Intraocular Pressure and Glaucoma

Overview of a Condition of Increased Pressure Within the Eye

May 30, 2009 Anthony Lee

Glaucoma is a frequently reported eye problem and one of the most common causes of blindness.

Glaucoma is an ophthalmologic condition characterized by visual impairment due to increased pressure in the eyeball. It typically occurs in the elderly, although individuals of any age may be susceptible. Glaucoma has been reported in approximately 14 million people around the world, making it the third leading cause of blindness worldwide.

Etiology and Pathophysiology

The eye contains two types of clear liquid substances. One is the gel-like vitreous humor in the posterior chamber between the back of the lens and the retina at the rear of the eye. The other is the aqueous humor in the anterior chamber between the cornea and the front of the lens. The latter, which is constantly produced and drained, is implicated in the pathophysiology of glaucoma.

The outermost portion of the anterior chamber is the cornea. Behind this layer is the iris, which changes the size of its opening called the pupil. The lens sits behind the iris and secured via fibers to the ciliary body. The ciliary body is the organ that produces aqueous humor that flows between the iris and lens, through the pupil to the front of the eye, and drains through the trabecular meshwork into Schlemm's canal.

Glaucoma generally occurs due to reduced drainage of aqueous humor, causing increased intraocular pressure. It may be primary without a known cause or secondary to another condition. The numerous causes of glaucoma are divided into two major categories:

• Open-Angle Glaucoma: Open-angle glaucoma occurs without a narrowing of the angle formed by the cornea and iris. This can involve obstruction of aqueous humor outflow by a foreign body, such as pigment particles (pigmentary glaucoma) and red blood cells following bleeding (hemorrhagic glaucoma), or pathologic processes in, around, or beyond Schlemm's canal.
• Closed-Angle Glaucoma: Closed-angle glaucoma occurs when there is reduction of the angle formed by the cornea and iris. This can occur due to processes that push the iris forward, such as intraocular tumors and lens displacement, and those that pull on the iris from the front, such as membrane contracture following mechanical trauma.

Whatever the cause, increased intraocular pressure gradually damages the optic nerve connecting the eye to the brain. This involves direct pressure on the optic nerve as well as reduction of the blood supply to the nerve. Some patients, however, may have glaucoma with normal or low intraocular pressure.

Diagnosis

Patients with glaucoma experience visual impairment in varying locations. For example, individuals may find that the center of their visual field is intact while their peripheral vision fades away, a phenomenon commonly referred to as tunnel vision. If the disease progresses, impairment eventually involves the entire visual field, resulting in blindness.

Physicians, particularly ophthalmologists, diagnose glaucoma by information from the patient history and further evaluation by several techniques:

• Visual Acuity Test: The physician uses an eye chart to determine the clarity of the patient's vision.
• Visual Field Test: By moving a small object in and out of the patient's field of vision, the physician can determine which parts of the visual field are impaired.
• Ophthalmoscopic Exam: The physician dilates the patient's pupil with special eyedrops and inspects the retina with a magnifying ophthalmoscope.
• Tonometry: By using an instrument that gently presses on the eyeball, a physician can estimate the patient's intraocular pressure.
• Pachymetry: This method determines the thickness of the patient's cornea using an ultrasound device.

Treatment

Glaucoma is treated medically or surgically depending on the nature of the condition. A variety of topical and oral drugs are available for glaucoma, such as timolol and pilocarpine. Laser surgery works by targeting the trabecular area and improve drainage of aqueous humor. Incisional surgery is also available, mainly for cases that benefit from adding a new means of fluid drainage.

References

• Merck Manual - Glaucoma
• National Eye Institute - Glaucoma

The copyright of the article Intraocular Pressure and Glaucoma in General Medicine is owned by Anthony Lee. Permission to republish Intraocular Pressure and Glaucoma in print or online must be granted by the author in writing.

Eye

What do you think about this article?

---

NOTE: Because you are not a Suite101 member, your comment will be moderated before it is viewable.

post your comment

What is 9+9?

Comments

May 31, 2009 7:40 PM

Guest :

Diet and specific nutrient supplementation can both help prevent the onset of glaucoma as well as help preserve vision for those with glaucoma.

There are number of peer review studies that show the importance of supplementing with a specific nutrients can help protect the optic nerve from damage including the following: alpha lipoid acid, bilberry, pine bark, gingko biloba, taurine, magnesium, vitamin B12,

Other studies have shown that a healthy diet which included, for example, at least 1 serving of green leafy vegetables such as kale and collard greens, decreased the risk of getting glaucoma for women by 69 percent (Coleman AL, Stone KL, Kodjebacheva G, Yu F, Pedula KL, Ensrud KE, Cauley JA, Hochberg MC, Topouzis F, Badala F, Mangione C ; Study of Osteoporotic Fractures Research Group)

Daily eye exercises also help maintain healthy vision. For a demo of 3 great eye exercises by Dr. Grossman, one of the Country's leading behavioral optometrists, go to <a href="http://www.youtube.com/watch?v=W10j2fL0hy0">http://www.y outube.com/watch?v=W10j2fL0hy0</a>

For more related research studies, see the "Research" section at <a href="http://www.naturaleyecare.com">Natural Eye Care for Glaucoma Prevention</a>

1 Comment: