1. Briefly define the following parts of the eye and their role in vision:
A. Optic Nerve: each of the second pair of cranial nerves, transmitting impulses
to the brain from the retina at the back of the eye.
It is where energy is converted into electrical energy so it can travel to the brain and trigger
responses. The optic nerve is a continuation of rods and cones which make up the retina.
However, at its head, there is a blind spot because there are no photoreceptors in this part of
the optic nerve. This blind spot does not cause problems for people when seeing.
B. Macula: an oval yellowish(means that it absorbs blue and violet light which would
harm the retina thus acting as a protector/ sunblock for the retina.
)area
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However, even patients with controlled diabetes can develop diabetic retinopathy.
It is important for diabetic patients to be examined yearly because there are no
symptoms of diabetic retinopathy so early detection and treatment can help reduce the
risk of permanent vision loss. two forms of diabetic retinopathy:
Nonproliferative: this is where exisiting blood vessels in the retina completely deteriorate. These
deteriorated blood vessels can become blocked or develop into aneurysms. Then fats, fluids,
and proteins leak out of the abnormal blood vessels. The fluids then collect in the retina and
cause the macula to swell, this is called edema. Edema impairs the vision responsible for
seeing fine detail and reading.
Proliferative: This is where new blood vessels grow on the surface of the retina which cause
small hemorrhages and bleeding. This causes scar formation which allows the clear gel of the
vitreous to adhere to the retina. This puts pressure on the shape of the vitreous causing it to
change its shape and tear the retina causing retinal detachment. It can treated can be treated
three ways:
Photcoagulation: A focal is used to burn the areas of the retina where the abnormal
Also, on the retina is the optic disk. There are no photoreceptors in this area, so any light that falls on this part of the retina is unseen and creates what is called the blind spot. (Hugh
1. Red – retinal arterioles, hemorrhaging, neovascularization, vascular anomalies, vascular tumors, retinal breaks, holes in retinoschisis, cilioretinal artery, and inner portion of thin areas of retina
Age related macular degeneration (AMD) is the leading cause of blindness in people over the age of 50. Every ten years after the age of 50 the prevalence of this disease increases exponentially. Many different factors contribute to the development of AMD including genetic, environment, and metabolic functions. Aside from smoking, abnormal blood pressure, and an unhealthy diet low in fruits and vegetables, many more studies are concluding that similar inflammatory and oxidative processes seen in other age related diseases are also playing a key role in the development of AMD. This disease affects the central areas of the retina and choroid. In return central vision is impaired while peripheral vision is usually not lost. AMD is seen in two different forms, the earlier nonneovascular (dry) type and the more advanced neovascular (wet) type. Each form has its own specific pathology and unique characteristics that set them apart. Fatty, protein deposits called drusens may be the key risk factor in understanding dry AMD pathology, progression, and treatment. Once the more advanced wet AMD is diagnosed, pathology and treatment are targeted around the formation and destruction of abnormal blood vessels, characteristic of the wet AMD eye. The increasing prevalence of AMD has influenced more investigation into what factors can be modulated to prevent the onset or to stop the progression of AMD. This text will discuss the pathology of drusens and the role of inflammation and
The most frequent ocular complications reported for all the AVM groups, are: vascular occlusions, aneurysm formation, intraretinal haemorrhage, exudation and cystoid macular oedema. Furthermore, neovascular glaucoma and open angle glaucoma have been described as a result of a retinal central vein occlusion [1].
The lower pressure in the vitreous cavity also allows the choroidal expansion. Normally, the pressure within the eye drives the fluid from the extravascular choroid outside via the sclera. However, under hypotonous conditions this pressure head is reduced thereby prolonging the time taken for the fluid to disappear.16 The choroidal detachment may also prolongs the
In the normal eye, the aqueous humor is the fluid circulation within and that also flows out via a drainage canal. When the outward flow is inhibited, there is a buildup of ocular pressure inside that causes damage, and this is called glaucoma. This condition can be traumatic for the patient as it has no cure. There are two categories that will be discussed in this paper and they are open angle glaucoma and closed angle glaucoma (The glaucoma you may be missing, 2013).
Glaucoma is the name given to a group of eye diseases that causes damage to the optic nerve fibers and can lead to progressive vision loss or blindness if left untreated. The damage is primarily a result of the buildup of intraocular pressure, which results when an imbalance occurs in the production and drainage of aqueous humour. However, some glaucoma is not distinguished by high intraocular pressure, but as optic nerve damage. In the human eye the ciliary body constantly creates aqueous humour to provide sustenance for surrounding tissues. To maintain a healthy balance as new fluid is produced, older fluid must leave the eye through the meshwork drainage system along the periphery of the iris. If too much aqueous humour is produced or the drainage system is not working properly, consequently intraocular pressure builds, causing optic nerve fiber damage and deterioration of vision.
This article discussed the eye disease, Glaucoma. There are two types of Glaucoma; open-angle and closed-angle. Open-angle Glaucoma there are no visual abnormalities, but there is a mechanical obstruction interfering with the drainage pathway. While closed-angle Glaucoma is a physical obstruction. Signs and symptoms of Glaucoma are; headache, nausea, vomiting, blurred vision, halo vision, and eye pain. Glaucoma progresses slowly and is asymptomatic at first. As the disease progresses symptoms appear, if symptoms are present then there is already irreversible damage to the eye. There is no cure for Glaucoma, treatment is aimed at slowing the progression of the disease. Diagnostic tests done to detect Glaucoma are; measuring IOP, evaluation of
85% of the AMD cases are classified as the dry from, yet wet AMD accounts for 90% of the total cases of legal blindness in AMD. In wet AMD, abnormal neovascular tissue, which was originated from the choriocapillaris, grow underneath the RPE monolayer or into the subretinal space. The newly immature blood vessels can leak fluid into the retina and cause degeneration of the RPE and retinal cells. If left untreated, the degenerated area will continue to enlarge. The end stage of wet AMD is marked by the formation of fibrotic disciform scars on the fovea, which will lead to a permanent central vision loss [3]. Identification of RPE-derived fibrotic cells in surgically excised fibrotic disciform scars from wet AMD patients[4] suggests that RPE cells undergo proliferation and an epithelium-to-mesenchymal transition (EMT) as a part of the wound healing response. Currently the use of anti-vascular endothelial growth factor (VEGF) therapy can ameliorate the condition; however, this treatment can not prevent the formation of scar tissues and can not restore the loss of RPE
Glaucoma is a group of eye disorders that cause blindness by hurting the optic nerve, which is the large nerve that is responsible for vision. In glaucoma, the optic nerve damage is related to a change in the fluid pressure that circulates around the eyeball. In many cases, Glaucoma occurs when the eye's fluid pressure is high, but it can also occur when the pressure is measured as normal.
Diabetic retinopathy (DR) is a common microvascular complication of diabetes. With increasing global prevalence of diabetes, DR is a major cause of vision impairment, which accounts for 5% of all blindness, affecting approximately 5 million people worldwide, and is characterized by the progressive occlusion of capillaries, leading to retinal nonperfusion.
The retina is a very delicate and thin layer in the back eye that helps with vision. It is light sensitive and “...acts like the film in a camera. Images come through the eye’s lens and are focused on the retina” (Retina: MedlinePlus Medical Encyclopedia, n.d). Like many parts of the
The surgery requires a small instrument that is inserted into eye which cuts the vitreous gel sack and sections out the gel. From here any further treatment can be carried out, whether it's to treat the retina with a laser or repair a
The optic nerve has to enter the confines of the eye somewhere in order to innervate the retina. Where it enters has no rods and cones (the very nerve endings of the optic nerve which allow us to see). Therefore, this is a "blind spot."
Visual processing in our brain cannot be done without actual vision. The anatomy of the eye is carefully arranged with all the parts that assist our vision in an optimal way. A layer of connective tissue called the sclera surrounds the eyeball. Underneath it is the choroid, which is rich in blood vessels that supply the eye. Attached to this layer is the lens by cililary muscles. The lens focus light to the retina and the amount of light entering is controlled by pupil dilation or constriction. Pupil dilation and constriction is regulated by the iris of the eye which consist of two layers of smooth muscle layers that contract or constrict to increase or decrease the diameter of the pupil respectively. The retina is the inner most layer of the eye. It the main site of photoreceptors that convert light energy into electrical energy where the information gets sent to the brain and is what we perceive as vision. (Marieb, 2014)