- Human pathology

Home > F. Pathology by regions > Head and neck > Head > Face > Orbits > Eyes > cone cells

cone cells

Thursday 8 March 2007

The visual processing of humans is primarily reliant upon the sensitivity of cone photoreceptors to light during daylight conditions. This underscores the importance of understanding how cone photoreceptors maintain the ability to detect light (light detection).

The vertebrate retina consists of a combination of both rod and cone photoreceptors.

Subsequent to light exposure, both rod and cone photoreceptors are dependent upon the recycling of vitamin A (retinol) to regenerate photopigments, the proteins responsible for detecting light.

Metabolic processing of vitamin A in support of rod photopigment renewal, the so-called "rod visual cycle", is well established.

However, the metabolic processing of vitamin A in support of cone photopigment renewal remains a challenge for characterization in the recently discovered "cone visual cycle".

In this review we summarize the research that has defined the rod visual cycle and our current concept of the novel cone visual cycle.

There are several arguments in favor of a functional cone-specific visual cycle: the identification of novel enzymatic activities that contribute to retinoid recycling, the observation of vitamin A recycling in cone-dominated retinas, and the localization of some of these activities to the Müller cell.

See also

- Eyes

  • retina and retinal cells
    • photoreceptors


- Muniz A, Villazana-Espinoza ET, Hatch AL, Trevino SG, Allen DM, Tsin AT. A novel cone visual cycle in the cone-dominated retina. Exp Eye Res. 2007 Aug;85(2):175-84. PMID: 17618621. Free in PMC