Glaucoma is a serious eye disorder which primarily occurs due to increased intraocular pressure in the eye, which results in the damaged optic nerve. Normally, the drainage system in the eye and is known as trabecular meshwork. It is located at the angle between the cornea and iris. The aqueous humor which is fluid in the eye is absorbed in the blood through the drainage system. The drainage of this fluid is extremely important for the health of the eye.
The intraocular pressure in the eye is strongly associated with the balance of production and drainage of fluid. To maintain the health of the eye, normal functioning of the drainage system is important. Impaired drainage system could lead to the buildup of fluid in the eye and as a result, elevated intraocular pressure in the eye.
Symptoms of Glaucoma
Types of Glaucoma
The classification of glaucoma depends on the anterior chamber angle findings and the presence and absence of the factors that increase intraocular pressure in the eye. Basically, glaucoma is categorized into two types - Primary glaucoma and secondary glaucoma.
Primary glaucoma is a type of glaucoma which occur when there is no known cause of elevated intraocular pressure. Primary glaucoma is of three types:
1. Open angle glaucoma
Primary open angle glaucoma is a type of glaucoma which includes both primary open angle glaucoma and normal tension glaucoma.
- Primary open angle glaucoma is a most common form of glaucoma and in this subtype of open angle glaucoma intraocular pressure exceeds the normal range during the progression of glaucomatous neuropathy. It is strongly believed that abnormally elevated level of intraocular level plays an important role in the development of glaucomatous neuropathy.
- Normal tension glaucoma is also known as normal pressure glaucoma, and it is a type of open angle glaucoma in which the damage to the optic nerve occurs without any exceeding pressure on the eye. Normal tension glaucoma is a rare condition and the exact cause of this type of glaucoma is not known. But there are certain risk factors for normal tension glaucoma such as poor circulation in the eye, cardiovascular disease, genetins, and gender. It is believed that women are more likely to suffer from normal tension glaucoma.
2. Angle closure glaucoma
Angle closure glaucoma is characterized by elevated intraocular pressure which results due to the closure of anterior angle chamber rather than any other cause. The main angle closure mechanisms in angle closure glaucoma are angle closure glaucoma with relative pupillary block and plateau iris.
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- Primary angle closure glaucoma with a relative pupillary block is of two types - acute and chronic. In the acute type, the extensive closure of the anterior chamber leads increased intraocular pressure within a short period of time. It is accompanied by decreased visual acuity and weakened light reflex. In the chronic type of primary angle closure glaucoma with a relative pupillary block, the closure of the anterior chamber occurs gradually and as a result, the increase in the intraocular pressure is mild and gradual.
- Plateau iris glaucoma is a type of angle closure glaucoma in which the anterior chamber angle closes due to pupillary dilation without the blockage of iris, and this is known as plateau iris mechanism. When plateau iris mechanism is responsible for the development of glaucoma.
3. Mixed glaucoma
Mixed glaucoma is the third and the last subtype of primary glaucoma and it is defined as a condition which refers to the cases in which the primary angle open glaucoma and primary angle closure glaucoma develops in a combination.
Secondary glaucoma is a type of glaucoma which occur when elevated intraocular pressure in the eye results from some other diseases. The classification of secondary glaucoma is done from several standpoints, such as mechanisms that can cause an increase in intraocular pressure, etiology and the means of treatment. Secondary glaucoma is categorized into two types:
1.Open angle mechanism in secondary glaucoma
Open angle mechanism in secondary glaucoma can be characterized into three. It is characterized by aqueous outflow resistance between the trabecular meshwork and anterior chamber which results from a fibrovascular membrane, and conjunctival epithelium. It can also be characterized by aqueous outflow resistance in the trabecular meshwork and it can result from problems like inflammatory material and iris pigment deposition. In the third case, it is characterized by aqueous outflow resistance posterior to schlemm's canal and it can occur due to increased episcleral venous pressure.
2. Angle closure mechanism in secondary glaucoma
Angle closure mechanism in secondary glaucoma can occur due to certain cases such as it can occur due to pupillary block and it can occur due to problems like swelling in the lens, goniosynechiae etc.. This type of secondary glaucoma can occur due to anterior movement of tissue posterior to the lens which can be caused by an anterior movement of the lens and ciliary edema. Lastly, it can also be caused due to goniosynechiae, without pupillary block or anterior movement of tissue posterior to the lens.