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Diane Nava, David S. Hammond, Christine F. Wildsoet; High Resolution Measurements Of Quisqualate-induced Retinal And Ocular Growth Changes. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3438.
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© ARVO (1962-2015); The Authors (2016-present)
It has been shown from previous myopia studies that a single injection of quisqualate (QA), which is known to selectively destroy specific groups of retinal amacrine cells, does not affect compensation to imposed hyperopic defocus or lens deprivation but disrupts the response to imposed myopic defocus. The purpose of this study was to examine the effects of this neurotoxin on retinal morphology and ocular growth using high resolution imaging.
5-day-old White Leghorn chicks were injected monocularly with either QA or saline (SS). After 6 days, they were fitted with -10, +10 or Plano lenses, and refractions and eye growth tracked using retinoscopy and A-scan ultrasonography. Retinal morphological changes were tracked using Bioptigen Spectral Domain Optical Coherence Tomography (SD-OCT) 4, 6, 8 and 10 days after monocular injections of either QA or SS in otherwise untreated chicks. Digital calipers were used to analyze images of the area centralis, to examine the effects on the different retinal sublayers.
Irrespective of the optical treatment, QA-treated eyes exhibited relative myopic shifts in refraction and increases in optical axial length relative to SS-treated eyes exposed to the same optical treatment. There were also significant effects on anterior and vitreous chamber depths as well as choroidal thickness with positive and plano lenses; anterior chambers were enlarged and choroids thickened. SD-OCT revealed significant overall retinal thinning, detectible 6 days after a single QA injection (p<0.01), and maintained over the monitoring period (day 8, p<.01; day 10, p<0.05). The ganglion cell layer (GCL), inner plexiform (IPL) and inner nuclear layers (INL) were most affected, with significant thinning of GCL and INL detected 4 days after the injection (p<0.05), their thicknesses stabilizing thereafter; IPL thinning occurred more slowly, reaching significance 6 days post-injection (p<0.05).
We confirmed the finding that QA disrupts compensation to imposed myopic defocus, but not hyperopic defocus, possibly reflecting QA-induced changes in anterior chamber growth. It is likely that QA eliminated critical amacrine cells as SD-OCT imaging showed that QA-induced retinal changes were largely confined to the GCL and INL, and complete before lens treatment began.
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