2. Aphakia
Aphakia means absence of crystalline lens
From an Optical point of view, aphakia is the absence
of the lens in the pupillary area.
3. CAUSES OF APHAKIA
Congenital aphakia
Surgical aphakia – removal of lens as in cataract
extraction
Aphakia due to absorption of lens – sometimes seen in
children after trauma
Traumatic extrusion of lens
Posterior dislocation of lens into the vitreous causes
optical aphakia
4. OPTICS IN APHAKIA
The lens is important in refraction and hence its removal
results in considerable decreased in the refractory power
of the eye
The eye becomes highly hypermetropic
The power of eye decreases from +60D to +44D
The power of accommodation lost
The posterior focal point lies behind the eyeball
5. CLINICAL FEATURES
Symptoms
Defective vision – due to high hypermetropia and loss
of accommodation
Erythropsia and cyanopsia – due to entry of infrared and ultraviolet
rays in the absence of the crystalline lens
6. Signs (anterior to posterior)
Limbal scar in case of surgical aphakia
Deep anterior chamber
Iridodonesis – tremulousness of the iris due to loss of support of
lens
Jet Black pupil
Fundus examination reveals a small hypermetropic fundus
Retinoscopy shows high hypermetropia
7. Treatment
:
Spectacles
Spectacles should be prescribed with about +10D lens for correction
of aphakia
It should also include correction for surgical astigmatism and +3D
for near vision
Nowadays spectacles are not preferred for use in aphakia
8. Methods of correction
• Unilateral
• Intraocular lens implant
• Contact lenses
• Epikeratophakia Laser surgery
• Bilateral
• Intraocular lens implant
• Spectacles – must be correctly centred and accurately fitted
• Contact lenses
9. Aphakia in children- Clinical picture
• Know-
• Unilateral/ bilateral
• Type & location of cataract
• Duration of cataract persisting
• Cause of the cataract & proper history
• Visual Acuity- generally have severe amblyopia of stimulus
deprivation type and often strabismic type in addition. In some, VA
may be normal
• Cover test- Adults may have latent, intermittent or manifest
strabismus. Children frequently have manifest secondary strabismus
10. Ocular motility & Binocularity--In cases of traumatic cataract, ocular
motility may be limited where there has been associated globe and/or
extraocular muscle damage
• Adults may demonstrate binocular single vision with latent or
intermittent strabismus. Children will not have binocularity due to
presence of dense amblyopia.
11. Problems with unilateral aphakia
• Secondary divergent deviation in adults
• – Secondary convergent deviation in young children
• Stimulus deprivation amblyopia plus strabismus amblyopia
12. Management strategy
• intraocular lens implant,
• contact lenses or
• epikeratophakia.
• Intraocular lenses give the least increase in image size(placed on
entrance pupil).
• Spectacles may be used with bilateral cases, but problems arise with
aberrations, prismatic effects, centration and weight, and they must
be a good fit to encourage tolerance with young children.
• Contact lenses provide a wider field of view than spectacles but have
a risk of infection and lack of oxygen supply to the cornea with
prolonged wear.
14. Adults
• With intermittent deviations, orthoptic exercises are used to improve
fusional reserves.
• The aim is for parallel visual axes with functional cases. In cosmetic
divergent deviations, aim for a slight overcorrection. Where there has
been a loss of fusion, occlusion, Bangerter filters or occlusive contact
lenses may be required (McIntyre & Fells 1996)
15. Children
• There is often a poor prognosis for vision in unilateral cataracts.
• A high incidence of ophthalmic complications, delay in establishing
daily contact lens wear and a failure to achieve good compliance with
occlusion therapy are factors associated with a poor visual outcome
• However, outcomes continue to improve with earlier surgery, better
optical correction of aphakia and occlusion methods (Ruth & Lambert
2006) and it is possible to achieve binocular function with early
surgery and less occlusion in those with good compliance with
contact lens and occlusion therapy (Brown et al. 1999).
• Contact lenses are fitted and occlusion is implemented to improve
vision. These patients usually require full-time total occlusion. Where
traditional occlusion has failed, occlusive contact lenses may be
trialled
16. • Posterior chamber intraocular lens implantation is a safe and
effective method for treatment of cataracts in children over the age
of 2 years. However, there is considerable debate as to the safety and
long-term effects of intraocular lens implantation in neonates.
17. Intraocular Lens Implantation &
Refractive Surgery
This is the preferred method nowadays
The lens can be implanted in the capsular bag or in the anterior
chamber
It eliminates most of the disadvantages associated with the use of
spectacles or contact lenses
Disadvantage include the complications associated with surgery
Refractive surgeries
18. References
• Borish Clinical Refraction
• Clinical Procedures in Primary Eye Care, Elliott
• Clinical optics, American Academy of Ophthalmology
