Glaucoma steals side vision first, often before anyone notices anything wrong
Glaucoma earned the nickname silent thief of sight because it usually erodes vision so gradually that people miss it. Raised pressure inside the eye is the best-known risk, yet many patients have normal pressure and many people with high pressure never develop damage. It is the world's second-leading cause of blindness.
Glaucoma is a family of eye diseases that harm the optic nerve, the cable carrying visual signals to the brain. Its name comes from an ancient Greek word for a gleaming blue-green or grey colour. Inside the eye, a fluid called aqueous humour supplies nutrients and keeps the eyeball in shape, normally draining away through a spongy tissue called the trabecular meshwork. In open-angle glaucoma that drainage is sluggish, so fluid builds up and pressure climbs. In closed-angle glaucoma the iris suddenly blocks the outflow.
The two forms behave very differently. Open-angle glaucoma typically causes no symptoms at first, then eats away at peripheral vision before central sight goes. Acute angle closure is an emergency, arriving with sudden eye pain, halos around lights, a red eye, nausea and rapidly worsening vision. Pressure above about 21 mmHg is the traditional warning line, but the link is loose: in one study of 1,636 people with high pressure and healthy eyes, only 9.5 percent of those left untreated developed glaucoma signs within five years, against 4.4 percent of those treated. Whether to treat everyone with raised pressure is therefore debated.
Risk rises with age, family history and steroid use. Having a sibling with open-angle glaucoma raises the risk roughly two- to four-fold, and several genes have been implicated. It is more common among African Americans, Latinos and Asian Americans, and angle-closure glaucoma is four times as prevalent in Asia as in North America. More than eight percent of Americans over eighty are affected.
In 2013 about 64.3 million people aged 40 to 80 were estimated to have glaucoma worldwide, a figure projected to reach 111.82 million by 2040. Treatment aims to lower eye pressure with drops, medication, laser or surgery, and caught early the disease can be slowed or even halted, which is why regular eye checks after 40 are stressed.
Source: Glaucoma
