Glaucoma: the silent thief of sight
Published : Feb 24, 2011 - 18:02
Updated : Feb 24, 2011 - 18:02
By Kee Chang-won, MD, Ph.D.
Glaucoma is an eye disorder in which the optic nerve suffers damage, permanently impacting vision and progressing to complete blindness if untreated.
Glaucoma has been nicknamed the “silent thief of sight” because the loss of vision normally occurs gradually over a long period of time. Once lost, this damaged visual field cannot be recovered.
Worldwide, it is the second leading cause of blindness. The first is cataracts, but vision affected by cataracts can be recovered through surgery. Therefore, glaucoma is the most common cause of irreversible blindness.
Glaucoma affects 1 in 200 people aged 50 and younger, and 1 in 10 over the age of 80.
Intraocular pressure (IOP) is controlled by the production of liquid called aqueous humor by the ciliary processes of the eye and its drainage through the trabecular meshwork. Raised IOP, above 21 mmHg, is a significant risk factor for developing glaucoma.
One person may develop nerve damage at a relatively low pressure, while another person may have high IOP for years and yet never develop damage.
Glaucoma can be divided roughly into two main categories, “open angle” and “closed angle” glaucoma.
Closed angle glaucoma can appear suddenly and is often painful; visual loss can progress quickly but the discomfort often leads patients to seek medical attention before permanent damage occurs.
Open angle, chronic glaucoma tends to progress at a slower rate and the patient may not notice that they have lost vision until the disease has progressed significantly. The only signs are gradually progressive visual field loss, and optic nerve changes such as increased cup-to-disc ratio on fundoscopic examination.
Increased IOP is the largest risk factor in most glaucomas, and people of African descent, elderly people with thinner corneal thickness, people with a family history of glaucoma are at higher risk for primary open angle glaucoma. Many East Asian groups and women are prone to developing angle closure glaucoma due to their shallower anterior chambers.
Those at risk are advised to have an eye examination at least once a year.
Diagnosing glaucoma should include measurements of the IOP, anterior chamber angle examination, examination of the optic nerve, and a formal visual field test. The retinal nerve fiber layer can be assessed with imaging techniques.
The modern goals of glaucoma management are to avoid glaucomatous nerve damage, preserve visual field and ensuring total quality of life for patients with minimal side effects. If the condition is detected early enough, it is possible to arrest the development or slow the progression with medical and surgical means, although there is not yet a cure for glaucoma.
Because IOP is only one of the major risk factors for glaucoma, lowering it via various pharmaceuticals and/or surgical techniques is currently the mainstay of glaucoma treatment.
As an IOP reducing medication, eye drops are usually used. There are several different classes of medications to treat glaucoma with different medications in each class.
Poor compliance with medications and follow-up visits is a major reason for vision loss in glaucoma patients. Patient education and communication must be ongoing to sustain successful treatment plans for this lifelong disease with no early symptoms.
The author is a doctor at Department of Ophthalmology of Samsung Medical Center. ― Ed.