During the early stages of glaucoma, vision loss is often imperceptible (red arrow).
Learn why open-angle glaucoma, often called the “silent thief of sight,” rarely causes symptoms in the early stages of the disease.
The loss of vision from open-angle glaucoma typically starts from the peripheral visual field, or “side vision,” which means it is often unnoticeable.
Only in moderate stages of the disease do these side vision deficits become more noticeable, but even then some patients do not know notice the symptoms. If one eye is more affected by glaucoma than the other, the healthier eye compensates since most visual activities involve the use of both eyes. Furthermore, only in late stages of glaucoma is the central vision affected, which means that many patients with advanced glaucoma still have 20/20 vision in the center. Because of this lack of symptoms, it has been estimated that of the 3 million Americans with glaucoma, 50 percent do not know they have it.
One of the major risk factors for glaucoma is high eye pressure. However, in the case of primary open-angle glaucoma, most patients do not experience symptoms from high eye pressure. This is another reason why glaucoma is called the “silent thief of sight.”
For many open-angle glaucoma patients, the eye pressure gradually increases over time, and because the change in eye pressure is not abrupt, there is often no eye pain. This is not to say that high eye pressure does not result in pain. However, eye pain is more typical in acute glaucomas, such as an acute angle-closure glaucoma attack. In this situation, the eye pressure suddenly spikes, and this results in eye pain or headache, cloudy vision due to corneal swelling, and eye redness. This is very different from primary open-angle glaucoma where, as mentioned above, there is typically no eye pain, central vision is good, and the eyes are not red.
Other Forms of Open-Angle Glaucoma
What about other forms of open-angle glaucoma? Some forms of secondary open-angle glaucoma include pseudoexfoliation or pigmentary glaucoma. However, like primary open-angle glaucoma, these glaucomas are also often symptomless. Sometimes, in pigmentary glaucoma, the eye pressure can abruptly increase when eye pigment is released, such as during intense exercise. In this case, the vision can also become cloudy. But overall, open-angle glaucomas do not cause symptoms until late stages of the disease.
Risk factors of primary open-angle glaucoma other than high eye pressure and age include family history, race (African American or Hispanic), myopia (nearsightedness), thin central corneal thickness, and possibly diabetes.
Because open-angle glaucoma is often symptomless, the National Eye Institute and the American Academy of Ophthalmology recommend that all adults age 40 or older have a dilated eye exam.