Glaucoma: Symptoms, Causes and Treatment

Glaucoma is a term used to signify a group of eye diseases that cause damage to the optic nerves. Glaucoma usually involves the loss of retinal ganglion cells, which if left untreated, could lead to permanent damage of the optic nerves, and consequently to the visual field. The optic nerves are responsible for receiving light from the retina, and sending them as impulses to the brain. Damage to the optic nerves leads to blindness and glaucoma has been found to be the second leading cause of blindness.

Causes of Glaucoma
Increase in intraocular pressure is considered to be one of the major contributing factors of glaucoma. However, in many instances, it is found to occur in persons having normal eye pressure, while some with constant high eye pressure may not develop the disease at all. Intraocular pressure depends on the production as well as drainage of a liquid known as aqueous humor, which nourishes the structure of the eye. Aqueous humor is produced by the ciliary bodies and it fills the anterior chamber of the eyes. This fluid is transported through a drainage system known as trabecular meshwork. Any factor that leads to blockage or reduction in the flow of aqueous humor through the trabecular meshwork causes accumulation of this fluid in the anterior chamber, thereby raising the interocular pressure of the eye. If left untreated, this condition can cause permanent damage to the optic nerves and retina.

Types of Glaucoma
Generally, glaucoma is divided in two categories, open angle and closed angle glaucoma. In case of open angle glaucoma, the flow of aqueous humor through the trabecular meshwork reduces, which causes accumulation of this fluid in the anterior chamber of the eye. This results in the increase in eye pressure or intraocular pressure. Open angle glaucoma is the most common form of glaucoma and is also known as chronic simple glaucoma. On the other hand, in closed angle glaucoma, the iris of the eye is pressed to the front against the trabecular meshwork, which narrows down the space between iris and cornea. This in turn prevents the flow of the fluid through the trabecular meshwork, leading to an increase in the intraocular pressure.

Besides these two main types of glaucoma, there are other types which have been found to occur. Congenital glaucoma is a rare type found among infants. Another type, known as secondary glaucoma is usually the result of some other disease like diabetes or tumors. Long term use of some medicines such as steroids can also cause this condition. Besides these, glaucoma can also occur due to problems of the eye, such as inflammation or ocular trauma.

Sometimes exfoliation syndrome occurs due to deposition of some whitish material on the lens and the drainage angle of the eye. This material can also increase the intraocular pressure by blocking the drainage system of the eye, along with the pigment of the iris. It is a common open angle glaucoma.

Pigmentary glaucoma occurs when the iris bends backwards, coming in contact with neighboring structures, particularly those found near the lens. Pigment layers at the back of the iris gets damaged as they rub against the lens. This leads to pigment particles getting released into the aqueous humor, blocking its flow through the trabecular system, with the consequent rise in the eye pressure. Glaucoma is more common in nearsighted persons.

Symptoms of Glaucoma
In the early stages, glaucoma may not show any symptoms. As the disease develops slowly, it is hardly detectable in the early stage. However, angle closure or closed angle glaucoma may show some symptoms like eye pain, red eye, along with headache, nausea, blurred vision and sensitivity to light. Generally in case of congenital glaucoma, it is difficult to recognize the symptoms due to young age of the child, but if a child shows sensitivity to light (photophobia), enlargement of the eyes due to increased eye pressure, watery or hazy eyes, squint or jerking eye movements, then it is a cause of concern.

Diagnosis and Treatment
Absence of symptoms makes detection of the disease in the early stage quite difficult. As people older than 40 years are more prone to this disease, they should go for regular eye checkups for assessment of intraocular pressure, done with the help of a tonometer. Ophthalmoscopy is a test carried out to evaluate the health of the optic nerves or change in the cup-to-disk ratio. Peripheral vision can be examined with the help of visual field tests. Besides these, optical coherence tomography (OCT), scanning laser polarimetry (GDx), and/or scanning laser ophthalmoscopy are some statistical imaging techniques, to assess the retinal nerve fiber layer.

Glaucoma can be effectively treated with medications like eye drops, to lower the intraocular pressure. There are many different medications available for treating glaucoma, but they may have side effects. If medication fails to improve the condition, then surgery, either laser or conventional ones can be carried out. Some common types of surgeries involved in treating glaucoma include laser trabeculoplasty and laser cilioablation, trabeculectomy and viscocanalostomy.

Studies have shown that older people are at a greater risk of developing open angle glaucoma due to myopia and thinner corneas. Some communities like Chinese, Japanese, Mongolian and Vietnamese fall in high risk zone for closed angle glaucoma, because of the shallower anterior chambers of their eyes. Diabetic patients are also more prone to this disease. Since glaucoma advances slowly without showing any symptom, people who are at a higher risk should go for eye examinations at regular intervals.