Acute and chronic forms of glaucoma

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Statistics show that approximately 20% of glaucoma cases are associated with narrow filtration angle between the cornea and the iris, which hinders the outflow of eye fluids so that high intraocular pressure (IOP) is caused. High IOP spikes and damages the optic nerve, which is responsible for transmitting images from the eye to the brain. Optic nerve damage in turn causes vision loss. Glaucoma is one of the leading causes of blindness due to exactly its damage to the optic nerve.

Acute forms of angle-closure glaucoma are the majority

There are mainly two types of angle-closure (closed-angle or narrow angle) glaucoma: acute angle-closure glaucoma and rare cases of chronic form narrow-angle glaucoma. As the name suggests, acute angle-closure glaucoma occurs suddenly without giving any sign in advance. It has some typical symptoms such as eye pain, headache, light halos, dilated pupils, and red eyes and so forth. This type of glaucoma is also accompanied with a sudden increase in intraocular pressure. If the high IOP is not removed within several hours, acute angle-closure glaucoma is quite likely to bring permanent vision loss. Once suffered from acute angle-closure glaucoma, patients should contact an eye doctor immediately for emergency treatment.

Chronic cases of narrow-angle glaucoma are exceptions

Exceptions do exist that some 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. This may be confusing that it is widely said that chronic glaucoma equals the open-angle type that is opposite to angle-closure form. However, there are definitely some chronic cases of glaucoma within the category of narrow-angle or angle-closure.

Two iris-related abnormalities may close the drainage angle

Narrow-angle glaucoma always causes an abnormal positioning of the iris. And there are different reasons for this situation. In a normal way, eye fluids produced by ciliary (behind the iris) flow 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 an extremely 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.

Other various reasons for narrowed filtration angle

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. As a result, the filtration angle is likely to narrow as people age. There is also anatomical difference between different races that Asians and Eskimos have narrower anterior chamber angles than whites. Angle-closure glaucoma does not occur at a same rate to men and women in some races.

How to deal with acute glaucoma

Acute forms of glaucoma may bring vision loss if high IOP is not removed within several hours. The drainage angle may be narrowed by some other factors, such as dim lighting, eye drop administration, medications such as antihistamine drops and the like. Finding the exact cause is critical for taking a right action. In most cases, symptoms of acute glaucoma will disappear once the underlying contributing factor is eliminated. 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.