Duane retraction syndrome is a congenital disorder of eye movement, characterized by an inability of the affected eye to move outwards (abduction). In some cases, this might also be manifested an inability of the eye to move inwards towards the nose (adduction). The condition is also associated with a retraction of the eyeball into the socket with attempted adduction, and a widening of the palpebral fissures on attempted abduction. There are three subtypes of Duane retraction syndrome; DRS Type 1 is characterized by restricted inwards movement, while Type 2 is characterized by restricted outward movement. Type 3 patients have both movements affected. In a large majority of the cases, the condition is unilateral, affecting only one of the eyes. This is usually the left eye, in most cases. The underlying etiology of DRS is a defect in some of the eye muscles (specifically the lateral and medial rectus muscles) receiving proper signal from the cranial nerves that innervate them.
DRS is a fairly common disorder, affecting 1 in 1,000 people worldwide, and accounts for 1-5% of all cases of strabismus. This condition is usually found isolated. However, it can also be found in association with other abnormalities, including cervical spine abnormalities Klippel-Feil syndrome, Goldenhar syndrome, heterochromia, and congenital deafness. Differential diagnosis includes Duane-radial ray syndrome, acro-renal-ocular syndrome, Bosley-Salih-Alorainy syndrome, Townes-Brocks syndrome, Athabaskan brainstem dysgenesis-related disorders, Wildervanck syndrome, horizontal gaze palsy with progressive scoliosis, Moebius syndrome and congenital fibrosis of extraocular muscles. Management of the condition is mainly supportive and involves wearing spectacles or contact lenses to correct refractive errors. Surgical intervention to try and correct the face turn and to align the eyes in primary position can be attempted. However, surgery cannot correct the underlying innervations defect and, therefore, cannot remove the strabismus.
Duane retraction syndrome usually presents as a sporadic disease. However, in about 10% of the cases, it presents in a familial fashion, with an autosomal dominant mode of inheritance. There is incomplete penetrance with variable expressivity. Defects in two separate loci have been implicated in the pathogenesis of this condition. The first locus on chromosome 8q13 causes Duane retraction syndrome-1. However, no candidate genes in this locus have been identified so far. The second locus identified is on chromosome 2q31. Mutations in the CHN1 gene on this locus have been identified to cause Duane retraction syndrome-2.