Most types of glaucoma are associated with narrow filtration angle, which hinders the outflow of eye fluids so that high IOP is caused. High IOP spikes and damages the optic nerve, which is responsible for images transmission from the eye to the brain. Optic nerve damage in turn causes vision loss.
There are mainly two types of angle-closure (closed-angle or narrow angle) glaucoma: acute angle-closure glaucoma and chronic forms of narrow-angle glaucoma. Acute angle-closure glaucoma occurs suddenly and has symptoms such as eye pain, headache, light halos, dilated pupils, and red eyes and so on. If the high IOP is not removed within hours, acute angle-closure glaucoma is likely to bring permanent vision loss. Once suffered from acute angle-closure, patients should contact an eye doctor immediately for emergency treatment. Chronic forms of narrow-angle glaucoma have no obvious symptoms and develop slowly. Both acute narrow-angle glaucoma and chronic angle-closure glaucoma cause at least part of peripheral vision loss.
Narrow-angle glaucoma always causes the abnormal positioning of the iris. And there are reasons for this situation. In a normal way, eye fluids produced by ciliary (behind the iris) flows easily through the pupil into the anterior chamber. Once the back of iris adheres to the lens, eye fluids can not pass through this pupillary channel. The blocked eye fluids will push the iris forward until it closes the drainage angle in the anterior chamber.
Another reason for narrow angle is iris plateau, which is caused by the extreme close distance between the iris and the ciliary body. In this case, the peripheral iris tissue bunches up in the filtration angel due to pupil dilation, so that the angle is narrowed.
Narrowed filtration angle is also associated with certain eye problems such as hyperopia. Hyperopic people are more likely to have shallow anterior chambers and narrow angles. A tumor behind the iris also increases the risk of angle-closure glaucoma. Normal aging always enlarges lens and increases pupil block. The filtration angle is likely to narrow as people age. There is also anatomical difference between races that Asians and Eskimos have narrower anterior chamber angles than whites. Angle-closure glaucoma does not occur equally between genders in some races.
Acute forms of glaucoma may bring vision loss if high IOP is not removed within several hours. The drainage angle may be narrowed by many factors such as dim lighting, eye drop administration, medications such as antihistamine drops and so on. All treatments for narrow-angle glaucoma aim at removing high IOP within a short period, such as systemic medications, topical glaucoma eye drops, and laser or non-laser glaucoma surgery.
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