RT Journal Article SR Electronic T1 The achiasmia spectrum: congenitally reduced chiasmal decussation JF British Journal of Ophthalmology JO Br J Ophthalmol FD BMJ Publishing Group Ltd. SP 1311 OP 1317 DO 10.1136/bjo.2005.068171 VO 89 IS 10 A1 D A Sami A1 D Saunders A1 D A Thompson A1 I M Russell-Eggitt A1 K K Nischal A1 G Jeffery A1 M Dattani A1 R A Clement A1 A Liassis A1 D S Taylor YR 2005 UL http://bjo.bmj.com/content/89/10/1311.abstract AB Aim: To describe the clinical spectrum of achiasmia, a congenital disorder of reduced relative decussation at the optic chiasm. Methods: A retrospective case note and patient review of nine children (four boys). Achiasmia was defined by the combination of a characteristic asymmetry of the monocular visual evoked potential (VEP) response to flash and neuroimaging showing reduced chiasmal size. Results: Three of the children had an associated skull base encephalocele with agenesis of the corpus callosum. In two patients achiasmia was associated with septo-optic dysplasia. Three patients had no neuroimaging abnormalities other than reduced chiasmal size and have no known pituitary dysfunction. One child had multiple physical deformities but the only brain imaging abnormality was reduced chiasmal size. Conclusions: Some children with disorders of midline central nervous system development, including septo-optic dysplasia and skull base encephaloceles, have congenitally reduced chiasmal decussation. Reduced relative decussation may co-exist with overall chiasmal hypoplasia. Children with an apparently isolated chiasmal decussation deficit may have other subtle neurological findings, but our clinical impression is that most of these children function well.