There are two types of photoreceptors involved in sight: rods and cones. Rods work at very low levels of light. We use these for night vision because only a few bits of light (photons) can activate a rod. Cones require a lot more light and they are used to see color.

three

These specialized cells are called photoreceptors. There are 2 types of photoreceptors in the retina: rods and cones. The rods are most sensitive to light and dark changes, shape and movement and contain only one type of light-sensitive pigment. That’s why you cannot see color very well in dark places.

Before Retinal Cells Die, They Regenerate, Penn Vet Blindness Study Finds. Until relatively recently, the dogma in neuroscience was that neurons, including the eye’s photoreceptor cells, rods and cones, do not regenerate. This is the reason that nerve damage is thought to be so grave.

Damage to the retina can lead to irreparable loss of vision in humans and other mammals because their retinas do not regenerate. When the retina is damaged, Müller glial cells proliferate and differentiate into the lost retinal neurons, effectively replacing injured cells with fully functional ones.

Currently, there is no treatment to stop a person with cone-rod dystrophy (CRD) from losing their vision. However, there may be treatment options that can help slow down the degenerative process, such as light avoidance and the use of low-vision aids.

Deterioration of Rods and Cones Deterioration of cones and rods can cause decreased sharpness in vision, increased sensitivity to light, impaired color vision, blind spots in the center of the visual field, and partial loss of peripheral vision.

Damage to cone cells can result in decreased clarity of vision (reduced visual acuity) when looking straight ahead (central vision), a reduced ability to see colors and an abnormal sensitivity to light (photophobia).

The cones cells enables us to see the colours and makes us distinguish between various colours. So if Rods and cones are not present in retina , then person cannot see the objects at nights and during day time the person cannot see the colours at day time. Person may suffer with blindness.

Cone–rod dystrophy phenotype may also be seen with specific mutations in genes that are typically associated with other retinal diseases. For example, ABCA4 is most commonly associated with Stargardt disease, but is also responsible for 30–60% of cases of autosomal recessive cone–rod dystrophies.

There are multiple genes which can cause Cone-Rod dystrophies, with mutations in these leading to a loss of cone and rod photoreceptor cells. Genes linked with this condition include ABCA4, CRX, GUCY2D and RPGR.

A child born with non-functioning cones will have achromatopsia. Mutations in the following genes are known to cause achromatopsia: ATF6, CNGA3, CNGB3, GNAT2, PDE6C and PDE6H.

Retinitis pigmentosa and other photoreceptor dystrophies The most common form of RP is a rod–cone dystrophy, characterized initially by night blindness, followed by progressive loss in the peripheral visual field in daylight, eventually leading to blindness after several decades.

Retinitis is a disease that threatens vision by damaging the retina — the light-sensing tissue at the back of your eye.