Differential changes of magnocellular and parvocellular visual function in early- and late-onset strabismic amblyopia.
OBJECTIVE
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 cone-modulated) grating with slow onset and an achromatic (L+M cone-modulated) 0.8-cpd grating with rapid onset using an adaptive


METHODS



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.
Davis
Alison R
AR
Moorfields Eye Hospital, City Road, London EC1V 2PD, United Kingdom.
Sloper
John J
JJ
Neveu
Magella M
MM
Hogg
Chris R
CR
Morgan
Michael J
MJ
Holder
Graham E
GE
D000293:Adolescent; D000328:Adult; D000550:Amblyopia / Q000503:physiopathology*; D015350:Contrast Sensitivity / Q000502:physiology*; D005829:Geniculate Bodies / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D013285:Strabismus / Q000503:physiopathology*; D015348:Vision, Binocular / Q000502:physiology; D014795:Visual Pathways / Q000503:physiopathology*