myopia

1. MYOPIA
MANOJ ARYAL
1
B. Optometry IOM
Maharajgunj Medical Campus

2. PRESENTATION LAYOUT
2
 Introduction
 Optics of myopia
 Classification
 Treatment of myopia
 Prognosis

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EMMETROPIA
 When parallel rays of light coming from infinity are
focused in sensitive layer of retinawith
accommodation being at rest.
 Components that maintain emmetropization are
axial length
AC depth
corneal curvature

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AMETROPIA
 Parallel rays of light coming from infinity (with
accommodation at rest) are focused either in front
or behind retina.
Further classified into
 Myopia :where the parallel rays of light coming
from infinity are focused in front of retina.
 Hypermetropia: where the parallel rays of light are
focused behind the sensitive layer of retina.
 Astigmatism :where the refraction varies in different
meridia.

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TYPES OF AMETROPIA
myopia
astigmatism
hypermetropia

6. Introduction
 Derived from two Greek root words
 (Greek: μυωπία, muōpia, from myein "to shut" - ops
(gen. opos) "eye“)
 Myopia or shortsightedness is a type of refractive error
in which parallel rays of light coming from infinity are
focused in front of retina with the accommodation is at
rest.
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7. Optics of myopia
 The optical system is too powerful for its axial length.
 Image of distant object on retina is made up of circle of
diffusion formed by divergent beam since the parallel
rays of light coming from the infinity are focused in front
of the retina.
 Far point is finite point in front of eye.
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8. Optics of myopia
 Nodal point is further away from retina.
 Accommodation in uncorrected myopes is not
developed normally,they may suffer from convergence
insufficiency, exophoria,and early presbyopia as they
grow.
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9. Image formation
 In myopia image formed in front of eye which
is corrected by placing the negative lenses.
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10. TYPES OF MYOPIA
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 Etiologically
 Axial myopia :result from increase in anterioposterior
length of eyeball.
 Curvatural myopia :occurs due to increased curvature
of cornea or lens or both.
 Index myopia :increase in refractive index of
crystalline lens assotiated with nuclear sclerosis.
 myopia due to excessive accommodation :occurs in
patients with spasm of accommodation.

11. TYPES OF MYOPIA CONTD…
 Clinically,
 congenital myopia.
 simple or developmental myopia.
 pathological or degenerative myopia.
 acquired myopia.
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12. Congenital myopia
 Present since birth.
 Seen more frequently in children who were born
prematurely or with various birth defects.
 Usually error is about 8-10D, which mostly remains
constant.
 May sometimes be associated with other congenital
anomalies such as cataract, microphthalmos, aniridia,
megalocornea.
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13. Congenital myopia contd..
 Early correction is desirable to help the children to
develop normal distance vision and perception of world.
Full cycloplegic refractive error including any
astigmatic correction should be prescribed.
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14. Simple myopia
 Aka physiological or school myopia.
 Physiological error not associated with any disease of
eye.
 Etiology:
result from normal biological variation in the
development of eye.
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15. Simple myopia etiology
Axial Physiological variation in
the length of the eyeball.
Curvatural Underdevelopment of
eyeball.
-------- Role of diet in early
childhood.
-------- Theory of excessive near
work.
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16. Simple myopia contd…
 Clinical pictures:
Symptoms:
 Poor vision for distance.
 Asthenopic symptoms
eye strain due to
dissociation between
convergence and
accommodation.
may develop convergence
weakness and exophoria
and supression in one eye.
 Change in psychological
outlook.
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17. Degree of myopia Visual acuity
-0.50 6/9-6/12
-1.00 6/18
-1.50 6/24
-2.00 6/36
-3.00 6/60
-4.00 4/60
-5.00 3/60
-6.00 2/60
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Degree of myopia Rough estimate of visual acuity

18. Simple myopia: SIGNS
 Eyes are large and prominent.
 Slight deep anterior chamber.
 Fundus is normal :rarely temporal myopic cresents may
be seen.
 Usually error does not exceed 6-8D
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19. Simple myopia :diagnosis
 Confirmed by performing retinoscopy.
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20. Pathological myopia
 Rapidly progressive error resulting in high myopia
usually apparent during 1st decade of life characterized
by increase in volume of posterior segment.
 Etiology:
no satisfactory hypothesis has emerged to explain
the etiology of pathological myopia.
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21. Pathological myopia contd
 However it is confirmed that genetic factors play a major
role.
 It is said that increased axial length, degenerative
changes in retina and vitreous, and pathological
complications are determined by different genes.
 Inheritance can be AD, AR ,X-LINKED
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Genetic factors General growth
(play major role)
↓
More growth of retina
↓
Stretching of sclera
↓
Increased axial length
↓
Degeneration of choroid
↓
Degeneration of retina
↓
Degeneration of vitreous
Features of
pathological
myopia
etiological hypothesis for pathological myopia
(Plays minor role)
Elongation of the eyeball
posterior to equator in
pathological myopia.

23. Pathological myopia contd…
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 Symptoms
 defective vision.
 muscae volitantes.
 night blindness.

24. Pathological myopia contd…
 Signs:
 Eyes are prominent, appearing elongated, and even
stimulating an exophthalmos.
 Cornea is large and anterior chamber is deep.
 Pupils are larger
 Refractive error:
increase by as much as 4.00D yearly
stabilizes at about the age of 20
but occasionally may progress until mid 30s``
frequently result in myopia of 10-20D
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Retinal changes in pathological myopia
 Optic disc:
 appears large and pale
 at temporal edge a characteristic myopic crescent
present.
 Degenerative changes:
 in retina and choroid are common.
 occurs tigroid appearance of fundus due to diffuse
attenuation of the RPE with visibility of large
choroidalvessels.

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 Foster- Fuchs spot may be present at macula
 It is a raised, circular, pigmented lesion developing after a
subretinal haemorrhage has been absorbed .
 In advanced cases there occurs Focal chorio-retinal
atrophy which is characterized by visibility of the larger
choroidal vessels and eventually the sclera, total retinal
atrophy, particularly at central area.
 There may be associated lattice degeneration and or snail
track lesions.
 Retinal tears, haemorrhage , retinal detachment may be
seen.

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 A posterior staphyloma is an ectasia or bulging of the
posterior sclera due to focal expansion and thinning .
 It occurs in about a third of eyes with pathological myopia,
and is virtually always peripapillary or involves the
macula.Staphyloma development can be associated with
macular hole formation.
 Degenerative changes of vitreous include:
liquefaction, vitreous opacities, PVD appearing as weiss
reflex.
 Visual field shows contraction and sometimes ring
scotoma may be seen.

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Fundus changes in myopia
Foster-Fuch’s
spotPeripapilary
and macular
degeneration

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Choroidal neovascularization
associated with
a lacquer crack and high
myopia.
Peripheral retinal degernerations :
A:Lattice degeneration,
B:Snail track degeneration
C:Acquired retinoschisis
D:white-with-pressure
E:Focal pigment clumps
F:Diffuse chorioretinal degeneration
G:Peripheral cystoid degeneration

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Pathological myopia :complications
 Rhegmatogenous retinal detachment (RD) is much more
common in high myopia, the pathogenesis including
increased frequency of posterior vitreous detachment, lattice
degeneration, asymptomatic atrophic holes, macular holes
and occasionally giant retinal tears.
 Foveal retinoschisis and macular retinal detachment
without macular hole formation may occur in highly myopic
eyes with posterior staphyloma, probably as a result of
vitreous traction
 Complicated cataract which may be either posterior
subcapsular or early onset nuclear sclerotic.
 Nuclear sclerosis.
 Vitreous haemorrhages.
 Choroidal haemorrhages and thrombosis.
 Primary open angle glaucoma.

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Systemic associations of high myopia
• Down syndrome
• Stickler syndrome
• Marfan’s syndrome
• Prematurity
• Noonan syndrome
• Ehlers–Danlos syndrome
• Pierre–Robin syndrome

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Acquired myopia
 Causes:
 index myopia : seen in nuclear sclerosis.
incipient cataract.
diabetic myopia occurs due to decrease in refractive
index of cortex.
 curvatural myopia
increase of corneal curvature in diseased conditions
like corneal ectasias, and conical cornea.
 positional myopia:
conditions producing anterior subluxation of lens.

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Acquired myopia contd..
 consecutive myopia
surgical overcorrection of hypermetropia
pseudophakia with overcorrecting IOL.
 pseudomyopia
also called artificial myopia.
produced in a conditions such as excessive
accommodation and spasm of accommodation.
may develop after too full a hypermetropic
correction in children.

34. Acquired myopia contd…
 Pseudo myopia correction
 Cycloplegic refraction
-always prescribe plus lenses.
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Acquired myopia contd..
 space myopia
experienced when the individual has no stimulation
for distance fixation.
never more than 0.75-1.50D

36. Acquired myopia contd…
 Night myopia or twilight myopia
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The emmetropic eye ,if accomodated for
the middle range of visusal spectrum,will
be slightrly myopic for the shorter
wavelengths.
Increased sensitivity to shorter wavelength
of light
Shift from photopic to scotopic vision at
twilight

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Acquired myopia contd…
 drug induced myopia
cholinergic drugs such as pilocarpine, echothiopate,
di-isopropyl fluorophosphate.
sulphonamides.

38. TYPES OF MYOPIA CONTD…
 According to amount:
 Classically:
 Very low : upto – 1.00D
 Low : –(1.00-3.00)D
 Medium : –(3.00-6.00)D
 High : –(6.00-10.00)D
 Very high : above –10.00D

39. TREATMENT OF MYOPIA
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 Optical treatment
 Surgical treatment
 General measures
 Visual hygiene
 Low-vision aids

40. Optical treatment
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Include prescription of appropriate concave lens
minimum acceptance providing maximum vision
should be prescribed.
never overcorrect myopia

41. Optical treatment CONTD…
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Guidelines for correcting low degree of myopia upto -
6D
 Children younger than 8yr should be fully corrected
and instructed to use their glasses constantly
 Adult younger than 30 yrs:
usually accept their full correction.
 Older than 30 yrs:
not able to tolerate a full correction over 3D if they
have never worn glasses before.
prescribe less than full correction with which the
patient has comfortable.

42. Optical treatment CONTD…
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 guidelines for correcting high myopia
 full correction can rarely be tolerated.
 undercorrect as little is compatible with comfort for
binocular near vision.
 undercorrection to the tune of 1-3D or even more may
be required.
 undercorrection is always better to avoid the problem of
near vision and minification of image.

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Modes prescribing concave lenses
 Spectacles
 Contact lenses

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TREATMENT OF MYOPIA
OPTICAL PRINCIPAL
UNCORRECTED
CORRECTED WITH GLASS
CORRECTED WITH CONTACT LENS
Prescription of appropriate CONCAVE LENSES .

45. Surgical treatment:
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Radial keratotomy
 Making deep (90 percent thickness radial incision in
the peripheral cornea leaving about 4mm central
optical zone.
 On healing flattens central cornea there by reducing
refractive power|(refractive error between -1.5to -6D.

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Photorefractive keratectomy
 Photoablation of excimer LASER.
 Which can accurately ablate corneal tissue to an exact
depth with minimal distortion of normal tissues.
Myopia is treated by ablating the central
anterior corneal surface so that it becomrs flatter.
 Approximately 10 micron of ablation corrects 1D of
myopia.

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 LASIK
Laser in situ keratomileusis
Currently most frequent performed refractive
procedure.
Can correct myopia upto -10D.
Automated microkeratone is used to raise corneal
flap.
Excimer laser applied to stromal bed and flap
again repositioned.

48. General measures:
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Balanced diet rich in vitamins and proteins
Early management of associated debiliating
diseases.

49. Visual hygienes:
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to avoid asthenopic symptoms
adequate illumination during close work
clarity of print should be good to avoid undue
ocular fatigue.

50. Low vision aids:
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Indicated in patients of progressive myopia with
advanced degenerative changes where useful
vision cannot be obtained with spectacles and
contact lenses.

51. Prophylaxis
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 genetic counseling for people having
pathological myopia, not to marriage with
pathological myopic peoples.

52. PROGNOSIS
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Simple myopia
Prognosis is good.
Error usually does not progress beyond 6-8D
Stablizes by the age of 21
Pathological myopia:
Visual prognosis is always guarded
Possibility of progressiove visual loss due to
degenerative changes and danger of complications
such as retinal detachment should be borne in mind.

53. References
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Theory and practice of optics and
refraction by AK Khurana
Borish’s clinical refraction
Internet

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