Astigmatism AVF (2).pptx . . . . . . . . . . .

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1. ASTIGMATISM BY: Komal Yaseen 1

2. Content: Introduction Etiology Classification Signs and symptoms Clinical tests Management 2

3. Astigmatism:  The term astigmatism (from a , meaning "lacking," and stigma, meaning " a point ") Astigmatism by definition is a condition where the parallel beam of light rays incident on the cornea after refraction are not focused to form a point image near or on the retina. 3

4. Spherical Vs Astigmatic cornea 4

5. Image in Astigmatism: 5

6. Etiology: Irregular curvature or RI of anterior corneal surface/posterior corneal surface. Irregular surface, RI and position of lens/IOL. The refracting power is not uniform in all meridians of both lens or cornea. 6

7. Classification: Based on Etiology. Based on Orientation of meridians Based on Focal points relative to retina 7

8. Based on Etiology: Curvature of cornea Irregular regular Axis not perpendicular Irregular surface of cornea Axis perpendicular 8

9. Orientation of meridians: 9

10. Principle meridian: WTR- with the rule astigmatism. -vertical meridian of cornea is more power Greatest power is with in 30 degree of vertical meridian. (60deg- 120 deg). ATR- against the rule astigmatism. - horizontal meridian of cornea is more power Greatest power is with in 30 degree of horizontal meridian(30deg-150deg). 10

11. Axis Orientation of WTR and ATR astigmatism 11

12. Based on Orientation of meridians: Oblique astigmatism: - Axis position is not near to 90 and 180. -Range of axis will be in 30-60deg and 120 and 150deg . 12

13. Focal point relative to retina. Simple astigmatism One of the focus falls on retina and the other one may fall in front of retina or behind retina Two condition. Simple Myopic astigmatism Simple Hypermatropic astigmatism 13

14. Continue… Compound astigmatism: - Both(2) the focal point lies in front of retina or behind the retina. -Compound Myopia - Compound Hypermetropia 14

15. Continue… Mixed astigmatism: - One focus lies in front of retina and other lies behind the retina. - one meridian is Myopic - other one Hypermetropic 15

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17. Irregular astigmatism: Irregular differences in curvature or refractive index of the optic components or misalignment of any optical component may lead to irregularity. Pterygium , corneal scars/healed ulcers Complication of refractive surgery. keratoconous 17

18. Signs and Symptoms: Visual acuity ↓ Difficulty in both near and distance Letter confusion Eyestrain Headache squinting 18

19. Vision with Astigmatism: 19

20. Clinical tests: -Objective tests: Autorefraction Keratometry Retinoscopy Corneal topography - Subjective tests JCC- Jacson’s cross cylinder Astigmatic Fan Stenopaeic slit 20

21. Management: Conservative management: Sphero -cylindrical lens Spherical soft contact lenses Spherical RGP contact lenses Toric soft contact lenses Surgical laser procedure: Photorefractive keratectomy(PRK) Laser in-situ keratomileusis (LASIK) 21

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