Eye Care Tips

Eyes are organs that detect the light. Different kinds of light-sensitive organs are basically found in a variety of animals. The simplest "eyes", in even unicellular organisms, do nothing but then detect whether the surroundings are light or dark, which is more sufficient for the entrainment of circadian rhythms and may allow to the organism to seek out or avoid light, but hardly it can be called vision.
Retina

The retina contains one form of the photosensitive cells important to vision—rods and cones—in addition to these photosensitive ganglion cells involved in the circadian adjustment but probably not involved in vision. Though structurally and metabolically similar, that the functions of rods and cones are quite different. Rod cells are highly very sensitive to light, allowing them to respond in the dim light and dark conditions; however, that they cannot detect color differences. These are the cells that allow to humans and other animals to see by moonlight, or with very little available light (as in a dark room).

Cone cells, equally, need high light intensities to respond and have a high visual acuity. Different cone cells that respond to different wavelengths of light, which allows an organism to see color. The shift from cone vision to the rod vision is why the darker conditions become, the less color objects seem to have.


The differences between rods and cones are helpful; apart from by enabling sight in both dim and light conditions, and they have further advantages.

The fovea, directly behind the lens, and consists of mostly densely-packed cone cells. The fovea gives humans a highly detailed central vision, by allowing reading, bird watching, or any other task which mostly requires staring at things. Its requirement for very high intensity light does cause problems for astronomers, as they cannot see those dim stars, or other celestial objects, using by central vision because the light from these is not very enough to stimulate cone cells. Because cone cells are above all that exist directly in the fovea, astronomers have to just look at stars through the "corner of their eyes" (averted vision) and where rods also exist, and where the light is properly sufficient to stimulate cells, allowing an individual to observe faint objects.
Rods and cones are both very photosensitive, but respond very differently to different frequencies of light. They contain those different pigmented

photoreceptor proteins. And Rod cells contain the protein rhodopsin and this cone cells contain different proteins for each color-range., which basically lowers the number of open Cyclic nucleotide-gated ion channels on the cell membrane, which also leads to hyperpolarization; this hyperpolarization of the cell all leads to decreased release of transmitter molecules at the synapse.
Diseases, disorders, and age-related changes

There are number of many diseases, disorders, and age-related changes that may affect to the eyes and surrounding structures.

With aging a prominent white ring that develops in the periphery of the cornea- called arcus senilis. Aging causes laxity and then downward shift of eyelid tissues and atrophy of the orbital fat. These changes contribute to the permananent etiology of several eyelid disorders such as ectropion, entropion, dermatochalasis, and ptosis. The vitreous gel then undergoes liquefaction (posterior vitreous detachment or PVD) and its opacities—visible as floaters—increasingly increase in number.