Optic chiasm formation in humans is independent of foveal development

• Published in: The European journal of neuroscience Vol. 22; no. 7; pp. 1825 - 1829
• Main Authors: Neveu, Magella M., Holder, Graham E., Sloper, John J., Jeffery, Glen
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.10.2005
• Subjects: Adult; albinism; Albinism, Ocular - pathology; Albinism, Ocular - physiopathology; aniridia; Aniridia - pathology; Aniridia - physiopathology; Evoked Potentials, Visual - physiology; Female; Fundus Oculi; Humans; Male; Middle Aged; optic chiasm; Optic Chiasm - pathology; Optic Chiasm - physiopathology; Photic Stimulation - methods; retinal blood vessels; Visual Fields - physiology; visual-evoked potential
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1111/j.1460-9568.2005.04364.x

A failure of human foveal development only occurs in two genetically determined conditions; aniridia (Pax6 mutation) and albinism (tyrosinase mutation). The chiasmatic pathways from this region are disrupted in albinism and central retinal blood vessel patterns are abnormal. It is assumed that these three abnormalities have a common mechanism. Here we investigate whether similar abnormalities are present in subjects with aniridia. Using fundus photographs it is shown that abnormal blood vessel patterns are present in aniridia, but these significantly differ from those in albinos. Using electrophysiological techniques, abnormal hemispheric projections through the chiasm are demonstrated in albinos, but aniridics do not differ from normal subjects. These results demonstrate that although mutations in Pax6 and tyrosinase both affect central retinal development, they have a fundamentally different impact on the formation of the retinal vasculature and the projections from this region. This strongly suggests that separate mechanisms regulate the development of the central retina and decussation patterns at the optic chiasm.