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Ronald G. Boothe, Tracy Louden, Akhila Aiyer, Alicia Izquierdo, Carey Drews, Scott R. Lambert; Visual Outcome after Contact Lens and Intraocular Lens Correction of Neonatal Monocular Aphakia in Monkeys. Invest. Ophthalmol. Vis. Sci. 2000;41(1):110-119.
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purpose. A monkey model was used to evaluate intraocular lenses (IOLs)
and extended-wear contact lenses (EWCLs) for the optical treatment of
infantile aphakia in humans. Specifically, the relative effectiveness
of EWCLs used alone and IOLs used in combination with EWCLs in
preventing amblyopia was assessed.
methods. A total of 33 rhesus monkeys was studied in this project, 24 assigned
to experimental treatment groups and 9 to normal controls. Contact
lenses made from a diffusing material or dyed opaque were placed on one
eye at birth to simulate an infantile cataract. A unilateral lensectomy
was then performed on the same eye within 2.5 weeks after birth. In 15
monkeys this was combined with implantation of an IOL. The eyes were
left aphakic in the remaining 9 animals. EWCLs were used to adjust the
optical correction of both aphakic and pseudophakic eyes to a near
point (3–5 D). Opaque lenses were used to maintain daily part-time
(∼70%) occlusion of the fellow eye. The primary outcome measure was
grating acuity assessed with behavioral methods. Some animals were also
assessed for acuity with sweep visually evoked potentials (VEPs) and
for optotype acuity (Landolt C) with behavioral methods.
results. Two of the animals with IOLs developed complications in the eye that
precluded completion of the behavioral assessment protocol. Only
behavioral outcomes obtained before or in the absence of surgical
complications are presented. There was a developmental delay in the
maturation of grating acuity in both eyes of both treatment groups.
Normal adult levels of grating acuity were eventually achieved in the
group treated with IOLs combined with EWCLs. Grating acuity was
significantly poorer than normal in aphakic eyes treated only with
EWCLs. Comparison of the two treatment groups revealed that
pseudophakic eyes treated with multifocal IOLs had significantly better
gating acuity than aphakic eyes. Assessments of optotype acuity and
sweep VEP acuity revealed amblyopic deficits in both pseudophakic and
conclusions. Given an absence of serious postoperative complications, neonatal
correction of aphakia with IOLs combined with EWCLs can lead to normal
grating acuity in a primate model. Correction with EWCLs alone was not
sufficient to produce normal grating acuity. Multifocal IOL treatments
combined with EWCL provided a significantly better outcome than EWCL
methods alone. However, neither IOL nor EWCL methods were able to
prevent amblyopia as evaluated using behavioral testing with optotypes
or with sweep VEPs.
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