Comparison between toric and spherical phakic intraocular lenses combined with astigmatic keratotomy for high myopic astigmatism
Zheng et al. Eye and Vision
Comparison between toric and spherical phakic intraocular lenses combined with astigmatic keratotomy for high myopic astigmatism
Lin-Yan Zheng 0
Shuang-Qian Zhu 0
Yan-Feng Su 0
Hu-Yong Zou 0
Qin-Mei Wang 0
A-Yong Yu 0
0 The Eye Hospital of Wenzhou Medical University , 270 Xueyuan West Road, Wenzhou 325000, Zhejiang , People's Republic of China
Background: To compare the outcomes of a toric phakic intraocular lens (PIOL) and a spherical PIOL combined with astigmatic keratotomy (AK) for the correction of high myopic astigmatism. Methods: This study enrolled patients with high myopic astigmatism, including 30 eyes (22 patients) that received a toric PIOL implantation (TICL group), and 32 eyes (24 patients) that received combined AK and a spherical PIOL implantation (AK+ ICL group). The outcomes were compared between the two groups before surgery, and at the following time points after surgery: 1 week, 1, 3, 6 months, and 1, 2 years. Results: Preoperatively, the mean manifest spherical equivalent (SE) was −14.14 ± 2.12 D in the TICL group and −14.83 ± 2.79 D in the AK + ICL group (P = 0.28), and the mean manifest refractive cylinder, −2.87 ± 1.09 D and −2. 58 ± 0.85 D, respectively (P = 0.28). Two years postoperatively, the mean safety index was 1.53 ± 0.55 in the TICL group and 1.60 ± 0.70 in the AK + ICL group (P = 1.00), and the mean efficacy index, 1.18 ± 0.45 and 1.38 ± 0.52, respectively (P = 0.86). The mean manifest refractive cylinder correction was 1.94 ± 1.07 D in the TICL group and 1. 39 ± 0.71 D in the AK + ICL group (P = 0.02). The mean changes in SE and refractive cylinder from 1 week to 2 years were less than 0.50 D in both groups. Conclusions: Both TICL implantation and AK + ICL implantation are a good alternative for correction of astigmatism in addition to high myopia. TICL implantation has better predictability in correction of high myopic astigmatism. Trial registration: NCT03202485
Astigmatism; High myopia; Phakic intraocular lenses; Astigmatic keratotomy
Phakic intraocular lenses (PIOLs) are regarded as an
alternative to the current modalities of refractive
correction for high myopia. The Implantable Collamer
Lens (ICL; STAAR Surgical, Switzerland) is one of the
options of regularly used PIOLs, and demonstrates its
safety and effectiveness in correcting spherical
refractive errors. Considering that astigmatism is common
in highly myopic eyes [
], a toric ICL (TICL)
implantation or combined astigmatic keratotomy (AK) and
ICL (AK + ICL) implantation may be a feasible
approach to correct both spherical and cylindrical
errors in these cases, offering optimum vision without
the use of spectacles for correcting astigmatism. Many
studies have compared outcomes between the TICL
and excimer laser corneal refractive surgery [
which demonstrated clear superiority of the TICL for
high myopic astigmatism. However, to our knowledge,
no comparisons between the TICL and the AK + ICL
implantation have been published. This prospective
study was to compare the postoperative outcomes of
TICL and AK + ICL implantation for the correction
of high myopia with astigmatism.
This prospective comparative study enrolled 30 eyes of
22 patients having TICL implantation, and 32 eyes of 24
patients having AK + ICL implantation for the
correction of high myopic astigmatism. All patients
underwent a complete ophthalmologic examination
including slit-lamp biomicroscopy, corneal topography,
corneal pachymetry, and dilated fundoscopy. The
inclusion criteria included: 1) age ranged from 18 to 40 years,
2) myopia greater than −8.00 diopters (D), and refractive
cylinder in the range of 1.50 D to 5.50 D, 3) for the
patients who were planned to undergo AK + ICL
implantation, the axial difference between the corneal
astigmatism and the manifest refractive astigmatism was
less than 10 degrees, 4) a stable refractive error during
the previous 2 years, 5) anterior chamber depth more
than 2.8 mm, 6) endothelial cell density (ECD) more
than 2500 cells/mm2, and 7) scotopic pupillary diameter
less than 7 mm. None of the subjects had significant
irregular astigmatism, corneal pathological changes,
glaucoma, ocular inflammation, or previous ocular trauma
This study followed the tenets of the Declaration of
Helsinki. All subjects provided informed consent and
approval was obtained from the Institutional Review Board
of the Eye Hospital of Wenzhou Medical University.
Postoperative follow-up visits were at 1 day, 1 week, 1,
3, and 6 months, and 1, 2 years. Uncorrected visual
acuity (UCVA), best corrected visual acuity (BCVA),
refraction, slit-lamp biomicroscopy, ECD, intraocular pressure,
and fundus examination were performed.
The PIOL size and power were determined following the
manufacturer’s recommendations. The PIOL
implantation technique for the TICL group was as follows: two
peripheral iridectomies were made with a neodymium:
YAG laser preoperatively. On the day of surgery, the
zero horizontal meridian was marked using a slit-lamp
while the patient was sitting upright. Surgery was
performed under pupil dilation and topical anesthesia. A
Mendez ring was used for measuring the required
rotation from the horizontal meridian. The TICL was
inserted through a 3.0 mm clear corneal incision with
viscoelastics into the anterior chamber. Then, the TICL
was placed in the posterior chamber, and was exactly
aligned to the cylinder axis of the patient’s required
cylinder correction. The remaining viscoelastics were
completely irrigated out of the anterior chamber with a
balanced salt solution. No acetylcholine chloride was
administrated for miosis. The incision was closed by
hydration without sutures.
For the AK + ICL group, the procedure was the same
as mentioned above except that AK was performed
before ICL implantation and no rotation of ICL was
required. The procedure of AK was briefly introduced as
follows: after marking the proposed AK incision site on
the corneal epithelium with a marker, the paired arcuate
corneal incisions perpendicular to the meridian with
stronger manifest refractive power were made according
to the Lindstrom nomogram by a diamond knife
adjusted to the planned incision depth. The incisions were
95% of the peripheral corneal thickness with an optical
zone diameter of 7 mm. Finally, the incisions were
irrigated with a balanced salt solution. The manifest
refractive astigmatism was selected as the target correction.
The surgical decision of TICL or AK in an eye with
astigmatism was based on the surgeon’s discretion and
the patient’s ability to afford the surgery. Where both
options were considered appropriate, we explained both
options to the patients and they were asked to make a
The patient was given eye drops of 0.5% levofloxacin
(Cravit; Santen Pharmaceutical Co. Ltd., Japan) and 0.1%
fluorometholone (Flumetholon; Santen Pharmaceutical Co. Ltd.,
Japan), to be used four times a day for the first
postoperative week and three times a day in the second postoperative
week; the eye drops were to be discontinued from the third
week onwards. The topical NSAID (Pranopulin; Santen
Pharmaceutical Co. Ltd., Japan) was used four times a day
for the first postoperative month. Patients were also given
vitamin A palmitate eye gel (Oculotect, Novartis
Ophthalmics AG, Switzerland) for use four times a day for
maintenance of tear film and a regular ocular surface.
Data were collected on standardized case-report forms,
and then entered into a central database for analysis.
Statistical analysis was performed with commercial
software (SPSS, ver. 19.0; SPSS, Chicago, USA). Normality
of data was checked using the Kolmogorov-Smirnov test.
Descriptive statistics for continuous variables were
calculated as means and standard deviations (SDs). For
averaging, visual acuity was converted to logMAR value,
and was back-calculated to Snellen acuity where noted.
Astigmatism was analyzed by the vector analysis [
Wilcoxon test and one-way ANOVA was used. The level
of significance was set at P < 0.05.
Table 1 shows the patients’ demographics. Before
surgery, there were no significant differences between the 2
groups in age, sex, manifest spherical equivalent (SE),
manifest cylinder, UCVA, or BCVA.
At all postoperative periods, there was no between-group
difference in the BCVA or the safety index (mean
postoperative BCVA/mean preoperative BCVA) (Table 2), and
BCVA was improved significantly from the baseline in
both groups (P < 0.001). Figure 1 shows the percentage of
eyes with no change in BCVA, gained 1 or more lines of
BCVA, and lost 1 line of BCVA 2 years after surgery.
At all postoperative periods, there was no
betweengroup difference in the UCVA or the efficacy index
(mean postoperative UCVA/mean preoperative BCVA)
(Table 2), and UCVA was improved significantly from
the baseline in both groups (P < 0.001). Figure 2 shows
the percentage of eyes that had a LogMAR UCVA of 0
or better, and 0.5 or worse 2 years after surgery.
At all postoperative periods, SE was significantly
improved from the baseline in both groups
(P < 0.001), and had no significant between-group
difference (Table 2). Figure 3 shows a scatterplot of the
attempted versus the achieved correction of SE 2 years
after surgery. Figure 4 shows the percentage of eyes
within ±0.50 D and within ±1.00 D of the attempted
correction of SE 2 years after surgery.
At all postoperative periods, the manifest astigmatism
was significantly improved from the baseline in both
groups (P < 0.001), and had a significant between-group
difference except for 1 week (Table 2). Figure 5 shows
the manifest astigmatism that was improved significantly
in both groups 2 years postoperatively.
Figure 6 shows the change in the manifest SE. There was
no significant difference between each postoperative time
in both groups. The mean change in manifest SE from
1 week to 2 years was 0.19 ± 0.32 D in the TICL group
and 0.32 ± 0.40 D in the AK + ICL group (P = 0.67).
Figure 6 shows the change in the manifest cylinder.
There was no significant difference between each
postoperative time in both groups. The mean change in
manifest cylinder from 1 week to 2 years was 0.05 ± 0.23
D in the TICL group and 0.15 ± 0.18 D in the AK + ICL
group (P = 0.30).
There were no significant differences in BCVA, UCVA,
safety index or efficacy index between each postoperative
time for both groups.
All surgeries were uneventful and there were no
significant intraoperative complications. One week
postoperatively, 1 eye in the TICL group and 2 eyes in the
AK + ICL group experienced glare at night, which
disappeared after 3 months. There were no clinically
significant axis deviation, pupillary block, cataract formation,
or pigment dispersion syndrome during the 2-year
observation period. There were no noted complications of
AK such as corneal perforation, delayed corneal
epithelialization, corneal edema, or infection.
Astigmatism reduces visual quality by causing glare,
monocular diplopia, asthenopia, and vision distortion
after the spherical refractive error is corrected by a
spherical PIOL in high myopic astigmatism patients.
The three primary treatment modalities to reduce
preexisting astigmatism at the time of PIOL surgery are
AK, limbal relax incisions (LRIs), and the implantation
of toric PIOLs. AK has succeeded in correcting
astigmatism and been shown to be a simple and effective
]. Compared with LRIs, AK has the
advantage of more effectively reducing astigmatism with
shorter incision lengths due to closer proximity to the
visual axis. Toric PIOL implantation, as a correction of
high myopic astigmatism, is safe, effective, and shows
good predictability and stability. Limitations of toric
PIOLs include the potential IOL rotation off alignment
postoperatively and cost of the procedure. To our
knowledge, no comparative study between TICL implantation
and AK + ICL implantation has been performed.
The current study shows that the refractive outcomes
and improvement in UCVA and BCVA were rapidly
achieved and remained stable in the TICL group
throughout the follow-up period. This agrees with the
reports in the literature [
]. The United States FDA
clinical trial of TICL [
] demonstrated that astigmatism
was reduced from 1.93 ± 0.84 D to 0.51 ± 0.48 D, and
postoperative BCVA was improved by at least one line
in 76.4% of patients, postoperative UCVA was better
than or equal to preoperative BCVA in 76.5% of patients.
In this study, TICL group showed that astigmatism was
reduced from −2.87 ± 1.09 D to −0.93 ± 0.78 D, and
postoperative BCVA was improved at least one line in
87% of patients while postoperative UCVA was better
than or equal to preoperative BCVA in 67% of patients.
The difference in postoperative cylinder may be due to
the different baseline cylinder. The baseline cylinder is
higher in our study than in Sanders’s study (2.87 D vs.
1.93 D) [
]. The results of this study are comparable to
the previous studies on TICL correcting high myopic
astigmatism, indicating that the refractive outcomes of
TICL in our study are common to the procedure.
However, the postoperative clinical outcomes of
AK + ICL implantation in high myopic astigmatism
patients have not been fully elucidated. In this study, the
AK + ICL group showed that astigmatism was reduced
from −2.58 ± 0.85 D to −1.19 ± 0.65 D. It was reported
that corneal astigmatism was reduced from 2.90 ± 0.78
D to 0.89 ± 0.52 D in patients having AK alone, and
from 2.97 ± 1.01 D to 1.02 ± 0.45 D in those having AK
combined with cataract surgery [
]. In the AK + ICL
group, 72% of cases were within ±1.00 D of the
attempted SE correction. The power calculation of ICL
is not affected by AK because AK does not change SE,
and the paired arcuate incisions of AK achieved a more
ideal corneal sphericity than that preoperatively, which
is known as the coupling effect [
]. In the AK + ICL
group, the postoperative BCVA was improved by at least
one line in 79% of patients, the postoperative UCVA was
better than or equal to preoperative BCVA in 66% of
patients. As far as stability, both groups seem to have
similar variations of SE and astigmatism during the period of
follow-up, which was less than 0.50D on average. These
results demonstrated AK + ICL group and TICL group
have comparable safety and efficacy in correction of high
But the magnitude of astigmatism correction in the
TICL group was significantly greater than that in the
AK + ICL group (1.94 ± 1.07 D vs. 1.39 ± 0.71 D),
indicating that TICL implantation had better predictability
in correcting high myopic astigmatism compared to
AK + ICL implantation. Generally, target of cylinder
correction in TICL is nearly zero. However, most of the AK
nomogram is not designed to target 100% of
preoperative cylinder correction to reduce the risk of
overcorrection. The magnitude of astigmatism correction of AK
depends on the size of the central optical zone and the
number, depth, and length of incisions. In this study, the
size of the optical zone and the number of incisions
were kept constant, and the length of incisions was
determined according to the same nomogram. The
shallower cut may be involved although the diamond knife
was adjusted to 95% of the peripheral corneal thickness.
The lack of predictability of astigmatism correction by
AK is probably related to the variation of achieved depth
of the incision [
]. In addition, the smaller change in
astigmatism produced after AK may be due to
intraoperative axis misalignment. Although clinically significant
axis deviation was not found in this study, intraoperative
misalignment could not be ruled out as a factor that
induced the postoperative axis deviation, which influences
the efficacy of AK. With the advent of femtosecond laser
technology, instead of using diamond knife, the
femtosecond laser assisted AK may reduce the deviation of
depth and size of corneal incisions to a minimum
because all the parameters (length, depth, and site) are
controlled and executed with submicron accuracy.
In this study, glare was noted in a total of 3 eyes,
including 1 eye in the TICL group and 2 eyes in the
AK + ICL group, which disappeared 3 months after
surgery. The presence of glare after surgery may be
associated with a small optical zone, large pupil and increased
irregular astigmatism. In this study, the optical zone of
PIOL and pupil size in both groups were comparable,
and the optical zone of AK was set at 7 mm to eliminate
induced irregular astigmatism. However, considering
that AK might have a slower wound-healing process,
and more time is possibly needed to restore stable
corneal architecture, the patients in the AK + ICL group
might experience more glare than those in the TICL
group. Chang et al [
] reported that 1 eye suffered from
persistent halo and disappeared 1 year after TICL
implantation. No patients reported glare 1 year after AK in
Akura’s study [
]. Budak et al [
] reported 1 patient
that complained of glare for 1 month after LRI. Patients
might have a certain degree of adaptation to glare. In
addition, no anterior subcapsular opacification was
observed in both groups during the follow-up period. An
incidence rate of postoperative anterior subcapsular
opacification had been reported from 2.7% to 7% in previous
studies of ICL [
10, 16, 17
]. Lindland and co-authors [
found that anterior subcapsular opacification may result
from the contact between the PIOL and crystalline lens.
The difference in occurrence of anterior subcapsular
opacification may be related to different sample sizes,
follow-up periods, and surgical techniques employed.
In conclusion, our results demonstrated that both TICL
implantation and AK + ICL implantation are good alternatives
for the correction of astigmatism as well as high myopia.
Compared with AK + ICL implantation, TICL implantation
has better predictability in correcting high myopic
astigmatism and preserves corneal contour by avoiding additional
corneal incisions due to AK. AK + ICL implantation has
advantages of lower cost to the patient and avoids the
potential rotation off alignment due to TICL. The limitations
of this study were a relatively small sample size and lack of
randomization. Further investigations with a larger number
of subjects and randomization are warranted.
This material is based upon work funded by the Nature and Science
Foundation of China (Grant No. 81570869), Nature and Science Foundation
of Zhejiang Province, China (Grant No. Y2110784), Zhejiang Provincial
Foundation of China for Distinguished Young Talents in Medicine and Health
(Grant No. 2010QNA018), Foundation of Wenzhou City Science & Technology
Bureau (Grant No. Y20140705), and Engineering Development Project of
Ophthalmology and Optometry (Grant No. GCKF201601). The funding
sources were not involved in any part of this study.
Design and conduct of study (AY); Collection (LZ, SZ, YS, HZ, AY),
Management (QW, AY), Analysis (LZ, SZ, YS, HZ, AY), Interpretation of data
(QW, AY). Preparation (LZ, QW, AY), review or approval of manuscript (AY);
and responsibility for the integrity of the entire study and manuscript (AY).
All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
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