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.
Khan & Aldahmesh (2006) described a 13-year-old female of normal karyotype (46, XX) suffering from bilateral Duane syndrome and bilateral aniridia. She had inward deviation of the eyes since birth. She developed deafness in early childhood. Uncorrected visual acuity was 20/100 in the left eye (OS) and 20/125 in the right eye (OD). She had an esotropia of 85 prism diopters (PD) at near and distance. In both eyes, she had -4 abduction (OU). Slit-lamp examination by indirect ophthalmoscopy with a 20 D lens showed minimal iris root for 360 degrees in the undilated pupil OU and hypoplasia in optic nerve and and foveal nerve OU. She underwent medial rectus muscle recession to 6-mm lateral rectus muscle resection OS, 8-mm lateral rectus muscle resection OD, and 13 mm from the limbus OU. Four years later, she suffered from a decreased vision OD over a period of 4 days. Slit-lamp examination revealed inferiorly subluxated lenses OU with a mild posterior subcapsular cataract OS and a dense cataract OD. At the age of 21, her vision was 20/80 OU with her aphakic refraction of +14 OD and +13.25 - 3.00 X 090 OS.
Khan & Oystreck (2006) identified 270 patients with Duane retraction syndrome (DRS) between 1982 and 2003 in King Khalid Eye Specialist Hospital. Of these, 37 patients (14%) were bilateral, and had documented signs of cocontraction. Of the 37 patients, 22 (59%) were males and 15 (41%) were females. Twenty five patients (68%) were bilateral Type I, 1 (3%) was bilateral Type II, and 9 (24%) were bilateral Type III. Most patients had the same type in both eyes, while two patients (5%) were mixed types (Type I OS, and Type III OD with Type II OS). Most patients had significant horizontal strabismus in primary position; 23 (62%) were esotropic and 6 (16%) were exotropic. In addition, four patients with horizontal strabismus had a concurrent vertical heterotropia. Abnormal head position was seen in 21 patients (57%) depending upon which eye was fixating. Six patients (16%) had amblyopia, and a family history of strabismus was reported in eight patients (22%). Five patients had ocular abnormalities, three had nonocular abnormalities, and one had ocular and nonocular abnormalities.
Khan et al. (2007) undertook a retrospective analysis of all cases diagnosed with DRS at the King Khaled Eye Hospital between 1982 and 2004. Of the 404 medical records studied, 45% were males, while 55% were females. There were more unilateral cases (86%) than bilateral, and among the unilateral cases, more cases had their left eyes affected (79%) than right eyes. Type I DRS was most common (78%), followed by Type III (19%) and Type I (4%). A family history of strabismus was seen in 13% of the cases, and 12% of the patients had other congenital anomalies in addition to DRS. Although there was s larger proportion of females compared to males in among the unilateral cases, it was the opposite in the bilateral cases. The overall features of DRS in Saudi Arabia were found to be similar to those reported from other parts of the world.
Bosley et al. (2016) studied a 14-year-old Saudi boy presenting with symptoms of both Duchenne Muscular Dystrophy (DMD) and Duane Retraction Syndrome (DRS). The parents of the patient were healthy and unrelated. The individual suffered from complete abduction defects and bilateral restriction of adduction with globe retraction. An attempted left gaze resulted in downshoot of the right eye while an attempted right gaze caused an upshoot of the left eye. He also had mild esotropia and left hypertropia without diplopia in primary gaze. His DMD symptoms included delayed speech development, mild mental retardation, elevated creatine kinase levels and progressive muscle wastage that resulted in lordosis and Gower’s maneuver while walking. A muscle biopsy found significant signs of dystrophy as well as defective histological stains for dystrophin protein. The patient also had a history of seizures in infancy with a single recurrence in childhood that did not require continued treatment. Multiplex Ligand-dependent Probe Amplification (MLPA) studies revealed the presence of duplications of exons 3 and 4 in the Dystrophin gene. The authors noted that this was the third reported case worldwide of a patient suffering from both DMD and DRS and the first case involving neurological features.