myopia
TRANSCRIPT
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MYOPIA MYOPIANISHITA AFRIN
B.OPTOM
3RD Batch
INSTITUTE OF COMMUNITY OPHTHALMOLOGY
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MYOPIA
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myein = “to shut” (Greek) ops = eye (Greek) nearsightedness
is a condition of the eye where the light that comes in does not directly focus on the retina but in front of it, causing the image that one sees when looking at a distant object to be out of focus, but in focus when looking at a close object.
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BY DEFINITION
Is a shortsightedness where parallel rays of light
coming from infinity are focused in front of the retina
when accommodation is at rest
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MECHANISMS OF PRODUCTION
o Axial myopia
o Curvatural myopia
o positional myopia
o index myopia
o myopia due to excess accommodation
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Optics of myopia
Far point is finite (In front of the eye)
Emmetropic eye it is at infinity
Higher the myopia the shorter the distance
Far point is 1meter from the eye ,there is 1D of
myopia
Nodal point is further away from retina
• Accommodation need not develop
normally resulting in Convergence
insufficiency and Exophoria
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CAUSES OF MYOPIA
Stretched eye
Hereditary
Biological variant- axial length
Hormonal secretions to the scleral tissue
Endocrine secretion
Absence of vitamin A- corneal distortion
Fatigue
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CAUSE
All myopia appears to cause by one of the follow:
Increased axial length
Shortened radius of curvature of one of
the refracting surfaces.
Changed index of one of the media
Decreased depth of anterior chamber.
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CLASSIFICATION OF MYOPIA
According to amount (Clinical Refraction 3rd edition – Borish)
ClassicallyVery low- up to –1.00D
Low – 1.00D to –3.00D
Medium -3.00D to –6.00 D
High –6.00D to –10.00D
Very high above –10.00D
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CLASSIFICATION OF MYOPIA
Age of onset – Grosvenor 1987
Congenital myopia: at birth esp. with LBW
Youth onset myopia:6years to teenage years.
Early adult onset myopia: age 20 to 40 years.
Late adult onset myopia: beyond the year 40.
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CLINICAL CLASSIFICATION
Congenital Myopia
Simple Myopia
Degenerative Myopia
Nocturnal Myopia
Pseudo Myopia
Induced Myopia
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Congenital myopia
Frequently seen in Premature babies
Marfan’s syndrome
Homocystinuria
Increase in axial length
Increase inOverall globe size
Since birth, diagnosed at age 2-3 years
If unilateral, as anisometropia, may develop amblyopia, strabismus
Usually 8-10 D, remain constant
Bilateral- difficulty in distant vision, hold things very close
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Associated conditions
Congenital Convergent squint
Cataract
Microphthalmos
Aniridia
Megalocornea
Congenital Separation of retina
Management
Early Correction is desirable
Retinoscopy under full cycloplegia
Early full correction desirable
Poor prognosis
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Simple / developmental myopia
Also known as physiological or school myopia
Physiological error not associated with any
disease of the eye
Etiology :
Not genetically determined
Inheritence is autosomal dominant
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Associated factors
Role of diet
Theory of excessive near work
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Clinical picture
Rarely present at birth
Rather born hypermetropic, become myopic
Begins at 7-10 years, stabilizing around mid
teens
Usually around 5D, never exceeds 8D
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Symptoms
Poor vision for distance
Asthenopic symptoms develop due to dissociation between accommodation and convergence
Convergence weakness, exophoria, suppression
Excessive accommodation inducing ciliaryspasm and artificially increasing the amount of myopia
Psychological outlook
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Signs
Large and prominent
Deep AC
Large, sluggishly reacting pupils
Normal fundus, rarely crescent
Usually doesn't exceed 6-8D
Retinoscopy under full cycloplegia
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Pathological / degenerative / progressive
myopia
Rapidly progressive associated with
degenerative changes in the eye
Etiology
Rapid axial growth of the eyeball outside the
normal biological variations of development
Role of heredity
Role of general growth process
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Genetic factors General growth process
More growth of retina
Stretching of sclera
Increased axial length
Degeneration of choroid
Degeneration of retina
Degeneration of vitreous
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Symptoms
Defective vision
floating black opacities
Night blindness
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Signs
EYE Large, prominent eyes simulating exophthalmos
CORNEA large
ANTERIOR CHAMBER deep
PUPILS are large and sluggish reacting to light
LENS show opacities at the posterior pole due to aberration of lenticular metabolism and due to overstretching anterior dislocation may also occur
VITEROUS degeneration,viterous liquefication,vitreousdetachment present as WEISS REFLEX
SCLERA thinning resulting in formation of STAPHYLOMA
VISUAL FIELD DEFECTS show Contraction and in some ring scotomas present
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Posterior vitreous detachment
myopic patient
posterior staphyloma
in B-scan
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DISC
Large in size
Myopic Crescent on the temporal side of the disc
Inverse myopia Myopic crescent situated nasally and supertraction of the retina temporally
called as INVERSE CRESCENT
Peripapillary Atrophy
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Myopic crescent
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MACULA
Foster-Fuchs fleck
RETINAL DETACHMENT
POSTERIOR STAPHYLOMA
RETINAL HOLES
TESSELLATED FUNDUS
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FOSTER FUCHS SPOT
RETINAL
DETACHMENT
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RETINAL HOLE
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TESSELLATED FUNDUS
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TreatmentOptical treatment
Appropriate concave lenses
Minimum acceptance providing maximum vision
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GUIDELINES
LOW DEGREES OF MYOPIA (Up to -6D)
IN YOUNG SUBJECTS
Defect should never be overcorrected and advised for constant use to avoid squinting and develop a normal ACCOMMODATION-CONVERGENCE reflex
IN ADULTS
Receiving spectacle for the first time,have the ciliary muscle that are unaccostomed to accommodate efficiently so that lens of slightly lower power(1 or 2 D) may be prescribed for reading,especially if engaged in to any greater extent.Abovethe age of 40 years,when accommodation fails physiologically, a weaker glass for near work is essential
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HIGH DEGREES OF MYOPIA
Full correction rarely be tolerated so we attempt to
reduce the correction as little as is compatible with
comfort for binocular vision. We prescribe the lens
with which the greatest visual acuity is obtained
without distress
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MYOPIA CORRECTION
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ADVANTAGES OF SPECTACLES
Economical
Allow incorporation of prism,bifocals,pal which can be used for the management of esophoria or any accommodative disorders accompanying myopia
Spectacles require less accommodation than contact lens for myopia that likelihood of accommodative asthenopia or near point blur in patients approaching presbyopia may be less
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SPECIAL LENS DESIGNING
Any prescriptions above -15.00 D require
Special lens designs to provide optimal visual acuity
and cosmesis.
Special lenses for high myopia- 1. ASPHERIC
LENSES
2. LENTICULAR MINUS LENS
3.MYODISC
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ASPHERIC LENSES
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LENTICULAR MINUS DESIGNS
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THE MYODISC
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SURGICAL TREATMENT
Epikeratophakia
RK
PRK
ISCR
Phakic IOL’S
LASIK
LASIKPRK
RK
ISCR
Phakic IOL’S
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THANK
YOU
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