Transcript Optical Correction of Pediatric Aphakia

Dr. Habes Batta
Pediatric Ophthalmic Consultant and Strabismologist
The correction of aphakia differs between
children and adults
 Myopic shift.
 Immature visual systems - risk of developing amblyopia
 More postoperative inflammatory response after the
Sx.
ANATOMY
 During early childhood, the refractive elements of the eye
undergo radical changes.
 At birth the cornea has refractive power ~ 52D in preterm
infants and ~ 48.0 D in term infants.
 At age 18 months, the cornea has refractive power ~ 43.5D.
 From this age on the curvature of the cornea remains about
the same.
 The crystalline lens undergoes a reduction in its power
during early childhood until age of 6 yrs.
ANATOMY
 The most important change - axial elongation.
 At birth the mean AxL = 17.0 mm.
 The first phase 0-2 years of life, AxL increasing ~ 4.4
mm.
 The second phase 2-6 years, AxL increasing ~ 1.5 mm.
 The last phase 6-13 yrs, AxL increasing ~ 1.0 mm.
AMBLYOPIA
 Animal experiments have shown
that visual deprivation during a
“sensitive period” results in
anatomic changes in the
visual cortex.
 These changes result in amblyopia.
 The sensitive period in humans extends up to 7 years of age.
 Because of the visual inattention of infants during early infancy, visual
deprivation during the first 6 weeks of life appears to have no lasting
consequences.
 However, after this 6-week “grace period,” even short intervals of visual
deprivation can have profound effects on the development of the
central visual pathways.
AMBLYOPIA
 Earlier visual deprivation - more severe amblyopia.
 Unequal stimulation of the two eyes - damaging the
development of the central visual pathways.
 Unilateral cataract or unilateral uncorrected aphakia -
profound effects on the visual development of the deprived
eye.
 The need to provide equal visual stimulation - important
considerations when trying to decide how best to correct a
child's eye optically.
INTRAOCULAR LENSES
 Numerous studies have shown improved visual outcomes in age-
matched children corrected with IOLs versus contact lenses.
 Ben Ezra and coworkers reported that 65% of children with
unilateral cataracts were able to see 20/40 or better after cataract
surgery and IOL implantation, compared with only 35% of eyes
corrected with contact lenses.
 Similarly, Greenwald and Glaser reported 20/40 or better visual
acuity in 75% of children 2 years of age or older after cataract
surgery and IOL implantation, compared with 48% of eyes
corrected with contact lenses.
 The improved visual outcome associated with IOLs -
related to the constancy of the optical correction.
 Pseudophakic children have been reported to have
superior binocularity and a lower incidence of
subsequent strabismus than children corrected with
contact lenses.
 Convenience of IOLs.
 Contact lenses require amount of care.
 IOLs also provide a constant correction, whereas even the
most compliant child will have periods of time when the
contact lens cannot be worn because of an ocular infection
or a lost or damaged lens.
 IOL provides an immediate optical correction after
implantation, whereas a delay of several days or even weeks
often occurs before contact lenses or glasses are dispensed.
 IOLs, unlike contact lenses, are not associated with
ongoing expenses.
 There is a controversy regarding the optimal technique for IOL
implantation in a child's eye.
 A child's eye differs in several significant ways from an adult eye.
 Opacification of the posterior lens capsule after cataract surgery.
 PCO can occur a few weeks after cataract surgery or years later.
 In older children, the posterior capsule is frequently left intact at
the time of cataract surgery and opened with a Nd:YAG laser
when opacification occurs.
 Alternatively, a primary posterior capsulotomy will be created
with anterior vitrectomy.
 The type of IOL implanted may also affect the incidence of posterior capsule
opacification.
 IOLs that create a symmetric radial stretch of the posterior capsule may increase the
contact between the convex IOL surface and the posterior capsule, thereby creating a
barrier to the central migration of epithelial cells.
 Acrylic lenses
may be associated
with both a
lower incidence
and a delayed onset
of posterior capsular
opacification.
 Possible reasons for the lower incidence of posterior capsular opacification with acrylic
lenses include the square edge of the lens, greater biocompatibility, and increased
capsular adherence.
 Finally, heparin-surfaced modified PMMA lenses have been reported
to reduce the cellular deposits on IOLs in a child's eye.
 Children are more likely to traumatize their eye after
cataract surgery.
 Superior incision has the advantage over a temporal
incision of allowing the brow to protect the incision
site.
 A sutureless incision is inappropriate in children.
POWER OF THE IOL
If an IOL --- < 6 years of age, the
ongoing axial elongation in the
presence of a relative stable corneal
curvature means that a myopic
shift will occur.
POWER OF THE IOL
 A variety of approaches have been used to compensate
for the myopic shift that occurs in pediatric eyes after
IOL implantation.
 IOL power is chosen that initially undercorrects a
child's eye ---------
 Because genetic factors also influence axial elongation,
they should also be factored into the decision as to
what IOL power to implant.
CONTRAINDICATIONS TO IOL
IMPLANTATION
 Active uveitis is an absolute contraindication.
 Microphthalmia.
CONTRAINDICATIONS TO IOL
IMPLANTATION
 Anterior chamber IOLs may result in corneal
endothelial decompensation or chronic inflammatory
changes of the uveal tract over time.
 Scleral fixation IOLs!
 The sutures may in time erode either through the
conjunctiva, resulting in endophthalmitis, or through
the sclera, resulting in subluxation of the IOL.
CONTACT LENSES
PediaBausch & Lomb SilSoft
contact lenstric
The treatment of choice in infants with bilateral aphakia
and in children of all ages with active uveitis or
inadequate capsular support.
 Contact lenses have several distinct advantages over
IOLs as a means of correcting aphakia in children.
 The power of the contact lens can easily be adjusted as
a child's eye elongates – particularly during the first 2
years of life.
 To treat infants with a contact lens immediately after
cataract surgery and then to implant an IOL after age
of 2 yrs.
 In recent years, rigid gas-permeable contact lenses
have become increasingly popular as a means of
correcting aphakia in children because of
1. Their lower cost,
2. Their availability in a greater range of powers,
3. Their ease of insertion and removal.
 Bausch & Lomb SilSoft contact lens ------.
 Keratometry readings can be taken during surgery to
facilitate the fitting of these lenses.
 Contact lenses can be associated with a good visual
outcome even in children with unilateral aphakia.
 Unfortunately, many children with unilateral aphakia
have a poor visual outcome when corrected with
contact lenses because of the time and constancy
required for their use.
GLASSES
 Rarely used to correct aphakia in children.
 For children with bilateral aphakia who are intolerant
of contact lenses.
 For the microphthalmic eyes - magnifying the
apparent size of the eyes.
 Although compliance is generally better with glasses
than contact lenses, some children who are
developmentally delayed may object to their use.
 Glasses are still commonly used even in pseudophakic or
contact lens-corrected children to provide a near
correction.
 The IOL or contact lens is used to provide the distance
correction and the bifocal segment for the near correction.
 Bifocals are typically prescribed when children are 18
months to 3 years of age.
 Multifocal IOLs may reduce the future need for glasses for
pseudophakic children.
 However, the factor limiting their use in children is again
the axial elongation that occurs, which would make it
difficult to make these children free of spectacles.
CONCLUSIONS
 During the last decades, the optical correction of aphakia
in children has changed radically from contact lenses to
IOLs.
 Superior visual outcomes have been achieved with IOLs so
that many aphakic children can now live nearly normal
lives.
 However, implanting an IOL in a child's eye differs from
implanting an IOL in an adult's eye.
 Further studies will be necessary to determine whether
multifocal IOLs should be used to correct aphakia in
infants and children.
REFERENCES
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