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Stuart G. Coupland, Michael O'Connor, Annick Fournier, John Hamilton, Olga Plekhanova; Investigation Of The Role Of Retinal Development In Human Amblyopia. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3907. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Amblyopia has been defined as a developmental disorder of pattern or spatial vision associated with strabismus, anisometropia, or form deprivation during the critical period of visual development in early life. Amblyopia is generally attributed to abnormal development of the visual cortex due to strabismus, image blur from refractive error, or a combination of these factors. Retinal involvement in amblyopia is more controversial. Kittens reared with experimentally induced strabismus have shown deficits in receptive field development in retinal ganglion cells. In this investigation we measured retinal nerve fiber layer (RNFL) thickness and photopic negative response (PhNR) amplitude in pediatric and adult strabismic and anisometropic amblyopes.
Fifteen adult and 7 pediatric cases with strabismic (13 eyes) and anisometropic (9 eyes) were examined. Clinical examination including BCVA, refractive error, slit lamp exam, EOM, strabismic evaluation and IOP. RNFL was measured in the peripapillary region with the SLO/OCT-7 (OPKO). PhNR was recorded using brief flashes of long-wavelength (red) were delivered over a rod-saturating (blue) background. ERGs were recorded using the Espion e2 visual electrodiagnostic system (Diagnosys LLC). The amplitude of the PhNR was determined.
RNFL thickness was significantly greater in anisometropic amblyopic eyes compared to fellow eyes (p=0.03); whereas, in strabismic amblyopic eyes there was no significant difference in RNFL thickness compared to fellow eyes. Similarly, PhNR amplitude was significantly larger in anisometropic amblyopic eyes compared to fellow eyes (p=0.02); whereas, in strabismic amblyopic eyes there was no significant difference in PhNR amplitude compared to fellow eyes. Increased RNFL thickness and larger PhNR amplitude suggests greater number of ganglion cells in anisometropic eyes.
Increased RNFL thickness (and increased PhNR amplitude) in anisometropic eyes might reflect the disruption of normal retinal ganglion cell apoptosis during postnatal development suggesting that the process requires sharply focused objects as appropriate stimuli. In strabismic amblyopic eyes objects are sharply focused on the retina allowing normal developmental apoptosis to occur.
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