This ocular disease is usually very subtle and often does not cause symptoms until late in the disease process when a significant amount of vision has already been lost. Damage to the visual system from glaucoma is permanent. Yet, most of this visual loss can be prevented if the glaucoma is detected early and treated adequately.

What is Glaucoma?

Glaucoma has traditionally been defined as a group of ocular diseases in which elevated intraocular pressure (IOP) causes damage to the optic nerve with a characteristic loss of visual field.

Typically, early in the disease, the damage to the optic nerve causes defects in the peripheral vision. Patients seldom notice these peripheral blind spots until much later (often many years later) when considerable damage has occurred and the defects threaten the central vision.

Glaucoma diagnosis is based on:

• Elevated intraocular pressures
  
• Damaged optic nerves
  
• Visual field (peripheral vision) loss

There are four basic forms of glaucoma:

1. Primary Open-Angle Glaucoma: This is by far the most common form of glaucoma and the one most difficult to recognize in its early stages. As many as one-half of patients with this type of glaucoma do not know they have it. It is much more prevalent in adults than in children, particularly in those adults who are over the age of 35. There may be a hereditary tendency, but this is not always the case. It is characterized by a gradual loss of the visual field with progressive cupping (atrophy) of the optic nerve head. About one-third of patients with primary open-angle glaucoma will not have an abnormally elevated IOP on a routine screening examination. Therefore, a comprehensive ophthalmologic examination is required to establish the diagnosis.
2. Secondary Glaucoma: This type of glaucoma can occur at any age and may be secondary to ocular trauma or surgery, drugs (topical steroids, for example), developmental abnormalities, or other systemic diseases (such as diabetes mellitus). An abnormally elevated IOP is almost always present in the secondary glaucomas.
3. Primary Angle-Closure Glaucoma: This is a less common type of glaucoma. It may develop very suddenly and be associated with severe eye pain, redness, decreased vision, and even cause nausea and vomiting. This form of glaucoma requires immediate medical treatment, followed by laser or surgical treatment. It can result in permanent loss of vision if not treated immediately.
4. Congenital Glaucoma: Glaucoma, characterized by elevated IOP and enlarged corneal diameters, rarely occurs at birth. Early treatment is needed to preserve vision.

High-Risk groups

Glaucoma occurs at a much higher frequency with age. American blacks have a much higher rate of glaucoma than whites. Risk factors for the development of glaucoma, other than age and race, include: previous eye trauma, family history of glaucoma, and diabetes mellitus.

Glaucoma Risk Factors include:

• Family history of glaucoma
  
• Diabetes
  
• Race (black)
  
• Previous eye trauma or surgery
  
• Topical (ocular) steroids

Findings

Intraocular pressure in adults is normally between 9 and 22 mmHg. Although many patients tolerate pressures above 22 mmHg., they are at an increased risk to develop glaucomatous visual damage. The higher the IOP, the greater the risk.

As mentioned previously, about one-third of patients with glaucoma will not demonstrate an elevated IOP at the time it is measured. The optic nerve head (optic disc) may be examined for signs of damage. In glaucoma, the size of the physiologic cup may appear enlarged or there may be an asymmetry in the cupping between the two eyes.

Treatment

Control of all forms of glaucoma is usually first attempted with medical therapy-topical (drops or ointments) or systemic. The following forms of treatment include:

1. Topical medications:
   1. beta-adrenergic blocking agents (such Tymoptic, Betoptic, Betagan),
   2. epinephrine type drops (Propine, Epifrin, Epitrate, Glaucon),
   3. miotics (pilocarpine of cholinesterase inhibitors).
2. Systemic medications:
   1. carbonic anhydrase inhibitors (Diamox or Neptazane).
   2. It is important to be aware of the systemic side effects of the glaucoma medications. Beta blockers can cause bradycardia, bronchospasm, heart failure or depression, and these effects may be additive with systemic beta blockers. The carbonic anhydrase inhibitors may cause paresthesias, lethargy, anorexia, electrolyte disturbances, kidney stones, depression, and loss of libido.
3. Laser treatment or Surgery
   Patients who don't respond to medical therapy may require laser treatment or surgery.

Recommendations

All patients at risk to develop glaucoma and those over the age of 35 need a periodic check of their intraocular pressures and an evaluation of the optic nerve heads by an ophthalmologist. The frequency of examination may need to be yearly, but is best determined by an ophthalmologist.

Although community glaucoma screenings and tonometry and fundus examinations in primary physicians' offices are valuable in detecting some undiagnosed patients, screening exams will fail to identify other patients, either because of normal intraocular pressures or because of difficulty in measuring IOP.

Finally, patients using glaucoma medications should be followed carefully for systemic side effects and possible adverse interactions with medications prescribed for non-ophthalmic disorders.

Reference: American Academy of Ophthalmology