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Rita Nieu, Alexandra Benavente-Perez, Ana Nour, Amy Pope, Carol Lin, Victor Lin, Suresh Viswanathan; Retinal ON-pathway responses in marmosets experiencing positive lens defocus. Invest. Ophthalmol. Vis. Sci. 2018;59(9):696.
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© ARVO (1962-2015); The Authors (2016-present)
Recent studies indicate that the ON pathway is essential for emmetropization. We are interested in determining whether the luminance gain of the ON-cone bipolar cells is different between animals experiencing positive or negative defocus during early visual development. Here we establish the relationship between the luminance gain of the ON-cone bipolar cells as determined by the slope of the b-wave intensity response function (IRF) of the photopic flash electroretinogram (ERG), choroidal thickness (ChT) and retinal thickness (RT) in marmosets experiencing positive lens defocus.
Cone mediated ERGs were recorded from anesthetized marmosets using an Espion system to 200ms duration white stimuli of increasing intensity (1.6 – 832 cd/m2) on a constant white (75 cd/m2) background. Marmosets had been treated for 10 weeks with +5D (n=5) or +10D (n=5) from 10 weeks of age, and ERG recordings were made 1-41 weeks after treatment. The amplitude of the ERG b-wave plotted as a function of flash intensity was fitted with the Naka-Rushton equation. The slope parameter of the fit was used as a measure of the luminance gain of ON-cone bipolar cells. Refractive error, ChT and RT were measured with the Nidek autorefractor and an A-scan ultrasound respectively.
Spherical equivalent (SE), ChT, RT and slope of b-wave IRF ranged from 0.05 to -3.94D, 0.32 to 0.41 mm, 0.22 to 0.26 mm and 0.43 to 1.41 respectively. These measures were not significantly different between the two positive defocus groups. ChT showed a greater tendency than RT to increase with age while the slope of the b-wave IRF tended to reduce; these effects were not statistically significant. While the slope of the b-wave IRF strongly decreased with increase in ChT (r=0.76, m=-10.18, p=0.0045), it did not correlate with RT.
Luminance gain of ON-cone bipolar cells, as determined by the slope of the IRF of the photopic ERG b-wave, reduces with increasing choroidal thickness in marmosets experiencing positive lens defocus. While it is possible that altered retinal sensitivity in eyes with thicker choroid may contribute to this reduction, increased resistance to current flow across a thicker choroid is a more likely explanation. This study provides baseline data for future comparison with lens-induced myopia marmosets that are known to exhibit choroidal thinning.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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