Open Journal of Ophthalmology, 2012, 2, 45-53 Published Online August 2012 (
Corneal Wavefront Aberrations in Patients Wearing
Multifocal Soft Contact Lenses for Myopia Control
Frank Spors1,2*, Donald J. Egan1,2, Jie Shen1,2, Lance E. McNaughton1,2, Stuart Mann1,2, Neil M. Patel1
1Western University of Health Sciences, Pomona, USA; 2College of Optometry, Pomona, USA.
Email: *
Received March 11th, 2012; revised April 20th, 2012; accepted May 14th, 2012
Purpose: The purpose of this study was to evaluate the change in corneal wavefront aberrations in young adults who
have been fit with multifocal soft contact lenses for myopia progression control. Findings have been analyzed for statis-
tical significance and clinical relevance and compared to reportedly successful Orthokeratology outcomes. Methods:
The dominant eye of 40 participants (27 women, 13 men; mean age 27.3 ± 3.2 years; range 23 to 39 years) was fit with
Proclear Multifocal center-distance lenses (Coopervision, Pleasanton, USA) having a variety of distance powers and
reading additions. Refractive errors were limited to a range of –6.00 D up to +1.00 D of sphere, and no greater than
–1.00 D of cylinder. Corneal wavefront measurements were performed over 6 mm diameters with a Zeiss Atlas 9000
corneal topographer (Zeiss Meditec, Dublin, USA) prior to, and following lens fitting. Data were converted into rec-
tangular Fourier optics terms M, J0, J45 and RMS values for each reading addition were statistically analyzed. Following
evaluation of statistical significance and clinical relevance, results were compared to published data from successful
Orthokeratology treatments. Results: Statistically significant changes in higher order aberrations were detected for
lenses of all reading additions. Lens groups with higher Add powers demonstrated stronger changes with increased sig-
nificance. Final RMS values relating to 2nd, 3rd and 4th Zernike orders reached clinical significance with a wavefront
error of 0.10 μm, the equivalent of 0.25 D. Moreover, as Add powers increased, 3rd and 4th order aberrations likewise
showed an increase. Pre-fitting astigmatism values accounted for the highest recorded aberrations and remained pre-
dominantly unchanged. Conclusion: Proclear Multifocal center-distance contact lenses were found to increase higher
order wavefront aberrations in a manner dependent on their Add power. In comparison to successful Orthokeratology
outcomes, the amounts of resulting aberrations are notably different.
Keywords: Multifocal Soft Contact Lenses; Wavefront Aberrations; Myopia; Myopia Progression Control;
Orthokeratology; Zernike Polynomials
1. Introduction
Myopia is one of the most common ocular anomalies in
the world [1]. Recent epidemiology studies cite a grow-
ing incidence of myopia that includes a heightened level
of severity [2,3]. The prevalence of myopia is estimated
to be 25% of adults in the United States [4]. In Taiwan,
Hong Kong, and Singapore however, the prevalence of
myopia in young adults is estimated at up to 60% to 80%
[5]. The Beaver Dam Report on longitudinal refractive
error changes in approximately 5000 people in the city
and township of Beaver Dam, Wisconsin, US, over a 10-
year period showed an increase in the prevalence of
myopia and even a possible increase in the prevalence
and severity of high myopia [6,7]. Due to the growth in
technology and knowledge within the fields of genetics,
studies have been conducted to identify genetic loci as-
sociated with various conditions, including myopia. To
date, an explanation for the onset and progression of
simple myopia is given by both genetic susceptibility,
especially associated with the PAX6 gene, and a con-
ducing environment [8,9]. However, the exact causes for
myopia progression are still unknown and under investi-
gation. A strong impact on the onset and progression of
myopia can be assigned to the retinal image quality [10].
Studies by Hung et al. in 2005 on infant monkeys dem-
onstrated that the peripheral retina influences eye growth
and refractive development and subsequently drives the
emmetropization process after birth. The image quality at
the central retina, the fovea, did not have an impact.
While form deprivation in the retinal periphery acceler-
ated elongation of the eye, resulting in myopia, even
complete elimination of the central fovea with LASER
ablation did not change the regular growth pattern [10].
Based on the convincing evidence provided by the Hung
*Corresponding author.
Copyright © 2012 SciRes. OJOph
Corneal Wavefront Aberrations in Patients Wearing Multifocal Soft Contact Lenses for Myopia Control
et al. study, peripheral retinal image quality in humans is
a matter of great interest that remains open to further
investigation. Here we have to differentiate between
lower order and higher order aberrations which can be
described by Zernike polynomials [11]. Zernike polyno-
mials form a complete set of functions that are orthogo-
nal over a circle of unit radius and serve as a set of basic
functions. This property therefore renders them suitable
for accurately describing wavefront aberrations. They are
usually expressed in polar coordinates, and are readily
convertible to Cartesian coordinates. These polynomials
are mutually orthogonal, and are therefore mathemati-
cally independent. They can be scaled which allows a
meaningful relative comparison between them. A common
way to depict them is the so called Zernike pyramid as
shown in Figure 1. In order to utilize Zernike polynomi-
als for wavefront analysis and to assess their impact on
the visual function, lower and higher orders become of
interest. Relevant lower order aberrations include sphere
and cylinder. Little is known about the impact of the
lower order aberration cylinder and all higher order ab-
errations on myopia progression. Numerous reports exist
about the impact of defocus, which equals the lower or-
der aberration sphere. While emmetropic and hyperopic
individuals tend to have a myopic defocus at their pe-
ripheral retina, myopic individuals have a relative hy-
peropic periphery [12]. A hyperopic defocus in the pe-
ripheral retina is likely to be a good stimulus for the on-
set and progression of myopia, independent of the central
focus quality. This hyperopic defocus is associated with a
prolate retinal shape, which has been found to be domi-
nant in myopes [13]. Such findings are particularly re-
markable since traditional tests used for determining
visual function, degree of ametropia and optical defocus
only assess the central retinal region. We can assume that
a key element to compensate for already existing amounts
of myopia and to inhibit further progression of myopia is
a specific retinal image profile. In order to allow good
visual acuity, this profile cannot be defocused in the cen-
tral retina. At the same time, in order to inhibit myopia
progression the image has to be myopically defocused or
emmetropic in the peripheral retina. Figure 2 depicts this
relationship. Historically, generating such a profile has
been a challenge for the broad variety of optical treat-
ment options and refractive surgery procedures that are
currently available. A common routine of compensating
myopic refractive error is the use of spectacle lenses with
negative refractive power. Interestingly, all single vision
spectacle lenses induce peripheral hyperopic defocus.
The magnitude of this effect escalates with increasing
refractive error and eccentricity [14]. In this manner it is
clear that the desired retinal image profile is not pro-
duced. Hence, while the standard approach to refractive
error correction is good for compensating central defocus
by allowing good central visual acuities, its utility for
myopia progression control would seem to be largely
unmet. Other non-surgical treatment options for vision
correction include unifocal contact lenses, Orthokeratology,
Figure 1. Zernike pyramid displaying individual color coded wavefront errors organized by Zernike coefficients up to the 7th
order. The Zernike notation contains the coefficient (Z), the order (subscript) and the radial frequency (superscript).
Copyright © 2012 SciRes. OJOph
Corneal Wavefront Aberrations in Patients Wearing Multifocal Soft Contact Lenses for Myopia Control 47
Figure 2. Relationship of different retinal shapes and peripheral retinal image quality (defocus) when the central refractive
error is zero for all displayed schematic eyes (chief rays cross at the nodal points).
multifocal contact lenses, and spectacle lenses with spe-
cifically designed multifocal free-form surfaces [15-17].
All of these systems have a varying potential to induce
peripheral myopic defocus and therefore may be benefi-
cial for myopia progression control. Orthokeratology
alters the corneal front surface in a way such that the
resultant optics produces a focused image at the central
retina and the desired myopic defocus at the peripheral
retina [18,19]. Regular soft contact lenses have the po-
tential to induce peripheral myopic defocus only if their
power exceeds –6.00 D [20]. Hence their value for myo-
pia progression control is very limited, since this pattern
ideally should start in the early phases of myopia devel-
opment. Multifocal contact lenses with a concentric
power structure such that the central portion contains the
distance power and the mid-peripheral portion carries the
near power provide a desired optical pattern. Originally
introduced for presbyopic patients, their use for myopia
progression control in young adults is an interesting ap-
plication and expansion of the fitting range. If soft con-
tact lenses are being used, their large diameter results in
relatively little movement during the blink cycle, so that
the lens optics stay aligned to the visual axis. This
alignment is desirable for a stable retinal image. The
front surface structures of such multifocal contact lenses
have the theoretical ability to mimic the altered anterior
corneal surfaces in Orthokeratology. Hence, the optics of
both systems should have comparable characteristics.
Accordingly, these lenses have been proposed as treat-
ment option for myopia control [21,22]. A similar princi-
ple has been proposed for specifically designed spectacle
lenses. Utilization of free form technology enables ma-
nufacturing of concentric lens surfaces with increasing
refractive power toward the periphery. However in con-
trast to a multifocal contact lens such a spectacle lens is
not in contact with the patient’s eye and it does not fol-
low the gaze as a contact lens does. Therefore, the de-
sired optical effect is only present for one particular gaze
position, which limits the treatment effect substantially
[16]. Of the aforementioned non-surgical options, to date,
the two systems that haven shown significant potential to
control myopia progression are Orthokeratology and
concentric multifocal center-distance contact lenses [23-
Orthokeratology, unlike unifocal spectacle lenses and
contact lenses, induces a characteristic higher order wave-
front aberration pattern which by itself may contribute to
the effect of controlling myopia progression [26]. If in-
stead, multifocal soft contact lenses are being used for
the same purpose, the resulting higher order wavefront
aberration patterns are expected to be comparable. How-
ever, where the rigid back surfaces of Orthokeratology
lenses induce evenly flattened centered corneal areas;
spherical soft lenses conform to the corneal shape and do
not neutralize any significant amount of astigmatism.
That usually limits their use in astigmats since most mul-
tifocal frequent replacement contact lenses are only avail-
able in sphere power. In clinical practice for example,
these lenses are usually fit on patients manifesting usu-
ally no more than 1.00 D of refractive astigmatism. Nev-
ertheless, with the prevalence of astigmatism among the
US population being estimated to be 36%, the likelihood
that multifocal contact lenses, when used for myopia
control, are being fit on astigmatic patients is relatively
high [27].
In further consideration of these two treatment modes
from a more technical standpoint, the central optical zone
of center distance multifocal lenses is approximately 1.5
mm - 2.5 mm smaller than the corneal treatment zone in
Orthokeratology (Figure 3). In relation to the patient’s
entrance pupil this likely results in different amounts of
higher order wavefront aberrations. The question is whe-
ther or not these differences are statistically and clini-
cally relevant.
In our study we measured the changes in wavefront
aberrations generated by concentric center-distance mul-
tifocal soft contact lenses from different Add power
groups and analyzed the statistical significance and clini-
cal relevance of these changes. Finally, we compared the
changes with those that have been well documented in
patients undergoing Orthokeratology [28]. All higher or-
der aberrations were evaluated. In addition, special em-
phasis was put on lower order residual astigmatism,
which, in contrast to Orthokeratology, cannot be fully
compensated for with the frequent replacement contact
lenses used in this study.
Copyright © 2012 SciRes. OJOph
Corneal Wavefront Aberrations in Patients Wearing Multifocal Soft Contact Lenses for Myopia Control
Figure 3. Cross sections of corneas for comparison of Or-
thokeratology (a), and a multifocal soft contact lens with
center-distance design (b). Local changes in surface radii
are displayed exaggerated and the optically relevant sur-
faces are drawn in red color. Flat surface radii are associ-
ated with low focal power, and steep surface radii are asso-
ciated with high focal power.
2. Objectives
The purpose of this study was to analyze the remaining
amount of astigmatism (2nd Zernike order) and higher
order wavefront aberrations (3rd to 7th Zernike order) in
young adults wearing concentric multifocal center-dis-
tance soft contact lenses with different Add powers. Since
local changes in refractive power for these contact lenses,
as well as for the patients’ corneas, are solely based on
local changes of front surface radii, these measurements
can be done with a corneal topographer. The analyses
were based on pre/post topographical measurements.
RMS values of grouped wavefront aberrations were eva-
luated. The statistical significance and clinical relevance
of these errors was further evaluated.
3. Methods
The dominant eyes of 40 participants were fit with vary-
ing powers of Proclear Multifocal D lenses (Coopervi-
sion, Pleasanton, USA). Corneal wavefront analysis was
performed for simulated 6 mm entrance pupil diameters
pre and post lens fit with the Zeiss Atlas 9000 corneal
topographer (Zeiss Meditec, Dublin, USA). The sphere
power of each selected lens was equal to the spherical
component of the individual distance refraction. Four
different Add powers (+1.00 D, +1.50 D, +2.00 D, +2.50
D) were fit on each patient. Fittings were evaluated 20
min after lens insertion following confirmation of good
fit and centration.
The research followed the tenets of the Declaration of
Helsinki and was approved by the IRB of Western Uni-
versity of Health Sciences (#11/IRB/073). All measure-
ments were conducted at the Health Education Center at
Western University of Health Sciences.
3.1. Subjects and Inclusion Criteria
Forty University students (27 women, 13 men) with ages
from 23 to 39 years (27.3 ± 3.2 years) were recruited for
this study. Refractive errors were limited to the recom-
mended fitting range of the tested lenses which includes
–6.00 D up to +1.00 D, and no greater than –1.00 D of
cylinder. Expressed in rectangular Fourier optics terms,
the mean spherical equivalent M was –2.69 D (SD 2.08
D), J0 was 0.00 D (SD 0.16 D), and J45 was 0.01 D (SD
0.13 D). Participants did not suffer from any eye disease
or injury and were not taking any ocular or systemic
3.2. Contact Lenses
Proclear Multifocal D lenses have a concentric progres-
sive front curve design. The distance power is in the lens
center and spreads over a diameter of 2.3 mm, followed
by an annular zone which is progressively increases in
focal power toward its periphery. The outermost opti-
cally relevant region is the near zone which extends to a
total diameter of 8.5 mm (Figure 4). The lens material,
omafilcon A, has a water content of 62%. Selected lenses
had a distance refractive power ranging from –6.00 D to
+1.00 D, and Add powers of +1.00 D, +1.50 D, +2.00 D,
and +2.50 D. All lenses had a base curve radius of 8.70
mm and a diameter of 14.4 mm. These contact lenses are
recommended for replacement on a monthly basis.
3.3. Topographical Measurements and
Wavefront Analysis
Topographical measurements were based on Placido ring
reflex image analysis and were done with the Zeiss Atlas
9000 corneal topographer, an accurate and widely used
clinical instrument [29]. Wavefront analysis was per-
formed before and after each lens fitting for each Add
power across the participants’ pupils, and limited to di-
ameters of 6 mm in order to have statistically comparable
data. Wavefront distortions have been displayed and ana-
lyzed in μm as shown in Figure 5. For further statistical
evaluation, data sets have been expressed in Zernike co-
efficients up to the 7th order. Corneal topographers cap-
ture images of illuminated Placido rings produced by the
first optical surface in the pathway of light. By analyzing
distortions of these images, wavefront aberrations can be
calculated, displayed as color coded wavefront maps,
Figure 4. Optically relevant zones of a Proclear Multifocal
D lens and their effects on the retinal image structure.
Copyright © 2012 SciRes. OJOph
Corneal Wavefront Aberrations in Patients Wearing Multifocal Soft Contact Lenses for Myopia Control
Copyright © 2012 SciRes. OJOph
Figure 5. Color coded maps of corneal wavefront aberration profiles across a standardized 6 mm entrance pupil including
2nd order astigmatism and higher order aberrations up to the 7th Zernike order. (a) uncorrected cornea; (b) Proclear Mul-
tifocal D lens with +2.50 D Add power; (c) difference map (b minus a).
and mathematically expressed with Zernike coefficients.
The nature of this measurement principle yields differ-
ences for the low order aberration 0
(sphere) between
the reading of the naked cornea and the reading with the
Proclear Multifocal D lens in place, since that’s a desired
change as given by the contact lens prescription. For that
reason, 0
values have been removed from the topog-
raphical wavefront analysis. However of interest are all
other wavefront errors, since they do also change due to
wearing this specific type of contact lens and they cannot
be selectively and purposeful corrected by ordering dif-
ferent contact lenses. Usually these are higher order ab-
errations, expressed as Zernike coefficients 3rd to 7th or-
In addition, one group of lower order aberrations, re-
fractive cylinders, is also not compensated for with this
specific type of multifocal soft contact lens, therefore the
astigmatic Zernike coefficients 2
and 2
have also
been included in the analysis. For further evaluation,
individual Zernike coefficients have been grouped per
Zernike order and converted into RMS values. Clinical
significance was assigned when a particular RMS value
exceeded 0.10 μm [30]. According to Fourier optics
transformation, this is equivalent to a refractive error of
0.25 D, given the fact that the pupil diameter is 6 mm.
The transformation equation is given by
where r is the pupil radius in mm.
3.4. Statistical Analysis
Statistical analysis was performed using the SPSS soft-
ware package (v. 17.0; SPSS Inc., Chicago, IL, USA).
Paired sample t-tests were conducted comparing the
mean RMS value of the 2nd through 7th Zernike order
for lenses with 4 different Add powers +1.00 D, +1.50 D,
+2.00 D, and +2.50 D to the mean RMS value of 40
dominant eyes. For statistical purposes, a p value lower
than 0.05 was considered statistically significant.
4. Results
The following 5 box-and-whisker diagrams (Figures 6 -
Corneal Wavefront Aberrations in Patients Wearing Multifocal Soft Contact Lenses for Myopia Control
10) display grouped RMS values of corneal wavefront
aberrations with and without Proclear Multifocal D con-
tact lenses in different Add powers. The bottom and top
of each box are the lower and upper quartiles, respec-
tively, and the line near the middle of the box is the median.
The small red line within the box is the mean. The ends
of the whiskers represent the minimum and maximum of
all RMS data. The horizontal dashed red line at 0.1 μm
represents the borderline of clinical significance. RMS
values above this line equal refractive errors of 0.25 D.
Figure 6. Box-and-whisker diagram of corneal wavefront
aberrations expressed as grouped RMS values per Zernike
Figure 7. Proclear Multifocal D, +1.00 D Add power, box-
and-whisker diagram, grouped RMS values of wavefront
Figure 8. Proclear Multifocal D, +1.50 D Add power, box-
and-whisker diagram, grouped RMS values of wavefront
Figure 9. Proclear Multifocal D, +2.00 D Add power, box-
and-whisker diagram, grouped RMS values of wavefront
Copyright © 2012 SciRes. OJOph
Current Distortion Evaluation in Traction 4Q Constant Switching Frequency Converters 51
Figure 10. Proclear Multifocal D, +2.50 D Add power, box-
and-whisker diagram, grouped RMS values of wavefront
Table 1 summarizes RMS values of wavefront aberra-
tions expressed as Zernike coefficients initially present
for the patients’ corneas and the mean difference and
standard deviation of their changes with the different
Add power groups. Clinically relevant aberrations and
aberration changes were present for the initial corneal
measurements and for all lens groups tested. Clinical
relevance has been assigned for RMS values above 0.1
μm which is the refractive equivalent of 0.25 D.
Statistical significance is predominantly given for
higher order aberrations and rises with increasing Add
power. For the lens group with +2.50 D Add power, all
aberration changes were statistically significant. In addi-
tion, clinically relevant wavefront aberrations in this
group were 2nd Zernike order (astigmatism) with a RMS
value of 0.63 ± 0.29 μm, 4th Zernike order with a RMS
value of 0.23 ± 0.06 μm, and 3rd Zernike order with a
RMS value of 0.18 ± 0.12 μm. Notably lower order ab-
errations decreased, but all higher order aberrations in-
creased. The highest increase was measured for 4th order
aberrations. Interestingly this lens group has been sug-
gested as the most effective for myopia progression con-
trol [31].
5. Discussion
Concentric multifocal center-distance soft contact lenses
have been proposed as a treatment for children and
young adults for the purpose of myopia progression con-
trol. In vivo, these lenses have the ability to mimic opti-
cal properties of corneas following successful Ortho-
keratology treatments, correcting refractive errors at the
central retina and inducing myopic defocus at the retinal
periphery. The advantages of using soft contact lenses
are expected, immediate comfort and ease of fitting. Soft
lenses typically have little to no awareness from the out-
set and the fitting parameters necessary are minimal sim-
plifying the fitting process and initial lens selection.
Since these lenses may compete with Orthokeratology
for being selected as the system of choice in myopia pro-
gression control, it was of interest to see what their in-
duced optical aberrations were and whether or not these
data are equivalent to those reported for Orthokeratology.
In our study we investigated the change in corneal
wavefront aberrations, especially astigmatism and higher
order aberrations which occurred when Proclear Multi-
focal D lenses of different Add power groups were worn.
With these lenses on the patients’ eyes we did find sub-
stantial amounts of astigmatism and higher order wave-
front aberrations for all tested lens groups. In general we
observed that lenses with higher Add power values had
larger changes in wavefront aberrations.
Statistically significant changes in aberrations, espe-
Table 1. RMS values of baseline corneal wavefront errors (Mean) and mean differences induced by Proclear Multifocal D
lenses (MD) as well as their standard deviations (SD); statistical significance (*) and clinical significance (†) have been as-
Cornea +1.00 D Add +1.50 D Add +2.00 D Add +2.50 D Add
2nd(Ast) 0.694 0.051 –0.022 0.021 –0.008 0.037 –0.035 0.021 –0.062* 0.026
3rd 0.139 0.009 –0.019* 0.009 –0.006 0.014 0.018 0.019 0.046* 0.019
4th 0.126 0.006 0.004 0.006 0.049***0.008 0.081*** 0.008 0.106*** 0.008
5th 0.025 0.003 0.010** 0.003 0.018*** 0.004 0.034*** 0.004 0.050*** 0.005
6th 0.017 0.002 0.008** 0.003 0.006** 0.002 0.012*** 0.003 0.017*** 0.004
7th 0.012 0.001 0.007** 0.002 0.004* 0.002 0.007*** 0.002 0.009* 0.004
MD: Mean Difference; SE: Standard Error of the Mean; Statistical significance: *p < 0.05; **p < 0.01; ***p < 0.001; Clinical significance: †.
Copyright © 2012 SciRes. OJOph
Corneal Wavefront Aberrations in Patients Wearing Multifocal Soft Contact Lenses for Myopia Control
cially for higher order aberrations, were detected for all
lenses. With all lenses the initial astigmatism decreased
and most of the higher order aberrations increased. We
further found that RMS values with lenses for 2nd (astig-
matism), 3rd and 4th Zernike order remained in clinically
significant amounts which was related to a wavefront
error of 0.10 μm or greater, the equivalent of 0.25 D. The
highest aberration was astigmatism which was present
for most patients initially, and although it was reduced
with contact lenses, it remained the dominant aberration
with all tested lenses. As anticipated, most lenses in-
creased 4th order aberration significantly, thus under-
scoring the effectiveness of these lenses for myopia con-
In a recent study, Lopes-Ferreira et al. investigated
central and peripheral states of objective refraction (low
order aberrations) with Proclear Multifocal D lenses.
They reported that only lenses with high Add power in-
duced the amount of peripheral myopization necessary
for effective myopia control [31].
With this same lens group (+2.50 D Add power), our
study revealed the clinically significant wavefront aber-
rations to be 2nd order astigmatism (lower order aberra-
tion) with a RMS value of 0.63 ± 0.29 μm, followed by
higher order aberrations from the 4th Zernike order with
a RMS value of 0.23 ± 0.06 μm, and 3rd Zernike order
with a RMS value of 0.18 ± 0.12 μm. In direct compari-
son to wavefront aberrations of the naked cornea, lenses
from this group decreased 2nd order astigmatism, but in-
creased all higher order aberrations in a statistically sig-
nificant manner.
Several authors report that Orthokeratology is a poten-
tial treatment system for myopia progression control [25,
26]. Multifocal soft contact lenses have been proposed
for the same purpose [21,22]. One can assume that in this
case wavefront aberrations would have a pattern similar
to Orthokeratology. However, our findings with Proclear
Multifocal D lenses differ from those reported by Joslin
et al. for wavefront aberrations following Orthokeratol-
ogy where astigmatism was almost eliminated and higher
order aberrations were increased to much higher values.
In their study, the resulting RMS values were 0.56 ± 0.37
μm for 3rd order aberrations, and 0.43 ± 0.15 μm for 4th
order aberrations [28]. These values are approximately
3-fold higher for 3rd order aberrations and almost 2-fold
higher for 4th order aberrations in comparison to the Pro-
clear Multifocal +2.50 D Add lenses, that being the lens
group with the highest Add power and evidently highest
aberrations analyzed in our study.
Therefore, in comparing lower and higher order wave-
front aberrations, Proclear Multifocal D soft contact lenses
and Orthokeratology are both seen as viable treatment
systems for myopia progression control with conceptu-
ally related, but remarkably distinct, optical outcomes.
Further studies are necessary to determine whether or
not the differences in the amount of aberrations as well
as their selective variation and changes have clinical rele-
vance for the course of myopia progression and myopia
progression control.
6. Acknowledgement
The authors thank Mark Andre and Coopervision for pro-
viding the Proclear Multifocal D lenses used in this study,
and Professor Jim Schwiegerling for providing the Zer-
nike Pyramid image depicted in Figure 1.
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