High eye pressure can creep up on you. You need to recognize it and stop it from causing further damage.
There’s a reason glaucoma screening is always done in your yearly eye exam: Typically, it is asymptomatic until it’s already done a good amount of damage to your optic nerve. Since the optic nerve can’t be repaired or restored, catching Glaucoma early–before you notice any changes in your vision–is the best way to prevent it from messing with your eyesight.
Although it is not always clear what causes Glaucoma, most types of Glaucoma, including multiple types, can be caused by something wrong and causes intraocular pressure (or IOP) to rise too high. Glaucoma does not always have to be caused by high eye pressure. (More on this later).
Before we go into the causes of each type, let’s review the basics of eye anatomy.
Glaucoma Caused by High Pressure
Okay, now imagine an eyeball. The cornea is the outermost layer. It acts as a protective layer that covers the delicate parts below. This includes the iris, the colored part of your eye that contracts and expands to reflect light. The pupil, the dark hole in the middle of your iris, is where the light enters. The retina is located behind the iris. It focuses light onto the backside of the eye. The optic nerve then converts the light into electrical signals sent to the brain by the retina.
Fluid, also known as aqueous humor, is found at the front of the eyes. A fluid called aqueous humor helps keep the eye plump. It also provides nutrients to the cornea and lens (since they don’t have a direct blood supply). The look constantly makes new fluid and then drains the old fluid at a pace that maintains healthy pressure. The trabecular meshwork is the area of spongy tissue that runs between the cornea (iris) and the eye. This drains normal eyes. High pressure can be caused by excessive fluid production or slow drainage.
“Most people don’t have an issue making fluid,” says Sriranjani Padmanabhan, MD, ophthalmologist and glaucoma specialist at UCSF Health. We suspect that the eye’s drainage system isn’t working correctly or doesn’t function as well as it should. Over time, high pressure essentially presses on the delicate optic nerve, says Christopher Starr, MD, an ophthalmologist at Weill Cornell Medicine and New York-Presbyterian. He explains that stress causes the fibers of the optic nerve to die slowly. Optic nerve fibers that pass cause signals to stop being sent from the eyes to the brain. This can lead to loss of vision. Glaucoma is a gradual process that causes vision loss and damage to the optic nerve fibers. It can take a while for it to become apparent.
Glaucoma can be classified into several types depending on its cause.
Primary Glaucoma Causes
Open-angle glaucoma cause
Open-angle Glaucoma is the most common type of Glaucoma. This occurs when fluid drains too slowly through meshwork. Dr. Padmadhaban explained that while the drain may look normal to the naked eye (which she described as looking like a series of colanders), there is something that makes the drainage area more resistant. Pressure builds up because the fluid is unable to drain as fast as it should. Glaucoma specialists are still trying to figure out what causes this, but age and genetics are significant risk factors.
Angle-closure glaucoma cause
Angle-closure Glaucoma is caused by the iris blocking the area where the cornea and iris meet. This prevents fluid from draining properly. This can happen slowly over time, similarly to open-angle Glaucoma, according to Merck Manual. It can also occur suddenly and cause severe headaches and blurred vision. This is a medical emergency.
This is not always the case. Sometimes genetics and personal eye anatomy can make it more familiar. According to Daniel Laroche, MD, director of Glaucoma Services and president of Advanced Eyecare of New York, and assistant professor of Ophthalmology at Mount Sinai School of Medicine, the most apparent cause is enlarging the lens within the eye. He explains that the lens gradually gets more prominent as we age and can eventually block or close off drainage angles.
Normal-tension glaucoma cause
Normal-tension Glaucoma can be described as an open-angle form of Glaucoma. It’s a type of Glaucoma that happens when the eye pressure level is average, according to the National Eye Institute (NEI). Dr. Padmadhaban states that the pressure is normal, and the drain appears to be working. However, the pressure is not low enough.
Experts aren’t sure what causes normal-tension Glaucoma. According to NEI, the theory is that some people’s optic nerves are just more sensitive and prone to damage than others, so even “normal” pressure levels can cause issues.
This type of Glaucoma can be technically diagnosed if the optic nerve damage is detected during an eye exam. To prevent further damage to the optic neuron, it must be treated. Most treatments that balance the fluid in the eyes to treat other types of Glaucoma can also control normal-tension Glaucoma.
Causes of congenital and childhood Glaucoma
Congenital Glaucoma is a condition in which fluid doesn’t drain properly from a baby’s eyes. What is the cause? Dr. Laroche explains that the drainage area of the eyes didn’t develop correctly for some reason. Experts aren’t sure why this happens or how to prevent it. However, sometimes there may be a genetic component. According to the American Association for Pediatric Ophthalmology and Strabismus, about 10% of primary congenital/infantile glaucoma cases are inherited. A few specific gene mutations have been linked to the disease. The good news is that most symptoms can be detected after birth and can be corrected with timely surgery.
Dr. Padmanabhan states that juvenile or childhood glaucoma, which is Glaucoma that develops in children under three years old, is very rare in the US. While many cases are not identifiable, others may be due to a different condition or disease.
Other factors can also cause glaucoma
Secondary Glaucoma occurs when Glaucoma is linked to or caused by another condition. Sometimes, health conditions may cause an increase in pressure. Other times, they can cause damage to the drainage area that eventually causes the pressure rise (angle-closure). Neovascular Glaucoma, for example, is secondary Glaucoma. This happens when additional blood vessels develop in the eye due to a medical condition. They cover the drainage areas.
According to NEI, the following are some of the most common causes of secondary Glaucoma:
- Diabetes or high blood pressure.
- Cataracts and surgery for cataracts
- Tumors in the eye.
- Inflammation of the eyes.
- Eye trauma/injury.
- Scarring due to an injury or previous eye surgery.
- Steroid eye drops are often used in chronic doses.