<Things you should know> The correct knowledge about glaucoma: Causes, symptoms, and treatment of glaucoma
Once you've passed the halfway point of your life, you naturally want to minimize the risks associated with aging and live a vibrant life. That's where glaucoma comes in, a condition whose incidence increases significantly after the age of 40. Glaucoma is an eye disease in which the optic nerve deteriorates, causing gradual loss or narrowing of the field of vision.
In its early stages, the condition can progress without the patient being aware of it, and if left untreated, it can lead to blindness. However, with early and appropriate treatment, it is possible to slow its progression.
This article, supervised by an ophthalmologist, explains the causes, symptoms, and treatment of glaucoma. Please use it as a reference.
![What is glaucoma?]()
What is glaucoma?
Glaucoma is by no means a rare disease. According to a survey by the Japanese Glaucoma Society (commonly known as the Tajimi Study), it is estimated that 5% of people over 40, or 1 in 20 Japanese people, have glaucoma.
There is another eye disease with a similar name, "cataract." While both share the common characteristic of increasing prevalence with age, they are completely different diseases. Cataracts are caused by clouding of the lens of the eye, resulting in blurred vision and increased sensitivity to light. Glaucoma, on the other hand, is caused by a decrease in the optic nerve.
Furthermore, while cataracts rarely lead to blindness in Japanese people, glaucoma is the leading cause of blindness.
![The mechanism and main symptoms of glaucoma]()
The mechanism and main symptoms of glaucoma
How glaucoma works
When we see something, the image projected onto the retina is transmitted to the brain via the optic nerve, and we perceive it as "seeing." In a healthy eye, the optic nerve is made up of a bundle of approximately one million nerve fibers.
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The mechanism of glaucoma (regarding the macula)
Glaucoma occurs when the optic nerve is damaged, causing a gradual reduction in nerve fibers.
When nerve fibers decrease, the area of vision that was previously covered by those fibers becomes harder to see.
Main symptoms of glaucoma
As it progresses, the area you can't see expands and your field of vision narrows.
When I say "invisible," I don't mean it looks like it's been completely blacked out; rather, the outlines are indistinct, and it appears hazy.
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Visual perception (image) when both the right and left eyes have glaucoma and different areas of visual field defects are observed.
While both eyes can see the child and the scenery, if you look using only the right or left eye (where glaucoma is affecting different parts of the field of vision), you will see things differently. This is because the brain compensates for the blind spot in one eye and creates a natural-looking image by correcting the missing areas.
What's frightening about glaucoma is that in its early and middle stages, it's difficult to notice that your vision is impaired, and it can progress without you realizing it.
There are several reasons why it's difficult to notice that there are parts that are not visible.
- Because the symptoms progress slowly over a period of 5 to 30 years.
- Because the other eye compensates for what one eye cannot see.
- Because the brain compensates for the parts that are not visible.
Once vision is lost due to glaucoma, it cannot be restored. It is not uncommon for significant vision loss to occur before it is noticed. This can lead to decreased visual acuity and even blindness.
![Main causes of glaucoma]()
Main causes of glaucoma
The cause of glaucoma is still not well understood. However, since the number of patients increases with age, aging is considered to be one of the risk factors.
Furthermore, glaucoma is known to be more likely to occur in people with high intraocular pressure. Intraocular pressure refers to the "pressure inside the eye" or the "firmness of the eye."
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About intraocular pressure
A fluid called "aqueous humor" circulates inside the eye. This aqueous humor is produced in a part called the "ciliary body" and drains out through a part called the "iridocorneal angle." The amount of fluid produced equals the amount drained, which keeps the intraocular pressure constant. The normal range for intraocular pressure is 10 to 20 mmHg.
When the amount of aqueous humor produced increases or the amount that flows out decreases, it accumulates in the eye, raising intraocular pressure. As a result, the optic nerve is compressed, damaged, and reduced in size.
Other risk factors for glaucoma include the following:
- High blood pressure, diabetes, migraine, sleep apnea syndrome
- myopia
- Genetics
- trauma
- Other eye diseases or surgical history, and any medications used.
Intraocular pressure tends to rise when the sympathetic nervous system is dominant. On the other hand, low systemic blood pressure reduces the amount of blood reaching the eyes, which is thought to be detrimental to the optic nerve. For these reasons, it is said that people who are tall, thin, perfectionistic, and have low blood pressure are more prone to developing this condition.
![Types of glaucoma]()
Types of glaucoma
Glaucoma can be classified into two types: "primary glaucoma," which occurs without any other underlying disease, and "secondary glaucoma," which is caused by an existing illness.
Primary glaucoma
This accounts for the majority of glaucoma cases. There are two types of this disease.
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Primary open-angle glaucoma
This type of glaucoma is caused by blockage in the angle of the aqueous humor drainage system, leading to increased intraocular pressure. In most cases, the pressure increase is relatively mild and the condition progresses slowly.
- ■ Normal-tension glaucoma
- Normal-tension glaucoma, in which the optic nerve is damaged despite intraocular pressure being within the normal range, is also classified as primary open-angle glaucoma. Japan has the highest prevalence of this type of glaucoma in the world.
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Primary angle-closure glaucoma
This type of glaucoma occurs when the angle of the eye, which is the outflow point for aqueous humor, narrows and closes, causing intraocular pressure to rise. It does not account for a large proportion of all glaucoma cases.
In some cases of primary angle-closure glaucoma, the angle of the eye closes rapidly, causing a sharp increase in intraocular pressure. This is called an acute glaucoma attack, and if treatment is delayed, it can lead to vision loss.
If you experience a rapid narrowing of your field of vision accompanied by the following symptoms, you should see an ophthalmologist immediately.
- eye pain
- headache
- Blurred vision
- Hyperemia
- nausea
Secondary glaucoma
Glaucoma is a condition in which intraocular pressure rises due to other eye diseases such as uveitis, surgery for those diseases, the use of medications such as steroid eye drops, or systemic diseases such as diabetes or brain disorders.
![Glaucoma examination and treatment]()
Glaucoma examination and treatment
Glaucoma can be checked at an ophthalmologist's office. If you are concerned, please see a doctor. The following are some of the glaucoma tests that are performed at ophthalmologists' offices:
Main testing methods
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Visual acuity test / Refraction test
We will examine the basic condition of your eyes.
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Intraocular pressure test
There are several methods for measuring intraocular pressure, including one that uses eye drops for anesthesia and compresses the cornea with an instrument, and another that uses a jet of air to compress the cornea. In recent years, rebound tonometers, which measure pressure from the rebound of a very small probe (needle), have also appeared.
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Gonioscopy
This is an examination performed to diagnose glaucoma. A special contact lens is placed over the eye, and light is shone on it to observe the condition of the angle. The examination is performed under anesthesia, so you will not feel any pain.
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Fundus examination
This examination involves dilating the pupil with eye drops to observe the back of the eyeball. The optic nerve head, where bundles of optic nerves are located, is at the fundus of the eye, and this examination is important because it diagnoses whether or not you have glaucoma based on the condition of the optic nerve head and the results of a visual field test.
In addition to observation with an ophthalmoscope, there is also a method that uses a slit-lamp microscope combined with a lens for fundus observation, illuminating the area with light for observation. In recent years, examinations using machines such as optical coherence tomography (OCT) to measure the thickness of nerve fibers from images have also become widespread. This makes it easier to detect even slight abnormalities in the optic nerve, thus making it easier to spot early-stage glaucoma.
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Visual field test
This test examines the degree of visual field loss. The patient sits facing the testing machine and presses a button when they see a light. While it can take several tens of minutes, it's an important test for understanding the progression of glaucoma. It's used not only for diagnosis but also for monitoring the condition's progress.
The cornerstone of glaucoma treatment is lowering intraocular pressure to prevent further loss of optic nerve tissue. Even in cases of normal-tension glaucoma, further lowering of intraocular pressure is often effective.
Treatments to lower intraocular pressure include medication, laser therapy, and surgery.
Main treatments
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Glaucoma medication
The treatment primarily involves eye drops. These mainly include medications that promote the drainage of aqueous humor, medications that suppress its production, and medications that aim to do both.
- ■ Medications that promote aqueous humor outflow
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- Prostaglandin-related drugs (PG-related drugs)
- Rho kinase inhibitors (ROCK inhibitors)
- Parasympathetic nerve stimulants
- Sympathetic nerve alpha-1 receptor blockers (alpha-1 blockers)
- Ion channel openers
- ■ Medications that suppress aqueous humor production
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- Sympathetic nerve β-receptor blockers (β-blockers)
- Carbonic anhydrase inhibitors
- ■ A drug that has both effects
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- Sympathetic nerve α2 receptor selective agonists (α2 agonists)
- Sympathetic nerve nonselective stimulants
These medications may be used individually or in combination. It is important to administer them correctly under the guidance of an ophthalmologist. In addition, medication may be administered by injection, intravenous drip, or oral medication.
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Laser treatment
These include laser trabeculoplasty, which involves irradiating the clogged trabecular meshwork at the angle of the eye with a laser, and laser iridotomy, which involves using a laser to create a small hole in the iris of the pupil to increase the drainage of aqueous humor.
Since anesthesia is used, there is almost no pain. This treatment can be performed on an outpatient basis.
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surgery
There are filtration surgeries such as trabeculectomy, which involves making a small hole in the edge of the eye to allow aqueous humor to drain out of the eye, and aqueous humor outflow pathway reconstruction surgeries such as trabeculotomy, which involves cutting open the blocked trabecular meshwork to allow aqueous humor to flow out.
Treatment methods according to the classification of glaucoma
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Primary open-angle glaucoma
Initially, drug therapy is administered to lower intraocular pressure. If this is not sufficiently effective, procedures such as laser trabeculoplasty or filtration surgery are performed.
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Primary angle-closure glaucoma
Because there is a risk of acute seizures, treatment will be administered to prevent them.
Preventive measures include laser iridotomy to prevent angle closure, and surgical removal of the iris. Cataract surgery is also considered effective.
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Secondary glaucoma
We prioritize treating the underlying disease. For example, if the glaucoma is associated with uveitis, we will treat the inflammation of the uveitis; if the glaucoma is caused by steroid medication, we will stop the medication.
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Childhood glaucoma
The treatment primarily involves surgery, such as trabecular meshwork and gonioscopy.
![Methods to prevent glaucoma]()
Methods to prevent glaucoma
Once optic nerve tissue is damaged by glaucoma, it cannot be restored. Early detection and treatment are paramount to maintaining your field of vision. After the age of 40, you should have regular eye examinations.
Furthermore, while it's not possible to completely prevent glaucoma, it is possible to improve the risk factors.
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It improves conditions such as high blood pressure, diabetes, and sleep apnea syndrome.
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Exercise moderately
Light exercise such as jogging or walking can improve blood flow to the eyes. Lower body exercises like squats can also help improve low blood pressure. However, avoid strenuous exercise that causes oxygen deprivation, as this can put a strain on the optic nerve.
Yoga and meditation are also effective in calming the sympathetic nervous system.
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Quit smoking
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Avoid situations that increase intraocular pressure.
Try to avoid pressing on your eyelids, squinting your eyes, or tightening your neck as much as possible.
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Be careful how you use smartphones, games, and computers.
Looking at a screen up close can also increase eye pressure. Keep the screen away from your eyes and avoid using it for extended periods.
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Do a self-check.
Simple self-check method (one eye at a time)
This is a simple test to help you notice any abnormalities in your vision. A diagnosis of glaucoma requires a visit to an ophthalmologist. Even if no abnormalities are found in the test, you should still have regular eye examinations.
![Common problems related to glaucoma (Q&A)]()
Common problems related to glaucoma (Q&A)
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Will lost vision ever be recovered?
Unfortunately, recovery is not possible. The important thing is to slow the progression of the disease as much as possible and preserve your current vision.
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If I undergo surgery, will I need to be hospitalized?
It depends on the patient's condition and circumstances. In recent years, some medical institutions have started performing trabeculotomy on an outpatient basis, but usually, hospitalization for several days to several weeks is required.
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What precautions should be taken after surgery?
Glaucoma surgery is generally safe, but the risk of complications is not zero, so follow-up is necessary. Always follow your doctor's instructions.
If you experience symptoms such as redness or blurred vision in your eyes, eye pain, or watery eyes, you may have an infection. See a doctor immediately.
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Supervised by: Professor Toru Nakazawa, Head of the Department of Ophthalmology, Tohoku University School of Medicine
Doctor of Medicine. Graduated from Tohoku University School of Medicine. After serving as head of the ophthalmology department at Public Karita General Hospital, research fellow at Harvard University's Department of Ophthalmology, and associate professor at the Tohoku University Graduate School of Advanced Visual Medicine, he assumed his current position in 2011. He has received numerous awards for his research on glaucoma.