2. The worldwide increase in myopia
49% (Rahi et al., 2010)
53.7% (Mallen et al., 2005)
70% (Lin et al., 1988)
84% (Lin et al., 1999)
35% (Blanco et al., 2008)
26.2% (Wang et al., 1994)
41.6% (Vitale et al., 2009)
82.2% (Wu et al., 2001)
85% (Woo et al., 2004)
87% (He et al., 2009)
3. Why do some eyes go myopic?
Risk factors
Near work (Rosenfield and Gilmartin, 1998)
Education (Saw et al., 2002 & 2004)
Ethnicity (O'Donoghue et al., 2010)
Genetics (Hammond et al., 2001)
Other risk factors (prematurity, diet, light
exposure, season of birth, higher IOP,...)
Principle structural correlate
Axial elongation of the vitreous
chamber (Atchison et al., 2004)
4. MRI modeling of the myopic eye
Singh KD, Logan NS & Gilmartin B. Three-dimensional modeling of the human eye based on
magnetic resonance imaging. Invest Ophthalmol Vis Sci 2006; 47: 2272-2279.
5. Peripheral optics of the eye
Peripheral optics is important in understanding:
Refractive error development
Process of emmetropisation
Supported by animal studies (e.g. Smith et al., 2005 & 2007, Hung et al., 2008)
Peripheral deprivation of visual signals produces central myopia.
Clear Vision
Form Deprived
Form Deprived
6. Central versus peripheral vision
Because resolution acuity is highest at the fovea and decreases
rapidly with eccentricity, it has been assumed that central vision
dominates refractive development.
7. Peripheral refraction studies
fovea
Back to 1930’s (Ferree et al., 1931, Ferree, 1932, Ferree & Rand, 1933)
Predict future myopia based on peripheral refraction (Hoogerheide et
al., 1971):
Emmetropic pilots with
relative peripheral hyperopia
► Central myopia
Emmetropic pilots with
relative peripheral myopia
► Remained emmetropic
12. Results: MSE
fovea M(D)
b)
SR Eccentricity (degree) IR
M(D)
c)
STR Eccentricity (degree) INR
M(D)
d)
SNR Eccentricity (degree) ITR
M(D)
a)
TR Eccentricity (degree) NR
14. Overall power of refraction (P)
SR
STR
TR
ITR
IR
INR
NR
SNR
Overall power of refraction
was calculated based on
Thibos et al., (1997)
recommendation:
The overall power of
refraction decreases with
increasing eccentricity.
Thibos LN, Wheeler W & Horner D. Power vectors: An application of Fourier analysis to the
description and statistical analysis of refractive error. Optom Vision Sci 1997; 74: 367-375.
15. Conclusions
Our findings show a relative hyperopic shift along the
horizontal, vertical and two oblique meridians for the
myopic group, and a relatively constant refractive profile
for emmetropic eye .
The relatively peripheral hyperopia in myopia suggests
that the myopic retina has a more prolate/less oblate
shape (longer axial length than equatorial diameter) than
emmetropic and hyperopic eyes.
16. Implication of peripheral refraction
Traditional Correcting
Lenses:
As a consequence of eye
shape and/or aspheric
optical surfaces,
“corrected” myopic eyes
often experience
significant hyperopic
defocus across the visual
field.
Image ShellCorrected
Myope
17. A better way to correct myopia?
Myopia Control Lenses:
By increasing the effective
curvature of field it would
be possible to correct
central errors and either
correct peripheral errors or
induced peripheral myopic
defocus.
Image Shell
(By bringing the peripheral image
forward)
Optimal
correction?
18. Myopia control studies
Design of the ophthalmic lenses with the aim of reducing the
progression of myopia in human eyes based on multiple axis
analysis of peripheral refraction.
19. Myopia control studies
BUT
The amount of hyperopic defocus in the periphery applied in these
studies is based on the average amount reported in peripheral
refraction studies....
Sankaridurg P et al. Decrease in rate of myopia progression with a contact lens designed to
reduce relative peripheral hyperopia. Invest Ophthalmol Vis Sci 2011; 52: 9362-9367.
Novel lenses
Traditional
lenses
20. Impact on visual performance
Peripheral refraction should be considered when assessing visual
performance?
I would like to thank the BCLA for the opportunity to present some of our research to you today. What I am going to discuss in next few minutes is to look at what happens to the myopic eye in terms of visual function.
Myopia has become an important topic for many reasons. It’s a major cause of visual impairment throughout the world and a high proportion of our CL patients in clinical practice are myopic. There has been a rapid increase in myopia prevalence in different populations reaching 80 percent in some East Asian communities and it is a risk factor for a range of ocular problems such as myopic degeneration.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
In terms of shape, myopic eyes tend to be greater in all dimensions than emmetropic eyes specially elongation of the vitreous chamber is known as the main indication of the myopic eye. Of relevance to us as eye care practitioners and researchers, is a potential loss of visual function in myopic eyes. Retinal stretching due to axial elongation of the myopic eye reduces the sampling density of retinal neurons which has implications for resolution acuity in the periphery.
