Differential Changes of Magnocellular and Parvocellular Visual Function in Early- and Late-Onset Strabismic Amblyopia

Abstract

PURPOSE.Studies in nonhuman primates show that monocular visual deprivation starting at different ages has different effects on cells in the parvocellular and magnocellular laminae of the lateral geniculate nucleus. The present study used color and luminance contrast sensitivity (CS) measurements to look for differences in parvocellular-and magnocellular-related visual function in human subjects with strabismic amblyopia. METHODS. Fifteen subjects with early-and 14 with late-onset strabismic amblyopia and similar ranges of visual acuity were studied, together with 15 subjects with normal vision. Contrast sensitivities were measured to an equiluminant (L-M conemodulated) grating with slow onset and an achromatic (LϩM cone-modulated) 0.8-cpd grating with rapid onset using an adaptive method. RESULTS. Luminance and color CS were lower in the amblyopic eyes than in the fellow eyes of all amblyopes. For luminance CS, this was due both to an increase in sensitivity of the fellow eye and to a reduction in sensitivity in the amblyopic eye. Color CS was greatly reduced in the amblyopic and fellow eyes of subjects with strabismic amblyopia of early-and late onset compared with subjects with normal vision. The reduction in color CS compared with luminance CS was significantly greater in eyes with late-rather than early-onset amblyopia. CONCLUSIONS. Parvocellular and magnocellular function are differentially affected in the amblyopic and fellow eyes of subjects with strabismic amblyopia. The difference is more marked in late-onset amblyopia than in early-onset amblyopia. (Invest Ophthalmol Vis Sci. 2006;47:4836 -4841)

Clinical Psychophysical Assessment of the ON- and OFF-Systems of the Magnocellular and Parvocellular Visual Pathways

“…Recently, an increasing number of studies have shown impairment in early-stage processing of visual information. This impairment is not only related to retina and eye diseases like glaucoma [17,21,[31][32][33] ambliopia and strabismus [34], melanoma-associated retinopathy [24,18,28], X-linked retinitis pigmentosa [26,35], congenital stationary night blindness [28], and neurological diseases as migraine [30] or Duchenne Muscular Dystrophy [29], but also to the neurocognitive or high-level of cortex processing disorders, such as schizophrenia [36,37], autism [38][39][40], working memory impairment [41] and dyslexia [25,[42][43][44][45].…”

A morpho-functional study of amblyopic eyes with the use of optical coherence tomography and microperimetry

“…Although anatomic anomalies of visual pathways in amblyopia are well known, 9 the results of studies in which authors evaluated concomitant retinal involvement remain controversial. [10][11][12][13][14][15][16] Some investigators have found an increased retinal nerve fiber layer thickness (RNFLT) 10,12 in amblyopic eyes, whereas others have found no significant differences.…”

Amblyopia: neural basis and therapeutic approaches

“…It has been documented that morphologic changes occurring during the late sensitive period selectively affect cells of the parvocellular pathway (17,21,(69)(70)(71) . It seems reasonable to re commend that treatment for amblyopia should be individualized, as some children with amblyopia may not respond to occlusion because of morphophysiologic dissociation between the magno-and parvocellular pathways (72) . (40) Reduces binocular function (32) , changes family routine (49) , may induce psychological problems (32) .…”