Glaucoma

The eye, like a balloon, has pressure that keeps it inflated. While this intraocular pressure (IOP) isn't the whole reason for glaucoma, when the IOP rises above the normal limits, the optic nerve, which sends information from the eye to the brain, can be damaged. Peripheral vision is affected first and, if left untreated, can eventually lead to blindness. Glaucoma is the second leading cause of blindness in the US because only half of those affected know they have it while the rest are unaware and untreated.

There are two types of glaucoma: open-angled and closed-angled, which refers to the angle formed between the iris and the cornea inside the eye (see photo), where the drainage pipes of the eye are.
- For the open-angle type of glaucoma, the angle is open but the drainage pipes (trabecular meshwork) are like a net which is clogged. The IOP is usually only moderately elevated and does not cause pain and the central vision is normal. That is why open-angle glaucoma is known as the "silent stealer or sight". For patients 50 years and older, it is important to have annual eye examinations to check the IOP to avoid optic nerve damage and peripheral vision loss.
- For the closed-angle type of glaucoma, the angle is closed and the iris has blocked off the drainage pipes, which causes the IOP to rise quickly with resultant eye pain, blurriness of vision, halos, and nausea. Sometimes a migraine headache can be confused the this kind of glaucoma, which is why eye pressures need to be measured. It is important to treat the attacks of glaucoma urgently as visual field may be severely or permanently affected if one waits too long.
Risk factors for glaucoma
- Age 60 years or older
- Immediate family members with glaucoma
- Asians (angle-closure risk is greater), African-Americans, and Hispanics
- Diabetics
- Systemic or inhaled steroid use
- High myopia (nearsightedness)
Treatment
- Open-Angle Glaucoma is treated with one or more eye drop medicines, short-term oral medicines, or several spots of laser to treat the drainage area. If not successful, surgery (trabeculectomy, trabeculotomy, or aqueous (tube) shunt) may be necessary.
- Angle-closure glaucoma (or shallow angles at risk) requires urgent laser treatment to create a very small hole in the iris peripherally to equalize pressure between the front and back chambers (like rooms) of the eye revent the drainage pipes from being blocked off by the iris.
- The purpose of any of these glaucoma procedures is to allow the fluid to drain from the eye more efficiently and lower IOP.
Frequency of examinations
- Initial exam for screening:
  - Under the age of 40, every 2 to 5 years
  - Ages 40 to 54, every 1 to 3 years
  - Ages 55 and older, every 1 to 2 years
- Followup exam after detection of disease: possibly days to weeks later to make sure higher IOP is lowered enough by medications. After that, followups are 3 months or sooner if moderate to advanced disease and more frequent testing is required; 6 months or sooner if glaucoma is suspicious but not definite or if IOP is well controlled and testing needed is infrequent.
Types of exam
- Eye microscope to check IOP and optic nerve cupping (optic nerve looks like a donut; the larger the inside opening relative to the outside circle, the greater the risk of optic neve damage).
- Visual field testing with special equipment to evaluate amount of peripheral vision lost
- Optical coherence tomography (OCT; special light scanning of the layers of the eye) to evaluate nerve fiber layer and optic nerve for physicial damage