1. 초독회
Influence of Overnight Orthokeratology on Axial Elongation in Childhood Myopia
R4 김보윤/AP.신선영

2. Introduction
It is generally thought that progression of youth-onset myopia is attributable to axial elongation
Myopia can be corrected by spectacles or contact lenses.
However, these treatments do not solve the problem of ocular axial elongation. .
Myopia is one of the most common ocular abnormalities in
humans. The prevalence of myopia is reported to be
between 25% and 30% in the developed countries,1,2 with the
incidence being higher among certain Asian populations (Lin
LLK, et al. IOVS 1996;37:ARVO Abstract 4600).
It is well known that myopia is often associated
with sight-threatening complications, such as retinal detachment,
macular degeneration, and glaucoma.7–10

3. What is Orthokeratology
: OK, ortho-K, corneal reshaping, corneal refractive therapy(CRT), vision shaping treatment(VST)
Specially designed and fitted rigid contact lens
Reshaping the corneal contour
Temporarily modify or eliminate refractive error
, mostly used for reduction of myopia

4. Purpose
This prospective study was conducted to assess the influence of overnight orthokeratology (OK) on axial elongation in children, with those wearing spectacles as controls
Myopia is one of the most common ocular abnormalities in
humans. The prevalence of myopia is reported to be
between 25% and 30% in the developed countries,1,2 with the
incidence being higher among certain Asian populations (Lin
LLK, et al. IOVS 1996;37:ARVO Abstract 4600).
It is well known that myopia is often associated
with sight-threatening complications, such as retinal detachment,
macular degeneration, and glaucoma.7–10

5. Method OK group(45명)/ spectacle group(50명) (single-vision glasses)
November 2002 and June 2007.
OK group(45명)/ spectacle group(50명) (single-vision glasses)

6. Reverse Geometry RGP Lenses
The nominal central thickness of the lenses
was 0.22 mm and the diameter was 10.6 mm.
wear their OK lenses every night for at least 7 consecutive hours.
4 curved OK lens
Emerald Lenses; Euclid Systems Corp., Herndon, VA, manufactured
from Boston XO material; Polymer Technology Corp., Wilmington,
MA) with a nominal Dk of cm2/s)(mL O2/mL mm
Hg).

7. Method-Baseline data Refraction, visual acuity, axial length
Before starting OK, spectacle
After 2 yrs
Axial length: laser interferometry (IOLMaster; Carl Zeiss Meditec)
axial length was measured 3 months after the start of OK
axial length was measured when the subject started wearing spectacles.
It has been reported that corneal thinning stabilizes by the end of
the week after OK,27 or that thinning continues for 1 or 2 months.28,29
. This device is very suitable for axial length measurements in children, thanks to its high reproducibility, precision, lack of direct contact,
The OK group returned for examination every 3 months and underwent slit lamp examinations for any adverse events. The OK lens fit was evaluated at these visits.
The control group returned for examination every 6 months.
OK lenses and spectacles were replaced if visual acuity was found to change by more than 0.30 logMAR units during the follow-up.
central corneal thinning caused by OK ranges from -12 to -19um over a span of 3 months

8. Result(1) At baseline, the two groups were comparable in terms of
spherical equivalent refractive error, uncorrected visual acuity,
axial length, age (unpaired t-test), and distribution of the sexes
(Mann-Whitney U test; Table 2). There were also no significant
differences in age distribution (8 –10, 11–13, and 14–16 years)
between the groups

9. Result(2)-after 2yrs f/u
baseline
2yrs after tx. P
Spherical equivalent refractive error
OK group
-2.55 ± 1.82 D
± 1.02 D
<0.0001
Spectacle group
± 1.66 D
-3.83 ± 1.76 D
Axial length
24.66 ± 1.11mm
25.05 ± 1.06mm
24.79 ± 0.80mm
25.40 ± 0.84mm
0.39 ± 0.27mm
In both groups, significant axial elongation was recognized during 2years (P ).
0.61 ± 0.24mm

10. Result(3) OK group Spectacle group
Increases in axial length were analyzed in relation to the
spherical equivalent refractive error at baseline. A significant
correlation was found between these parameters in the OK
group (Pearson’s correlation coefficient; r , P
0.0076), but not in the control group (r , P
Generally, the cornea becomes more oblate (with a
flat central area and increasing power toward the periphery)
when more severe myopia is corrected by OK lenses with a very
flat base curve. This probably leads to a greater decrease of
hyperopic defocus at the periphery, thus exerting a greater suppressive
effect on axial growth.
when the baseline myopia is more severe, the axial elongation after OK is less marked.

11. Hyperopic defocus Peripheral rays form shell of images behind
peripheral retina
Axial rays
Focus on
Retina
a visual feedback response to the defocus produced by the eye’s refractive state.
the peripheral retina is able to influence ocular growth and refractive
Mutti et al.42,43 reported that
myopic children have greater relative hyperopia in the periphery with respect to axial refraction, indicating a prolate ocular shape (an axial length exceeding the equatorial diameter), compared with relative peripheral myopia and an oblate shape (an equatorial diameter exceeding the axial length) for emmetropes and hyperopes,
suggesting that hyperopic defocus in the periphery promotes axial myopia in humans.
Stimulate eye elongation
to match the image shell
to the oblate retina
Hyperopic peri
-pheral defocus
 MYOPIA 11

12. Modified Corneal Shape from Ortho-K
Shell of images coincide with
retinal contour
Axial ray focus on retina
Reduced hyperopic
peripheral defocus
Reduced stimulation
for eye elongation

13. Conclusion
Although OK cannot completely arrest axial elongation in myopic children, it can retard it to a certain extent,
suggesting the potential of this treatment for slowing the progression of myopia.

14. 근시는 왜 진행할까?
많은 가설
Excessive accommodation & uncoordinated eye growth mediated by retinal signals as resposnse to prolonged near work

15. 어떻게 하면 근시 진행을 막을 수 있을까?
눈체조
핀홀안경 침 안경 약물 CL

18. 안경
안경을 끼면 눈이 더 나빠지나요?
저교정
Bifocal or progressive addition lens

19. 안약 안압하강제 Atropine : 0.5% Pirenzepine Unacceptable for longterm therapy
Like atropine, muscarinic (M1) antagonist, less likely to produce mydriasis & cycloplegia (M3)

20. 원래 1년으로 계획된 연구로
처음에 참여한 174명 중 84명 (48%) 만이
동의한 것을 주목해야 함
부작용 : 논문에는 약간의 충혈(2명), follicle (1명)
만 보고

21. Possible Future Treatments
Correction of pph ametropia/aberrations
Visual signal from fovea may not be essential for normal eye growth
Pph retina appear to be able to regulate emmetropinization & induce myopia in response to abnormal visual input
Provision of extensive outdoor activity