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MACULAR CAROTENOIDS

MACULAR CAROTENOIDS

Eye and its structure
Anatomy of the Eye
Eye is formed from both mesenchyme and ectoderm and is an intricate sense organ. Ectoderm derived from retina that is formed by neural tubes, smooth muscles of iris and optic nerves. On the side of head, exterior ectoderm forms conjuctival epithelium and corneal, lacrimal glands and lens. The mesenchyma forms sclera, cornea, choroid, iris, cell lining the anterior chamber and part of vitreous body. The protective structure of eye includes the lids, orbits and sclera. Sockets are the two orbits that are present in the skull at the front.

The eyeball
In the orbital cavity eye ball is located. This cavity gives the strong bony structure along with protection. In ocular movement, this cavity provides the six extrinsic muscles that help for this function.  anteriorly 

The cornea 
The transparent structure and the compressed dome shaped is present in front of iris and pupil that is called as cornea. In the sense, it is an exceptional tissue that has nerve fibers only that are sensory nerves mostly whereas there are no blood vessels present in it. 
Cornea serves as a filter by the quality of being translucent. It is almost 700 μm at the periphery and 500 μm thick in the center and has a diameter of 11 mm roughly. 
Due to edema, cloudy cornea and increased smattering light can be resulted and in severe conditions complete opacity of cornea may be resulted by the swelled stroma. 

The Sclera
Sclera is dense and it can form eye ball posteriorly five-sixth. The sclera in children gives a bluish tinge and in adults it is white. Due to deposition of fat, in older people it gives a yellowish tinge.  

The iris and the crystalline lens
Iris is the part of an eye that blocks surplus light from entering in the eye and gives color to the eye. A magnifying glass is present behind the iris and is called lens that helps in focusing light. 

The Retina
Retina is a part of an eye that is thin and contains the layers of supporting cells, nerves and photoreceptors. It is also called as the brain’s sight center, where vision takes place which is the most vital part. 

Photoreceptor layer
The cone and rod cells that are the two photoreceptors make the photoreceptor layer and is a very subtle part of an eye. The main function of the photoreceptors is the modification of photons of light and photo transduction into electrical signals. In the exterior segment discs of photoreceptors pigments are present in the membranes. In the yellow, blue and green parts of the spectrum the cone pigments give peaks of absorption. In the blue-green part of the spectrum pigments of rod give peaks of absorption.  Cones are adjusted to light that are too bright and can resolve color vision and fine details. In all segments of retina the density of cones and rods is not same.  Towards the periphery the number of rod increases rapidly and rods are not present at fovea. While in the case of cones their number rapidly decreases towards periphery and they are dense much at fovea. Cones and rods have an extended slender shape. 

The retinal pigment epithelium (RPE)
RPE is a light absorbing outer layer of the retina. It is comprises on a single layer that contains cubical cells. This is a layer in between choroid and retina.  The reflected and spotted light is immersed by melanin in the RPE which is a black color pigment. By the photoreceptor cells the waste products are produced and these are disposed as well as processed by RPE.  By the passage of age when a person becomes older it is sometimes unable for RPE to discard this waste. This removal of waste results in dry macular degeneration which is a result of distortion of retina.   


Against the infused drugs tear film is the basic physiological barrier. The transport of drugs takes place through cornea in the anterior chamber. For systematic administered drugs the main barriers are retinal capillary endothelium and retinal pigment epithelium. To reach the vitreous an invasive strategy is an intravitreal injection. Drugs can be conceded away either by aqueous flow or by the venous blood flow  from the anterior chamber. By the blood retinal barrier. Or through diffusion drugs can be distant into the anterior chamber from the vitreous.
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The visual process 
The visual process starts when the light is fused or immersed in the exterior segment of photoreceptors cells.  The main 5 classes of retinal neurons interrelates and do the ensuing encoding.
The information is encoded by this interface of neurons. Through the ganglion cells the furthermore information is sent to the pathway of central visual. 
For normal functions of retina a huge number of glial cells are accountable. Muller cells are the most important glial cells that are involved in metabolite metabolism, neurotransmitter and chromophore recycling. For neural retina’s proper functioning RPE cells are crucial. These includes, the transport and storage of vitamin A derivatives, phagocytosis of exterior segments of photoreceptors, recycling of the visual pigment and so many functions other than this. 





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