MYOPIA REFRACTIVE ERROR.pdf
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This document discusses myopia (nearsightedness) including its causes, classifications, signs and symptoms, and treatment options. Myopia occurs when the eyeball is too long or the refractive power is too strong for the eye length, causing light to focus in front of the retina. It is classified based on progression rate, anatomy, degree, age of onset, and whether it involves degenerative changes. Symptoms include blurred distant vision. Treatment includes optical correction with glasses or contacts and refractive surgery procedures like LASIK. Advanced myopia can lead to retinal damage and complications like detachment.
MYOPIA REFRACTIVE ERROR.pdf
- 3. Refractive status of the eye The ocular refractive status refers to the locus within the eye conjugate with optical infinity during minimal accommodation.* Under these conditions: In an emmetropic eye, incident parallel rays of light are brought to a focus upon the retina. In a hyperopic (or hypermetropic) eye, incident parallel rays of light are brought to a focus behind the retina. In a myopic eye, incident parallel rays of light are brought to a focus in front ofthe retina.
- 4. Refractive status of the eye Ametropia, or the absence of emmetropia, may be produced by variations in: 1. The relative location of the optical elements of the eye with respect to the retina. 2. The relative refractive power of the optical elements with respect to the location of the retina
- 5. Refractive errors Ametropia: a refractive error is present • Myopia: Near sightedness • Hyperopia(Hypermetropia): Far sightedness • Astigmatism: the curvature of the cornea and/or lens is not sphericaland therefore causes image blur on the retina
- 6. Refractive errors • Anisometropia: a refractive power difference between the 2 eyes (> 2D) • Aniseikonia: a difference of image size between the 2 eyes as perceived by the patient • Aphakia: (Phakos=lens), aphakia is no lens • Pseudophakia: artificial lens in the eye
- 7. Myopia
- 8. Myopia
- 9. Myopia Results from an eye having excessive refractive power for its axial length. This may be due either to the eye having a relatively long axial length or to increased dioptric power of one or more of the refractive elements.
- 10. Myopia Term myopia was derived by Galen from the words myein ("to close") and ops ("eye"). Galen observed that nearsighted people partially closed their eyes to see better.
- 11. Optics Of Myopia In myopia the eyeball is usually deformed ; the deformation occurs at the posterior part of the globe only ,the anterior part is normal. The eyeball is usually large and looks prominent. When adducted the equator can be seen.
- 12. Optics Of Myopia
- 13. Classifications Rate of myopic progression Anatomical features of myopia Degree of myopia Physiological and pathological myopia Hereditary and environmentally induced myopia theory of myopic development Age of myopia onset
- 14. Rate of myopic progression- Donders Three categories of myopia: Stationary: Stationary myopia is generally of low degree (-1.50 to -2.00 D) and arises "in the years of development. remains stationary during adulthood Temporarily :early teens and progresses until the late 20s. After this age, the rate of myopia progression approaches zero. Permanently progressive:. Permanently progressive myopia ascends rapidly until around 25 to 35 years of age, and thereafter advances more slowly.
- 15. Based on Anatomical features Axial: increased Axial length of eyeball Refractive:refractive system is too powerful for the axial length of the eye. Boris further divided in to Ref.Myopia into: 1. Curvatural- reduced radius of curvature of one or more refractive surfaces produces increased dioptric power. 2. Index-one or more ofthe refractive indices ofthe media are anomalous.increased refractive index of lens withnuclear sclerosis 3. Anterior chamber myopia:deeper in anterior chamber depth increases the refractive power of the eye
- 16. Degree of myopia Low (<3D) Medium –(3-6D) High – (>6D)
- 17. Physiological and Pathological Myopia Physiological myopia: in which each component of refraction lies within the normal distribution for that population. Physiological/school myopia Commonest type Results due to normal biological variations in developmentof eye Age of onset- 7-10yrs Moderate severity-<5D,neverexceeds8D No degenerativechanges
- 18. Pathological myopia Refractive anomalies determined by the presence in the optical system of the eye of an element which lies outside the limits of the normal biological variations. Malignant or degenerative myopia - degenerative changes, particularly in the posterior segment of the globe. Most frequently found in high (>6 D) degrees of myopia Age of onset-early adultlife Progressive in nature
- 19. Pathological myopia Also called degenerative/ progressive myopia Related to heredity Increased axial length, degenerative changes in retina, choroid, vitreous changes
- 20. Classification Based on Age of Onset myopia on the basis of the subjects' age at the time of reported myopia onset. 1. Congenital myopia-Myopia is present at birth and persists through infancy 2. Youth-onset myopia -The onset of myopia occurs between 6 years of age and the early teens. 3. Early adult-onset myopia -The onset of myopia occurs between 20 and 40 years of age. 4. Late adult-onset myopia -Myopia onset occurs after 40 years of age.
- 21. Congenital myopia Common in premature babies or with birth defects Stationary(8-10D) Associated with Increase in axiallength Esotropia Other congenital anomalies of eye Early and full correction under cycloplegia Poor prognosis in unilateral cases with severe myopia and anisometropia
- 22. Other types myopia Night myopia: increased myopia under low iluminance conditions was first reported in 1789. produced by an increased accommodative response (typically on the order of 0.50 to 1.00 D) under degraded stimulus conditions. Pseudo myopia: results from a spasm of the ciliary muscle
- 23. Pathological changes in myopia Optic disc appear large and pale Degenerative changes in retina & choroid Vitreous degeneration Posterior staphyloma
- 24. Myopic Crescent
- 25. Lacquer Cracks Breaks in Bruch’s membrane
- 26. Foster – Fuchs's spots
- 30. Complications Macular hemorrhage Retinal tears, detachment Vitreous hemorrhage Choroidal hemorrhage Complicated cataract Nuclear sclerosis Primary open angle glaucoma
- 31. Clinicalfeatures-Symptoms Distant blurred vision Half shutting of eyes Asthenopic symptoms Floating black opacities infront of the eye Night blindness Divergent squint
- 32. Signs Prominent eyeballs Large cornea Anterior chamberis deep Large &sluggishly reacting pupil Fundus examination-changes seen only in pathological myopia
- 34. Optical treatment Minimum acceptance providing maximum vision Low myopia(<6D): Young children : glasses required only if Isometropia <2years ≥ -4.0D 2-3years ≥ -3.0D Anisometropia: ≥ -2.5D Give full correction under cycloplegia Avoid overcorrection
- 35. Adults: <30years-full correction >30years-less than full correction with which patient is comfortable for nearvision. HIGH MYOPIA under correction is done to avoid near vision problem minification of images contact lenses are better(to avoid image minification)
- 36. Surgicaltreatment Radial keratotomy Lamellar corneal refractiveprocedures Laser based procedures PRK LASIK LASEK C-LASIK E-LASIK
- 37. Miscellaneous corneal refractiveprocedures Orthokeratology Intracorneal contact leses Intra stromal corneal ring segments Gel injectable adjustable keratoplasty Intraocular refractiveprocedures Phakic refractive lenses Refractive lense exchange
- 38. Thank you