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Bradyopsia
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Bradyopsia

Bradyopsia is a rare vision condition where the eyes adapt slowly to changing light conditions and may struggle with moving objects, typically caused by mutations in the RGS9 or RGS9BP genes.

Overview

Bradyopsia is a rare condition that affects vision. The term "bradyopsia" is from the Greek words for slow vision. In affected individuals, the eyes adapt more slowly than usual to changing light conditions. For example, people with this condition are blinded for several seconds when going from a dark environment into a bright one, such as when walking out of a darkened movie theater into daylight. Their eyes also have trouble adapting from bright light to dark conditions, such as when driving into a dark tunnel on a sunny day.

Some people with bradyopsia also have difficulty seeing some moving objects, particularly small objects moving against a bright background. As a result, they often have trouble watching or participating in sports with a ball, such as soccer or tennis. People with bradyopsia can have reduced sharpness (acuity) of vision, although acuity may depend on the conditions under which vision is tested. Visual acuity may appear to be severely affected if it is tested under bright lights, but it can be near normal if tested in a dim environment. The ability to see colors and distinguish between them is normal.

The vision problems associated with bradyopsia become apparent in early childhood. They are usually stable, which means they do not worsen over time.

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.

Learn more about the genes associated with Bradyopsia

  • RGS9
  • RGS9BP

Inheritance

This condition is inherited in an autosomal recessive inheritance, 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

  • PERRS
  • Prolonged electroretinal response suppression

Frequently Asked Questions

Using high‑contrast, larger‑size balls (e.g., bright orange or yellow) and playing on matte, non‑glossy surfaces improves visibility. Wearing tinted lenses that reduce glare and increase contrast can also aid tracking. Some patients benefit from “slow‑motion” practice drills, where a coach or video playback slows the motion, allowing the visual system to register the movement before attempting full speed.
The sudden glare overwhelms the retina because the photoreceptors and downstream signaling pathways reset slowly. To lessen the effect, give your eyes a few seconds to adjust by looking toward a shaded area first, wear sunglasses with photochromic lenses that darken quickly, and use a brimmed hat to reduce direct light. Gradual exposure, such as stepping into a dimly lit hallway before full daylight, also helps the visual system adapt more smoothly.
Currently, no FDA‑approved drugs specifically target the RGS9 or RGS9BP pathways. Low‑vision rehabilitation programs focus on environmental modifications (e.g., controlled lighting, contrast‑enhancing filters) and visual training exercises that may improve functional adaptation over time, but the underlying genetic defect remains stable. Clinical trials of gene‑replacement or pharmacologic modulators are in early research stages and not yet available outside experimental settings.
Yes, annual exams with a retinal specialist are recommended. Tests include full‑field electroretinography (ERG) to assess rod and cone recovery times, dark‑adaptation curves, and kinetic visual field testing under varying illumination. These objective measures help document stability and guide any future therapeutic trials.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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