Volume 3, Issue 3, September 2018, Page: 43-46
Normal Tritan Discrimination in Amblyopia Suggests Preservation of Koniocellular Function
Ross Littlewood, Midland Eye Clinic, Midland, Australia
Received: Oct. 9, 2018;       Accepted: Oct. 23, 2018;       Published: Nov. 15, 2018
DOI: 10.11648/j.ijovs.20180303.12      View  97      Downloads  6
Abstract
Background: Human stereoscopic vision is a psychological abstraction emerging from sufficiently grouped monocular signals within a broader unity of simultaneous binocular perception. Incongruent central signals inevitably arise when moving through a visual landscape, due to changing asymmetries of perception, producing signal rivalry. Humans have an evolved capacity to dynamically inhibit incongruous or ambiguous signals in order to maintain a coherent unity of stereoscopic perception, a facility sometimes exploited by optical illusions. Unlike the beneficial mental construct that arises from physiological inhibition, the amblyopic inhibition is permanently unilaterally destructive, has a large field size, is associated with irreversible signal inhibition at the dorsal lateral geniculate nucleus (dLGN), and leads to structural alterations in dLGN that can be demonstrated histologically. Recent reports suggest amblyopic signal inhibition at the dLGN may be selective, preferentially involving the parvocellular system and sparing the koniocellular system. It is not yet known whether physiological inhibition is also pathway specific, but it would be surprising if it were not. The two chromatic opponent systems display differing vulnerabilities in a number of disease states, including optic neuritis and toxic neuropathies, and they followed independent evolutionary paths during phylogenetic development from small primates into apes and humans with larger eyes. Tritan contrast is conducted exclusively by the koniocellular system as far as the striate cortex, so clinical tests of tritan contrast may provide information about koniocellular function in humans. If koniocellular function is not inhibited in amblyopia then tritan discrimination tests may be normal in amblyopic eyes. Objective: In this study the C test for tritan discrimination was employed as a proxy for koniocellular function to discover whether tritan discrimination was affected in proportion with achromatic contrast in the amblyopic eye of 18 amblyopic adults. Method: The tritan contrast and logmar visual acuity results were compared between eyes, using two non parametric statistical tests. Results: The C test scores for tritan discrimination were statistically similar in the normal and amblyopic eyes, but mean logmar acuity scores were significantly different, with a mean of 0.76 in the amblyopic eyes compared to 0.18 in the non-amblyopic eyes. Conclusion: This finding is consistent with preservation of koniocellular signal perception despite parvocellular signal inhibition in amblyopic eyes.
Keywords
Amblyopia, Koniocellular, Tritan, C Test
To cite this article
Ross Littlewood, Normal Tritan Discrimination in Amblyopia Suggests Preservation of Koniocellular Function, International Journal of Ophthalmology & Visual Science. Vol. 3, No. 3, 2018, pp. 43-46. doi: 10.11648/j.ijovs.20180303.12
Copyright
Copyright © 2018 Authors retain the copyright of this article.
This article is an open access article distributed under the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Reference
[1]
S. H. Hendry, and R. Clay Reid, (2000). “The Koniocellular pathway in primate vision,” Ann Rev Neurosci, Vol. 23, 2000, pp. 127-153.
[2]
M. H. Mobarhan, G. Halnes, P. Martinez-Cañada, T. Hafting, M. Fyhn, and G. T. Einovoll, “Firing-rate based network modelling of the dLGN circuit: Effects of cortical feedback on spatiotemporal response properties of relay cells,” Plos Comput Biol, Vol. 14, No. 5, 2018, e1006156.
[3]
J. J. Nassi, and E. M. Callaway, “Parallel processing strategies of the primate visual system,” Nat Rev Neurosci, Vol. 10, 2009, pp. 360-372.
[4]
R. F. Hess, B. Thompson, G. A. Gole, and K. T. Mullen, “Deficient responses from the lateral geniculate nucleus in humans with amblyopia,” Eur J Neurosci, Vol. 29, No. 5, 2009, pp. 1064-70.
[5]
A. Miki, G. T. Liu, Z. G. Goldsmith, C. S. Liu, and J. C. Haselgrove, “Decreased activation of the lateral geniculate nucleus in a patient with anisometropic amblyopia demonstrated by functional magnetic resonance imaging,” Ophthalmologica, Vol. 217, No. 5, 2003, pp. 365-9.
[6]
L. C. Sincich, K. F. Park, M. J. Wohlgemuth, and J. C. Horton “Bypassing V1: a direct geniculate input to area MT,” Nat Neurosci, Vol. 7, 2004, pp. 1123-1128.
[7]
R. F. Hess, B. Thompson, G. A. Gole, and K. T. Mullen, “The amblyopic deficit and its relationship to geniculo-cortical processing streams,” J Neurophysiol, Vol. 104, No. 1, 2010, pp. 475-83.
[8]
R. Littlewood, and F. Hyde, “The “C test” for tritan discrimination,” Color Res Appl, Vol. 43, No. 1, 2018, pp. 58-64.
[9]
L. T. Chylak, J. K. Wolfe, D. M. Singer, M. C. Leske, M. A. Bullimore, I. L. Bailey, J. Friend, D. McCarthy, and S. Y. Wu, “The Lens Opacities Classification System III,” JAMA Ophthalmology, Vol. 111, No. 6, 1993, pp. 831-836.
[10]
A. Cheng, U. T. Eysel, and T. R. Vidyasagar, “The role of the magnocellular pathway in serial deployment of visual attention,” Eur J Neurosci, Vol. 20, No. 8, 2004, pp. 2188-2192.
[11]
R. A. Barton, “Binocularity and brain evolution in primates,” P Natl Acad Sci USA, Vol. 101, No. 27, 2004, pp. 10113-10115.
[12]
D. Giaschi, S. Narasimhan, A. Solski, E. Harrison, and L. M. Wilcox, “On the typical development of stereopsis: Fine and coarse processing,” Vision Research, Vol. 89, 2013, pp. 65-71.
[13]
C. A. Curcio, K. A. Allen, K. R. Sloan, C. L. Lerea, J. B. Hurley, I. B. Klock, and A. H. Milam, ”Distribution and morphology of human cone photoreceptors stained with anti-blue opsin,” J Comp Neurol, Vol. 312, No. 4, 1991, pp. 610-624.
[14]
F. Tong, M. Meng, and R. Blake, “Neural bases of binocular rivalry,” Trends Cogn Sci, Vol. 10, No. 11, 2006, pp. 502-511.
[15]
S. Zeki and D. H. Ffytche, “The Riddoch syndrome: insights into the neurobiology of conscious vision,” Brain, Vol. 121, No. 1, 1998, pp. 25-45.
[16]
J. Sanchez-Lopez, C. A. Pedersini, F. Di Russo, N. Cardobi, C. Fonte, V. Varalta, M. Prior, N. Smania, S. Savazzi, and C. A. Marzi, “Visually evoked responses from the blind field of hemianopic patients,” Neuropsychologia, Vol. 17, 2017, pp. 30377-9.
[17]
D. M. Levi, C. Yu, S. G. Kuai, and E. Rislove, “Global contour processing in amblyopia,” Vision Research, Vol. 47, No. 4, 2007, pp. 512-524.
Browse journals by subject