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3. 3 MYOPIA Short sightedness Myopia is a greek word meaning *close the eye* Refractive error I Parallel rays of light coming from infinity are focused in front of the retina. Accommodation is at rest

4. 4  Mechanism of production Axial Curvatural Positional Index Myopia due to excessive accommodation

5. 5  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 1mt from the eye,there is 1D of myopia Nodal point is further away from retina Accommodation need not develop normally resulting in Convergence insufficiency Exophoria

6. 6 TYPES OF CLASSIFICATION Clinical Classification Degree of Myopia Age of Onset

7. 7 Clinical Classification Congenital Myopia Simple Myopia Degenerative Myopia Nocturnal Myopia Pseudo Myopia Induced Myopia

8. 8 Degree of Myopia Low Myopia(<3D) Medium Myopia(3- 6D) High Myopia(>6D)

9. 9 AGE OF ONSET Congenital Myopia Youth-Onset Myopia(<20 yrs of age) Early Adult-Onset Myopia(20-40 yrs of age) Late Adult-Onset Myopia(>40 yrs of age)

10. 10 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

11. 11  Associated conditions 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

12. 12 Simple / developmental myopia Physiological error not associated with any disease of the eye  Etiology : Normal biological variation in development of eye Inheritence

13. 13  Associated factors Role of diet Theory of excessive near work

14. 14  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

15. 15  Symptoms Poor vision for distance Asthenopic symptoms develop due to dissociation between accommodation and convergence  Convergence weakness, exophoria, suppression  Excessive accommodation inducing ciliary spasm and artificially increasing the amount of myopia Psychological outlook

16. 16  Signs Large and prominent Deep AC Large, sluggishly reacting pupils Normal fundus, rarely crescent Usually doesn't exceed 6-8D Retinoscopy under full cycloplegia

17. 17 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

18. 18 Genetic factors General growth process More growth of retina Stretching of sclera Increased axial length Degeneration of choroid Degeneration of retina Degeneration of vitreous

19. 19  Symptoms Defective vision Muscae volitantes / floating black opacities

20. 20  Signs  EYE Large, prominent eyes simulating exophthalmos  CORNEA large  ANTERIOR CHAMBER deep  LENS show opacities at the posterior pole due to aberration of lenticular metabolism and due to overstretching anterior dislocation may also occur

21. 21  VITEROUS degeneration,viterous liquefication,vitreous detachment present as WEISS REFLEX  SCLERA thinning resulting in formation of STAPHYLOMA  VISUAL FIELD DEFECTS show Contraction and in some ring scotomas present

22. 22  DISC Large in size Myopic Crescent on the temporal side of the disc Choroidal Crescent Supertraction of the retina Inverse myopia Myopic crescent situated nasally and supertraction of the retina temporally called as INVERSE CRESCENT Peripapillary Atrophy

23. 23  MACULA Foster-Fuchs fleck  RETINAL DETACHMENT  POSTERIOR STAPHYLOMA  RETINAL HOLES  TESSELATED FUNDUS

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27. 27 Treatment Optical treatment Appropriate concave lenses Minimum acceptance providing maximum vision

28. 28 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.Above the age of 40 years,when accommodation fails physiologically, a weaker glass for near work is essential

29. 29 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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31. 31 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

32. 32 DISPENSING SPECTACLES IN HIGH MYOPIA High index lens materials Lighter lens materials Reduced eyesize of selected frames Minus lenticular lens designs

33. 33 ADVANTAGES OF CONTACT LENS Contact lens provides cosmosis Large retinal image size and slightly better visual acuity in severe myopia

34. 34 SURGICAL TREATMENT Epikeratophakia RK PRK ISCR Phakic IOL’S LASIK LASIK PRK RK ISCR Phakic IOL’S

35. 35 Photorefractive Keratectomy (PRK) Involves direct laser ablation of corneal stroma after removal of corneal epithelium mechanically or using a laser beam. Done using Excimer laser MUNNERLYN EQN: depth of ablation (micrometer)=[diameter of optical zone(mm)] ² × 1/3power(Diopter) For myopic a large amount of ablation is done in central cornea than in the periphery. Give good results for -2D to -6D of myopia

36. 36 LASIK Laser Assisted In situ Keratomileusis Method:Anterior flap of cornea is lifted with a keratome and excimer laser is used to sculpt the stromal bed to change the refractive error of eye Corrects 0.5 to 12D of myopia and upto 8D of astigmatism Guidelines:Age more than 18yrs BCVA better than 6/12 Stable refraction for last 1yr Absence of corneal disease & ectasia Note: (1) In no case the residual bed thickness after the ablation should measure 250microns so as to avoid central corneal ectasia (2) Ideally the ablation should be done within 30sec of the preparation of flap

37. 37 LASEK Laser subepithelial Keratomileusis Indications: Low myopia Irregular astigmatism LASIK complications in contralateral eye Thin corneal pachymetry Predisposition to trauma Glaucoma suspect

38. 38 Method: Simple inexpensive procedure that involves creation of epithelial flap after exposure to 18% alcohol for 25sec & subsequent replacement of flap after laser ablation

39. 39 RK Radial Keratotomy It refers to making deep corneal incisions(initially 16,now down to 4) in the peripheral part of cornea leaving about 4mm central optical zone The incisions are made almost down to the level of Descemet’s Membrane These incisions on healing flatten the central cornea thereby reducing its refractive power For low to moderate degree of myopia(-1.5 to - 6D of myopia)

40. 40 Epikeratophakia For high degree of myopia (upto 20D) Method: The epithelium is removed & then a pocket is fashioned under the edge of the remaining epithelium & into this is inserted the cryolathed donor homograft Preserved material can also be used

41. 41 NON CORNEAL INTERVENTIONS (A) REMOVAL OF CLEAR LENS We know that an aphakic eye is strongly hypermetropic If an eye with an axial myopia of -24D is deprived of its lens it will become emmetropic without any correcting lens Note: Whenever surgery on clear lens is contemplated the eye is examined thoroughly for abnormalties like Raised IOP,Vitreous & retinal degeneration etc

42. 42 (b)Phakic intraocular lenses An IOL of appropriate power is implanted inside the eye without touching normal crystalline lens thus without disturbing accomodation Method can be used to correct both myopia & hypermetropia Phakic IOL types: PC IOL Angle supported IOL Iris claw lens

43. 43 INTRA CORNEAL RING(ICR) IMPLANTATION ICR implantation into the peripheral cornea approx.upto 2/3 rd of stromal depth can also be considered for correction of myopia It results in a vaulting effect that flattens the central cornea decreasing the myopia The procedure has the advantage of being reversible

44. 44 For Further Queries Contact : Ms. Priyanka Singh Head – Optometry Service Email – optometry@venueyeinstitute.org

45. 45 Thank you