Glaucoma is a disease that affects the optic nerve, the part of the eye that receives the images we send to the brain. When damage to the optic nerve fibers occurs, blind spots develop. These blind spots usually go undetected until the optic nerve is significantly damaged. If the entire nerve is destroyed, blindness results. Glaucoma is a leading cause of blindness in the U.S., especially in older people. Loss of sight from glaucoma can often be prevented with early treatment.
A clear liquid called aqueous humor circulates inside the front portion of the eye. The front of the eye is constantly producing a fluid called aqueous humor. A healthy eye will continually produce small amounts of aqueous humor, while an equal amount flows out of the eye through a microscopic drainage system to maintain a healthy level of pressure within the eye. When normal drainage becomes slowed or blocked, pressure increases. When this pressure rises to abnormal levels, it can put extra stress on the optic nerve, causing significant damage. Optic nerve damage results in loss of vision, and ultimately blindness.
There are several different types of glaucoma, the two most common types being chronic open-angle glaucoma and closed-angle glaucoma.
Chronic open-angle glaucoma is the most common form of the disease and the risk of developing chronic open angle glaucoma increases with age. With this type of glaucoma, pressure gradually increases inside the eye causing damage to the optic nerve, usually over an extended period of time. There are no symptoms in the early stages. Peripheral vision is usually the first to deteriorate and as the disease becomes more advanced, blank spots begin to appear in one’s vision. If left untreated, it eventually leads to blindness. The best way to avoid serious vision loss is early diagnosis and treatment.
Risk factors for chronic open-angle glaucoma include:
- Advanced age
- Family history of the disease
- Higher-than-normal intraocular pressure
- Certain ethnic races, particularly those of African or Hispanic descent
- Certain diseases or conditions, especially diabetes, migraine headaches and poor circulation
- Previous eye trauma or surgery
Closed-angle glaucoma is less prevalent, but is considered a true eye emergency. This type of glaucoma occurs when the iris (the colored portion of the eye that controls the pupil) moves or dilates in such a way that it blocks off the drainage channels in the eye completely. Since the fluid cannot exit the eye, the pressure inside the eye builds rapidly and causes an acute closed-angle attack. This is considered a medical emergency in which an ophthalmologist should be contacted immediately to avoid any loss of vision.
Symptoms of closed-angle glaucoma include:
- Severe eye pain
- Headache
- Blurred vision
- Nausea or vomiting
- Rainbow-colored halos around lights
High risk factors for closed-angle glaucoma include:
- Extreme farsightedness
- An iris that is abnormally large or far back in the eye
- Advanced age
- Heredity
- Certain ethnic races, especially Asians
Treatments for glaucoma: There is a wide range of treatments for the disease including topical and oral medications, laser surgery, traditional surgery, and, most recently, minimally invasive glaucoma surgery (MIGS). The goal of treatment is to lower the eye pressure and help prevent further damage to the optic nerve.
The first line of treatment in glaucoma is usually eyedrops taken daily. These medications lower eye pressure, either by decreasing the amount of aqueous fluid produced within the eye or by improving the outflow through the drainage angle. Occasionally, oral carbonic anhydrase inhibitors may be prescribed to slow down the aqueous fluid production within the eye. The treatment (or combination of treatments) for an individual is chosen based on the type of glaucoma and other details of the particular case.
Laser surgery may be recommended for treatment of both open and closed angle glaucoma. In open-angle glaucoma, the laser is used to modify the drainage system (trabeculoplasty) and increase fluid outflow, thus reducing the eye pressure. In closed-angle glaucoma, the laser creates a hole in the iris (iridotomy) to re-establish normal drainage and reduce the pressure inside the eye
Lastly, surgery may be considered if medication and laser treatment are not adequate to prevent further damage to the optic nerve. A common surgery for the treatment of open-angle glaucoma is trabeculectomy, where a doctor creates a small flap in the sclera (the white part of the eye) to create a new drainage channel for the aqueous fluid to leave the eye. Another option which might be appropriate for some patients is a minimally invasive glaucoma surgery (MIGS) procedure. If indicated, MIGS could result in a lowering of the intraocular pressure through the use of a less invasive technique that might involve less risk.
