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Bradyopsia is a rare retinal condition characterized by prolonged electroretinal response suppression that affects vision.

Etiology
Bradyopsia can be caused by recessive mutations in the RGS9 (chromosome 17q23-q24) or R9AP (chromosome 19q13.11) genes.

Signs and symptoms
Bradyopsia normally appears during early childhood. The vision problems associated with this disorder remain stable in affected individuals. Bradyopsia leads to difficulties adjusting to changes in brightness, light intensity, and reduced sharpness (acuity) of vision. People with this disorder adapt to changing light conditions more slowly. For example, when driving out of a dark tunnel into a bright environment, people with this condition are blinded temporarily. Also, they lack the ability to see moving objects. Consequently, people with bradyopsia face difficulty when participating in activities with small objects moving against a bright background, such as sports with a ball.

Diagnosis
Diagnosis can be established on clinical grounds through electroretinography, a test to measure the electrical response of the eye's light-sensitive cells (rods and cones). This test consists of two phases: dark and light.

Dark Phase
 * 1) Put drops in eyes to dilate pupils.
 * 2) Place retractor on both eyes to hold them open.
 * 3) Place electrical sensor (electrode) on each eye.
 * 4) Flash lights with increasing intensity and different colors.
 * 5) Measure the electrical activity of the retina in response to the light.

Light Phase
 * 1) Readjust eyes to a light environment.
 * 2) Place retractor on both eyes to hold them open.
 * 3) Place electrical sensor (electrode) on each eye.
 * 4) Flash strobe light of repeated white flashes.
 * 5) Measure the electrical activity of the retina in response to the light.

Inheritance Pattern
Bradyopsia is inherited through an autosomal recessive pattern. Thus, in each cell, both copies of the gene have mutations. The parents of an individual with this type of autosomal recessive condition do not demonstrate symptoms of bradyopsia; however, the parents do carry one copy of the mutated gene.

Genetics
Mutations in either the RGS9 or R9AP can cause bradyopsia. These genes play a vital role in the vision of an individual. When light enters the eye, it exhausts the specialized proteins

(photoreceptors). This triggers chemical reactions which produce an electrical signal, interpreted by the brain as vision. Although, photoreceptors must return to their resting state before being stimulated again. The RGS9 and R9AP genes play a key role in allowing photoreceptors to recover after light exposure.

Therefore, mutations in either gene hinder photoreceptors from returning to their resting state in response to light. In a normal individual, this process occurs in a fraction of a second; however, in people with bradyopsia, it can take ten seconds or longer. This delay leads to a difficulty adapting to changing light conditions and, in some cases, temporary blindness.