ERRORS OF REFRACTION

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By: lissyc62 (27 month(s) ago)

sir i need your power point presentation on errors of refraction

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ERRORS OF REFRACTION: 

ERRORS OF REFRACTION EMMETROPIA

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AMETROPIA MYOPIA HYPERMETROPIA ASTIGMATISM

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HYPERMETROPIA

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AETIOLOGY OF HYPERMETROPIA Axial Hypermetropia Commonest form Axial shortening of eye ball 1mm=3D

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Curvatural Hypermetropia Curvature of cornea/lens flatter 1mm increase = 6D

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Index Hypermetropia Decrease in refractive index of Lens Also seen in Diabetes

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Positional Hypermetropia Posteriorly placed lens

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Aphakia

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Clinical Types Of Hypermetropia Three clinical Types I] Simple/Developmental II] Pathological III] Functional

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Simple/Developmental Hypermetropia -Commonest form -Results from normal biological variations in the development of eyeball -Includes Axial and Curvatural types of Hypermetropia

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Pathological Hypermetropia -Due to congenital/acquired conditions I.Index Hypermetropia II.Positional Hypermetropia III.Aphakia IV.Consecutive Hypermetropia

S: 

S Functional Hypermetropia

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Nomenclature Of Hypermetropia -Total Hypermetropia Latent Manifest Facultative Absolute

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Clinical Features -Symptoms *Asymptomatic *Asthenopic Symptoms *Defective vision with asthenopia *Defective vision

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Signs of Hypermetropia -Small eyes -Cornea smaller -Anterior chamber is shallow -Small optic disc -Shot silk retina -Short AP length of eyeball

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Complications

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Treatment

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APHAKIA

APHAKIA: 

APHAKIA Causes -Congenital absence of lens -Surgical Aphakia -Aphakia due to absorption of lens matter -Traumatic -Posterior dislocation of lens

APHAKIA: 

APHAKIA

APHAKIA: 

APHAKIA Optics Of Aphakic Eye Eye becomes highly hypermetropic Total power of eye is +44D Anterior focal point 23mm infront of the cornea Posterior focal point is 31mm behind the cornea Total loss of accommodation

APHAKIA: 

APHAKIA

APHAKIA: 

APHAKIA Clinical Features Symptoms -Defective vision -Erythropsia and Cynopsia

APHAKIA: 

APHAKIA Signs -Limbal Scar -Deep Anterior Chamber -Iridodonesis -Jet Black Pupil -Two purkinje’s images -Hypermetropic small disc -Retinoscopy shows high hypermetropia

APHAKIA: 

APHAKIA

APHAKIA: 

APHAKIA TREATMENT -Spectacles -Contact Lenses -I O L -Refractive Corneal Surgery

APHAKIA: 

APHAKIA

PSEUDOPHAKIA: 

PSEUDOPHAKIA

MYOPIA: 

MYOPIA

CLASSIFICATION OF MYOPIA *Etiologicl Classification *Clinical Classification

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Etiological Classification -Axial Myopia Due to increase in axial length of eyeball Commonest form -Curvatural Myopia Increased curvature of cornea/lens -Positional Myopia Anterior placement of lens -Index Myopia Increase in the refractive index of lens -Accommodative Myopia

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Clinical Types Of Myopia Congenital Myopia

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Simple Myopia commonest form Physiological error 2% at 5 years age/14% at 15 yrs age school myopia

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Etiology of Simple Myopia -Axial length of eye ball -Curvatural -Diet -Genetical -Excessive near work

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Clinical Features of Simple Myopia Symptoms -Poor distant vision -Asthenopic Symptoms -Half shutting of the eyes

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Signs of Simple Myopia -Prominent eyeballs -Deep AC -Large pupils with sluggish reaction -Temporal myopic crescent -Magnitude of refractive error

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Diagnosis of simple myopia

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Pathological Myopia Etiology -Heredity -General growth process

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Clinical Features Symptoms -Defective vision -Muscae volitantes -Night Blindness

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Signs of Pathological Myopia -Prominent eyeballs -Large cornea -Deep AC -Slightly large Pupils -Fundus Changes

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COMPLICATIONS *Retinal Detachment *Complicated Cataract *Vitreous Haemorrhage/Choroidal Haemorrhage *Squint

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TREATMENT -Optical -Surgical/Laser -Low Visual Aids -General Measures -Genetic Counselling

ASTIGMATISM: 

ASTIGMATISM

TYPES OF ASTIGMATISM -Regular Astigmatism -Irregular Astigmatism

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REGULAR ASTIGMATISM

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Etiology of Regular Astigmatism Corneal Astigmatism

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Lenticular Astigmatism Curvatural

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Positional

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Index Astigmatism

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Retinal Astigmatism

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Types Of Regular Astigmatism -With the rule Astigmatism -Against the rule Astigmatism -Oblique Astigmatism -Bioblique Astigmatism

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Oblique Astigmatism

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BI OBLIQUE ASTIGMATISM

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Refractive Types of Regular Astigmatism -Simple astigmatism simple myopic astigmatism simple hypermetropic astigmatism -Compound astigmatism compound myopic astigmatism compound hypermetropic -Mixed astigmatism

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SYMPTOMS -Defective vision -Blurring of objects -objects appear elongated -Asthenopic symptoms

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Signs -Different power in two meridia -Oval or tilted Optic disc -Head tilt -Half closure of the lids

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Investigations -Retinoscopy -Keratometry -Astigmatic fan test -Jacksons cross cylinder test

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Treatment -Optical -Contact lenses -Surgical

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IRREGULAR ASTIGMATISM

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Etiology of Irregular Astigmatism -Curvatural -Corneal Scars -Keratoconus -Index -Cataract

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Symptoms -Defective vision -Distortion of objects -Polyopia

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Investigations -Placidos disc test -Corneal topography

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Treatment Optical Contact lenses PTK Excimer laser Surgical Keratoplasty

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ANISOMETROPIA -Isometropia Equal refraction in two eyes -Anisometropia Unequal refraction in two eyes

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Etiology of Anisometropia -Congenital/Developmental anisometropia -Acquired anisometropia Aphakia IOL power errors

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Clinical Types of Anisometropia -Simple anisometropia -Compound anisometropia -Mixed anisometropia -Simple astigmatic anisometropia -Compound astigmatic anisometropia

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Status of Binocular Vision inAnisometropia

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Diagnosis Retinoscopy Treatment Spectacles Contact lenses Anesokonic glasses

ANISEIKONIA Images on the visual cortex from the two retinae are abnormally unequal

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ACCOMMODATION -Ability to bring divergent rays from a near object to a point of focus on retina -It is due to increase in the power of crystalline lens -Due to increase in the radius of curvature of the lens

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- -Far point -Near point -Range of accommodation -Amplitude of accommodation

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ANOMALIES OF ACCOMMODATION -Presbyopia -Insuffiency of Accommodation -Spasm of Accommodation -Paralysis of Accommodation

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PRESBYOPIA -Physiological insufficiency of accommodation -Not a Refractive Error -Decreased near vision -Decrease in amplitude of accommodation/increase in punctum proximum[near point]

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-Near point at age 10 years-----7cm -Near point at age 40 years----25cm -Near point at age 45 years----33cm Amplitude of accommodation 100/near point

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Causes 1.Age related changes in the Lens 2.Age related decrease in ciliary muscle power

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Causes of premature presbyopia -Uncorrected Hypermetropia -General debility -Chronic simple Glaucoma

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Symptoms of Presbyopia Difficulty in near vision Asthenopia

s: 

s Treatment of Presbyopia -Optical convex lenses -Surgical/Laser

INSUFFICIENCY OF ACCOMMODATION : 

INSUFFICIENCY OF ACCOMMODATION

INSUFFICIENCY OF ACCOMMODATION: 

INSUFFICIENCY OF ACCOMMODATION Accommodation power is less than the age normal Causes Premature sclerosis of lens Weakness of ciliary muscle Primary open angle glaucoma

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Clinical Features -Presbyopia symptoms -Asthenopia

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Treatment -Treat the cause -Near vision spectacles -Accommodation exercises

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PARALYSIS OF ACCOMMODATION -complete absence of accommodation -Cycloplegia

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Causes -Drug induced cycloplegia -Internal Ophthalmoplegia -Paralysis of accommodation[III N Palsy]

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Blurring of near vision Photophobia Receding of near point

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Treatment -Self recovery -Dark glasses -Convex lenses

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SPASM OF ACCOMMODATION -Exertion of abnormally excessive accommodation Causes -Drug induced Miotics[DFP] -Spontaneous spasm of accommodation

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Clinical Features -Defective Vision due to induced myopia -Asthenopia

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Diagnosis -Retinoscopy Treatment -Relaxation of ciliary muscle[Atropine] -Treat the cause

RETINOSCOPY: 

RETINOSCOPY