What is Glaucoma?
Glaucoma is a group of diseases or conditions that lead to damage of the eye’s optic nerve. Open-angle is the most common type of glaucoma. Acute-angle glaucoma is less common. Early diagnosis and treatment is critical for both types since damage from glaucoma can lead to blindness.
Causes and Symptoms
One of the most common causes of glaucoma is abnormally high intraocular pressure. Clear fluid flows in to the eye’s anterior chamber to feed nearby tissues and then leaves the chamber at the open angle where the cornea and iris meet. When the fluid reaches the angle, it flows through a spongy drain. If the fluid filters out slower than it enters, pressure inside the eye increases.
On rare occasions, low-tension or normal-tension glaucoma can develop without increased eye pressure.
Primary open-angle glaucoma signs and symptoms include:
- Gradual loss of peripheral vision, usually in both eyes
- Tunnel vision in the advanced stages
Acute angle-closure glaucoma signs and symptoms include:
- Eye pain
- Nausea and vomiting (accompanying the severe eye pain)
- Sudden onset of visual disturbance, often in low light
- Blurred vision
- Halos around lights
- Reddening of the eye
- Elevated internal eye pressure.
- Age–Risk increases after age 60.
- Ethnic background–African-Americans older than age 40 have much higher risk than do Caucasians. People of Asian descent have an increased risk of developing acute angle-closure glaucoma. People of Japanese descent may be more likely to have normal-tension glaucoma.
- Family history of glaucoma.
- Medical conditions–Diabetes, heart diseases, high blood pressure, and hypothyroidism can all increase the risk.
- Other eye conditions –Severe eye injuries, eye tumors, retinal detachment, eye inflammation, and lens dislocation can trigger glaucoma, as can certain eye surgeries
- Being nearsighted or farsighted.
- Long-term corticosteroid use–Using corticosteroid medications, especially eye drops for a long period of time may increase the risk of developing secondary glaucoma.
The American Academy of Ophthalmology recommends a comprehensive eye exam for all adults starting at age 40. Those without glaucoma risk factors should have a follow-up exam every three to five years after that. Those with risk factors or those over 60 should be screened every one to two years. Recommendation for African-Americans is periodic eye exams starting between ages 20 and 39.
Glaucoma is detected through a comprehensive dilated eye exam that may include any or all of the following:
- Visual acuity test–eye chart test measures vision at various distances.
- Visual field test–measures peripheral vision
- Dilated eye exam— drops are placed in the eyes to widen, or dilate, the pupils. A special magnifying lens examines the retina and optic nerve for signs of damage
- Tonometry–measures pressure inside the eye with an instrument called a tonometer. Numbing drops may be applied for this test.
- Pachymetry–measures the thickness of the cornea using an ultrasonic wave instrument
Lowering eye pressure in the early stages of glaucoma slows progression of the disease and helps save vision. There are surgical, pharmacological, and natural treatments that help lower pressure and manage the disease.
- Laser trabeculoplasty helps aqueous humor (fluid) drain out of the eye, and is increasingly popular as an intermediate step between drugs and conventional surgery.
- Conventional surgery makes a new opening for the fluid to leave the eye. Laser and conventional surgical treatments may save remaining vision, but they do not improve sight already lost from glaucoma.
- Drainage implants surgery –a small tube is inserted into the eye to facilitate draining fluid from the eye.
- Beta Blockers or Prostaglandin eye drops are often prescribed to lower the intraocular pressure by reducing how much fluid is produced or helping fluid drain from the eye. Reducing pressure helps slow optic nerve damage, decreasing the rate of vision loss.
- Alpha-adrenergic agonists reduce the production of fluid and increase its outflow from the eye
Exercise is well known to reduce ocular pressure and appear to have more dramatic effects in people with glaucoma than healthy subjects; these effects appear to be long-lasting, but disappear with a month of inactivity. A recent study has shown reductions in intraocular pressure following strenuous exercise in healthy young subjects and a return to baseline 30 minutes following exercise. The study also reported a significant increase in pulsatile ocular blood flow that returned to baseline levels between 5 and 10 min after cessation of exercise.
Studies have shown that coffee consumption increases intraocular pressure (IOP), ocular perfusion pressure (OPP), and ocular pulse amplitude (OPA). A 2011 review discovered that, caffeine had no significant effect on IOP in normal subjects, but there were significant effects in subjects with ocular hypertension and glaucoma. While there is some debate as to the clinical relevance of these findings, it is generally suggested that persons with active disease limit or avoid caffeine.
Studies have shown that as many as 80% of people with glaucoma who consume an entire quart of water over the course of twenty minutes experience elevated IOP. To be safe, people with glaucoma are encouraged to consume water in small amounts throughout the day.
Various antioxidants, including vitamins A, C, E, flavonoids, glutathione and others, are thought to protect retinal ganglion cells (the cell type damaged by glaucomatous optic neuropathy).,, Studies measuring consumption of foods high in antioxidants have been conflicting, with some showing protection, and others not. A diet high in antioxidant foods as well as supplementation is generally recommended as a low-risk preventative step.
While still in the preliminary stages of investigation, a few small studies have suggested that Ginkgo may have a role in glaucoma support. While ginkgo supplementation did not reduce intraocular pressure (IOP), it did appear to improve visual field damage in a select group of normal-tension glaucoma patients. Ginkgo has been studied for its ability to alter Blood flow, and these improvements in ocular blood flow may account for its ability.
Omega-3 fish oils (DHA, EPA) have decreased intraocular pressure and ganglion cell function in two preliminary animal studies. While no studies using omega-3 fish oils in humans have been performed, the benefits of these oils are well researched and the side effects are limited suggesting a trail of omega-3s would be.
Other Professional Resources
National Eye Institute: Glaucoma Facts
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