This document discusses aphakia, which is the absence of the crystalline lens from the eye. It covers the causes of aphakia, the optics and clinical features of the condition, and the various methods used to correct refractive errors in aphakic patients, including spectacles, contact lenses, and intraocular lenses. The advantages and disadvantages of each correction method are presented, as well as common problems experienced by newly corrected aphakic patients.

1. APHAKIA:
Advantages and Disadvantages of Aphakics
Correction, Types of Aphakic Correction,
Problems of Newly Corrected Aphakics
Suraj Chhetri
B.optometry
16th Batch

2. PRESENTATION LAYOUT
 Introduction
 Causes of aphakia
 Optics of aphakia
 Clinical features
 Types of aphakic correction
 Advantages and disadvantages of aphakic correction
 Problems of newly corrected aphakics

3. INTRODUCTION
• Literally Aphakia means absence of crystalline lens from the
eye
• Optically Aphakia means absence of lens from pupillary area
and it does not takes part in refraction

4. CAUSES OF APHAKIA
• Congenital absence of lens (rare condition)
• Aphakia due to absorption of lens matter after trauma of eye
in children
• Traumatic extrusion of lens from eye ( rare condition)
• Posterior dislocation of lens in vitreous (traumatic or
spontaneous ) optical aphakia
• Surgical aphakia occurring after removal of cataractus lens is
the most commonest presentation
• Heritable disorder associated with dislocation of lens
1. Marfan’s syndrome
2. Weill-marchesani syndrome
3. Homocystinuria

5. Heritable disorders reported with subluxation of lens
1. Alport’s syndrome
2. Craniofacial dysostosis
3. Aniridia
4. Megalocornea
Ocular disorder which can lead to subluxation of lens
1. Buphthalmos
2. Intraocular tumor
3. Mature or hypermature cataract
4. Exfoliation syndrome

6. OPTICS OF APHAKIA
 Can be discussed under following topics
1. Changes in cardinal points of the eye
2. Image formation in the aphakic eye
3. Visual acuity in aphakia
4. Accommodation in aphakia
5. Binocular single vision and aphakia

7. CHANGES IN CARDINAL DATA OF EYE
• Power of eye reduce to 44 D , eye become high hyperopia
• Anterior focal point become 23.2 mm in front of the cornea
• Posterior focal point become 31 mm behind the cornea
• The two principle points are almost at the anterior surface of
cornea
• Nodal points are very near to each other and located about
7.75mm behind the anterior surface of cornea

8. IMAGE FORMATION IN APHAKIA
Average image magnification reported by different methods
of aphakia correction
Spectacle : 33%
Contact lens : 10%
AC IOL : 2-5%
PC IOL : 0 %( about)

9. VISUAL ACUITY IN APHAKIA
• The large image falsifies the VA recorded on the Snellen’s
chart
• VA recorded theoretically better than the actual VA in terms
of visual angle
• A vision of 6/9 with corrected aphakic eye should be
equivalent to 6/12 of an emmetropic eye because of high
magnification of spectacle (33%)

10. ACCOMMODATION IN APHAKIA
• Due to absence or loss of lens from its position
accommodation become zero

11. BINOCULAR SINGLE VISISON AND APHAKIA
• Presence of aniseikonia is detrimental to the development of
BSV ( < 5% aniseikonia )
• Monocular aphakic child , the major hindrance to
development of BSV due to possibility of high aniseikonia
• Unilateral aphakic corrected with spectacle , usually develop
annoying diplopia
• As soon as possible operation of another eye in bilateral
cataract
• Because during this period as the eye dissociated
convergence become poor , streopsis and even fusion may
not be attained

12. OPTICAL DEFECT IN APHAKIA
• Acquired high hyperopia
• Against the rule astigmatism
• Absence of accommodation
• Change in colour vision
• The amount of astigmatism is +1.00 D to +3.00D cyl * 180
But gradually diminishes

13. COLOUR VISION IN APHAKIA
• The crystalline lens constitute a barrier function separating
anterior to posterior segment
• Complete intracapsular extraction of lens results in barrier
deprivation syndrome , it cause disturbances of aqueous
hydrodynamics and biochemical equilibrium
• Removal of lens increases the intensity of incident short
wave-length of light
• These two consequences of cataract surgery may cause
microcirculatory disturbance and structural changes in
macular area of aphakia
• So acquired B-Y colour vision defect seen in aphakic patients 1
1( marion marre, Ernst marre and Dorothea fulle in dresden 1987)

14. CLINICAL FEATURES
• SYMPTOMS
only symptom in aphakia is marked defective vision for far and
near

15. SIGNS
 Most deep anterior chamber (iris has no support )
 Iridodonesis i.e tremulousness of iris
 Pupil is jet black in colour
 Absence of 3rd and 4th purkinje‘s image
 Absence of lens from patellar fossa , best elucidated on slit
lamp examination
 Fundus examination show small hyperopic disc
 Retinoscpy reveals high hypermetropia
 Linear scar at the upper limbus if cataract surgery done

16. TREATMENT
Spectacles
Contact lens
IOL(intraocular lens)
Refractive corneal surgery

17. SPECTACLES
• Optical principle is to correct the error by convex lens of
appropriate power
• Spectacles prescription has been the most commonly
employed method of correcting aphakia in the past

18. Predicting the power of an aphakic lens
• Laurance suggested the power of spectacle lens
• Example : +2.00 D hyperopic before surgery required aphakic
lens is approximately +12.00 D
• Retzlaff and karff described formula of predicting aphakic
refraction
• Where ,L = axial length of eye , K = preoprative keratometry
finding in diopters
Faphakic= +11.00 D + (1/2)Fpre-aphakic
Faphakia = 80.4 – 1.65 L -0.7 K

19. ADVANTAGES OF SPECTACLE CORRECTION
Easy
Safe
Inexpensive

20. DISADVANTAGES OF SPECTACLE CORRECTION
1. Increased retinal image size
2. Decreased field of view
3. Presence of ring scotoma
4. Increased lens aberrations
5. Motion of object in field of view
6. Appearance of the wearer
7. Increased ocular rotations
8. Demand on convergence

21. INCREASED RETINAL IMAGE SIZE
• If correcting lens is placed at anterior focal point of the eye,
size of retinal image directly proportional to the anterior focal
length and inversely proportional to the refracting power of
the eye.
• Retinal image size ( aphakia/emmetropia)
• (23.23/17.05) = (58.64/43.05) = 1.36
• Or increased in retinal image size of 36%
• In practice lens place closer distance decreases the size of
retinal image but in aphakia magnification (aprrox. 28%)

22. • In B/L aphakia greatly increased image size means that
aphakic patients must adapt to new size- distance relationship
• In unilateral aphakia corrected with spectacles BSV impossible
due to high magnification
• Sometimes aphakic patients achieve central visual acuity that
exceeds the best VA obtained before surgery due to
magnification of retinal image size
• Increased magnification may permit the prescribing of
weaker reading addition
Familiar object not only appear to be much larger , they
also appear to be much closer

23. DECREASED FIELD OF VIEW
• Base to the center prismatic effect of high plus lens reduce
the size of a field of view
• Peripheral field of view
tanφ = y (E-F)
where, φ =one half of angular field of view
E = vergence of light at entrance pupil of eye
y = one half of lens aperture
Central field of view
tanθ= y ( S-F)
Where S = vergence of light at center of rotation of eye
F = power of the correcting lens

24. • With standard parameter lens of 12.50 D show loss of
peripheral field of view only about 7% but loss of macular
field about 17 %
PRESENCE OF RING SCOTOMA
Base in prismatic effect of strong plus lens causes angular gap
in object space completely around the lens which is know as
ring scotoma
center to the ring scotoma wearer has corrected vision

25. • Ring scotoma moves in opposite direction of the eye
movement ( roving eye scotoma )
• Ring scotoma creates different problems especially from
2 - 10 feet ,which is generally in ordinary room
Factors effect on size and position of ring scotoma
1. Lens power
2. Vertex distance
3. Lens size
4. Pupil size
5. Lens thickness
6. Base curve
Except vertex distance and pupil size all other show
direct relation with size of ring scotoma

26. JACK-IN THE BOX PHENOMENON
• Object seems to jump in and out of field of view as it moves
out of and into the ring scotoma
• Simply sudden disappearance and sharp reappearance of the
object in visual space with ring scotoma

27. INCREASED OCULAR ROTATION
• Angle of eye turning in changing fixation from one object
point to another increases in comparison to emmetropic.
• Due to prismatic effect

28. INCREASED LENS ABERRATIONS
• Spherical and coma occurs only for large aperture so aphakic
with small pupil are affected very little by these aberrations
• Off axis aberrations ,oblique astigmatism and curvature of
image which can effect on patients visual acuity and contrast
• Tscherning ellipses limits up to -23.00D to + 8.00 D so it could
not cover the aphakic patients
• So oblique astigmatism can eliminated by making at least one
surface aspheric

29. • Pincushion distortion- change in magnification across the field
of view of a lens. To control distortion in aphakic steeply
curved lenses required
• Axial and transverse chromatic aberration can not be
eliminated by single refractive medium
• Transverse chromatic aberration is more bothersome because
image location and magnification differ for different
wavelength ,which primarily the tangential meridian of
oblique astigmatism

30. • Thus controlling the tangential error effect , transverse
chromatic aberration can be attenuated
oblique astigmatism and curvature of image are the most
important aberration and have been the main targets of
lens designer

31. MOTION OF OBJECT IN THE FIELD OF VIEW
• When high plus error holds the eyes steady and moves head
to any object then marked reversed motion (against motion)
of the field of view is experienced
• This is due to prismatic( base in ) in the direction of head
movement
• This motion often referred to as swim
• swim can be avoided by moving the eyes from one fixation
point to another while the head stationary but this may
produce distortion
• Best procedure is to turn head slowly so that head and eye
moves slowly

32. APPEARANCE
• Apparent enlargement of eye and their unusual appearance
behind bulbous , thick lens
• General awkwardness of the patients bearing and
movement
( both impression originate from magnification and distortion
effect of the lens )
• lenticular lens provide good optical performance in central
part but poor cosmetic appearance ( bull’s eye or fried egg)
due to high magnification confined to central portion of the
lens

33. DEMANDS OF CONVERGENCE
• In ordinary condition, convergence of visual axis towards near
fixation point creates base out prismatic effect
• So while reading eye must converge more than low power
spectacle . This can place strain to positive fusional vergence
and may lead to discomfort
• This effect can be reduced by placing distance center closer
together than the patient’s distance PD
• Or by incorporate base in prism with aphakic lens

34. CONTACT LENSES
• Aphakic contact lens is not very common in practice
• It is treatment of choice who are unsuitable for IOL
implantation or who have experienced a failed IOL implants
• Common in unilateral aphakia
• Contact lens provide less image magnification (about 5-7%)
which make possibility of BSV in uniocular aphakia
– Provide BSV only where fellow eye has useful vision
• Can achieve only 140 seconds of arc (titmus)
• 80% with intermittent suppression 2–
2( Guilin et al. 1980)

35. GENERAL PROCEDURE
• 6-10 weeks post surgical to permit healing/ settling of power
• Find any contraindication for CL fit
• Spectacle Refraction
• Measurement of Ocular dimension
– Keratometry
– Pupil size, shape, position
– Eyelids integrity
– CL fitting
• Over refraction (astigmatism / near addition)
• BSV
– After care

36. CONTACT LENS OPTIONS FOR APHAKIA
• Hydrogel lenses : cases with low astigmatism or failed RGP
lens wearers
• RGP lenses : cases with high corneal astigmatism and corneal
distortion
• Silicone elastomer : cases with low astigmatism and pediatric
aphakic patients
• Scleral lenses : patients with significant corneal distortion
• Tinted lenses :to attenuate bright light and offer some UV
protection
• DW or EW contact lenses based on manual dexterity . EW is
best suited to poor lens handling patients

37. PEDRIATIC CONTACT LENS FITTING
IMPORTANT AND STRONG NECESSITY
• Time of fitting
• Length of wearing
• Lens material
• Fitting

38. FITTING TECHNIQUE
RGP lenses
• Keratometry based technique
 Record post-operative keratometry
 Start trial lens 0.5 – 1 mm flatter
 Centration and movement is determine
 Study flourescein pattern
o Minimal apical clearance is the goal
 Retinoscopy over the lens
 Calculate final lens prescription

39. FITTING TECHNIQUE
RGP Lens
Diagnostic lens fitting: experience based
 Insert the diagnostic lens
 Observe centration and movement
 Fluorescein pattern study
 Central posterior area steeped until small apical air bubble
appear
 Final trial lens flatter by 0.5-1 mm
 Push up test
 Retinoscopy over lens
 Calculate final lens power

40. FITTING TECHNIQUE
Soft lens
 Limit the feasibility of frequent lens handling
 Pediatric soft lens parameter
o BC : 7.5- 7.8 mm
o TD : 13.7mm
o Power : + 20.00 D to 35.00 D
• Fitting procedure , same as adult contact lens fitting
• Younger the child and higher the power , steeper is the lens
• Diagnostic lens fitting technique

41. FITTING SILICONE ELASTOMERS
• B & L silsoft
• Parameters
 Material : elastoflicon
 Water content : 0.2%
 FDA material group I
 Oxygen permeability (DK) : 340
 Oxygen transmission : 70
 BC : 7.5 , 7.7 , 7.9 , 8.1 , 8.3 mm
 TD : 11.30 mm , 12.50 mm
 Power : +12.00 D to +20.00 D (in +1.00 D steps)
+23.00 D to + 32.00 D ( in +3.00 D steps)
 Back optic zone : 7 mm
 Central thickness : 0.51mm to 0.71 mm

42. FITTING PROCEDURE
• Examine that eye are ready to fit with contact lens
• Determine the parameter of the first trial lens
 Corneal diameter
 Keratometry (optional)
 Base curve selection : should be one step flatter than the
steepest lens available
As per age starting base curve
< 1 year = 7.5 mm
1-2 year = 7.7 mm
> 2 year = 7.9 mm

43. FITTING PROCEDURE
• Approximate power = add + 2.00 to 3.00 D more power in
mean refractive error
Starting point could be
+ 30.00 D for 6 month child
+ 27.00 D for 1 year child
+23.00 D for 2 year child
+21.00 D for 3 year child

44. ADVANTAGE OF CONTACT LENS IN APHAKIA
• Image magnification is 7-8 % and this
magnification is usually tolerated by the
patients
• Increase in the visual field.
( both central and peripheral)
• In monocular cases diplopia is usually
absent with retention binocularity.
• Cosmetically it is well accepted.

45. DISADVANTAGES OF CONTACT LENS IN APHAKIA
• Foreign body sensation
• Corneal complications
• Lens spoilage
• Spectacles may be required over contact
lenses for reading
• High +Rx lenses more likely to decentered

46. ADVANTAGES OF HYDROGEL LENSES
• Offer good initial comfort
• Less prone to displacement
• Offer good centration
• Stable positioning of the optics over the eye during the
blinking and eye excursions
• Stabilize promptly , after insertion

47. DISADVANTAGES OF HYDROGEL LENSES
• Poorer oxygen transmission
• Aggravate existing dry eye problems
• Greater care and maintenance needs
• Higher overall costs
• Limited parameter available
• Handling can be more difficult
• May discolor with topical medications
• Uptake of preservatives

48. RGP LENS ADVANTAGE IN APHAKIC PATIENTS
• Provide optimum vision correction
• Fewer eye complications
• Easier lens care
• Customized designs possible
• Curves and BVP can be modified

49. IOL IMPLANTATION
• IOL implantation in cataract ,has good outcome
• Difficult to implant IOL in congenital cataract due to small
size of eyeball
• IOL power may hamper the emmetropization process due to
inappropriate IOL size and power
• In unilateral cases, primary implantation is indicated as soon
as the patient is fit for anesthesia, ideally between 2 and 3
months of age. The earlier the surgery is done, the better the
chance that deep amblyopia can be overcome3
3(Yanoff & Duker: Ophthalmology, 3rd ed.)

50.  In case of unilateral congenital cataract most studies
suggested that surgery after 6 weeks of life is less likely to
result good visual acuity3
3(systemic pediatric ophthalmology 3rd ed.)
 In B/L congenital cataract difference between surgery of two
eye must be less than 6 weeks
 B/L congenital cataract is more common than unilateral
 If major blood vessels can not be distinguished from
central portion of the cataract significant visual deprivation
can be expected from moderately size partial cataract 4
4 (systemic pediatric ophthalmology 3rd ed.)

51. • Rapid growth of eye ball up to 2 years of age makes difficult to
chose power of IOL
• Ideally, the pediatric IOL should be available in diameters of
the range 10.5–12mm
• The material from which the IOL is made must have a long
track record of safety. PMMA( Polymethyl methacrylate )is
currently the best material to be used for children5
5(Yanoff & Duker: Ophthalmology,3rd ed)
IOL in pediatric age group

52. Some author prefer under correction by 30% to child below the
age of 1 year

53. ADVANTAGES OF IOL IMPLANTAION
• Little image magnification
• No spherical and prismatic aberration
• Minimum or no aniseikonia
• Normal peripheral field
• Cosmetically well accepted

54. DISADVANTAGES OF IOL IMPLANTATION
• Risks and complications may be more
o Infections
o Expulsive choroidal hemorrhage
o Cystoid macular edema
o Retinal detachment
o Corneal edema
o Dislocation of IOL ( child rubbing eye)
o Posterior capsular opacities
• It needs specially qualified surgeons and
sophisticated instrument.
• The cost is more

55. REFRACTIVE CORNEAL SURGERY IN APHAKIA
• Refractive corneal surgery is under trial for correction of
aphakia . It includes
• Keratophakia : keratoplasty in which corneal tissue from a
donor is frozen, shaped, and inserted into the cornea of a
recipient
• Epikerakophakia : surgical procedure in which a donor cornea
is transplanted to the anterior surface of the patient's cornea
• Hyperopic – laser assisted in situ keratomileusis : corrective
eye surgery in which a flap of the corneal surface is raised and
a thin layer of underlying tissue is removed using a laser

56. PARAMETERS OF APHAKIA LENSES
• Critical lens specification and fitting includes
 Vertex distance
 Pantoscopic tilt
 Centration
 Lens weight and thickness
 Adjustment of the spectacles

57. VERTEX DISTANCE
Effective power Fb = (Fa/1-dFa)
Where d = vertex distance ,
As the vertex distance reduce though power of plus lens
become more powerful but image made small
Thus it is advice to place spectacles as much as close to eye to
reduce vertex distance

58. PANTOSCOPIC TILT
• Spectacle lens are tilted around horizontal axis to improve
their appearance on wearer’s face
• Tilt is typically 8-10 degree
• In aphakia to minimize the weight , optical center should fall
at the geometric center and the optic axis should pass
through the center of rotation by altering the vertical position
of the frame on the face

59. WEIGHT AND THICKNESS
• Lens that correct aphakia are thick and heavy
• Weight can reduce by CR-39 plastics but thickness increased
(lower index of refraction)
• Thickness reduce by high index glasses but weight remain
heavy
• Lenticular aphakic lens reduces both thickness and weight
but unattractive
• Weight and thickness can reduce by using symmetrical small
eye sized frame and lenses with essentially knife- edge
thickness

60. POSITION OF OPTICAL CENTRE
• Small error in PD produce significant effect in aphakic lens
• Corneal reflection method prefer for monocular PD in
aphakia (irregular pupil due to surgery)
SPECTACLE ADJUSTMENT
Because of aphakic lens are heavy , they tend to slip down on
the nose
Small misalignment and change in position introduce large
error

61. SOME ADDITIONAL FACT ABOUT APHAKIC LENS DESIGN
• Aspheric front surface reduce the effects of aberration ,
weight ,thickness , magnification and size of ring scotoma by
reducing power in periphery of lens
• One of the main advantage of aspheric front surface , it
improve appearance of lens
• Steeper back surface curve has advantage of reducing
distortion , lens reflections and sensitivity to difference to
vertex distance

62. • Straight – top segment is relatively wide at the top and has
little image jump as the line of sight enter the segment
• Increasing amount of oblique astigmatism induced as the
visual axis move downward through the lens
• So bifocal segment of aphakic lenses should place as high as
possible

64. High chance of UV radiation damage to aphakic retina, due to
 In absence of lens ,increased amount of concentrate
radiations energy receives by the retina
 Coefficient of absorption of radiation by retina is greater for
UV radiation than that for visible radiation
So it is essential to incorporate UV absorbing filter and
aphakic patient also wish to have one of the light tint for
general wear
such tint have advantage of improving the appearance of
lenses and reducing glare

65. DISPENSING-LENS SELECTION
• Aim of Lens selection
– Reduce lens weight.
– Reduce lens thickness
– Reduce spectacle magnification
– Increase field of view
– Minimize lens aberration
– Offer choice of optimum multifocal style and
position
– Provide protection from glare and UV radiation.

66. LENS SELECTION FOR APHAKIA
– High index plastic
– Aspheric lenses
– Lenticular lenses
– Light tints and UV protection
– Anti reflection coating

67. FRAME SELECTION FOR APHAKIC LENS
• Effective diameter of lens increases as the frame deviates
from round or oval shape which is not more than 2 mm larger
than eye size
• Frame difference greater than 9mm should be avoid because
high plus lens tend to be thick on top and bottom edges which
gave apparent look high plus lens even stronger

68. • Because field of view increased and magnification decreased
as plus lens are moved closer to the eye , frame should hold
closer as possible to the eye
• Adjustable nosepads become more necessity as they offer
advantage of versatility in allowing modification of vertical
position of the frame

69. • Comfort cable temples help to the glasses from slipping down
the nose
• Frame with thick eyewires should be avoid because an
eyewire may increase the width of the ring scotoma

71. UNILATERAL APHAKIA
• Spectacle correction in unilateral aphakia have
following difficulties
1. Difference in size of retinal image of two eyes
2. Large prismatic effects encountered in the peripheral portion
of the lenses
• Magnification difference is so great that BSV impossible . This
high magnification intolerable to the patient , so we have
three options
i. Not correct the operated eye
ii. Correct and occlude the un-operated eye
iii. Prescribe contact lens for aphakic eye

72. • Unilateral aphakia corrected by contact lens , the amount of
residual aniseikonia (5-7%) makes normal BSV difficult .
Yet many unilateral aphakics appears to have comfortable
vision with contact lens
• Residual aniseikonia in aphakia corrected by contact lens
depends upon following factors
A. Refractive error before operation and its type ( axial or
refractive )
B. Any alteration of power of cornea caused by the surgery
C. Individual variations in the dimensions of the primary
refracting component
D. Shape factor for the spectacle magnification formula

73. • Ogle, Burian and Bannon plotted residual aniseikonia (unilateral
aphakia) on the basis of pre-cataract data, which summarized
as
 In high myopia before cataract onset( where axial or
refractive) , residual aniseikonia can be minimize by fitting
contact lenses of the both eye
 In high hyperopia before cataract onset (whether axial or
refractive ) , residual aniseikonia can be minimize by fitting
contact lens on the aphakic eye and spectacle lens on the un-
operated eye

74.  Enoch has suggested that BSV may be restored in unilateral
aphakia by fitting the aphakic eye with reverse Galilean
telescope which brings about minification of retinal image
 The plus necessary for eyepiece of telescope is added to
contact lens prescription for aphakic eye and minus power of
telescope objective is supplied in the form of spectacle lens

75. PROBLEMS OF NEWLY CORRECTED APHAKICS
• Annoying diplopia if uniocular aphakia corrected with
spectacles
• Due to high magnification familiar object not only appeared to
be much larger , they also appeared to be much closer
• Peripheral distortion when aphakia correction with spectacle

76. • Asthenopia due to increase demand of convergence
• B-Y colour vision defect
• Appearance of ring scotoma in ordinary room condition
• Poor cosmetic appearance

77. REFERENCES