Recognizing Bradyopsia in Children
Arif O. Khan, MD
Cleveland Clinic Abu Dhabi
Abu Dhabi, United Arab Emirates
Introduction: Bradyopsia is a rare but probably under-diagnosed stationary form of cone dysfunction due to biallelic mutations in the gene RGS9 (regulator of G-protein signaling 9) or R9AP (regulator of G-protein signal 9-anchoring protein). Although the condition is congenital, most descriptions in the literature are of adult patients. The purpose of this report is to highlight clinical features of children referred to a pediatric ophthalmologist who were found to harbor a homozygous RGS9 mutation.
Methods: Retrospective case series.
Results: 5 affected children ranging from 6-16 years old (3 families) harbored the same homozygous RGS9 frameshift mutation (p.Pro108Hisfs*18; NM_207391.2). Findings included photophobia, variable decreased visual acuity, improved pinhole visual acuity despite no significant refractive error, and normal structural ophthalmic examination. Some had been previously diagnosed with functional visual loss. Extended electroretinography and/or suspicion for the condition led to appropriate genetic testing and confirmation of the diagnosis.
Discussion: Diagnosis can be challenging in young children because structural ophthalmic examination is typically normal and visual acuity can improve with pinhole despite no significant refractive error.
Conclusion: The diagnosis of bradyopsia should be considered in children with structurally-normal eye exams who have photophobia and improved pinhole acuity despite no significant refractive error.
References: Kooijman AC, Houtman A, Damhof A, van Engelen JP. Prolonged electro-retinal response suppression (PERRS) in patients with stationary subnormal visual acuity and photophobia. Doc Ophthalmol Adv Ophthalmol. 1991;78(3-4):245-54.
Nishiguchi KM, Sandberg MA, Kooijman AC, Martemyanov KA, Pott JWR, Hagstrom SA, et al. Defects in RGS9 or its anchor protein R9AP in patients with slow photoreceptor deactivation. Nature. 2004 Jan 1;427(6969):75-8.