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OPN1MW gene

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

OPN1MW gene

The OPN1MW gene provides instructions for a light-sensitive pigment in the retina, playing a vital role in the perception of color.

Normal Function

The OPN1MW gene provides instructions for making a protein essential for normal color vision. This protein is found in the retina, the light-sensitive tissue at the back of the eye. The retina contains two types of light receptor cells: rods (for low light) and cones (for bright light and color).

The OPN1MW gene creates an opsin pigment sensitive to light in the middle of the visible spectrum (yellow/green light). Cones containing this pigment are called middle-wavelength-sensitive or M cones. When light hits these cones, the photopigment triggers chemical reactions that generate electrical signals transmitted to the brain. The brain combines input from all three types of cones to produce normal color vision.

Health Conditions Related to Genetic Changes

Color vision deficiency

Genetic changes involving the OPN1MW gene can cause red-green color vision defects. These often result from structural rearrangements where the OPN1MW and OPN1LW genes swap genetic material (recombination), leading to deletions or the formation of hybrid pigment genes.

  • Deuteranopia: A form of red-green color vision deficiency resulting from a total loss of M cone function.
  • Deuteranomaly: A less severe defect occurring when a partially functional hybrid pigment gene replaces the normal OPN1MW gene.
  • Blue cone monochromacy: A rare, severe form of color vision deficiency that reduces visual sharpness and the ability to perceive most colors. This occurs when genetic changes, such as the deletion of the locus control region (LCR), prevent both OPN1MW and OPN1LW genes from functioning normally.

Other Names for This Gene

  • CBBM
  • GCP
  • green cone photoreceptor pigment
  • green cone pigment
  • green-sensitive opsin
  • M-pigment
  • middle-wave-sensitive pigment
  • OPN1MW1
  • OPSG_HUMAN
  • opsin 1 (cone pigments), medium-wave-sensitive
  • photopigment apoprotein

Frequently Asked Questions

Diagnosis usually involves a series of specialized eye tests, such as the Ishihara plates or the Farnsworth D-15 test, which assess a person's ability to distinguish between different colors. For a definitive genetic diagnosis, especially in rare or severe cases like blue cone monochromacy, genetic testing of the OPN1MW gene and surrounding regions may be performed.
Currently, there is no cure or specific treatment to correct color vision deficiencies caused by OPN1MW gene mutations. However, certain colored lenses or apps can sometimes help individuals distinguish between colors more easily in specific situations, though they do not restore normal color perception. Research into gene therapy is ongoing for some forms of inherited vision loss.
Yes, color vision deficiencies related to the OPN1MW gene are typically inherited in an X-linked recessive pattern. This means males are more commonly and severely affected because they have only one X chromosome. Females are usually carriers and may have normal vision or very mild symptoms. A male with an OPN1MW-related deficiency will pass the gene to all his daughters, making them carriers, but not to his sons. A female carrier has a 50% chance of passing the gene to each child, meaning sons have a 50% chance of being affected and daughters have a 50% chance of being carriers.
Individuals with blue cone monochromacy face significant daily challenges beyond just color perception. They often experience severely reduced visual sharpness (low visual acuity), extreme sensitivity to bright light (photophobia), and involuntary eye movements (nystagmus). This can impact activities like reading, driving, recognizing faces, and navigating in varying light conditions, often requiring visual aids, tinted lenses, and adaptations in educational and professional settings.
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.