APHAKIA AND PSEUDOPHAKIA

1. APHAKIA
AND
PSEUDOPHAKIA
PRESENTER- DR. SHWETA
MODERATOR- DR. ANUBHA MITTAL

2. DEFINITION
 Absence of crystalline lens.
 Lens is absent from the pupillary line and
does not take part in refraction.

3. CAUSES
 Congenital absence of lens.
 Surgical aphakia.
 Aphakia due to absorption of lens matter.
 Traumatic extrusion of lens.
 Posterior dislocation of lens.

4. OPTICS OF APHAKIA
CHANGES IN CARDINAL DATA OF EYE
 Eye becomes highly hypermetropic.
 Total power of eye +44 D.
 Anterior focal point becomes 23.2 mm in front of cornea.
 The posterior focal point is about 31mm behind the cornea.
 The two principal points are almost at the anterior surface of cornea.
 Nodal points are located about 7.75 mm behind the anterior surface of
cornea.

6. ACCOMODATION IN APHAKIA
 Total loss of accommodation.
 Glasses for near and distance are required.
BINOCULAR VISION
 Aniseikonia of 5% is compatible with binocular vision
 In aphakia aneisokonia is detrimental to development of normal
binocular vision

7. CLINICAL FEATURES
 Defective vision for near and far.
SIGNS
 Limbal scar
 Anterior chamber is deeper
 Iridodonesis
 Pupil – jet black
 Purkinje’s image test- 2 images
 Fundus examination- hypermetropic small disc
 Retinoscopy- high hypermetropia

8. TREATMENT
 By convex lens.
MODALITIES FOR CORRECTING APHAKIA
 Spectacles
 Contact lens
 IOL
 Refractive corneal surgery

9. BY SPECTACLES
 Most common
 +10 D is used
 Cylindrical lens required in surgically induced aphakia
 Additionally +3 to +4 D for near vision
ADVANTAGES
 Cheap
 Easy and safe method

10. DISADVANTAGES
[1] IMAGE MAGNIFICATION
 Image size depends on axial length and keratometry reading
 1D of convex power leads to about 3 % magnification of image, thus 10 D = 30%
 Difference of image size between the two eyes of about 7 % is tolerable
 beside that give rise to diplopia i.e., two images of one object are seen one small
(from normal eye) and other larger (from aphakic eye).
 Objects appear larger they appear falsely closer than reality, and this leads to
physical in-coordination.
 Not useful in unilateral aphakics

11. [2] ROVING RING SCOTOMA
Edge of a convex lens acts as a prism
Higher the power of the convex lens the greater
is the prism angle (alpha).
Light falling on the prism bends towards its base
by an angle alpha/2 .

12.  Aphakic spectacles, the angle alpha being large, the light falling at the
edge of the lens bends towards the center of the lens (base of prism)
 And does not reach the pupil and is, therefore, not seen.
 Resulting in an area of the visual field which is not visible to the
patient, or scotoma.
 And because the edge of the lens is present all around the lens like a
ring, so it gives rise to a ring shaped scotoma.
 Position of this scotoma is not fixed in the visual field because the eye
keeps moving (or roving) in relation to the aphakic spectacle.

13. JACK-IN-THE-BOX-PHENOMENON

15. [3] PIN CUSHION AFFECT
Magnification of image is more at the
periphery of the lens due to prism
Effect, objects appear stretched out (large,
nearer, elongated in radial direction) at the
corners like a pin-cushion.
Moving objects appear to be faster
Straight lines become curves

16. 4) RESTRICTED VISUAL FIELD
 Both monocular and binocular vision is restricted
 50° all around
5) COLOUR VISION
 PT may complain of colored hue
 Due to absence of natural filter of crystalline lens
6) COSMETIC BLEMISH
 Eyes appear larger
 Seen more in young aphakics
7)THICK AND HEAVY GLASSES

17. CONTACT LENS
ADVANTAGES
 Less magnification of image
 No chromatic aberrations
 No prismatic affect
 Wider field of vision
 Cosmetically acceptable
 Better for uniocular aphakics

18. DISADVANTAGES
 More cost
 Cumbersome to wear-both for young and old age
 Corneal complications may be associated

19. INTRAOCULAR LENS IMPLANTATION
Secondary IOLs-
 PCIOL IRIS CLAW LENS SFIOL

20. REFRACTIVE CORNEAL SURGERY
[1] KERATOPHAKIA
A lenticule prepared from donor cornea
is placed between the lamellae of the
patient’s cornea

21. [2] EPIKERATOPHAKIA
A lenticule prepared from donor
cornea is stitched over the
surface of patient’s cornea after
removing the epithelium

22. PSEUDOPHAKIA
 Condition of aphakia when corrected with implantation of IOL is called
as pseudophakia.
 Also called Artiphakia

23. CALCULATION OF IOL POWER
Most common method is SRK I (Sanders Retzlaff
and Kraff) by regression formula
P = A-0.9k-2.5L
P = power of IOL
A = constant
L = axial length of eyeball

24. SRK II
Based on axial length, A constant is
modified as
If L is <20 mm - A +3
20-20.99 mm - A+2
21-21.99 mm - A+1
22-24.50 mm - A
>24.50 mm - A-1.5
MODIFIED SRK-II
A constant is modified as-
If L is <20 mm - A +1.5
20-21 mm - A +1.0
21-22 mm – A + 0.5
22-24.5 mm- A
24.5-26 mm – A -1.0
>26 mm - A -1.5

25.  SRK/T – Retinal thickness is also measured.
more accurate for long eyes i.e. >26mm.
 Holladay- used in eye with AL 24.5 – 26mm.
 Hoffer q – best for short eyes i.e AL <19mm.

26. REFRACTIVE STATUS OF PSEUDOPHAKIC
EYE
 Emmetropia
 Consecutive myopia
 Consecutive hypermetropia
 Astigmatism

27. EMMETROPIA
 It is produced when the power of the IOL
implanted is exact. It is the most ideal
situation. Such patients require plus
glasses for near vision

28. CONSECUTIVE MYOPIA
occurs when IOL implanted overcorrects the
refraction of eye.
Such patients require glasses to correct
myopia for distance vision.
May or may not require glasses for near
vision.

29. CONSECUTIVE HYPERMETROPIA
occurs when underpower IOL is
implanted
such patients require plus glasses for
distance vision and additional +2 to +3 D
for near vision.

30. ASTIGMATISM
Varying degree of surgery-
induced astigmatism is also
present

31. SIGNS OF PSEUDOPHAKIA
 Surgical limbal / corneal scar
 Anterior chamber is deep
 Mild iridodonesis
 Purkinje image test – 4 images
 Pupil is blackish with shining reflex