1. Aphakia and its correction

2. Definition The lens is absent from the pupillary area
Congenital absence
Dislocation into the vitreous
Extruded outside the eye
Surgically removed
Absorption of the lens matter

3. Effects of Aphakia Changes in the cardinal data of the eye
Image formation in the aphakic eye
Visual acuity in aphakia
Accommodation in aphakia
Binocular vision in aphakia

4. Changes in the cardinal data of the eye
Eye is highly hypermetropic
Power is reduced to 44D (60D)
Anterior focal point is 23.2 mm in front of cornea (17.2mm)Posterior focal point is 31mm behind cornea (24.4mm)

5. Changes in the cardinal data of the eye
Principal points are at the anterior surface of cornea ( 1.5mm behind)
Nodal points are 7.75 mm behind anterior surface of cornea (7.2mm)

6. Image formation in the aphakic eye
Image size in aphakia corrected with spectacles is 30% magnified
Image size in aphakia corrected with contact lens is magnified by 4.5 to 5%

7. Visual acuity in aphakia
Visual acuity of spectacle corrected eye is recorded better than actual visual acuity in terms of visual angles

8. Accommodation in aphakia
Total loss of accommodation
Bifocal or progressive spectacles
Multifocal IOLs

9. Binocular vision in aphakia
Monocular aphakia corrected with spectacles will result in aniseikonia
Can be corrected with IOL or Contact lens

10. Clinical features Associated abnormalities Operative scar at limbus
Deep AC
Iridodonesis
Jet black pupil
Absent Purkinje images (3,4)
Associated abnormalities
High hyperopia
Fundus exam -small disc

11. Correction of aphakia Spectacle Contact lens Intra-ocular lens
Refractive corneal surgery

12. Total power
Total dioptric power = +58 D Cornea= +42 D Lens= +16 D Refractive state = Emmetropia
11/17/2018

13. Total power
Total dioptric power = +42 D Cornea= +42 D Lens= +0 D Refractive state = High Hypermetropia
11/17/2018

14. Total power
A high power (thick) convex lens is required to correct vision
11/17/2018

15. Spectacle correction
+10 D lens with correction of associated astigmatism ( usually ATR )
Add + 3 D for near vision ( Total +13D )
Advantages
Cheap
Easy
safe

16. Spectacle correction Many disadvantages Heavy glasses
Poor cosmetic appearance

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19. Spectacle correction Many disadvantages
Magnification of 30% - unilateral aphakia, assess distance

20. Magnification Spectacle magnification= Corrected image size
Uncorrected image size
Anterior focal distance in ametropia
Anterior focal distance in emmetropia
= = 30 % magnification
17.05
11/17/2018

21. False depth
False depth perception
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22. False depth
False depth perception
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23. False depth
False depth perception
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24. False depth
False depth perception
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25. False depth
False depth perception
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26. False depth
False depth perception
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27. False depth
False depth perception
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28. Spectacle correction Many disadvantages Restricted field of vision
Roving ring scotoma

29. Ophthalmology is easy
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30. thalmology is
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31. Ophthalmology is easy
Ring scotoma-
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32. ?
almology
Ring scotoma-
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33. Ophthalmology is easy
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35. Ring scotoma-
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50. Roving Ring scotoma-
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51. Jack in the box-
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52. Spectacle correction
Spherical aberrations – pincushion defect

53. Aphakic glasses Pin cushion effect
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54. Spectacle correction Spherical aberrations – pincushion defect
Coloured vision
Separate glasses for near

55. Total power
Total dioptric power = +58 D Cornea= +42 D Lens= +16 D Refractive state = Emmetropia
11/17/2018

56. Total power
Total dioptric power = +42 D Cornea= +42 D Lens= +0 D Refractive state = High Hypermetropia
11/17/2018

57. Total power
CONTACT LENS
11/17/2018

58. Contact lenses +13 D contact lens
For near vision – spectacle correction is needed ( Add +3D )
Advantages-
Less magnification
Less prismatic distortions
Better field of vision
Better cosmetically
Better for uniocular aphakia
Disadvantages-
Requires good maintenance
Cost
cumbersome

59. Intra-ocular lens Lens is placed inside the eye Positions and power
ACIOL- +17D
Iris fixated- +18D
PCIOL- +20 D
Advantages
Good optics
Permanent
Disadvantages-
Surgical procedure - complications

60. Intra Ocular Lens
Parts
Optic
Haptic
Material
PMMA
Silicone
Hydrogel

61. Refractive Corneal Surgery
Keratophakia
Epikeratophakia
Hyperopic Lasik - Can correct small amounts of hyperopia up to 4 D