Chronic simple glaucoma
It is the most common and most insidious form of glaucoma. Often referred to as the "silent thief of sight" so as to highlight the absence of pain or other symptoms. With this type of glaucoma the "angle" (ie the channel through which the aqueous humor drains from the eye) remains open (open-angle glaucoma), but gradually loses its functionality. Thus, over time and advancing age, intraocular pressure increases as does the risk of optic nerve damage.
Normal pressure glaucoma
Some people have an optic nerve that is more sensitive to pressure resulting intraocular pressure values that are generally considered "normal" likely to cause visual damage. In these cases, the new imaging technologies of the optic nerve fibers significantly help in easily identifying even the smallest defects, thus, preventing any unpleasant consequences before it is too late.
In some people, the iris (the colored part of eye) is very close to the angle / drainage canal of the eye, resulting in narrowing and reducing its functionality. These people usually have small eyes and hyperopia.
Under certain conditions (eg darkness or dim lighting), it is possible for the iris to be shifted further forward and lead to complete obstruction of the angle and a sudden increase in intraocular pressure.
The symptoms are rather severe and include extremely intense pain in the affected eye, blurred vision and colored circles like rainbows around lights, although headache, nausea or vomiting can also co-exist.
Acute glaucoma is an emergency condition and if not treated immediately by a specialist ophthalmologist, may even lead to blindness within a few hours.
Glaucoma due the use of corticosteroids
The use of corticosteroid drugs in any form (skin creams, eye drops, inhalations, injections, etc.) may raise intraocular pressure within a few days or weeks because of direct effect these drugs have on the eye's drainage system. Upon discontinuation of the drugs in intraocular pressure returns to pre-administration levels, although long-term use may keep the pressure elevated for months after their discontinuation.
Other forms of glaucoma
As previously mentioned glaucoma is caused by a number of diverse causes and a variety of mechanisms.
Some syndromes are quite common in the general population, such pseudoexfoliation syndrome and pigment dispersion syndrome, result in the deposition of particle in the angle (the drainage of the eye) and obstructing it, just like blocking the sink with foreign objects. This reduces the amount of aqueous humor fluid that can be discharged in unit time, leading again to the accumulation and increased intraocular pressure.
The lens of the eye (located behind the iris) may also be responsible for the obstruction of the angle / drainage canal in various ways. For example, with "phacolytic" glaucoma, the release of "material" from a lens with overripe cataract can block the angle, causing a painful increase in intraocular pressure.
Various ischemic causes, such as diabetes, carotid stenosis, etc., promote the formation of a membrane from pathological vessels called "neovascular membrane." With the progression of the disease, this membrane grows and contracts, pulling the iris forward and obstructing the angle.
Glaucoma can also be induced through different mechanisms of ocular tumors, trauma, surgery, etc.
Congenital glaucoma is a special group of glaucoma that usually develops in the first 3 years of life, occurring in 1:10000 births. Given that the eye is still delicate at this age, increased pressure causes swelling of the eye resulting in a clinical manifestation called "buphthalmos" because the eye grows and resembles the "eye of a bovine". In addition, the child is restless, has teary eyes, photophobia and closes or rub his/her eyes. All these symptoms should alarm parents enough to immediately rush to an ophthalmologist for thorough examination.