Strabismus in patients with neurofibromatosis type 1-associated optic pathway glioma

Purpose To characterize the incidence, type, natural history, and treatment outcomes of strabismus in pediatric patients with neurofibromatosis type 1 (NF1) and optic pathway glioma (OPG). Methods The medical records of consecutive patients diagnosed with NF1 and OPG at our neurofibromatosis clinic since 1985 were reviewed retrospectively. We noted age at diagnosis, reason for referral to our clinic, ophthalmologic examination results, presence or absence of strabismus, strabismus type and treatment, and final results of treatment. Results A total of 76 patients were included. Of these, 22 (28.9%) had strabismus: 5 (22.7%) had esotropia and 17 (77.2%) had exotropia; of those with exotropia, 10 (45%) also had hypotropia. In 12 patients (54.5%), strabismus was present at the first ophthalmologic examination. The development of strabismus preceded the diagnosis of both NF1 and OPG in 4 (5.3%) patients and the diagnosis of OPG in another 2 (2.6%) patients with known NF1. In 16 (76%) patients, the strabismus was sensory. Five patients (22.7%) underwent surgery, which resulted in a deviation angle of <10^Δ in 1 patient, <20^Δ in 2 patients, and >20^Δ in 2 patients. Conclusions Strabismus was the presenting symptom and led to the diagnosis of OPG in a subset of patients, including those who did not have a previous diagnosis of NF1. Exotropia, especially associated with a hypotropia, was the most common strabismic deviation seen in these patients. Sensory strabismus was the most common type seen in this population. Deviations of <10^Δ may be difficult to achieve with strabismus surgery.