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Toric Orthokeratology Effectiveness on Correcting Astigmatism: A Narrative Literature Review
Shih Kae Chew*
University Isabel I de Castilla, Spain
Submission: July 13, 2018; Published: September 21, 2018
*Corresponding author: Shih Kae Chew, School of Advanced Education Research and Accreditation, C/ Germanas 31ºC, 12001 Castellón de la Plana (Spain), Spain.
How to cite this article: Shih Kae Chew. Toric Orthokeratology Effectiveness on Correcting Astigmatism: A Narrative Literature Review. JOJ Ophthal.
2018; 6(5): 555703. DOI: 10.19080/JOJO.2018.07.555703
Numerous studies demonstrated toric orthokeratology (Ortho-K) may reduce moderate to high astigmatism. Astigmatism commonly appears together with ametropia. Spherical Ortho-K lens is effective against low central corneal astigmatism, in patients with less than 1.50 D with-the-rule astigmatism. This review assesses toric orthokeratology studies performed by different researchers between 2007 and 2017. Author performed literature search for studies and case reports about toric Ortho-K, on scientific databases (PubMed, Wiley Online Library, ScienceDirect) and online journals Contact Lens & Anterior Eye and Eye & Contact Lens according to different inclusion and exclusion criteria. Eleven results describing toric Ortho-K were included in this review followed by a synthesis of findings. Results show that toric periphery/alignment zone Ortho-K can improve lens centration for astigmatic correction and the combination of toric reverse zone and toric alignment zone (full toric/dual toric/real toric) is more effective for medium to high astigmatism. More published studies and statistical analysis are required to investigate the effectiveness of toric orthokeratology for medium to high astigmatism. Comparison of different type of toric orthokeratology design must be included for future research, as the published studies reviewed are mainly toric periphery, and full toric only appeared in case reports and editorials/anectodal.
Orthokeratology (orthoK) was first introduced in 1960s to slow down myopia progression. Orthokeratology lens is a reverse geometry gas permeable contact lenses, in which the curvature of the center is flatter than the periphery. They are available in spherical and toric design. OrthoK lenses temporarily improve uncorrected visual acuity (UCVA) in the daytime without spectacles or contact lenses, after overnight wear and removal of lenses upon wake up. OrthoK lenses flatten the central cornea, and their change in corneal power lead to a change in overall ocular refraction. Myopia is a common ocular disorder and high myopia is associated with higher risk of retinal disease, glaucoma and cataract. Myopia occurs at very young age and may progress very fast to high myopia. Astigmatism is a type of refractive error where the light does not focus evenly on retina, leading to blur vision at all distances. Astigmatism is due to differences in the curvature of the cornea or crystalline lens of the eye. In this review, we will focus on corneal astigmatism, not lenticular astigmatism. Astigmatism is associated with ametropia  and commonly co-exists with myopia. Many myopic patients are also astigmatic . Spherical Ortho-K is effective in low to moderate myopia and low refractive astigmatism but is not sufficient for moderate refractive astigmatism . Chang et al.  stated, “the incidence of astigmatism was about 33.6% in Asian children aged 5-17 years old and this value significantly increases
with age”. This review is important to search for suitable toric
orthokeratology (toric Ortho-K) for reducing moderate to high astigmatism.
The author has been fitting spherical Ortho-K to patients and would like to explore toric options for moderate to high corneal astigmatism. Astigmatism commonly appears together with ametropia. Spherical Ortho-K has diopter limit (D) for astigmatism correction
Author performed literature search for studies and case reports about toric Ortho-K, on scientific databases (PubMed, Wiley Online Library, ScienceDirect) and online journal website Contact Lens & Anterior Eye and Eye & Contact Lens. Papers were included if they specifically focused on orthokeratology for myopia and astigmatism. Papers had to have a particular focus upon “toric orthokeratology” in order to be included within this literature review. Inclusion criteria for the papers are full article, English written, and published between 2007 and 2017. Case report and case series are included and articles outside of the time frame were included if they mentioned astigmatism changes. Articles that are non-English, not full text article and no source quoted are excluded. PubMed produced 17 results with “toric AND orthokeratology” search, Wiley produced 31 results and ScienceDirect produced 55 results. Contact Lens &
Anterior Eye journal produced 55 results while Eye & Contact
Lens journal produced 73 results. Eleven results describing toric
orthokeratology were included in this review.
Literature search using database and keywords
2) Wiley Online Library
Online journal website:
1) Contact Lens and Anterior Eye
2) Eye & contact Lens
a) Full article
b) Year 2007-2017
c) English written
d) Case Report/Case Series
e) Article not in 2007-2017 but mentioned astigmatism
changes in orthokeratology
Chen & Cho  performed a case series using Menicon
Z-Night toric periphery Ortho-K to limit myopia progression and
correct the initial astigmatism in 2 subjects with high myopia
and high astigmatism. Two subjects showed different responses
to astigmatism reduction after 12 months. Chen, Cheung & Cho
 performed non-randomized longitudinal 2-years study using
Menicon Z-Night toric periphery Ortho-K to determine toric
Ortho-K effectiveness for myopia control in myopic children with
moderate to high astigmatism in 80 subjects, with 43 Ortho-K
subjects versus 37 control wearing single vision spectacle.
Results showed astigmatism was reduced in Ortho-K group of
Chen, Cheung & Cho  performed 1-month non-randomized
longitudinal study, which is part of 2013 TO-SEE study in Paper
2. Same setting was applied and results showed toric Ortho-K
reduce refractive astigmatism.
Chan, Cho & De Vecht  presented a case report on single
subject using Menicon Z-Night toric periphery for 15 months.
Result showed toric periphery Ortho-K can be effective for high
Chang et al.  performed retrospective, observational,
double-blinded study for toric Ortho-K. They investigated and
compared effectiveness of general and toric Ortho-K in corneal
toricity in 19 subjects in Group I using spherical Ortho-K and
15 subjects in Group II using toric Ortho-K (toric alignment and
reverse zone). After 3 months, results showed toric Ortho-K
reduced corneal toricity.
López-López, et al.  presented a case report for a single
subject using Paragon dual axis toric Ortho-K (toric alignment
and reverse zone) for limbus-to-limbus astigmatism, with a
duration of 12 months.
Baertschi & Wyss  presented a case report on successful
treatment of high astigmatism with FOKX (Falco, Switzerland)
toric Ortho-K (toric periphery and reverse zone) on a single
subject case report.
Luo, Ma & Liang  performed self-controlled clinical
study without control group for 24 subjects using Lucid toric
Ortho-K (toric alignment and reverse zone) for 12 months. The
results showed toric Ortho-K correct low to moderate myopia in
adolescents with moderate to high astigmatism.
Pauné, Cardona & Quevedo  assessed the performance
of double tear reservoir toric Ortho-K Precilens (France) in a
retrospective study for correction of myopia and astigmatism
in 32 patients (right eye only) for the period from Jan 2008 to
Dec 2010. The statistical analysis results showed toric Ortho-K
reduced refractive astigmatism.
Byul, Kyu, Sun, Su, Kyug  evaluated the effectiveness and
safety of Lucid toric Ortho-K in a multi-institute, prospective
single group clinical trial of 19 subjects (31 eyes) with combined
myopia and astigmatism. The duration was 1 month. Results
showed toric Ortho-K reduced a relatively small amount of
astigmatism (0.63±0.98 D).
Calossi  studied the effectiveness of ESA dual toric
Ortho-K on corneal toricity and refractive astigmatism in a
single subject case report for 18 months. The results showed
astigmatism can be corrected in cases where cylindrical
component is higher than spherical component.
In this review, the researchers from the papers retrieved
are put into two groups. Group 1 used toric periphery Ortho-K
(also known as toric alignment zone) and group 2 used full toric
Ortho-K (toric alignment and reverse zone). In group 1, Chen &
Cho , Chen et al. , Chen et al.  and Chan et al.  used
Toric periphery Ortho-K (spherical design at back optic zone and
reverse zone of the lens, toric at alignment zone) in their studies.
In group 2, Chang et al. , López-López et al. , Baertschi
& Wyss , Luo et al. , Pauné et al. , Byul et al. 
and Calossi  used Full toric Ortho-K (toric at reverse zone,
alignment zone, and may extend to toric back optic zone) in their
Byul L et al.  did not mention type of toric Ortho-K
specifically in their studies, as each brand name may have toric
periphery or full toric (toric alignment and reverse zone). Full
toric Precilens (France) in Pauné et al.  study consists of five
toric area which produce double tear reservoir (double reverse
zone), Whether this design would further reduce astigmatism
compared with two toric area (toric alignment and reverse
zone) would require further study in the future. The purpose of
designing toricity in optical zone and having opposite meridian
steepness in optical and alignment zone is unknown.
As this review only involves one paper describing a five
toric area double reservoir, author suggests future toric Ortho-K
category for: simple toric Ortho-K (toric periphery), full toric
(toric alignment and reverse zone), real toric (more than one
reverse reservoir) for comparison.(Table 2)
Astigmatic cornea has different types of astigmatism
(corneal central astigmatism, limbus-to-limbus, oblique, WTR
and ATR), thus there is a trend now using software for toric
Ortho-K lens design. Higher astigmatism may require software
fitting as different corneal meridian requires different lens
toricity for reducing astigmatism. In this review, we shall look
at each study apply empirical software fit or trial fitting. Chen &
Cho , Chen et al. , Chen et al.  and Chan et al.  used
Menicon Easy Fit Software for Menicon Z-Night Toric Ortho-K
empirical fit. Baertschi & Wyss , and Pauné et al. 
depended on Ortho-K software for the lens fitting, but the name
of the software was not specifically mentioned.
In the Lucid Toric study by Luo et al. , the researcher
mentioned trial lens fit but did not specifically mention using a
set of Ortho-K trial lenses or combination of software and trial
lenses. Chang et al.  used trial fit but did not mention using
spherical or toric Ortho-K trial lenses in Lucid Toric study. Byul
et al.  used trial lens for their study, but again, they did not
mention type of trial lenses in the Lucid Toric trial fitting. López-
López et al.  performed trial fit using spherical Paragon
CRT trial lens, combined with last topography, over-refraction
results to manufacturer to calculate the dual axis Paragon CRT
parameters. No software is available at researcher for empirical
fitting procedure. Calossi  did not mention empirical or trial
fit in the ESA bitorica Ortho-K lens fitting.(Table 3 & 4)
In this review section, we discovered Menicon Z-Night toric
provides Easy Fit software for examiner to perform empirical
fit at examiner terminal. FOKX toric requires fitting software
at the lab terminal and parameters decided by the lab. Lucid
toric requires trial lens or combination of trial lens and fitting
software, and whether the software at examiner or lab terminal
cannot be confirmed. Whether combination of toric trial lenses
and fitting software will be a better option depends on future
Chen & Cho  conducted a toric Ortho-K case series research
which involved two subjects, one subject did not return after
twelve months monitoring. Chen et al.  did a non-randomized
study for one-month duration, which formed part of 2013 nonrandomized
longitudinal two years study, involving 80 subjects
(43 Ortho-K subjects vs. 37 control). There may be systematic
bias due to non-randomized study . Chan et al.  conducted
one high astigmatic case report on toric periphery Ortho-K and
managed to show great reduction of corneal toricity in right eye
by 87.5 percent and 67.6 percent in left eye.
A retrospective observational study involving 34 cases was
done by Chang et al.  for three months duration. This study is
double blinded as both the researchers and subjects do not know
the design of lenses. The limitation is short duration and has two
different lens designs, one spherical and one toric design, sourced
from different manufacturers. López-López et al.  performed
a full toric study in a case report of single subject, for one year
of duration. We are not sure why the researcher performed trial
fitting using spherical Ortho-K and the lab decided the toric lens
design with results submitted by the researcher. Obviously this
is a case of limbus-to-limbus astigmatism and spherical has little
chances to achieve good centration, shown in the result of the
study. Baertschi & Wyss  presented a case report for a single
subject using full toric Ortho-K lens but did not specify the study
duration. Luo et al.  self-controlled clinical study is a case
series without control group, involving 24 subjects for one-year
duration. Pauné et al.  performed retrospective studies for
32 patients from Jan 2008 to Dec 2010. Byul et al.  conducted
a case series involving 23 subjects for four weeks duration. The
study duration is short and there was no control group available.
Calossi  presented a case report using full toric but that is
limited to a single subject, with astigmatic component higher
than spherical component.
Although case reports and case series showed promising
results in reducing moderate to high astigmatism with toric
Ortho-K lens, we shall need a larger subject group and prefer a
randomized control study for a statistical analysis.(Table 5)
Although astigmatism correction in Ortho-K is limited to
1.50D, but astigmatism commonly co-exists with myopia and
there is trend the higher astigmatism is increasingly popular.
Author included the toric Ortho-K case reports in this review as
there are limited studies that specifically look into astigmatism
All the toric Ortho-K lenses in the review are for both lens
centration and astigmatism reduction. Although Menicon Z-Night
toric periphery are mainly for lens centration, but the effect of
refractive astigmatism reduction is significant in TO-SEE study
by Chen et al. . Full toric may produce better astigmatism reduction as full toric provides perfectly closed reverse-zone
in every meridian, but this will need a larger subject group and
Centration is very important before the toric Ortho-K can
be effective on reducing astigmatism. A decentered lens may
increase instead of decreasing the amount of astigmatism .
Chen & Cho  did not specifically mention the type of
astigmatism, but from the refractive errors in the study, it was
With-the-rule (WTR) astigmatism. WTR astigmatism was used
in the studies of Chen et al. , Chen et al. , Chan et al. ,
Baertschi and Wyss , Luo et al.  and Calossi . Central
corneal astigmatism was specifically mentioned in the study by
Chen et al. .
In Calossi  case report, the astigmatism component
is higher than the spherical component, and this served as a
good resource for future study as the general Ortho-K requires
a spherical component higher than the astigmatism component
and the astigmatism is less than 1.50D. López-López et al. 
investigated limbus-to-limbus astigmatism in single subject
case report. Chang et al.  and Byul et al.  did not mention
the type of astigmatism in their studies but only excluded
limbus-to-limbus in their study. Pauné et al.  study involved
a combination of axis orientation. Specification of type of
astigmatism is suggested in future studies as different type of
toric Ortho-K may be effective at different type of astigmatism.
At this section review, there is limited ATR astigmatism and
limbus-to-limbus studies with toric Ortho-K, only Pauné et al.
 looked into ATR and oblique astigmatism, and limbus-tolimbus
astigmatism by López-López et al. .(Table 6)
All researchers reported that both refractive astigmatism
and corneal astigmatism (corneal toricity) changes took place,
except in Calossi  which showed only refractive astigmatism
had changed. Note that Calossi  study involved refractive
astigmatism which is higher than spherical power.(Table 7)
When we look at this review section of main ideas, take note
that significant is not statistically significant, as some studies
are not statistically analysed. Significant changes implied
the astigmatism reduction is more than 0.75D in refractive
astigmatism or corneal astigmatism/toricity. The table shows
that astigmatism changes are significant with both toric
periphery (toric alignment zone) and full toric (toric alignment
and reverse zone), except in Byul et al. .(Table 8
Take note the reported significant changes may only involve
a small sample subjects in case report or case series. We shall
have more reliable results if we have a larger sample with control
group and longer study duration.
Byul et al.  results showed small change of astigmatism
may be due to undefined type of astigmatism, non-specified
type of toric Ortho-K, and short study duration. Calossi  case
report showed there is residual astigmatism at the third month.
At the 18th month, residual astigmatism was not mentioned. We
must be cautious when treating patients with higher cylinder
component than spherical component, and patient consultation
is very important to meet their expectations.
Chen and Cho , Chang et al. , López-López et al. ,
Baertschi & Wyss , Luo et al. , Pauné et al. , Byul et al.
 and Calossi  did not define the range of moderate or high
corneal astigmatism. Chen et al.  did not define the moderate
or high astigmatism in their one-month study, but provided
inclusion criteria for WTR astigmatism 1.25D to 3.50 D for axes
180±20. Chen et al.  defined high corneal astigmatism for
subjects more than 1.50D cylinder. Chan et al.  defined WTR
corneal toricity less than 1.50D as low to moderate astigmatism,
and high corneal toricity for WTR astigmatism more than 1.50D.
As the population’s average astigmatism will change over time,
it is imperative to define low/moderate/high astigmatism and
updates made known, for Ortho-K fitter and examiner to have a
better guideline for toric Ortho-K cases.
The researchers that used vector analysis for refractive
astigmatism and corneal astigmatism changes are Chen et al. 
who used Power vectors, Chang et al.  who used CRAVY vector
analysis and Pauné et al.  who used Thibos vector. Vector
analysis is important to assess the corneal changes induced
by Ortho-K lens in pre- and post-treatment . Mountford
& Pesudovs  stated there are three types technique used:
Bailey-Carney vector analysis, Alpins vector analysis and
Corneal topography analysis. Whether corneal topography
analysis replaced the first two analysis or vector analysis still
has its value, we shall leave it to the future researcher who may
look into this.
Spherical Ortho-K lenses can reduce corneal astigmatism up
to 1.50 D with-the-rule astigmatism at the central 2 millimetre
chord . In this review, we look at relationship between toric
Ortho-K and moderate to high astigmatism.
Although Chen & Cho , Chen et al. , Chen et al.  and
Chan et al.  used Toric periphery Ortho-K in their studies,
all results show significant change of refractive astigmatism. The
studies by Chang F et al. , López-López et al. , Baertschi &
Wyss , Luo et al. , Pauné et al. , Byul et al.  and
Calossi  showed significant change in refractive astigmatism
and corneal astigmatism.
It was interesting to note that Group 1 researchers’ intention
of using toric periphery Ortho-K is for better centration of
Ortho-K lenses on astigmatic cornea, resulting in reduction of
astigmatism. Group 2 researches using Full toric Ortho-K aim
at myopia control and reduction of astigmatism. Baertschi &
Wyss  pointed that the correction of corneal astigmatism
requires a perfectly closed reverse-zone in every meridian and
that is only possible with toric reverse zone Ortho-K lenses. The
majority of the studies reviewed involved a small amount of
subjects. We shall need a bigger sample of subjects to study toric
Ortho-K effect on correcting astigmatism, specifically refractive
and corneal astigmatism.
Different researchers may have their own definition of
moderate to high astigmatism. We shall need a common
agreement on the range of moderate to high astigmatism in future
studies for comparison. We need to categorize the toric Ortho-K
(partial, full, real) and disclose their specifications to determine
the effectiveness of correcting astigmatism in any study. Ortho-K
fitters may need to work closely with Ortho-K lab for various
options in cases of myopic with low astigmatism, myopic with
high astigmatism, high myopic with low astigmatism, high
myopic with high astigmatism, astigmatism component is higher
than myopic component, hyperopic with astigmatism, limbusto-
limbus astigmatism and presbyopic with astigmatism.
Author is concerned about reduction of astigmatism as
astigmatism commonly co-exists with myopic patients  and
a higher astigmatism is getting more common (Harvey et al.
2006). Prevalence of astigmatism is as high as that of myopia in
Korea and East Asia at 60%, and this value significantly increases
with age . The myopia control effect of orthokeratology will
be less than successful if residual refractive error of astigmatism
is high and cannot be corrected. These particular subjects who
undergone the orthokeratology will have poor visual acuity
when the lenses are removed upon wake up. Toric Ortho-K is
important in helping the subject undergone myopia control and
allow subjects to see clear without the lenses in daytime, by
correcting the astigmatism or kept to the minimum. The results
of this review provide new and united evidence to toric Ortho-K
effectiveness in correcting astigmatism. This new evidence will
be important to encourage future study to apply randomized
controlled trial with toric Ortho-K. If we continue focus only
on myopia with low astigmatism, we deprive the opportunity
of moderate to high astigmatism subjects to receive “free from
spectacles in the daytime” and myopia control effects [21-29].
It is important to explore toric Ortho-K effectiveness in
correcting astigmatism, both refractive and corneal type. This
paper has reviewed the evidence between toric Ortho-K and
astigmatism. Following the review of 11 academic papers, the
evidence presented here suggested that toric Ortho-K reduce
astigmatism and provide good lens centration on astigmatic
As well as discovering that toric Ortho-K is able to reduce
astigmatism, this review has also unearthed that different type
of toric Ortho-K (toric periphery and full toric) has different
effectiveness on low and moderate to high astigmatism.
In summary, Toric Ortho-K is effective for lens centration
and for correcting medium to high astigmatism. More published
studies and statistical analysis are required to investigate
the effectiveness of toric orthokeratology for medium to
high astigmatism. Comparison of different type of Toric
Orthokeratology design must be included for future research, as
the published studies reviewed are mainly toric periphery, and
full toric only appeared in case reports and editorials/anectodal
I would like to thank Mr. Raúl Pérez of the School of Advanced
Education, Research and Accreditation (SAERA), Spain, as the
reader of this thesis, and I am gratefully indebted to him for his
very valuable comments on this thesis.
Besides Mr Raúl Pérez, I would like to thank Dr. Chan
Mooi Kwai of University of Science Malaysia (USM, Molecular
medicine) for her insightful comments and encouragement,
but also for the hard question which incented me to widen my
research from various perspectives.
My sincere thanks also go to Oliver Gubler, Managing Director
of Falco Linsen AG, who provided access to the information of
FOKX toric orthokeratology lenses.
Finally, I must express my very profound gratitude to my
family and friends for providing me with unfailing support
and continuous encouragement throughout my study and
through the process of researching and writing this thesis. This
accomplishment would not have been possible without them.