REFRACTIVE ERROR MYOPIA AND ITS MANAGEMENT.pptx

OPTOMETRY
REFRACTIVE ERROR

1. VISUAL OPTICS Ajna M Wilson M. Optom

2. MYOPIA

3. SHORT SIGHTEDNESS DIOPTERIC CONDITION IN WHICH INCIDENT PARALLEL RAYS COME TO A FOCUS ANTERIOR TO THE LIGHT SENSITIVE LAYER OF RETINA WITH ACCOMODATION AT REST . MYOPIA

4. OPTICS OF MYOPIA The optical system is too powerful for its axial length. Image of distant object on retina is made up of circle of diffusion formed by divergent beam since the parallel rays of light coming from the infinity are focused in front of the retina. Far point is finite point in front of eye. Nodal point is further away from retina. Accommodation in uncorrected myopes is not developed normally, they may suffer from convergence insufficiency, exophoria, and early presbyopia as they grow

5. AXIAL MYOPIA COMMONEST FORM INCREASE IN ANTERO-POSTERIOR LENGTH OF THE EYEBALL CURVATURAL MYOPIA INCREASED CURVATURE OF CORNEA, LENS OR BOTH POSITIONAL MYOPIA PRODUCED BY ANTERIOR PLACEMENT OF CRYSTALLINE LENS IN EYE INDEX MYOPIA INCREASE IN THE REFRACTIVE INDEX OF CRYSTALLINE LENS ASSOCIATED WITH NUCLEAR SCLEROSIS MYOPIA DUE TO EXCESSIVE ACCOMODATION SPASM OF ACCOMODATION ETIOLOGICAL CLASSIFICATION

6. Congenital myopia Simple or developmental myopia Pathological or degenerative myopia Acquired myopia which may be Post traumatic Post keratitic Drug induced Pseudomyopia Space myopia Night myopia Consecutive myopia CLINICAL VARIETIES

7. Since birth Diagnosed by 2-3 years Mostly unilateral Manifests as anisometropia CONGENITAL MYOPIA

8. Associated with cataract, micropthalmos, aniridia, megalocornea, congenital separation of retina .

9. Developmental myopia- commonest variety School myopia (school going age 8 -12 years) Etiology Axial type : physiological variation in length of eye ball precocious neurological growth during childhood SIMPLE MYOPIA

10. Curvatural type Underdevelopment of eye ball Role of diet in early childhood Role of genetics Prevalence in children both parents myopic(20%) One parent myopic(10%) No parent myopic(5 %)

11. Symptoms Poor vision for distance(short sightedness) Asthenopic symptoms Half shutting of eyes CLINICAL PICTURE

12. Signs Prominent eyeballs Anterior chamber - deeper than normal Pupils- Large, sluggishly reacting Fundus- normal; rarely temporal myopic crescent may be seen Magnitude of refractive error Increasing at rate -0.5+- 0.30/ year. Does not exceed 6 to 8 Diagnosis Confirmed by performing retinoscopy

13. Degenerative/ progressive myopia Rapidly progressive error which starts in childhood at 5-10 years of age High myopia in early adult life with degenerative changes PATHOLOGICAL MYOPIA

14. Role of heredity Heredity linked growth of retina is the determinant in developmental myopia Sclera due its distensibility follows retinal growth but choroid undergoes degeneration due to stretching, which in turn causes degeneration of retina Progressive myopia is Familial More common in chinese,japanese,arabs and jews Uncommon among negroes,nubians and sudanese ETIOLOGY

15. Role of general growth process Lengthening of the posterior segment of globe commences only during the period of active growth and ends with termination of active growth

16. Genetic factors (play major role) General growth process(minor) More growth of retina Stretching of sclera Increase axial length Degeneration of choroid Degeneration of retina Degeneration of vitreous

17. Defective vision Muscae volitantes Floating black opacities in front of eyes Degenerated liquified vitreous Night blindness SYMPTOMS

18. Prominent eye balls Elongation of eye ball mainly affects posterior pole and surrounding area Cornea-large Anterior chamber -deep Pupils-slightly large ,react sluggishly to light SIGNS

19. Fundus examination: Optic disc large and pale Temporal edge presents a characteristic myopic crescent Peripapillary crescent encircling the disc may be present, where choroid and retina is distracted away from disc margin Super traction crescent may be present on nasal side (retina pulled over disc margin)

20. Degenerative changes in retina and choroid Common in progressive myopia Characterized by white atrophic patches at macula with a little heaping of pigment around them

21. FOSTER-FUCH’S SPOT: Dark red circular patch due to sub- retinal neo vascularization and choroidal haemorrhage Present at macula CYSTOID DEGENERATION – at periphery Advanced cases: Total retinal atrophy in central area

22. Posterior staphyloma Due to ectasia of sclera at posterior pole It may be apparent as an excavation with vessels bending backward over margins

23. Degenerative changes in vitreous include: Liquefaction Vitreous opacities Posterior vitreous detachment(PVD)- Weiss’ reflex

24. Visual fields Contraction Ring scotoma may be seen ERG reveals subnormal electroretinogram due to chorioretinal atrophy

25. Retinal detachment Complicated cataract Vitreous haemorrhage Choroidal haemorrhage Strabismus fixus convergence COMPLICATIONS

26. ACQUIRED MYOPIA Post traumatic Post keratitic Drug induced Pseudomyopia Space myopia Night myopia Consecutive myopia

27. Optical treatment of myopia Concave lenses Basic rule – minimum acceptance providing maximum vision Modes of prescribing concave lens- Spectacles Contact lens TREATMENT OF MYPOIA

28. Contact lenses are used in case of high myopia as they avoid peripheral distortion and minification produced by strong concave spectacle lens

29. Radial keratotomy Photo refractive keratectomy (PRK) Laser Assisted In-situ Keratomileusis (LASIK) Extraction Of Clear Crystalline Lens Phakic intraocular lens Intracorneal Ring (Icr) Implantation Orthokeratology SURGICAL TREATMENT OF MYOPIA

30. General measures : Balanced diet rich in vitamins and proteins Early management of associated debilitating disease Low vision aids indicated in patients with progressive myopia with advanced degenerative changes Prophylaxis Genetic counselling