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Errors of refraction
This document discusses different types of refractive errors: - Emmetropia is the normal state where light focuses on the retina with accommodation at rest. - Ametropia is an abnormal refractive state where light does not focus on the retina with accommodation at rest. There are three main types: myopia, hypermetropia, and astigmatism. - Hypermetropia (farsightedness) is where light focuses behind the retina at rest. It has multiple causes and clinical types. Treatment options include glasses, contact lenses, refractive surgery.
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Errors of refraction
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- 2. • Emmetropia • Itis state of refraction wherein the parallel rays of light coming from infinity are focused at the sensitive layer of retina with the accommodation being at rest. • Ametropia • It is a state of refraction when the parallel rays of light coming from infinity are focused either in front or behind the sensitive layer of retina in one or both meridian with accommodation at rest. • Types:- • a)Myopia • b)Hypermetropia • C) Astigmatism
- 3. Hypermetropia long sightedness •Def:-It is a refractive state of the eye wherein parallel rays of light coming from infinity are focused behind the retina with accommodation being at rest. • Etiology 1. Axial 2. Curvatural 3. Index 4. Positional 5. Absence of lens 6. Consecutive
- 4. • Clinical Types 1.Physiological 2. Non-physiological Congenital _________Acquired Microphthalmos -------- ------- senile Nanophthalmos ----------------positional Microcornea --------------------Aphakia Posterior subluxation of lens---consecutive Aphakia ----------------------------axial ------------------------ Curvatural ------------------------ pseudophakic 3. Functional ----------- 3rd nerve palsy. • Total hypermetropia = latent + (facultative + absolute) • Hypermetropia: variation with age At birth At 5-7 yrs. After 50 yrs.
- 5. Clinical features Symptoms • Asymptomatic •Asthenopic • Defective vision • Both Signs • Size of eye ball • Cornea • Anterior chamber • Retinoscopy • Fundus examination • A-scan ultrasonography
- 7. Myopia shortsightedness • Def:-Itis a type or refractive error in which parallel rays of light coming from infinity are focused in front of the retina when accommodation is at rest. Grading of Myopia American optometric association • Low <3D • Moderate 3-6D • High > 6D • • Etiological classification 1. Axial 2. Curvatural 3. Positional 4. Index 5. Due to excessive accommodation 1. Clinical varieties of Myopia:- 1) Congenital 2) Simple or developmental 3) Pathological or degenerative 4) Acquired
- 15. Astigmatism • Def:- It isa type of refractive error wherein the refraction varies in different meridian. Consequently the rays of light entering the eye can not converge to a point focus but form focal lines. Broadly two types:-Regular and Irregular
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- 21. Surgical options forMyopia
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