Frequency
Bradyopsia appears to be rare. Only a few affected individuals worldwide have been described in the medical literature.
Causes
Bradyopsia can be caused by mutations in the RGS9 gene or in the RGS9BP gene (which is also known as R9AP). These genes provide instructions for making proteins that are necessary for normal vision. The proteins are found in light-detecting cells in the eye called photoreceptors. When light enters the eye, it stimulates specialized pigments in these cells. This stimulation triggers a series of chemical reactions that produce an electrical signal, which is interpreted by the brain as vision. Once photoreceptors have been stimulated by light, they must return to their resting state before they can be stimulated again. The RGS9 and RGS9BP proteins play an essential role in returning photoreceptors to their resting state quickly after light exposure.
Mutations in either the RGS9 or RGS9BP gene prevent photoreceptors from recovering quickly after responding to light. Normally they return to their resting state in a fraction of a second, but in people with mutations in one of these genes, it can take ten seconds or longer. During that time, the photoreceptors cannot respond to light. This delay causes temporary blindness in response to changing light conditions and interferes with seeing small objects when they are in motion.
In some people with bradyopsia, no mutations in the RGS9 or RGS9BP gene have been found. The cause of the condition in these individuals is unknown.
Inheritance
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Other Names for This Condition
- PERRS
- Prolonged electroretinal response suppression
Additional Information & Resources
Genetic Testing Information
Genetic and Rare Diseases Information Center
Patient Support and Advocacy Resources
Catalog of Genes and Diseases from OMIM
Scientific Articles on PubMed
References
- Cheng JY, Luu CD, Yong VH, Mathur R, Aung T, Vithana EN. Bradyopsia in an Asian man. Arch Ophthalmol. 2007 Aug;125(8):1138-40. doi: 10.1001/archopht.125.8.1138. No abstract available. Citation on PubMed
- Hartong DT, Pott JW, Kooijman AC. Six patients with bradyopsia (slow vision): clinical features and course of the disease. Ophthalmology. 2007 Dec;114(12):2323-31. doi: 10.1016/j.ophtha.2007.04.057. Epub 2007 Sep 12. Citation on PubMed
- Michaelides M, Li Z, Rana NA, Richardson EC, Hykin PG, Moore AT, Holder GE, Webster AR. Novel mutations and electrophysiologic findings in RGS9- and R9AP-associated retinal dysfunction (Bradyopsia). Ophthalmology. 2010 Jan;117(1):120-127.e1. doi: 10.1016/j.ophtha.2009.06.011. Epub 2009 Oct 8. Citation on PubMed
- Nishiguchi KM, Sandberg MA, Kooijman AC, Martemyanov KA, Pott JW, Hagstrom SA, Arshavsky VY, Berson EL, Dryja TP. Defects in RGS9 or its anchor protein R9AP in patients with slow photoreceptor deactivation. Nature. 2004 Jan 1;427(6969):75-8. doi: 10.1038/nature02170. Citation on PubMed
- Vincent A, Robson AG, Holder GE. Pathognomonic (diagnostic) ERGs. A review and update. Retina. 2013 Jan;33(1):5-12. doi: 10.1097/IAE.0b013e31827e2306. Citation on PubMed
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