01.07
Citation:
Lai KR, Zhang XB, Yu YH, Yao K. Comparative clinical outcomes of Tecnis toric
IOL implantation in femtosecond laser-assisted cataract surgery and
conventional phacoemulsification surgery. Int J Ophthalmol
2020;13(1):49-53
INTRODUCTION
Cataract surgery has evolved into a
period of refractive procedure. Advances in cataract surgery have improved
patients’ outcomes and expectations. Corneal astigmatism is one of the major
refractive errors that decreases postoperative visual acuity and visual
quality. In a study of 4540 cataractous eyes, corneal astigmatism was found to
be between 0.25 and 1.25 diopters (D) in 64.4% of eyes and 1.50 D or higher in
22.2% of eyes[1] . In a study of 4831 cataractous
eyes in South China, the mean corneal astigmatism was 1.01 D; 67.7% of eyes had
astigmatism of 0.25 to 1.25 D, and 27.5% had astigmatism of 1.25 D or higher[2]. In another study in China, 29.7% had astigmatism of
1.25 D or higher[3].
In recent years, toric intraocular
lenses (IOLs) have been widely used for correcting corneal astigmatism.
Numerous studies have demonstrated effective and safe clinical outcomes on the
part of various toric IOL models, including the Acrysof toric IOL (Alcon
Laboratories, Inc., Fort Worth, TX, USA) and the Tecnis toric IOL (Abbott
Medical Optics, Inc., Santa Ana, CA, USA)[4-7].
The main concern regarding toric IOL implantation is postoperative IOL
rotation. Each degree of rotational deviation from its intended axis can result
in an approximately 3.3% reduction in cylindrical power[8].
A deviation of 30 degrees negates all potential astigmatism correction. Thus,
the rotation stability of toric IOLs is critical to clinical use. An intact and
well-centered capsulorhexis with a 360-degree overlap with the IOL optics helps
ensure optimal centration and good stability[9-10].
Femtosecond laser-assisted cataract
surgery (Femto phaco) has increased in the past few years, and has been
reported as an effective and safe technique for the surgical management of
cataract[11]. Recent studies have demonstrated
reduced ultrasound energy, reduced corneal endothelial cell loss, higher
capsulorrhexis precision[12-14],
and better IOL decentration with Femto phaco as compared to Conventional phaco[15]. In the present research project, we conducted a
prospective study to investigate the effect of Femto phaco on short-term visual
outcomes, residual refractive cylinder, and rotation stability after Tecnis
toric IOL implantation as compared with Conventional phaco.
SUBJECTS AND METHODS
Ethical Approval After obtaining approval from the
Institutional Review Board, this prospective study was conducted at the Eye
Center, the Second Affiliated Hospital, School of Medicine, Zhejiang
University, and it adhered to the tenets of the Declaration of Helsinki. It was
registered at http://www.clinicaltrials.gov (identification number
ChiCTR-OPS-14005285). Thirty-seven eyes from 33 patients (Femto phaco group)
and 40 eyes from 36 patients (Conventional phaco group) with the implantation
of the Tecnis Toric IOL were enrolled in the present study. Written informed
consent was obtained from all patients after a full explanation of the study
was provided.
The inclusion criteria were age
>18y, decreased visual acuity due to cataract, and preoperative corneal
astigmatism greater than 0.75 D. The exclusion criteria were irregular cornel
astigmatism, corneal abnormality, previous corneal surgery, pupil abnormality
(small pupil, fixed pupil or irregular pupil shape), pseudoexfoliation
syndrome, uncontrolled glaucoma, history of uveitis, history of retinal
detachment, or another ocular disease that may affect postoperative visual
acuity (e.g., macular degeneration, cystoid macular edema, diabetes
retinopathy, or optic atrophy). Subjects were also excluded based on
intraoperative findings or complications, including zonular damage,
capsulorrhexis tear, capsular rupture, vitreous loss, anterior chamber hyphema,
and uncontrollable intraocular pressure.
Before cataract surgery, eligible
patients were interviewed regarding their medical histories and underwent a
full preoperative ophthalmic evaluation, including uncorrected distance visual
acuity (UDVA) and corrected distance visual acuity (CDVA) measurements,
slit-lamp examination, applanation tonometry, corneal endothelial cell count,
dilated funduscopy, and ultrasonic pachymetry and biometry according to
a standardized protocol. Corneal astigmatism was measured with an optical
biometer (IOLmaster, Carl Zeiss, Jena, Germany) and corneal topography
(Pentacam, Oculus, Rochester, NY, USA).
Surgical Techniques All surgeries were performed by the
same surgeon (Yao K). According to our standard protocol, a topical non-steroid
anti-inflammatory drug (NSAID, pranoprofen, Senju Pharmaceutical Co., Osaka,
Japan) was applied to patients in Femto phaco group four times one day
preoperatively to maintain intraoperative pupil dilation. Pupillary dilation
was achieved via the application of one drop of tropicamide every 15min
three times before surgery.
Before pupillary dilation,
horizontal markings (0° and 180°) were made under the slit lamp, with the
subject seated upright to prevent cyclotorsion while in the supine position.
The axis of the incisions and the axis for the placement of the IOL were marked
with an angular ring. All the preoperative markings were performed by the same
assistant (Lai KR).
The Femto phaco procedures involved
anterior capsulotomy and lens fragmentation using a LenSx Laser System (Alcon
Inc., Aliso Viejo, CA, USA). The anterior capsulotomy diameter was
Measurements Subjects were evaluated one day, one
week, and one month postoperatively. The assessments included UDVA, CDVA,
manifest refraction, and slit-lamp examination. The orientation of the Tecnis
Toric IOL was evaluated at one week and one month after surgery via
slit-lamp (Haag-Streit BQ900, Zug, Switzerland) examination with a reticle of
5-degree markings by viewing the cylinder axis of the IOL after pupillary
dilation. The corneal topography was analyzed using a Pentacam (Oculus) at one
month postoperatively.
Statistical Analysis Statistical analyses were performed
with SPSS Version 16.0 (SPSS, Inc., Chicago, IL, USA). Differences between the
groups were tested with a t-test or Chi-square test when appropriate. A P-value
of less than 0.05 was considered statistically significant.
RESULTS
The results exclude subjects who
discontinued treatment or were lost to follow-up (Femto phaco group, n=4;
Conventional group, n=4). A total of 37 eyes from 33 patients and 40
eyes from 36 patients were included in Femto phaco and Conventional phaco
groups, respectively. Patient demographics and baseline characteristics were
shown in Table 1. All the subjects were Han Chinese. The mean age was
73.5±12.2y (range: 41 to 89y) in Femto phaco group and 71.2±14.0y (range: 42 to
90y) in Conventional phaco group (P=0.437). The proportion of female
subjects was 45.9% (17/37) in Femto phaco group and 50.0% (20/40) in
Conventional phaco group (P=0.722). Average preoperative corneal
astigmatism was 1.57±0.58 D and 1.50±0.85 D in Femto phaco and Conventional
phaco groups, respectively (P=0.667). The predicted postoperative
residual astigmatism was 0.23±0.20 D and 0.19±0.23 D in Femto and Conventional
phaco groups, respectively (P=0.418).
Table 1 Patient demographics and
baseline characteristics
mean±SD
Parameter |
Femto phaco group (n=37) |
Conventional phaco group (n=40) |
P |
Age (y) |
73.5±12.2 |
71.2±14.0 |
0.437 |
Female |
45.9% |
50% |
0.722 |
Corneal astigmatism (D) |
1.57±0.58 |
1.50±0.85 |
0.667 |
Predicted postop. residual
astigmatism (D) |
0.23±0.20 |
0.19±0.23 |
0.418 |
SD: Standard
deviation; D: Diopters; Femto phaco: Femtosecond laser-assisted cataract surgery; Conventional
phaco: Conventional phacoemulsification surgery.
There were no significant differences in UDCA and CDVA
between the two groups at 1mo postoperatively. In Femto phaco group, 16.2%,
64.9%, and 97.3% of patients had UDVA values of 20/20, 20/25, and 20/40 or
better, as compared with 15.0%, 45%, and 90% in Conventional phaco group,
respectively (χ2=0.022,
3.059, and 1.686, P=0.883, 0.080, and 0.194; Figure 1). In Femto phaco
group, 54.1%, 89.2%, and 100% of eyes had postoperative CDVA values of 20/20,
20/25, and 20/40 or better, as compared with 47.5%, 75%, and 95%, in
Conventional phaco group, respectively (χ2=0.33, 2.601, and 1.899, P=0.566, 0.107, and
0.168; Figure 2).
Figure 1 UDVA in both groups at 1mo
postoperatively.
Figure 2 CDVA in both groups at 1mo
postoperatively.
Three eyes (8.1%) had an IOL rotation of more than 5° in
Femto phaco group, as compared with six eyes (15%) in Conventional phaco group
one month after surgery. However, there was no significant difference between
two groups in this regard (χ2=0.884,
P=0.347; Figure 3). With regard to the residual astigmatism, 23 eyes
(62.2%) and 20 eyes (50%) had astigmatism of 0.50 D or less at 1mo
postoperatively in Femto phaco and Conventional phaco groups, respectively (χ2=1.153,
P=0.283; Figure 4). There was a significant difference between the groups
regarding residual astigmatism values of 1.0 D or less [35 eyes (94.6%) in
Femto phaco group vs 30 eyes (75%) in Conventional phaco group, χ2=5.61, P=0.018;
Figure 4].
Figure 3 IOL rotation in both groups
at 1mo postoperatively.
Figure 4 Residual astigmatism in
both groups at 1mo postoperatively aP<0.05.
DISCUSSION
The rotation stability of the IOL in
the capsule is one of the most important factors in toric IOL implantation. The
misalignment of a toric IOL may increase residual astigmatism and reduce the
likelihood of spectacle independence. Some earlier toric studies showed IOL
rotations of more than 10° in 50% of cases and more than 30° in 20% of cases[16]. Many advances have been made in terms of both IOL
designs and surgical techniques that promote stability. After implantation, the
fusion of the anterior and posterior capsules around the IOL haptics and optic
border plays an important role in preventing IOL rotation. Thus, it is
beneficial for the capsulorhexis to be well-centered and smaller than the
diameter of the lens optic to provide 360° of overlap. The diameter of the
Tecnis Toric IOL optic is
A previous study has shown that IOL
rotation is more likely to occur in larger myopic eyes that have what
subjectively appear to be large-diameter capsular bags[19].
Therefore, in the present study, patients with very high levels of myopia were
not enrolled. There were only five and four eyes with IOL spherical power
values of less than 16 D, with values ranging between 10 and 13 as well as 12.5
and 15, respectively, in Femto phaco and Conventional phaco groups.
The surgically induced astigmatism
(SIA) is also an important factor in the implantation of a toric IOL. The
amount of SIA depends on several factors, including the size, shape,
architecture, and location of the incision. Although a femtosecond laser is
theoretically expected to induce lower and more stable SIA values because of
the precise architecture and the resulting three-planar self-sealing incision,
the clinical outcomes of previous studies have been controversial. Our team
reported that the use of femtosecond laser CCIs for cataract surgery resulted
in higher SIA values, and manual CCI is recommended in femtosecond
laser-assisted cataract surgery[20]. Thus, we
performed manual CCIs in both groups to control this variable in the present
study.
Posterior corneal astigmatism also
makes some contribution to the total cornea astigmatism. Koch et al[21] reported that the mean magnitude of posterior corneal
astigmatism was -0.30 D and that about 9% of eyes had >0.5 D of posterior
corneal astigmatism. In a study of Chinese patients, the mean posterior corneal
astigmatism was 0.28±0.16 D and 87.04% of eyes had <0.5 D of posterior
corneal astigmatism[22]. Most of the posterior
corneal astigmatism was against-the-rule. Posterior corneal astigmatism had a
limited effect on the results in most cases, and methods of measuring it are
not well-established, but the estimation of corneal astigmatism via
Scheimpflug imaging may help in the accurate measurement of total corneal
astigmatism.
The present study mainly focused on
early clinical outcomes, and end point of the 1-month follow-up was selected. A
previous study has shown that IOL rotations occurred within 10d
postoperatively, and there were no significant IOL rotations in any cases after
1mo postoperatively[23]. Chang reported that
there were no cases in which the IOL rotated by as much as 5 degrees between
the 1-day and 1-month postoperative visits[19].
In our study, the mean rotation between the 1-week and 1-month postoperative
visits was 1.33±1.66 and 1.08±2.34 degrees in Femto phaco and Conventional
phaco groups, respectively. Furthermore, the corneal astigmatism of the
All the cases in the present study
were performed by the same experienced surgeon in one medical center.
Therefore, a multi-center study with surgeons having different levels of
experience should be performed later. In conclusion, Femto phaco group had
significantly more subjects with the residual astigmatism of ≤1 D but no
significant differences in rotation stability and visual outcomes as compared
with Conventional phaco group after the application of the Tecnis toric IOL in
this cohort.
ACKNOWLEDGEMENTS
Foundation: Supported by Zhejiang Province Key
Research and Development Program (No
Conflicts of Interest: Lai KR, None; Zhang XB, None; Yu
YH, None; Yao K, None.
REFERENCES