myopia

MYOPIA MYOPIANISHITA AFRIN

B.OPTOM

3RD Batch

INSTITUTE OF COMMUNITY OPHTHALMOLOGY

MYOPIA

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.

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

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

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

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.

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

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

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

Myopic crescent

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MACULA

Foster-Fuchs fleck

RETINAL DETACHMENT

POSTERIOR STAPHYLOMA

RETINAL HOLES

TESSELLATED FUNDUS

FOSTER FUCHS SPOT

RETINAL

DETACHMENT

RETINAL HOLE

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

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

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

ASPHERIC LENSES

LENTICULAR MINUS DESIGNS

THE MYODISC

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SURGICAL TREATMENT

Epikeratophakia

RK

PRK

ISCR

Phakic IOL’S

LASIK

LASIKPRK

RK

ISCR

Phakic IOL’S

THANK

YOU