|
Controlling Astigmatism &
Nearsightedness in Developing Youth
ABSTRACT:
Background
The progressive worsening of myopia and/or astigmatic
refractive errors is a serious concern for
both the child and their parents. The treatment
procedure known as orthokeratology has been
shown to slow the rate of progression in children.
This study attempted to replicate these findings.
Methods
The “No-mold” retrospective refractive data from 20
children (40 eyes) who subsequently chose
orthokeratology treatment were obtained from patient
records. The duration of refractive data
varied from as little as 2 to as much as 82
months.
The “Molded” phase included 28 children (56 eyes).
Baseline data included refraction,
Simulated K (Sim K) and topographic maps. They were
fit with Wave custom designed
orthokeratology mold lenses. Treatment duration was 7
to 57 months.
The “Unmolded” phase involved discontinuing
orthokeratology treatment until flat Sim K
returned to within 1D of pre treatment or 14
days.
Results
The mean change in spherical equivalent refractive
error (SEQ) during the No-mold phase was -
.37D per year. The mean change in SEQ during the
Molded/Unmolded phase was -.03 D per year.
Conclusions
Orthokeratology treatment does slow the progression of myopia in
children.
INTRODUCTION
The worsening of myopic and/or astigmatic refractive
errors is a serious concern for both the
affected child and their parents. Typical solutions
include the use of spectacles and/or
contact lenses. Neither of these choices addresses the
concern surrounding progressive
changes in refractive error but, in fairness to the
clinician, there are few good options to present
which work simply and predictably. There are many
factors which are associated with these shifts
in myopic refractive error such as: genetics (1, 2,
3), phoria (4, 5), near vision demands (6, 7),
ethnicity (8, 9), sex (10) and younger age (11).
Options to slow the progression in refractive error
are unpredictable and at times inconvenient.
Atropinization (12, 13) is one of the most successful
forms of intervention but the side effects
greatly outweigh the outcomes. Bifocals and
progressive addition lenses have some effect (3, 14,)
but they are cumbersome for youth with active
lifestyles. Daytime wearing of rigid gas permeable
lenses has been shown to slightly reduce the
progression but at rates which are of limited value to
the patient (15, 16).
An effective, predictable and reproducible method to
reduce the rate of change of myopia and
astigmatism is Orthokeratology (also known as Corneal
Molding (CM), Corneal Reshaping,
Corneal Refractive Therapy, Advanced Orthokeratology
and Custom Accelerated Orthokeratology
to name a few). Orthokeratology employs the nightly
wearing of rigid gas permeable lenses
(corneal molds) which reshape the curvatures of the
cornea and provides great unaided vision
during waking hours.
Several studies have demonstrated the effectiveness of
orthokeratology. The Loric Study (20)
followed patients over 12 months and concluded that
Orthokeratology has a positive effect on
slowing the progression of nearsightedness and
astigmatism. The Orthokeratology and Adolescent
Myopia Control study (21), a 3 year retrospective
study, found that those who participated in
orthokeratology had an average increase in myopia of
only -0.67D over three years versus the
expected -1.50D of change over the same period of
time. In 2007, Gerowitz, Eiden and Davis
initiated a similar FDA approved, 5 year corneal
molding – myopia control study of 300 youths
ages 8 through 14. The outcome is pending.
Methods
This study was designed to replicate the findings that
orthokeratology slows the normal
progression of myopia/astigmatism.
The study enrolled 28 youth. Seven were male and 21
were female. Age ranged from 4 to 20
years. Age at commencement of orthokeratology
treatment ranged between 9 and 16 years.
Subjects’ ethnicities were 27 Caucasians and 1
African-American. Subjects’ pretreatment refractive
error ranged from sphere of -1.00DS to -5.25DS (mean =
-2.33D) and cylinder of plano to -1.00
(mean = 0.17DC). Mean SEQ was
-2.25D.
No Mold Phase :
Historical refractive data were obtained from a subset of 20
subjects of the
study group (40 eyes). They were established patients
with active medical charts but had not yet
begun orthokeratology treatment.
The rate of progression of their myopia during this
phase was calculated as the difference
between the SEQ at their first visit to the office and
the SEQ just prior to initiating orthokeratology
treatment.
Mold Phase :
This phase included all 28 youth (56 eyes). Refractive data prior
to
orthokeratology treatment were as follows: mean SEQ =
-2.25D (range -1.00 to -5.50), mean sphere
= -2.23D (range -1.00 to -5.25), mean cylinder =
0.17DC (range plano to
-1.00).
Upon choosing orthokeratology, baseline data were
collected which included a noncycloplegic
refraction, topography (Scout-Eyequip), intraocular
pressure and age of parents’ onset of
myopia/astigmatism.
The corneal molding lenses were custom designed using
the captured topography maps and
Wave Software System. .
The dispensing visit consisted of educating the
patient on the wear, insertion and removal
processes and care of the lenses. A variety of care
regimens were prescribed based on clinical
judgment. These included Optimum and Boston cleaning
and rewetting systems, Sauflon peroxide
system, Allergan rewetting products and lens cleaning
sponges. Following the training, unaided
vision was measured. Then the patient was allowed to
recline, closing their eyes for 30 minutes.
Immediately upon opening their eyes, acuities were
measured and the fit was assessed with white
light and NaFl. The molds were removed and
topographies and unaided acuities were measured.
Though all patients initially wore their molds every
night, the lens wearing schedule eventually
varied among the 28 subjects: Seven wore the lenses
every night, 18 wore them every second night
and 3 wore then every third night. This schedule was
determined by the patient and their desired
endpoint acuity.
Follow up visits included one-week, one-month, three
months and six months as determined by
the investigators. On rare occasion, a mold lens was
changed to improve fit or post wear acuity.
The treatment was considered successful if at the 3
month visit, the patient was “20/happy”,
topography was homogenous and no corneal pathology was
observed. The duration of
orthokeratology treatment varied per subject ranging
from 7 to 57 months.
Unmold Phase: Given the clinical nature of this study and
inconvenience to the patient,
whenever possible, an effort was made to correlate
discontinuing lens wear with any unscheduled
mold lens replacement (lost or broken). Otherwise,
patients complied with the request to unmold.
Lens wear was discontinued and unmolding was
considered complete when a subject’s flat
Simulated-K returned to within 1.00D of their Sim K
prior to molding or 14 days had elapsed since
discontinuing lens wear. During the unmolding process,
noncycloplegic refractions were performed
at 3 to 7 day intervals until reversal was
complete.
The rate of progression of myopia for the molded
patients was calculated as the difference
between the SEQ just prior to molding and the SEQ after unmolding
was complete.
Results
Results for all phases are presented in Figure 1.
Figure 1 superimposes both the No Mold and
Molded/Unmolded phase data. The X axis represents the
duration of the phases in months.
No Mold Phase :
This phase included the subset of 20 established
patients (40 eyes). The mean change in SEQ
showed a progression of -0.37D per year. This is
represented in Figure 1 by the blue data diamonds
and blue trend line.
Unmold Phase:
This phase included all 28 subjects (56 eyes).
The reversal requirement was achieved by 27 of 28
subjects within two weeks (within 1D of
pretreatment Sims K). In fact 44 of 54 eyes were
within .5D of Sim K and 49 of 54 eyes were
within .75D of original Sim K. Only 1 subject failed
and was excluded from the study.
During the mold to unmold phase, the mean SEQ
progression rate was only -0.03D per year.
Conclusions
The CANDY study demonstrated that Orthokeratology does
both significantly reduce and even
stop the rate of change of nearsightedness and
astigmatism in developing youth (ages 9-18). This
effect was independent of the age of initiation of
orthokeratology and the premolding refractive
error.
This reduction in the rate of change occurs for youth
in all the familial risk groups (neither, one
or both parents myopic by age 18).
The IOP had no effect on myopic
progression.
Discussion
The CANDY study attempted to determine if
orthokeratology halted refractive error change or
simply masks the change due to the molding of the
corneal surface. By unmolding the treatment
and allowing the Sim K’s to return to baseline levels,
we believe some progress has been made to
answer this question. The CANDY subjects had an
average premolding
progression in their SEQ
of- 0.37D per year. This rate of progression in myopic
children is coincident with published
literature (11). These subjects’ SEQ was essentially
halted during the duration of their molding to
an impressive mean rate of -.03D per year after being
unmolded.
There is some concern that the 2 week duration of the
reversal phase was insufficient despite the
fact that the Sim Ks of 49 of the 54 subjects were
within .75D of their baseline Sim K’s. This issue
should be the basis for further study. Data obtained
from trials using longer reversal periods would
provide more complete data.
Though Hyman, Marsh-Tootle et.al (COMET 2005) showed
that there is a greater progression in
myopic SEQ in their 6 to 7 year old age group and a
slowing in the rate of progression by their
oldest age grouping (10 to 11 years), there was
progression in all the populations they followed.
When the CANDY study reviewed the age of those molded,
from 9 years to 18 years, essentially no
correlation between age and progression of SEQ was
found.
Since the CANDY study was initiated by evaluating
patients who had previously established
various wearing schedules of their corneal molds,
other interesting conclusions surfaced. Some
patients did not need to wear their molds every night
to achieve visual success yet they had the
same myopia/astigmatism stabilization. The patients
who were best suited to sleep in their molds
only every second to third night were those with lower
refractive errors and steeper Sim K’s. For
this reason the authors submit that there is a greater
incentive to mold the younger eye at lower
refractive errors. Clinicians should present to the
higher risk/lower SEQ patients and their family
that:
1.) orthokeratology when done in the early stages of
myopia is more cost effective,
2.) because their SEQ is low, it allows the child to
wear the lenses every other night
3.) it is more acceptable for a younger patient to
experience any partial unmolding during the
alternate days when the lenses were not worn
4) it is better to stop axial elongation when the eye
is still shorter, reducing the risk of retinal
detachment.
The population of eligible patients in this study was
significantly skewed toward a white
population (27 White, 1 Black, 0 Hispanic and 0
Asians). As it has been shown that there is a
greater incidence of and progression of SEQ in the
Asian populations (19), a similar study within a
primarily Asian population would be even more
powerful.
The CANDY study was designed to investigate if
orthokeratology slows the progression of
myopia (with or without astigmatism). The study was
not designed to investigate how specifically
designed corneal molds affect the eye/vision.
Additionally, the goal of each patient was to have
good vision (with and without the molds), good fit and good
comfort; hence, liberal
boundaries
were granted on the complicated designs
of the reverse geometry lenses. All designs were similar
in
they were tied to the global goals of
success. An evaluation of the various designs does reveal
more
similarities than differences among the
molds.
Despite the repeatable results of ‘myopia
control’ by orthokeratology, some caution should be
exercised in promoting this as a
predictable way to halt the refractive error changes. Not all
studies
have found such consistent reduction in
refractive error progression (Reim 2003). One of the
limitations of this study is size of
population. Larger, well controlled trials are needed to
further
validate the findings of this and other
orthokeratology studies.
The investigators continue to monitor all
those in the Candy study and are expanding their
centers while broadening the data base.
Additional variables which may be monitored are central
corneal epithelial thicknesses and total
central corneal thickness and axial length. They look
forward to presenting their future
findings.
About the
authors:
Dr. Peter E. Wilcox is in solo private
practice in Hayes, Virginia. He received his OD from
UAB and attended a Residency at
PCO.
Dr. David Bartels is in group practice in
Buffalo, NY. He received his OD at ICO.
The authors would like to extend their
gratitude to Caroline Guerrero Cauchi, O.D., F.O.A.A.
and Richard Anderson, O.D., F.O.A.A. for
their editorial assistance in preparing this article.
On a personal note, being one of the
investigators and the father of two of the subjects, I am
pleasantly surprised at the outcome of
the study. My daughter and son both mold every 72 hours.
They have been threatened with myopic
progression if they don’t mold more often, only to fall
on
deaf ears. I don’t know the correct
number of nights needed to hold the progression back but
both
my children are doing fine. Corneal
Molding has become the norm in my family and it is very
gratifying to observe no change in my
children’s vision over many years. David Bartels OD.
. | 
