Duane-radial ray syndrome, also known as Okihiro syndrome, is an autosomal dominant disorder characterized by upper limb anomalies, ocular anomalies, and, in some cases, renal anomalies. The combination of the 3 findings was earlier referred to as 'acro-renal-ocular syndrome. The ocular anomalies usually include Duane anomaly, but this finding may be absent in some patients. Similarly, renal anomalies are not always seen and may not have been investigated, particularly in cases reported before routine renal imaging . Other less common features include sensorineural deafness and gastrointestinal anomalies, such as imperforate anus. The Holt-Oram syndrome (142900), caused by mutation in the TBX5 gene (601620) on chromosome 12q24, shows similar anomalies of the upper limb, but can be differentiated from Duane-radial ray syndrome by the absence of ocular and renal anomalies and the presence of severe congenital heart defects . Causes : DS is a miswiring of the eye muscles, causing some eye muscles to contract when they shouldn't and other eye muscles not to contract when they should. Alexandrakis G & Saunders RA state that: In most cases, the abducens nucleus and nerve are absent or hypoplastic, and the lateral rectus muscle is innervated by a branch of the oculomotor nerve. However, there may be contributing mechanical abnormalities This view is supported by the earlier work of Hotchkiss who reported on the autopsy findings of two patients with Duanes syndrome. In both cases the sixth cranial nerve nucleus was absent, as was the sixth nerve, and the lateral rectus muscle was innervated by the inferior division of the third or oculomotor cranial nerve. This misdirection of nerve fibres results in opposing muscles being innervated by the same nerve. Thus, on attempted abduction, stimulation of the lateral rectus via the oculomotor nerve will be accompanied by stimulation of the opposing medial rectus via the same nerve; a muscle which works to adduct the eye. Thus, co-contraction of the muscles takes place, limiting the amount of movement achievable and also resulting in retraction of the eye into the socket. The mechanical factors noted by Miller and Clark above are generally regarded as arising secondary to loss of innervation. During corrective surgery fibrous attachments have been found connecting the horizontal recti and the orbital walls and fibrosis of the lateral rectus has been confirmed by biopsy. This fibrosis can result in the lateral rectus being 'tight' and acting as a tether or leash. Co-contraction of the medial and lateral recti allows the globe to slip up or down under the tight lateral rectus producing the up and down shoots characteristic of the condition.