Glaucoma is a progressive disease that affects the optic nerve (the structure of the eye that transmits information from the eye to the brain). Although there are many etiologies of glaucoma, it is most commonly associated with elevated eye pressure inside the eye. While some types of glaucoma may cause acute pain and loss of vision, most types of glaucoma can develop over many years without causing pain or affecting vision until its advanced stages.
While there is not just one cause of glaucoma, patients with a family history of glaucoma and/or consistently elevated eye pressures have a greater risk of developing glaucoma.
There is currently no cure for glaucoma, but there are many treatment options that can slow the progression of the disease if properly managed. Once vision is lost, it cannot be restored. Left untreated, glaucoma can cause blindness. For these reasons, regular eye exams and early detection are critical.
Types of Glaucoma
Chronic (Open Angle) Glaucoma
This is the most common type of glaucoma, especially in those of African American and Hispanic descent. The angle refers to the space between the iris and the cornea through with the aqueous fluid (the thick watery substance that fills the space between the cornea and the lens of the eye) circulates to maintain a constant eye pressure. In open angle glaucoma, there is nothing blocking the flow of the aqueous fluid; instead, there is either a filtering, draining or reabsorption problem with the aqueous fluid inside the eye. As a result, the pressure inside the eye builds up. The pressure pushes on the optic nerve head and causes progressive atrophy (damage).
Normal Tension Glaucoma
This is a form of open angle glaucoma that is not related to high eye pressures. This means that glaucomatous damage may occur even when the patient has relatively low eye pressures. Reduced blood supply to the optic nerve may also play a role in normal tension glaucoma.
Acute (Angle Closure) Glaucoma
This is the most common cause of glaucoma for those of East Asian and Inuit Alaskan descent. This is the most visually threatening form of glaucoma as it may result in acute vision loss and ocular pain. When the angle is closed, the fluid is unable to circulate inside the eye, causing a rapid increase in eye pressure that requires emergent care. The signs are usually serious and may include blurred vision, severe headaches, eye pain, nausea, vomiting or seeing rainbow-like halos around lights. Occasionally, the condition may be asymptomatic, similar to open angle glaucoma. During a comprehensive examination, those who are at risk for angle closure glaucoma may also be treated with lasers to prevent an acute angle closure attack of glaucoma.
Secondary glaucoma refers to glaucoma that is caused by other systemic or ocular conditions not directly related to the anatomical structure or fluid drainage system. These include diabetes, leukemia, sickle-cell anemia, uveitis (ocular inflammation), arthritis, cataracts, eye injuries, steroid drug use and the growth of unhealthy blood vessels, among others.
In rare cases, some ocular surgeries, such as retinal repair surgeries, may increase the risk of developing glaucoma.
Once diagnosed, glaucoma will need to be controlled. The treatment varies depending on the type of glaucoma. For open angle glaucoma, initial treatment may include ocular topical medications or lasers to lower the eye pressures. For angle closure glaucoma, treatment may involve lasers and oral medications. Although the eye pressures are an important measure of treatment progress, it is more important to manage the progression of the optic nerve head damage; this progression can only be managed with a thorough eye examination and supplemental testing. If the progression of glaucoma cannot be managed with ocular topical medications, further lasers and surgical intervention will be needed to slow down the progression. The following describe the most common laser and surgeries for glaucoma:
Common surgeries include:
- Laser Peripheral Iridotomy (LPI)– For patients who have narrow angles or angle closure glaucoma, a small opening is made in the iris (the colored portion of the eye) to equalize the pressure difference inside the eye, and allow the angle between the iris and cornea to widen and facilitate the circulation of the fluid inside the eye.
- Argon Laser Trabeculoplasty (ALT) and Selective Laser Trabeculoplasty (SLT)– For patients with primary open angle glaucoma, ALT or SLT laser is directed at the iris (the colored portion of the eye) to help lower the eye pressure inside the eye. This laser treatment may be used as an alternative to adding ocular topical medications or in combination with ocular topical medications. ALT and SLT are effective in about 75% of patients in lowering eye pressure. SLT may be repeated.
- Nd: YAG Laser Cyclophotocoagulation (YAG CP)– For more advanced cases of glaucoma, a laser may directed at the ciliary body (the structure in the boy that produces the fluid inside the eye) to inhibit it from further production of fluid.
- Filtering Microsurgery (Trabeculectomy)– For patients who continue to have uncontrolled glaucoma despite topical ocular medications and laser treatments, filtering surgery is needed. A new drainage passage is created between the sclera and the chamber inside the eye where the fluid circulates to improve the eye pressure.
- Tube Shunt Surgery– A tube shunt (an artificial channel) may be recommended for patients with neovascular (abnormal growth of new, weakened blood vessels) glaucoma, failed filtering surgery, or susceptibility to developing scar tissue. The tube shunt is inserted in the eye to facilitate drainage.