Coloboma is a congenital eye defect, which is represented by missing pieces of tissue (gaps or notches) in eye structures.
The eye consist of several protective layers and cavities. The outer layer consists of the sclera and the cornea. The front part of the sclera is covered by a transparent membrane called conjunctiva, involved in protecting the eyes and lining the inside of the eyelids. The cornea is a dome-shaped structure in the front of the eye that encloses the anterior chamber of the eye. It is transparent, allowing light to enter the eye, and along with the lens helps focus and direct light onto the retina.
The middle layer of the eye includes the iris, the ciliary body, the lens and the choroid. The iris gives a person’s distinct eye colour, controls the size of the pupil and hence the amount of light entering the eye. It separates the anterior and posterior chambers in the front part of the eye. These chambers contain the aqueous humour, which is important in nourishing the lens and cornea. The lens is a shear, flexible structure, which changes its shape and hence participate in focusing one’s vision on close or distant objects. The vitreous humor is a jelly-like substance that fills the back portion of the eye. It has a structural function and is involved in maintaining the eye’s shape, but also helps transmitting the light to the retina. The choroid is a membrane found between the sclera and the retina. It lines the back of the eye and is rich in blood vessels. It is highly pigmented in order to absorb light and prevent scattering.
The inner layer- the retina lines the inside of the back part of the eye and is the light-sensitive part. It is rich in photoreceptor cells and each photoreceptor is linked to...
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...Willer, G.B., Smith, K., Gregg, R.G., and Gross, J.M.(2008) Zebrafish blowout provides genetic evidence for Patched1-mediated negative regulation of Hedgehog signaling within the proximal optic vesicle of the vertebrate eye, Developmental Biology 319(1):10-22
Sanyanusin P., A.McNoe L., J.Sullivan M., Weaver R.Grey. Eccles M.R. (1995) Mutation of PAX2 in two siblings with renal-coloboma syndrome, Human Molecular Genetics Vol. 4, No. 11 2183-2184
Torres M, Gómez-Pardo E., Gruss p. (1996) Pax2 contributes to inner ear patterning and optic nerve trajectory , Development 122, 3381-3391
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The widespread involvement of Retinal Pigment Epithelium (RPE), flat (placoid) nature of the lesions and absence of overlying serous retinal detachment and minimal choroidal involvement lead Gass to conclude RPE was primary focus of inflammation.(1) ...
The MECP2 gene makes a protein, also called MECP2, believed to play a pivotal role in silencing, turning off or regulating the activity of other genes. The MECP2 mutation (change in the gene) causes the turn-off/regulatory mechanism to fail, allowing other genes to function abnormally(Rett Syndrome - NORD). Rett syndrome is a genetic disorder of developmental failure of brain maturation. This is thought to occur when subsets of neurons and their connections are disrupted during a dynamic phase of brain development. This deviation occurs at the end of pregnancy or in the first few months of life during the critical phases of synapse development. How mutations in MeCP2 lead to Retts is not well understood but is the focus of intense research.
Sousounis, k., A. Ogura, and P.A. Tsonis. 2013. Transcriptome Analysis of Nautilus and Pygmy Squid Developing Eye Provides Insights in Lens and Eye Evolution. PLoS ONE 8(10): e78054
There's a disease that lurks among young children even to this day. It's a direct result of a mutation in the genes that could result in the removal of the eye. Both boys and girls are affected, and one in every fifteen to thirty thousand babies is infected every year (Ambramson, Ch1). This eye corrupting, chromosomal abnormality shows up in about 300-350 new cases each year. It is called retinoblastoma.
Macular degeneration in general can affect many people in minor or drastic ways. People who experience this form often complain of vision loss when they are in dim light, especially when they are reading. The "dry" type is often characterized by a more gradual loss of vision compared to the "wet" type. Signs of this disease include an increase in drusen, which is an accumulation of a yellow-white substance, in the underside of the macular retina. A loss of cells can be seen in the macula. The macula is our sensitive sight region, where intricate detail can be seen. Thus, vision in this area is helpful and necessary to drive, read, focus on small details, and recognize familiar faces. The macula is located in the back of the eye known as the retina. The macula is only about 5 mm in diameter, and includes the fovea, which gives us our detailed central vision. If a person suffers from the "dry" form in one eye they will be more likely to develop it in the other eye as well.
This is a representation of the eye's lens system. This eye has no eye condition, such as nearsightedness or farsightedness, and the lens is drawn in its relaxed position. The light rays are focused appropriately on the retina. The thickness of the cornea is 0.449 mm, the distance from the cornea to the lens is 2.
Amblyopia is a condition in which visual acuity in one eye is greatly reduced. It is caused by lack of stimulation or disuse during visual development (Rose, 1998). Because the eye is not fully developed at birth (Jarvis, 1992, as cited in Rose, 1998), infants need stimulation to complete the visual neural pathway. When one or both eyes are inhibited, for example due to misalignment of one eye (strabismus) or a large difference in refractive power between two eyes (anisometropia), the neural pathway for the inhibited eye develops abnormally, or does not develop at all. At approximately six years of age eye development is complete (Stager, 1990, as cited in Rose, 1998). Before visual development is complete amblyopia can be treated. If it is caught and treated at an early age, normal vision can be preserved (Rose, 1998).
Fluid circulating inside the front portion of the eye is produced by a structure called the ciliary body, which is located behind the iris. This fluid moves through the opening of the pupil, passes into the space between the iris and the cornea, and drains out of the eye through a tissue called the angle. With glaucoma, the passing of fluid through the angle is either reduced or suddenly stops, and amounts of fluid inside the eye increase. This high fluid pressure hurts the nerve fibers and the eye's optic nerve and causes blind spots. It may lead to blindness in some cases.
of the eye, this is what gives form to the eyeball. The vascular tunic has three
Another important interaction is with Bax, a protein in the Bcl-2 family, that is important in apoptotic pathways. PrPC is known to inhibit Bax activity, preventing apoptosis in fetal neurons.1 Other proteins that are known to interact with PrPC include, but are not limited to, the Grb2 signal transduction adapter protein, TREK-1 potassium channel, tubulin, N-Cell adhesion molecule, and synapsin 1b, which is involved in synaptic vesicle trafficking.1 Because of its broad physiological cellular involvement, PrPC has the potential to influence many cellular functions. Although there have been somewhat mixed results, some PrPC knockout mice have shown normal development, followed by neuronal decline, due to a lack of the Prnp
One sub-system under the sensory system is the visual system; the main sense organs of this are the eyes. The eye is the sensory organ that allows us to detect light from external stimuli. When a light ray is detected, the eye converts these rays into electrical signals that can be sent to the brain in order to process the information and giv...
The incredible thing about the human eye is that it can see objects to as far as 2 miles long.That’s almost 35 football fields! Let’s consider the mechanics of the eye. The eye is a clear ball with water-like fluids in there.You have the front of the eyeball which is translucent called the cornea. It’s extremely thin and its job is to protect the eye by refracting light that comes through. The next part of the eye is the pupil, which mostly everyone knows about.It is the black portion in your eye. Did you know that it gets its color from when light entering the eye is absorbed and it doesn’t leave the eye. You may also notice that when you’re looking at the pupil, you can see a different colored circle in them. This is called the iris, and it varies among everyone. Your actual eye color is determined by a pigment in the iris.The genes from your parents set a human’s eye color. The iris’s job is to widen or close depending on how bright or dark it is. If its bright and the sun is basically beaming down on you, the iris will adjust so your pupil will get smaller to only let a certain amount of light in. If you’re in the dark, your iris adjusts so your pupil will get bigger so a greater...
The images formed on the two retinas are so unlike that they cannot be blended in the brain. Thus, a double image is perceived. The condition is known as diplopia, or double vision. Prismatic lenses are prescribed to correct this defect.Imperfections in the cones of the retina, resulting from heredity or disease, cause defective color vision. This is known as color blindness, or Daltonism. In total color blindness, everything appears in shades of gray.