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...
... middle of paper ...
...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
Viringipurampeer I. A., Ferreira T., DeMaria S., Yoon J. J., Shan X., Moosajee M., Gregory-Evans K., Ngai J., Gregory-Evans C. Y., (2012) Pax2 regulates a fadd-dependent molecular switch that drives tissue fusion during eye development, Human Molecular Genetics, Vol. 21, No. 10 2357–2369
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.
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.
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
The four main components of the eye that are responsible for producing an image are the cornea, lens, ciliary muscles and retina. Incoming light rays first encounter the cornea. The bulging shape of the cornea causes it to refract light similar to a convex lens. Because of the great difference in optical density between the air and the corneal material and because of the shape of the cornea, most of the refraction to incoming light rays takes place here. Light rays then pass through the pupil, and then onto the lens. A small amount of additional refraction takes place here as the light rays are "fine tuned" so that they focus on the retina.
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.
parts to it; the choroids, ciliary body, and the iris. The choroids is what provides
An inspection of the modern animal phyla will reveal that eyes are just as diverse as they are complex. Some organisms like the rag worm have pigmented cup eyes while other like he box jellyfish have two lens eyes and two pairs of pigment pit eyes. To account for the diversity in eye structure, we must first examine the eye ‘prototype’, the original structure that was acted upon by evolution. The simplest organ that can be considered an eye is composed of a single photoreceptor cell and a single pigment cell, without any lens or other refractive body (Arendt, 2003). Such organs are know as eyespots, and...
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.
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...
This protects the eye from becoming dry.The Cornea, a part of the sclera, is the transparent window of the eye through which light passes. The focusing of the light begins in the cornea.Behind the Cornea is a watery fluid called the aqueous humor. This fluid fills a curved, crescent shaped space, thick in the center and thinner toward the edges. The cornea and the aqueous humor together make an outer lens that refracts, or bends, light and dire...