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• Presented by – Ashith Tripathi (B. Optom)
• Guided by – Mr. Gaurav Dubey Sir ( M.
Optom, Faculty at UPUMS, Saifai, Etawah, U.
P.)
APHAKIA
Literally means – absence of crystalline lens from the eye.
Optical point of view – it may be considered a condition in which the lens is
absent from the pupillary area and does not take part in refraction.
It produces a high degree of hypermetropia.
PSEUDOPHAKIA -
The condition of aphakia when
corrected with implantation of an
IOL .
Refractive status of a
pseudophakic eye –
1. Emmetropia
2. Consecutive myopia
3. Consecutive hyperopia
4. SIA
CAUSES
• Congenital absence of lens. ( may occur is a very rare condition.)
• Surgical aphakia ( commonest presentation.)
• Aphakia due to absorption of lens matter.
Traumatic extrusion
of lens from the
eye.
Posterior dislocation
of lens in vitreous
produces optical
aphakia
OPTICS OF APHAKIA
Von Helmholtz
Benito Daza De Valdes
Optics of aphakia can be discussed under following heads:
• Changes in cardinal data of eye
• Image formation in the aphakic eye
• Visual acuity in aphakia
• Accommodation in aphakia
• Binocular vision and aphakia
Changes in cardinal data of the eye
• The eye becomes highly hypermetropic.
• Total power of eye is reduced to about + 44 D from +
60 D.
• Anterior focal point becomes 23.2 mm in front of eye.
• Posterior focal point is about 31 mm behind the
cornea,( about 7 mm behind the eyeball ).
Image formation in aphakia
• The image size can vary from 20% to as much as 50%.
• Average image magnification reported by different methods of aphakia
correction –
• Spectacle – 33%
• Contact lens – 10%
• Anterior chamber IOL – 2 to 5 %
• Posterior chamber IOL – 0 %
Visual acuity in aphakia
• The Snellen’s visual acuity in spectacle –
corrected aphakia is falsified due to a large
image size.
• The visual acuity of 6/9 in a spectacle –
corrected aphakic eye should be
considered equivalent to 6/12 of an
emmetropic eye.
Accommodation in aphakia
• There occurs a total loss of accommodation due to
absence of lens.
• Bifocal or two separate pairs of glasses – one for
distance vision and another for near vision are
required.
• Progressive or varifocal glasses, perhaps, provide
better alternative.
Binocular vision and aphakia
• Presence of aniseikonia
• In monocular aphakic children –
aniseikonia of 30% due to anisometropia. ( such children usually develop
suppression amblyopia.)
when spectacles are given for correction of uniocular aphakia in adult patient –
binocular single vision is difficult or impossible. ( usually develop diplopia )
In binocular aphakia – binocularity is not always present.
• IOLs – largely solved the problems associated with uniocular aphakia.
Clinical features
• Symptoms – the only symptom in aphakia is marked defective vision for near
and far.
• Signs –
• Limbal scar may be seen in surgical aphakia,
• Anterior chamber is deeper than normal,
• Purkinje image test shows only two images,
• Slit lamp examination, fundus examination, retinoscopy .
Treatment
• Optical principle is to correct the error by convex lenses of appropriate
power.
• Modalities of correcting aphakia include –
1. Spectacles,
2. Contact lens,
3. IOL
4. Refractive corneal surgery.
spectacles
• It is most commonly employed method of correcting
aphakia in the past.
• An addition of +3 to +4 D is required for near
vision to compensate for loss of accommodation.
• Advantages – cheap, easy and safe method.
Disadvantages of spectacles
• It includes –
• Image magnification – 30%
average
• Spherical aberrations – pin
cushion distortion
Prismatic aberration produces Roving
– ring scotoma ( usually describe as
jack – in - the – box phenomenon)
• Restricted field of vision – about 50 degree around
• Coloured vision – complain of coloured hue in the vision ( due to natural
filter of crystalline and chromatic aberration )
• Problem of near vision – thick bifocal glasses are especially difficult to
adjust with.
• Cosmetic blemish – thick glasses are cosmetically embarrassing.
• Cumbersome to use – very thick and heavy
CONTACT LENSES
• Advantages –
1. Less magnification of image
2. Elimination of aberration and prismatic effect of thick glasses
3. Wider and better field of vision
4. Cosmetically more acceptable
5. Better suited for uniocular aphakia
Disadvantages
• More cost
• Cumbersome to wear, especially in
old age and in childhood
• Corneal complications may be
associated
Intraocular lens implantation –
nowadays best available method of
correcting aphakia .
Anterior chamber IOL implant
Posterior chamber IOL implant
Refractive corneal surgery
1. Keratophakia –
lenticular prepared
from the donor
cornea is placed
between the lamellae
of the patient`s
cornea.
•Epikeratophakia–
a lenticule prepared from the donor
cornea is stitched over the surface
of patient`s cornea after removing
the epithelium.
• Hyperopic laser – assisted in situ keratomileusis ( LASIK ).
Reference
• Optics and refraction - A. K. Khurana
• Photos - from Google
• Wikipedia

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Aphakia - Ashith Tripathi

  • 1. • Presented by – Ashith Tripathi (B. Optom) • Guided by – Mr. Gaurav Dubey Sir ( M. Optom, Faculty at UPUMS, Saifai, Etawah, U. P.)
  • 2. APHAKIA Literally means – absence of crystalline lens from the eye. Optical point of view – it may be considered a condition in which the lens is absent from the pupillary area and does not take part in refraction. It produces a high degree of hypermetropia.
  • 3. PSEUDOPHAKIA - The condition of aphakia when corrected with implantation of an IOL . Refractive status of a pseudophakic eye – 1. Emmetropia 2. Consecutive myopia 3. Consecutive hyperopia 4. SIA
  • 4. CAUSES • Congenital absence of lens. ( may occur is a very rare condition.)
  • 5. • Surgical aphakia ( commonest presentation.) • Aphakia due to absorption of lens matter.
  • 7. Posterior dislocation of lens in vitreous produces optical aphakia
  • 8. OPTICS OF APHAKIA Von Helmholtz Benito Daza De Valdes Optics of aphakia can be discussed under following heads: • Changes in cardinal data of eye • Image formation in the aphakic eye • Visual acuity in aphakia • Accommodation in aphakia • Binocular vision and aphakia
  • 9. Changes in cardinal data of the eye • The eye becomes highly hypermetropic. • Total power of eye is reduced to about + 44 D from + 60 D. • Anterior focal point becomes 23.2 mm in front of eye. • Posterior focal point is about 31 mm behind the cornea,( about 7 mm behind the eyeball ).
  • 10. Image formation in aphakia • The image size can vary from 20% to as much as 50%. • Average image magnification reported by different methods of aphakia correction – • Spectacle – 33% • Contact lens – 10% • Anterior chamber IOL – 2 to 5 % • Posterior chamber IOL – 0 %
  • 11.
  • 12. Visual acuity in aphakia • The Snellen’s visual acuity in spectacle – corrected aphakia is falsified due to a large image size. • The visual acuity of 6/9 in a spectacle – corrected aphakic eye should be considered equivalent to 6/12 of an emmetropic eye.
  • 13. Accommodation in aphakia • There occurs a total loss of accommodation due to absence of lens. • Bifocal or two separate pairs of glasses – one for distance vision and another for near vision are required. • Progressive or varifocal glasses, perhaps, provide better alternative.
  • 14. Binocular vision and aphakia • Presence of aniseikonia • In monocular aphakic children – aniseikonia of 30% due to anisometropia. ( such children usually develop suppression amblyopia.) when spectacles are given for correction of uniocular aphakia in adult patient – binocular single vision is difficult or impossible. ( usually develop diplopia ) In binocular aphakia – binocularity is not always present.
  • 15. • IOLs – largely solved the problems associated with uniocular aphakia.
  • 16. Clinical features • Symptoms – the only symptom in aphakia is marked defective vision for near and far. • Signs – • Limbal scar may be seen in surgical aphakia, • Anterior chamber is deeper than normal, • Purkinje image test shows only two images, • Slit lamp examination, fundus examination, retinoscopy .
  • 17. Treatment • Optical principle is to correct the error by convex lenses of appropriate power. • Modalities of correcting aphakia include – 1. Spectacles, 2. Contact lens, 3. IOL 4. Refractive corneal surgery.
  • 18. spectacles • It is most commonly employed method of correcting aphakia in the past. • An addition of +3 to +4 D is required for near vision to compensate for loss of accommodation. • Advantages – cheap, easy and safe method.
  • 19. Disadvantages of spectacles • It includes – • Image magnification – 30% average • Spherical aberrations – pin cushion distortion
  • 20. Prismatic aberration produces Roving – ring scotoma ( usually describe as jack – in - the – box phenomenon)
  • 21. • Restricted field of vision – about 50 degree around • Coloured vision – complain of coloured hue in the vision ( due to natural filter of crystalline and chromatic aberration ) • Problem of near vision – thick bifocal glasses are especially difficult to adjust with.
  • 22. • Cosmetic blemish – thick glasses are cosmetically embarrassing. • Cumbersome to use – very thick and heavy
  • 23. CONTACT LENSES • Advantages – 1. Less magnification of image 2. Elimination of aberration and prismatic effect of thick glasses 3. Wider and better field of vision 4. Cosmetically more acceptable 5. Better suited for uniocular aphakia
  • 24. Disadvantages • More cost • Cumbersome to wear, especially in old age and in childhood • Corneal complications may be associated
  • 25. Intraocular lens implantation – nowadays best available method of correcting aphakia .
  • 27.
  • 29. Refractive corneal surgery 1. Keratophakia – lenticular prepared from the donor cornea is placed between the lamellae of the patient`s cornea.
  • 30.
  • 31. •Epikeratophakia– a lenticule prepared from the donor cornea is stitched over the surface of patient`s cornea after removing the epithelium.
  • 32. • Hyperopic laser – assisted in situ keratomileusis ( LASIK ).
  • 33.
  • 34. Reference • Optics and refraction - A. K. Khurana • Photos - from Google • Wikipedia