Author Affiliations: Strabismus and Neuro-ophthalmology Division, R. P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
A 50-year-old male patient from a nonconsanguineous marriage (case 1) was seen with outward deviation of both eyes since birth. He and his 2 sons (case 2, 24 years old, and case 3, 21 years old) had similar concerns of outward deviation of eyes. There was no history of any orthoptic treatment like occlusion, prism, or convergence exercises. There was no other medical or surgical ailment in either the father or the sons. Pedigree analysis revealed no similar ailment in any family member other than the father and his 2 sons; the only other issue was a stillbirth.
On ocular examination of the father, visual acuity was 6/6 OD with −1.0 diopter sphere and −3.5 diopters cylinder, axis 80°, and 6/9 OS with −1.0 diopter sphere and −3.0 diopters cylinder, axis 80°. Examination of the anterior and posterior segments was normal and unremarkable. He had gross limitation of adduction (−3) in both eyes, 80–prism diopter exotropia at distance, and 85–prism diopter exotropia at near (Figure 1A). There was no limitation of vertical eye movements. The forced duction test revealed only a tight lateral rectus on both sides. An intraoperative forced duction test confirmed a mildly tight lateral rectus, and a thin empty sheath of medial rectus (MR) was found in both eyes (Figure 2A). A decision was made to do split vertical rectus transposition and Foster augmentation (Figure 2B) with lateral rectus recession of 10 mm on each side. Magnetic resonance imaging of the patient showed thin MR muscle on both sides (Figure 3). Postoperative recovery was uneventful. His deviations measured 25 prism diopters exotropia at distance and he had limited adduction (−1) after 4 weeks (Figure 1B). Subsequent follow-up after 3 months and 6 months did not show any further change.
Figure 1. Preoperative and postoperative photographs of case 1. A, Large-angle exodeviation and a prominent forehead (cases 2 and 3 had similar findings). B, Postoperative photograph after bilateral lateral rectus recession and partial vertical rectus transposition.
Figure 2. Intraoperative views. A, Aplasia of the distal medial rectus muscle with an empty sheath and anterior ciliary vessels alone. B, Partial vertical rectus transposition (white arrows) and Foster suture augmentation (black arrows).
Figure 3. Magnetic resonance imaging of case 1 showing thin medial rectus muscle (orbital fibers) on both sides (arrows).
Both his sons had similar large exodeviations. Magnetic resonance imaging in both cases revealed thin MR on both sides while intraoperatively, only an empty muscle sheath was seen. They were managed similarly with good postoperative results. Follow-up of both cases was satisfactory with minimal (<20–prism diopter exotropia) deviation.
Agenesis or hypoplasia of the extraocular muscles1 have been grouped as congenital cranial dysinnervation disorders with absent muscle development or abnormal innervation of the target muscle. Magnetic resonance imaging may show affected muscles and cranial nerves to be normal, hypoplastic, or absent.2- 4 There is only 1 reported case of unilateral agenesis of MR muscle by Girard and Neely5 in 1958 and another case of bilateral agenesis of MR muscle by Houtman et al6 in 2009. However, familial occurrence of this anomaly has never been reported, to the best of our knowledge.
Our case appears to be a very rare case of autosomal dominant aplasia of MR seen in a male patient and his 2 sons. In all 3 cases, MR was not absent on the magnetic resonance image, which only showed mild hypoplasia; however, the intraoperative findings showed only a thin sheath of muscle capsule. As pointed out by Demer et al,3 the orbital and global fibers have differences in fiber types, fiber sizes, electromyography characteristics, vascular content, and metabolic activity. It is speculated that these cases had a lack of development of global fibers but complete development of orbital fibers. More research is needed into this differential development of the extraocular fibers in the future.
Congenital strabismus in humans can result from mutations in a number of genes, including PHOX2A, SALL4, HOXA1, ROB03, and KIF21A, that are essential to the normal development of brainstem motor neurons or axons. Because of the nonspecific nature of the disorder, genetic analysis was not possible in our case.
The aim of this case report was to highlight the possible separate global and orbital development of MR and the management of relatively larger deviations and to be ready to alter the surgical plan based on intraoperative findings. The management of these types of cases is very challenging and involves supramaximal recessions and muscle transpositions in cases of muscle palsy. The management by partial vertical rectus transposition with Foster augmented sutures and lateral rectus recession had reasonable postoperative surgical success in all our cases as well and avoided an anterior ischemic complication.
Correspondence: Dr Pradeep Sharma, Strabismus and Neuro-ophthalmology Division, R. P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi 110029, India (firstname.lastname@example.org).
Published Online: April 9, 2013. doi:10.1001/jamaophthalmol.2013.2889
Conflict of Interest Disclosures: None reported.
Singh A, Sharma A, Sharma P. Congenital Bilateral Aplasia of Medial Recti in a Family. JAMA Ophthalmol. 2013;131(6):798-800. doi:10.1001/jamaophthalmol.2013.2889