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SUBJECTS:
FOREWORD
The GLAUCOMA is a complex disease, with a chronical and progressive trend and nowadays it is still the subject of research and study. The different multiform clinical conditions induce to establish more and more advanced and reliable diagnostic techniques in order to allow more precocious and correct diagnosis. In the meantime, the therapies involving both collyrium and laser and surgery, are aimed to produce more and more enduring results.
Glaucoma is a pathology that involves thousands of different aspects and most of times it can underhandedly but irreversibly affect the sense of sight: we have to remember that glaucoma is the second world wide cause of blindness.
For this reason, patient is the most important element for the treatment of the glaucoma disease, as he must co-operate accepting to undergo long therapies and periodical analyses. This “contract” between doctor and patient is the “winning ace”: in fact a relationship of mutual trust will reward the first one for his efforts and the second one for his perseverance, and the prize is the best of results, that is the preservation of the sense of sight.
For a better comprehension about rising, development and damages produced by this disease, it is necessary to supply some information about the eye anatomy, the intraocular pressure and the visual field.
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ANATOMY
The eyeball is similar to a sphere, such as a football balloon, consisting of different layers.
Starting from the outer part, we find the fibrous shell called "sclera", whose fore portion is called "cornea". This last part is perfectly transparent and is similar to a real glass having a spherical shape. Behind cornea, we have a space called "anterior chamber", whose rear boundary is "iris"(the eye colored part), where you can see a central hole: the pupil. This structure acts as a diaphragm for the light that enters inside the eye. It changes its diameter according to the amount of light of the environment where we are, thus maintaining the best lighting conditions inside the eye.
The "crystalline lens", is located behind iris and it is a transparent lens conveying the rays of light inside the eye. A transparent, gelatinous substance called "vitreous body " is contained inside the eye cavity behind the crystalline lens..
The whole eye inner surface is coated by the "retina" that consists of millions of nerve cells which are sensitive to light. The prolongation of these cells, like very thin and tiny threads, are grouped into larger and larger bundles (more than a million per eye) thus constituting the "optic nerve". The optic nerve can be compared to an electric wire that comes out from the eye rear part, carrying the visual nervous impulses up to the brain, where they shall be decoded and transformed into visual images. The point of connection between this wire and the eye rear part is called "papilla".
All the structures mentioned till now have to be nourished for maintaining their functionality. Feeding is assured both by the blood vessels circulating inside the eye and by a liquid substance produced inside that organ: the "aqueous humor". This transparent liquid containing a lot of feeding substances is produced behind iris by some organelles called "cilial processes". The aqueous humor laps the crystalline surface and flows through the pupil foramen to the anterior chamber until reaching contact with cornea. The aqueous humor is absorbed at the "angle between iris and cornea" by a grilled frame, that can be compared to a sponge, called "trabeculate", acting as a real gutter pipe that discharges it outside the eye.
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THE INTRAOCULAR PRESSURE
We can compare the intraocular pressure to the strength provided by the air inside our football balloon, that without an adequate pressure would deflate. In the eye this strength is not actuated by the air, but by the aqueous humor, which is constantly balanced between the "tap" that inlets it (the cilial processes), and the outlet hole (the trabeculate). So a constant balance is assured for preserving a correct and adequate pressure inside the eyeball. If this balance is altered, the consequence will be a raise of the eye internal pressure: the glaucoma disease will therefore start to develop.
The normal intraocular pressure varies between 12 and 20 mmHg, with a trend towards higher values in the morning, and lower ones in the evening and during the night.
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THE VISUAL FIELD
We can define the "visual field" as the portion of surrounding environment within which we can perceive images without displacing our looking direction. If our eyes are healthy and we are looking at a castle on the top of a mountain, besides the castle, we will perceive the mountains, the sky, the trees and so on: this is our visual field
In the normal visual field, we have only one dark area called blind spot, corresponding to the projection in the space of the optic disk. Either when we look through one or through both eyes, this small area is not perceived.
When both eyes are correctly operating, the visual field is wide (upper picture), but when a glaucoma is in progress, it can be reduced (central picture) until reaching the condition when a patient thinks to look through a tunnel (lower picture).
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