Influence of overnight orthokeratology lens fitting decentration on corneal topography reshaping
Chen et al. Eye and Vision
Influence of overnight orthokeratology lens fitting decentration on corneal topography reshaping
Jiaojie Chen 1
Wei Huang 1
Rong Zhu 1
Jun Jiang 1
Yiyu Li 0 1
0 Eye Hospital of Wenzhou Medical University , 270 West Xueyuan Road, Wenzhou, Zhejiang 325027 , China
1 School of Optometry and Ophthalmology, WenZhou Medical University , WenZhou, ZheJiang , China
Background: This retrospective study was designed to investigate the sole influence of orthokeratology (OK) lens fitting decentration on the Zernike coefficients of the reshaped anterior corneal surface. Methods: This study comprised a review of 106 right eyes and measurements of corneal topography both before OK and at 1-month follow-up visit. A routine was designed to calculate local corneal surface astigmatism and assist the determination of OK lens fitting decentration from pupil center. The pupil-centered corneal Zernike coefficients of baseline (PCCB) and post-treatment (PCCP) were calculated. Meanwhile, the OK-lens-centered corneal Zernike coefficients of post-treatment (OCCP) were also calculated and considered as the presumptive ideal fitting group without decentration. Relationships between lens fitting decentration and the change of Zernike coefficients including (PCCP − PCCB) and (PCCP − OCCP) were analyzed. Results: Patients with a mean age of 11 ± 2.36 years old had an average spherical equivalent refractive error of −3.52 ± 1. 06 D before OK. One month after treatment, OK lens fitting decentration from pupil center was 0.68 ± 0.35 mm. RMS of 3rd-order (P < 0.05), RMS of 4th-order (P < 0.001) and RMS of total high order (P < 0.001) corneal Zernike coefficients were increased in PCCP by comparing with OCCP, which was solely caused by lens fitting decentration. Nevertheless, no significant difference was observed in C02 (P > 0.05). For the high order corneal Zernike coefficients in (PCCP - OCCP), radial distance of decentration was correlated with C3−1 (r = −0.296, P < 0.05), C13 (r = −0.396, P < 0.001), and C04 (r = 0.449, P < 0.001), horizontal decentration was significantly correlated with C13 (r = 0.901, P < 0.001) and C15 (r = 0.340, P < 0.001), and vertical decentration was significantly correlated with C3−1 (r = 0.904, P < 0.001). Conclusions: OK lens fitting decentration within 1.5 mm hardly influenced the change of corneal spherical power for myopia correction, but significantly induced additional corneal high order Zernike coefficients including C3−1, C13, C04, and C51.
Orthokeratology; Lens fitting decentration; Zernike coefficients; Contact lens; Corneal topography
Modern orthokeratology (OK) is a clinical nonsurgical
method for temporary myopia correction and even
controlling myopic progress in adolescents [
professional inspection, clinical monitoring and careful
personal hygiene management, the safety of overnight
OK treatment has repeatedly been confirmed [
Overnight OK lens reshapes cornea surface by flattening
the central cornea and relatively steepening the
midperipheral cornea for the desired myopia correction [
]. Corneal reshaping may also lead to a decreased
thickness of the central cornea with an increased thickness
of the mid-peripheral cornea [
]. It has been
proved that myopia correction with OK lens is mainly
attributed to anterior corneal surface reshaping [
However, a slight but statistically significant change on
the posterior corneal surface in the early phase of OK
progress was also reported [
Corneal reshaping results in the disparity of corneal
surface power between the central flattened corneal
region and the annular surrounding region. It is easy,
however not precise enough, to identify the central
treatment zone (TZ) based on corneal curvature maps or
power maps provided by computer-assisted
]. The estimated displacement from
pupil center to the nominal TZ center represents lens
The change of corneal topography as well as corneal
and ocular aberrations induced by OK can be influenced
by lens fitting decentration [
]. Previous studies
focused on the difference of corneal surface or wavefront
] between baseline and post-treatment,
therefore demonstrating the joint effect of corneal reshaping
and lens fitting decentration that commonly happened
simultaneously. Since the ideal fitting case without any
decentration is impracticable in the clinic, it is still
challenging to answer the following question: How to clarify
the sole influence of OK lens fitting decentration on
corneal topography reshaping within the pupil aperture?
The best answer to this question relies on the
construction of intended corneal surface reshaped under an ideal
The modal Zernike approach has been extensively
used for the representation of corneal topography [
and ocular wavefront [
] because of its simple
analytical form for surface curvature and power extraction
as well as visual quality evaluation. In this paper, we
described corneal surface morphology with Zernike
coefficients and proposed a novel corneal surface
astigmatism map to identify the TZ of OK on the cornea and
the lens fitting decentration. Two subregions were taken
from the reshaped corneal surface, which were the
pupil-centered corneal region and the TZ-centered
corneal region. The TZ-centered corneal region was
considered to mostly mimic the presumptive ideal
corneal surface reshaped under a perfect fitting condition.
Comparison of corneal Zernike coefficients between the
two areas was performed for the first time to reveal the
individual effect of OK lens fitting decentration on
corneal topography reshaping.
A total of 106 subjects (36 males and 70 females),
ranged from 7 to 21 years old, mean 11 ± 2.36 years,
were reviewed in this retrospective study. The subjects
were all treated at the Eye Hospital of Wenzhou Medical
University and were asked to wear OK lenses no fewer
than 8 h per night. The inclusion criteria comprised a
spherical refractive error of less than −6.00 DS with
refractive astigmatism of −1.50 DC or less, best-corrected
distance visual acuity of logMAR (logarithm of the
minimum angle of resolution) 0.0 or better before treatment,
and radial distance of OK lens fitting decentration of less
than 1.5 mm to prevent sclera from being covered.
Additionally, no OK lens wear in the last six months, no
contact lens wear within at least one-month
pretreatment, no current ocular or systemic disease, and no
use of medications that might influence refractive error.
All subjects were treated according to the tenets of the
Declaration of Helsinki.
Orthokeratology lens and lens fitting
We selected two popular brands of the OK lens with the
universal and similar four-curve design concept. One of
them was the Lucid OrthoK lens, and the other was the
Euclid OrthoK lens for overnight wear. Lucid OrthoK
lenses (Lucid Korea Co Ltd., South Korea) were
manufactured with the hexafocon-A material (Boston XO, DK =
100 × 10− 11[cm2/s][ml O2/ml × mm Hg], Polymer
Technology Corporation). Euclid OrthoK lenses (Euclid
Systems Corporation, America) were manufactured with
Boston Equalens II material (DK = 90 × 10− 11 [cm2/s][ml
O2/ml × mm Hg], Polymer Technology Corporation). All
these lenses possess a reverse-geometry design. The
overall diameter range of OK lenses is 10.2 mm to 11.2 mm,
and the central thickness is 0.22 mm to 0.23 mm.
All of these patients were treated by the doctor who
had been working in the field of OK treatment at the
Eye Hospital for over ten years. The most suitable trial
lens was selected based on the corneal topography and
the desired visual acuity for the initial lens-wearing trial.
According to the fitting evaluation under corneal
fluorescein pattern, a micro-adjustment would be made
during the following trials. The final lens was ordered by
the doctor through manufacturer’s guidelines combined
with parameters of the most suitable trial lens.
All the patients took a detailed list of ocular
examinations including slit-lamp evaluation, fluorescein staining,
subjective refraction and corneal topography both before
OK lens fitting and at 1-month follow-up visit. Corneal
profiles were measured with Medmont E300
VideoKeratography (Medmont International Pty Ltd., Victoria,
Australia, Model E300 U) by a specialized technician
within one hour after OK lens removal. And each of the
profiles was the best-focus image (the accuracy greater
than 95%) from the four frames which were captured
automatically. The Medmont E300 uses Placido rings to
map corneal surface and provides the extrapolated
topography data over a maximum ring diameter of 12 mm
with 2500 discrete output points uniformly spaced with
the subgrid size of 0.24 mm × 0.24 mm.
Lens fitting decentration and corneal Zernike coefficients
Unlike the conventional methods that utilized corneal
axial curvature, tangential curvature, or mean curvature
to assist the determination of lens fitting decentration
], the new method proposed here has used
corneal surface astigmatism map calculated from the
principal curvatures of the anterior corneal surface with
the theory of differential geometry [
First, the measured anterior corneal surface within an
aperture of 10 mm in diameter was fitted using Zernike
polynomials expansions [
] defined in Cartesian
coordinate with the radial order of n and angular frequency
of m. A large number of Zernike terms (up to an order of
16) were required to improve fitting accuracy due to the
freeform features of the cornea. The achieved RMS fit
error covering all the data points was less than 0.03 μm.
At each point of corneal surface S = S(x, y), principal
curvatures, denoted κ1 and κ2, which are maximum and
minimum curvatures in the normal planes were solved
with analytic method [
EG− F2 κ2−ðEN þ GL−2FMÞκ þ LN −M2
E ¼ 1 þ Sx; F ¼ SxSy; G ¼ 1 þ Sy ; L
¼ qffi1ffiffiffiþffiffiffiSffiffiSxffiffixx2ffiffiffiþffiffiffiffiffiSffiffiffiy2ffi ; M ¼ qffi1ffiffiffiþffiffiffiSffiffiSxffiffiyx2ffiffiffiþffiffiffiffiffiSffiffiy2ffiffi ; N
þ Sx þ Sy
where Sx, Sy, Sxx and Sxy are the first and second
derivatives along the horizontal and vertical directions, and Sxy
is the crossed second derivative.
The directions of normal plane where the curvature
takes its maximum and minimum values are always
perpendicular, if κ1 does not equal κ2, and are called the
principal directions determined by
αi ¼ arctan −
; i ¼ 1; 2
Principal powers were then defined as the product of
principal curvatures and the difference of refractive
indexes of the medium separated by the corneal surface.
The difference of two principal powers at each point
represented the local corneal surface astigmatism
(LCSA) with axis given by principal direction α1 of the
high power κ1.
Figure 1 shows both the tangential power map
supplied by the Medmont E300 and the proposed LCSA
map which demonstrated the considerable corneal
irregular astigmatism [
] across the reshaped cornea
surface. During the overnight OK treatment, OK lens
wear forced central cornea region to be flattened and
mid-peripheral cornea region to be relatively steepened,
thereby generating the minimum LCSA in the transition
zone connecting the two areas. The dark elliptic rings
depicted in Fig. 1c and Fig. 1f highlight the trajectory of
minimum LCSA (being close to zero diopter),
meanwhile represent the effective boundary between base
curve and reverse curve of OK lens fitting on the cornea.
The ring was elliptical, not circular in shape because of
the inherent corneal spherocylinder.
Corneal region encircled by this elliptic ring
represented the central TZ of OK on the cornea and was
called the OK-lens-centered cornea region. Lens fitting
decentration was the displacement from the center of
the elliptic ring to the pupil center. Temporal
displacement and inferior displacement from pupil center mean
a negative horizontal lens fitting decentration and a
negative vertical lens fitting decentration, respectively.
Two subregions with an aperture size of 4 mm in
diameter were then taken from the reshaped corneal
surface, which comprised the pupil-centered corneal
region and the OK-lens-centered corneal region. Figure 2
shows that the two subregions were marked on LCSA
map and separated from the corneal surface. Since the
OK-lens-centered corneal region was always covered by
the base curve of the OK lens, the corneal geometry
features except piston and tilt components of this region
should be insensitive to lens fitting decentration and
therefore might best mimic the presumptive ideal
corneal surface reshaped without fitting decentration.
In this study, all the subjects were chosen to have a lens
fitting decentration of less than 1.5 mm, so that sclera would
not interact with the OK lens. The two subregions separated
from the reshaped corneal surface were fitted using Zernike
polynomials to obtain the pupil-centered corneal Zernike
coefficients of post-treatment (PCCP) and the
OK-lenscentered corneal Zernike coefficients of post-treatment
(OCCP), respectively. Meanwhile, the pupil-centered corneal
Zernike coefficients of pre-treatment (PCCB) were also
calculated as a baseline. Note that, each Zernike polynomial
represented a corneal surface deformation mode.
SPSS Statistics 18.0 (IBM Statistics, Armonk, NY) was
used for statistical analysis of the lens fitting
decentration and the corneal Zernike coefficients. Data from
right eyes were used for analysis. Each Zernike
coefficient and root-mean-square (RMS) of 3rd order, 4th
order and total high order (3rd to 7th order) Zernike
coefficients were compared for each pair of PCCB,
OCCP and PCCP using the paired t-test. The difference
between PCCP and PCCB and the difference between
PCCP and OCCP were analyzed concerning lens fitting
decentration (e.g., horizontal and vertical decentration,
the radial distance of decentration) using Pearson
correlation (r) test. A P value less than 0.05 was considered
One hundred six subjects (36 males and 70 females) were
evaluated with their mean age of 11 ± 2.36 (mean ± standard
deviation, range 7 to 21 years). Before treatment, spherical
equivalent refractive error was −3.52 ± 1.06 D (range −1.25
to −5.75 D) with spherical refractive error of −3.35 ± 1.01 DS
(range −1.00 to −5.25 DS) and astigmatism of −0.47 ±
0.38 DC (range 0.00 to −1.50 DC). After 1-month OK lens
wear, 104 eyes got the uncorrected visual acuity of logMAR
0.1 or better (98.1%). Radial distance of lens fitting
decentration was 0.68 ± 0.35 mm (range 0.05 to 1.49 mm), horizontal
decentration was −0.40 ± 0.46 mm (range −1.24 to +
0.98 mm) and vertical decentration was −0.15 ± 0.45 mm
(range −1.40 to + 0.93 mm). For horizontal displacement,
there were 16 eyes (15.1%) observed a nasal decentration,
and 90 eyes (84.9%) observed a temporal decentration. For
vertical displacement, there were 44 eyes (41.5%) observed a
superior decentration, and 62 eyes (58.5%) observed an
inferior decentration. There were 52 eyes (49.1%) observed a
decentration in the inferotemporal quadrant, 38 eyes (35.8%)
in the superotemporal quadrant, 10 eyes (9.4%) in inferonasal
quadrant, and 6 eyes (5.7%) in the superonasal quadrant.
Zernike modes near the center of Zernike pyramid, which
can profoundly affect the visual performance [
chosen from PCCB, OCCP, and PCCP and listed in Table 1
including their comparisons.
Comparison of OCCP with PCCB in Table 1 reveals
that the presumptive ideal OK lens fitting (corneal
reshaping without lens fitting decentration) could cause a
significant decrease in C02 (P < 0.001) and a substantial
High orders RMS 0.48 ± 0.14 1.12 ± 0.49 1.47 ± 0.90 0.000* 0.000*
Abbreviations: PCCB = Pupil-centered corneal Zernike coefficients of baseline/pre-treatment; OCCP = OK-lens-centered corneal Zernike coefficients of
posttreatment; PCCP = Pupil-centered corneal Zernike coefficients of post-treatment
*P < 0.001 (paired t test), significant statistical significance
†P < 0.05(paired t test), statistical significance
increase in RMS of 3rd-order (P < 0.001), RMS of
4thorder (P < 0.001) and RMS of high order (P < 0.001)
Zernike coefficients, but no change in C04 (P > 0.05).
Comparison of PCCP with PCCB in Table 1 reveals that
the actual OK lens fitting (corneal reshaping combined
with lens fitting decentration) resulted in a significant
decrease in C02 (P < 0.001) and a considerable increase in C0
(P < 0.001), RMS of 3rd-order (P < 0.001), RMS of
4th-order (P < 0.001) and RMS of high order (P < 0.001) Zernike
coefficients of pupil-centered corneal region.
Comparing PCCP with OCCP in Table 1 shows the
sole effect of lens fitting decentration, which did not
cause significant change in C02 (P = 0.095 > 0.05) but a
substantial increase in C04 (P < 0.001), RMS of 3rd-order
(P = 0.038 < 0.05), RMS of 4th-order (P < 0.001) and
RMS of high order (P < 0.001) Zernike coefficients.
According to the significant difference of C−1 (P =
0.021 < 0.05), C13 (P < 0.001), C04 (P < 0.001), C24 (P =
0.007 < 0.05), C15 (P < 0.001) between PCCP and PCCB
(see Table 1), Table 2 lists the correlations between lens
fitting decentration and the modification of Zernike
coefficients calculated by (PCCP − PCCB).
According to the significant difference of C3−1 (P = 0.011
< 0.05), C13 (P < 0.001), C04 (P < 0.001), C15 (P = 0.028 <
0.05) between PCCP and OCCP (see Table 1), similar
analysis was performed to obtain the correlations between
lens fitting decentration and the change of Zernike
coefficients calculated by (PCCP − OCCP) in Table 2.
Figures 3, 4, 5 show correlations between lens fitting
decentration and the modification of Zernike coefficients
calculated by (PCCP−PCCB). Radial distance of
decentration was significantly correlated with C13 (r =
−0.379, P < 0.001) and C04 (r = 0.531, P < 0.001) as shown in
Fig. 3. Horizontal decentration was substantially correlated
with C13 (r = 0.730, P < 0.001), C24 (r = −0.301, P < 0.05) and
C15 (r = 0.369, P < 0.001) as shown in Fig. 4. Vertical
decentration was significantly correlated with C3−1 (r = 0.693, P <
0.001) and C24 (r = 0.275, P < 0.05) as shown in Fig. 5.
Figures 6, 7, 8 show correlations between lens fitting
decentration and the change of Zernike coefficients
determined by (PCCP−OCCP). Radial distance of decentration
was significantly correlated with C3−1 (r = −0.296, P < 0.05),
C13 (r = −0.396, P < 0.001), and C04 (r = 0.449, P < 0.001) as
illustrated in Fig. 6. Horizontal decentration was
significantly correlated with C13 (r = 0.901, P < 0.001) and C15 (r
= 0.340, P < 0.001) as shown in Fig. 7. Vertical
PCCP − PCCB
PCCP − OCCP
C13 −0.379* 0.730* / −0.396* 0.901* /
C04 0.531* / / 0.449* / /
C42 / −0.301† 0.275† / / /
C15 / 0.369* / / 0.340* /
Abbreviations: PCCP = Pupil-centered corneal Zernike coefficients of
posttreatment; PCCB = Pupil-centered corneal Zernike coefficients of
baseline/pretreatment; OCCP = OK-lens-centered corneal Zernike coefficients of post-treatment
*P < 0.001 (Pearson correlation (r) test), significant statistical significance
†P < 0.05 (Pearson correlation (r) test), statistical significance
Fig. 5 The correlations between vertical decentration and Zernike coefficients in (PCCP−PCCB). a C3−1. b C2
Fig. 6 The correlations between radial distance of decentration and Zernike coefficients in (PCCP − OCCP). a C3−1. b C13. c C0
Owing to the effectiveness of controlling myopic progress
in adolescents [
], there is an increasing prevalence of
OK treatment that has been chosen by more than 1.5
million adolescents in China . Fortunately, the safety of OK
lens treatment also has repeatedly been confirmed both for
short-term and long-term therapy [
]. However, fitting
decentration cannot be avoided entirely during the
procedure. In our study, we investigated the sole influence of
overnight OK lens fitting decentration on corneal topography
with our new method, differing from the previous study
dealing with the joint effect of corneal reshaping and lens
fitting decentration [
To accurately calculate the OK lens fitting decentration
on the cornea, LCSA maps were proposed for the first
time to our best knowledge to assist the determination of
OK-lens-centered corneal region or the TZ of OK.
Contrasting the previous methods using surface power or
surface curvature [
], a distinct trajectory of
minimum corneal surface astigmatism could be observed
on LCSA map, which facilitated the accurate identification
of OK lens position and even the working boundaries of
the segmented curves of the OK lens on the cornea.
By comparing the Zernike coefficients calculated for
the pupil-centered corneal surface and the
OK-lenscentered corneal surface, the divergence between PCCP
and PCCB demonstrated the combined effect of corneal
reshaping and lens fitting decentration that has been
discussed previously [
]. However, the difference
between PCCP and OCCP revealed the sole influence of
lens fitting decentration on the reshaped corneal surface,
which has received little attention.
A number of previous studies [
17, 19–21, 24–27, 29, 35,
] focusing on the corneal or ocular wavefront aberrations
have uncovered a decrease in defocus C02 and the increase
in the vertical primary coma C3−1 , horizontal primary coma
C13, primary spherical C04, and RMS of high order wavefront
aberrations owing to overnight OK lens wear. Similar
results from the Zernike coefficients of corneal surface (see
PCCP vs. PCCB in Table 1) were found in this study, which
could account for the intended myopic correction [
and the induced wavefront aberrations.
Moreover, the sole influence of lens fitting
decentration on corneal topography was revealed by comparing
PCCP with OCCP, finding that lens fitting decentration
could cause a further increase in RMS of 3rd order,
RMS of 4th order and RMS of high order corneal
surface Zernike coefficients but no significant change in C02.
It means that lens fitting decentration had an insufficient
effect on the change of corneal spherical power, which may
differ from the previous opinion of Yang et al. [
found that there was a definite tendency between refractive
error and lens fitting decentration. Hiraoka et al. [
believed that fitting decentration was related to the
refractive error. This controversy is the result of some critical
factors, such as slightly diverse assessment parameters,
distinct methods for the determination of fitting
decentration, and different data processing methods of Zernike
coefficients involved. The evidence supports our result about
C02 is that 98.1% subjects got the uncorrected visual acuity
of logMAR 0.1 or better after 1-month treatment regardless
of the diversity of lens fitting decentration.
Several studies have probed the relationship between
lens fitting decentration and individual 3rd order Zernike
coefficients of corneal aberrations [
] or ocular
19, 21, 35
]. Here, based on the Zernike coefficients
of corneal surface, the similar results obtained were that
the horizontal primary coma C13 was correlated with
horizontal decentration (Fig. 4a and Fig. 7a) while the vertical
primary coma C−1 was correlated with vertical
tion (Fig. 5a and Fig. 8) both for (PCCP−PCCB) and
(PCCP−OCCP). Furthermore, because of the higher level
of correlation observed in Fig. 7a than that in Fig. 4a, the
conventional analysis method based on (PCCP–PCCB)
may underestimate the influence of horizontal lens fitting
decentration on C13. The same problem may arise with C3−1
by comparing Fig. 8 with Fig. 5a.
Remarkably, we found that perfect OK lens fitting
might bring in an obvious change of C13 statistically but
not C−1 as shown in OCCP vs. PCCB in Table 1. The
main reason may be the corneal physiological difference
along horizontal visual field [
]. Apart from the
relationship between principle meridian and 3rd order
Zernike coefficients, C13 was also found to be related to
radial distance of decentration with a comparable level
of correlation both for (PCCP – PCCB) and (PCCP –
OCCP) (Fig. 3a and Fig. 6b), while C−1 was related to
dial distance of decentration only for (PCCP – OCCP)
(see Fig. 6a). So, it may imply that the change of C13 was
caused by the shared effect of corneal reshaping and lens
fitting decentration, while C−1 was more easily affected
by OK lens fitting decentration and could be
compensated by corneal reshaping.
The same as the previous results [
20, 26, 27
spherical C04 underwent a statistical increase both by
comparing PCCP with PCCB or comparing PCCP with
OCCP (see Table 1). Figure 3b and Fig. 6c also
demonstrate the positive correlation between C04 and radial
distance of decentration. However, the absence of statistical
difference between OCCP and PCCB for C04 (see Table 1)
indicates that the change of C04 might be caused by lens
fitting decentration. Because of the complex interaction
between C02 and C04 [
40, 42, 44
], the change in C04 of
corneal surface due to lens fitting decentration could bring
in additional wavefront aberration of defocus.
It is interesting to find that horizontal secondary
astigmatism C24 in (PCCP – PCCB) was negatively correlated
with horizontal decentration (Fig. 4b) and positively
correlated with vertical decentration (Fig. 5b), while there
was no significant change of C2 either in OCCP vs.
PCCB or in PCCP vs. OCCP (see Table 1). So, the
change of C24 may be caused by the composite effect of
lens fitting decentration and corneal reshaping.
The correlation between horizontal secondary coma
C15 and horizontal decentration was found to be similar
both for (PCCP – PCCB) and (PCCP – OCCP) as shown
in Fig. 4c and Fig. 7b. We may deduce that the change
of C15 was solely induced by lens fitting decentration and
insensitive to the interaction between corneal reshaping
and lens fitting decentration. According to the statistical
difference of vertical secondary coma C−1 between OCCP
and PCCB (see Table 1), the change of C−1 was possibly
associated with corneal reshaping but neutralized with
lens fitting decentration. Additionally, the combination
of C13 and C15 of cornea surface may cause horizontal
coma-like wavefront aberration, since Applegate et al.
] and Chen et al. [
] had pointed out that the
individual Zernike coefficients with the same sign and
angular frequency could be combined to interact.
When it came to the direction of lens fitting
decentration, it was observed that temporal decentration, inferior
decentration, and inferotemporal decentration accounted
for 84.9%, 58.5% and 49.1% of all the fitted OK lenses,
respectively. Such a tendency to inferotemporal
decentration has been reported in several studies [
18–20, 22, 35
However, the different tendency to the superotemporal
decentration might also be possible [
]. The temporal
decentration was due to the steeper temporal side of
cornea than the nasal side [
]. The vertical
decentration was presumed to be a composite result of eyelid
tension, lens design and fitting technology [
One limitation of this study is that only corneal
topography was quantified, the influence of fitting decentration
on visual quality such as ocular wavefront or contrast
sensitivity function was not taken into consideration. Another
limitation is that fitting decentration was not phased in
magnitude to clarify the levels of correlation with corneal
Zernike coefficients which may provide the basis for
fitting decentration classification in the clinic.
The composite effect of corneal reshaping and lens fitting
decentration of the OK lens on corneal topography was
scrutinized using the conventional method based on
comparing PCCP with PCCB. The sole influence of OK lens
fitting decentration on the reshaped corneal surface was
revealed by comparing PCCP with OCCP. OK lens fitting
decentration within 1.5 mm can scarcely influence the
change of corneal spherical power for myopia correction,
but may significantly induce additional corneal high order
Zernike coefficients including C3−1 , C1, C0, and C1.
3 4 5
LCSA: local corneal surface astigmatism; logMAR: logarithm of the minimum
angle of resolution; OCCP: OK-lens-centered corneal Zernike coefficients of
post-treatment; OK lens: orthokeratology lens; PCCB: pupil-centered corneal
Zernike coefficients of baseline / pre-treatment; PCCP: pupil-centered corneal
Zernike coefficients of post-treatment; TZ: treatment zone
This work was supported by the Scientific and Technological Program of
Wenzhou [Y20160438, G20160033]; National Natural Science Foundation of
China ; Natural Science Foundation of Zhejiang Province [LY14F050009,
LY16H120007]; and National Key Research and Development Program of China
Availability of data and materials
The datasets used and/or analyzed during the current study are available
from the corresponding author on reasonable request.
JC analyzed data, contributed to discussion and wrote the manuscript. WH
and RZ collected and analyzed data. JJ conceived the study, participated in
the discussion and revised the manuscript. YL designed, conducted the
study, contributed to discussion and edited the manuscript. All authors have
read and approved the final manuscript.
Ethics approval and consent to participate
Consent for publication
The authors declare that they have no competing interests.
1. Swarbrick HA . Orthokeratology review and update . Clin Exp Optom . 2006 ; 89 ( 3 ): 124 - 43 .
2. Cheung SW , Cho P , Fan D. Asymmetrical increase in axial length in the two eyes of a monocular orthokeratology patient . Optom Vis Sci . 2004 ; 81 ( 9 ): 653 - 6 .
3. Si JK , Tang K , Bi HS , Guo DD , Guo JG , Wang XR . Orthokeratology for myopia control: a meta-analysis . Optom Vis Sci . 2015 ; 92 ( 3 ): 252 - 7 .
4. Wen D , Huang J , Chen H , Bao F , Savini G , Calossi A , et al. Efficacy and Acceptability of Orthokeratology for Slowing Myopic Progression in Children: A Systematic Review and mMeta-Analysis . J Ophthalmol . 2015 ; 2015 :360806. https://doi.org/10.1155/ 2015 /360806.
5. Walline JJ. Myopia Control : A Review. Eye Contact Lens . 2016 ; 42 ( 1 ): 3 - 8 .
6. Xie P , Guo X . Chinese Experiences on Orthokeratology. Eye Contact Lens . 2016 ; 42 ( 1 ): 43 - 7 .
7. Rah MJ , Jackson JM , Jones LA , Marsden HJ , Bailey MD , Barr JT . Overnight orthokeratology: preliminary results of the Lenses and Overnight Orthokeratology (LOOK) study . Optom Vis Sci . 2002 ; 79 ( 9 ): 598 - 605 .
8. Na KS , Yoo YS , Hwang HS , Mok JW , Kim HS , Joo CK . The Influence of Overnight Orthokeratology on Ocular Surface and Meibomian Glands in Children and Adolescents . Eye Contact Lens . 2016 ; 42 ( 1 ): 68 - 73 .
9. Liu YM , Xie P. The Safety of Orthokeratology-A Systematic Review . Eye Contact Lens . 2016 ; 42 ( 1 ): 35 - 42 .
10. Mountford J. An analysis of the changes in corneal shape and refractive error induced by accelerated orthokeratology . Int Contact Lens Clin . 1997 ; 24 ( 4 ): 128 - 44 .
11. Swarbrick HA , Wong G , O'Leary DJ . Corneal response to orthokeratology . Optom Vis Sci . 1998 ; 75 ( 11 ): 791 - 9 .
12. Yoon JH , Swarbrick HA . Posterior corneal shape changes in myopic overnight orthokeratology . Optom Vis Sci . 2013 ; 90 ( 3 ): 196 - 204 .
13. Alharbi A , Swarbrick HA . The effects of overnight orthokeratology lens wear on corneal thickness . Invest Ophthalmol Vis Sci . 2003 ; 44 ( 6 ): 2518 - 23 .
14. Choo JD , Caroline PJ , Harlin DD , Papas EB , Holden BA . Morphologic changes in cat epithelium following continuous wear of orthokeratology lenses: a pilot study . Cont Lens Anterior Eye . 2008 ; 31 ( 1 ): 29 - 37 .
15. Owens H , Garner LF , Craig JP , Gamble G . Posterior corneal changes with orthokeratology . Optom Vis Sci . 2004 ; 81 ( 6 ): 421 - 6 .
16. Chen D , Lam AK , Cho P . Posterior corneal curvature change and recovery after 6 months of overnight orthokeratology treatment . Ophthalmic Physiol Opt . 2010 ; 30 ( 3 ): 274 - 80 .
17. Stillitano IG , Chalita MR , Schor P , Maidana E , Lui MM , Lipener C , et al. Corneal changes and wavefront analysis after orthokeratology fitting test . Am J Ophthalmol . 2007 ; 144 ( 3 ): 378 - 86 .
18. Yang X , Zhong X , Gong X , Zeng J . Topographical evaluation of the decentration of orthokeratology lenses . Yan Ke Xue Bao . 2005 ; 21 ( 3 ): 132 - 5 .
19. Hiraoka T , Mihashi T , Okamoto C , Okamoto F , Hirohara Y , Oshika T. Influence of induced decentered orthokeratology lens on ocular higher-order wavefront aberrations and contrast sensitivity function . J Cataract Refract Surg . 2009 ; 35 ( 11 ): 1918 - 26 .
20. Wang W , Mao XJ . Effect of overnight orthokeratology on corneal surface morphology and corneal aberrations . Chin J Optom Ophthalmol Vis Sci . 2011 ; 13 ( 4 ): 269 - 73 .
21. Chen Y , Jiang J , Mao XJ , Lu F. The dynamic influence of induced decentered orthokeratology lenses on higher-order wavefront aberrations . Chin J Optom Ophthalmol Vis Sci . 2013 ; 15 ( 11 ): 656 - 61 .
22. Maseedupally VK , Gifford P , Lum E , Naidu R , Sidawi D , Wang B , et al. Treatment Zone Decentration During Orthokeratology on Eyes with Corneal Toricity. Optom Vis Sci . 2016 ; 93 ( 9 ): 1101 - 11 .
23. Joslin CE , Wu SM , McMahon TT , Shahidi M. Is "whole eye" wavefront analysis helpful to corneal refractive therapy? Eye Contact Lens . 2004 ; 30 ( 4 ): 186 - 8 .
24. Hiraoka T , Matsumoto Y , Okamoto F , Yamaguchi T , Hirohara Y , Mihashi T , et al. Corneal higher-order aberrations induced by overnight orthokeratology . Am J Ophthalmol . 2005 ; 139 ( 3 ): 429 - 36 .
25. Hiraoka T , Okamoto F , Kaji Y , Oshika T. Optical quality of the cornea after overnight orthokeratology . Cornea . 2006 ; 25 ( 10 Suppl 1 ): S59 - 63 .
26. Gifford P , Li M , Lu H , Miu J , Panjaya M , Swarbrick HA . Corneal versus ocular aberrations after overnight orthokeratology . Optom Vis Sci . 2013 ; 90 ( 5 ): 439 - 47 .
27. Lian Y , Shen M , Huang S , Yuan Y , Wang Y , Zhu D , et al. Corneal reshaping and wavefront aberrations during overnight orthokeratology . Eye Contact Lens . 2014 ; 40 ( 3 ): 161 - 8 .
28. Santodomingo-Rubido J , Villa-Collar C , Gilmartin B , Gutiérrez-Ortega R , Suzaki A . The effects of entrance pupil centration and coma aberrations on myopic progression following orthokeratology . Clin Exp Optom . 2015 ; 98 ( 6 ): 534 - 40 .
29. Santolaria Sanz E , Cerviño A , Queiros A , Villa-Collar C , Lopes-Ferreira D , GonzálezMéijome JM . Short-term changes in light distortion in orthokeratology subjects . Biomed Res Int . 2015 ; 2015 :278425. https://doi.org/10.1155/ 2015 /278425.
30. Schwiegerling J , Greivenkamp JE , Miller JM . Representation of videokeratoscopic height data with Zernike polynomials . J Opt Soc Am A Opt Image Sci Vis . 1995 ; 12 ( 10 ): 2105 - 13 .
31. Iskander DR , Collins MJ , Davis B . Optimal modeling of corneal surfaces with Zernike polynomials . IEEE Trans Biomed Eng . 2001 ; 48 ( 1 ): 87 - 95 .
32. Iskander DR , Morelande MR , Collins MJ , Davis B . Modeling of corneal surfaces with radial polynomials . IEEE Trans Biomed Eng . 2002 ; 49 ( 4 ): 320 - 8 .
33. ISO. Ophthalmic optics and instruments-reporting aberrations of the human eye . Switzerland: International Organization for Standardization. ISO 24157 : 2008(E).
34. Lakshminarayanan V , Fleck A . Zernike polynomials: a guide . J Mod Opt . 2011 ; 58 ( 7 ): 545 - 61 .
35. Faria-Ribeiro M , Belsue RN , López-Gil N , González-Méijome JM . Morphology, topography, and optics of the orthokeratology cornea . J Biomed Opt . 2016 ; 21 ( 7 ): 75011 .
36. Gray A , Abbena E , Salamon S. Modern differential geometry of curves and surfaces with Mathematica . 3rd ed. Chapman & Hall CRC : Boca Raton; 2006 .
37. Barsky BA , Klein SA , Garcia DD . Gaussian power with cylinder vector field representation for corneal topography maps . Optom Vis Sci . 1997 ; 74 ( 11 ): 917 - 25 .
38. Thibos LN , Hong X , Bradley A , Applegate RA . Accuracy and precision of objective refraction from wavefront aberrations . J Vis . 2004 ; 4 ( 4 ): 329 - 51 .
39. Wang M. Irregular astigmatism diagnosis and treatment . Slack Incorporated: Thorofare; 2007 .
40. Applegate RA , Sarver EJ , Khemssara V . Are all aberrations equal ? J Refract Surg . 2002 ; 18 ( 5 ): S556 - 62 .
41. Applegate RA , Ballentine C , Gross H , Sarver EJ , Sarver CA. Visual acuity as a function of Zernike mode and level of root mean square error . Optom Vis Sci . 2003 ; 80 ( 2 ): 97 - 105 .
42. Chen L , Singer B , Guirao A , Porter J , Williams DR . Image metrics for predicting subjective image quality . Optom Vis Sci . 2005 ; 82 ( 5 ): 358 - 69 .
43. Hiraoka T , Kakita T , Okamoto F , Oshika T. Influence of ocular wavefront aberrations on axial length elongation in myopic children treated with overnight orthokeratology . Ophthalmology . 2015 ; 122 ( 1 ): 93 - 100 .
44. Applegate RA , Marsack JD , Ramos R , Sarver EJ . Interaction between aberrations to improve or reduce visual performance . J Cataract Refract Surg . 2003 ; 29 ( 8 ): 1487 - 95 .
45. Atchison DA , Scott DH . Monochromatic aberrations of human eyes in the horizontal visual field . J Opt Soc Am A Opt Image Sci Vis . 2002 ; 19 ( 11 ): 2180 - 4 .
46. Woo GC , Chow E , Cheng D , Woo S . A study of the central and peripheral refractive power of the cornea with orthokeratology treatment . Int Contact Lens Clin . 1994 ; 21 : 132 - 6 .
47. Dingeldein SA , Klyce SD . The topography of normal corneas . Arch Ophthalmol . 1989 ; 107 : 512 - 8 .