Evaluation of the Functions of the Parvocellular and Magnocellular Pathways in Strabismic Amblyopia

Abstract

Purpose: To evaluate the functions of the magnocellular and parvocellular pathways in strabismic amblyopia. Methods: Visual evoked potentials produced by achromatic and chromatic stimuli in 14 children with strabismic amblyopia were compared with those in 14 age-matched control subjects. The achromatic sine-wave grating with low spatial frequency was used to stimulate the magnocellular pathway, whereas the parvocellular pathway was stimulated by the chromatic sine-wave grating (isoluminant red-green) with low and high spatial frequencies. Results: When the achromatic stimuli with low spatial frequency were used, the latencies of the N1 and P1 components and the amplitude of the N1-P1 complex were similar in the children with strabismic amblyopia and the control subjects. There also were no differences between the amblyopic and non-amblyopic eyes of the children with strabismic amblyopia. When chromatic stimuli with low and high spatial frequencies were used, the latencies of the N1 and P1 components were significantly longer and the amplitude of the N1-P1 complex was significantly smaller in the children with strabismic amblyopia than in the control group. When the amblyopic and non-amblyopic eyes of the children with strabismic amblyopia were compared, the latencies of the N1 and P1 components were longer and the amplitude of the N1-P1 complex was smaller in the amblyopic eyes. Conclusion: In strabismic amblyopia, the cells in the parvocellular pathway may be more involved, whereas the magnocellular pathway may be relatively spared. Journal of Pediatric Ophthalmology and Strabismus 2002;39:215-221.

Differential activation of cerebral blood flow by stimulating amblyopic and fellow eye

“…Evaluation of the parvocellular and magnocellular pathways in strabismic or anisometropic amblyopia by visually evoked potentials has shown that the function of the parvocellular pathway in the amblyopic eye is selectively impaired [9,25]. Our results confirm these findings and further demonstrate that the impairment is selectively greater for the contra-lateral projections.…”

Chromatic and luminance contrast sensitivity in fullterm and preterm infants

“…In humans, the bulk of the data reports greater deficits in aspects of vision thought to be mediated by the P pathway (deficits for high spatial frequency stimuli: Bradley & Freeman, 1981; Hess & Howell, 1977; Levi & Harwerth, 1977, deficits for red/green chromatic stimuli: Davis, Sloper, Neveu, Hogg, Morgan, & Holder, 2006; Demirci, Gezer, Sezen, Ovali, Demiralp, & Isoglu-Alkoc, 2002; but see Zele, Pokorny, Lee, & Ireland, 2007). Corroborating the human results, studies of visually deprived animals have reported that morphological changes are greater within the P layers, compared to the M layers, of the LGN (Hendrickson et al, 1987; LeVay, Wiesel, & Hubel, 1980 and see von Noorden, Crawford, & Levacy, 1983 for greater P disruption in the LGN of a single human).…”

Effects of prematurity on the development of contrast sensitivity: Testing the visual experience hypothesis

“…In support of the notion that P pathway development relies more on visual experience than the M pathway come from studies investigating amblyopic adults who had abnormal visual experience during development. The bulk of those studies report greater deficits in aspects of vision thought to be mediated by the P pathway (Davis, Sloper, Neveu, Hogg, Morgan & Holder, 2006; Demirci, Gezer, Sezen, Ovali, Demiralp & Isoglu-Alkoc, 2002; but see Zele, Pokorny, Lee & Ireland, 2007). …”