What is a Glaucoma?
Glaucoma is a group of eye diseases which results in a damage to the optic nerve and causes, if untreated, reduction of the visual field and loss of vision, up to blindness. This damage is often caused by an abnormally high pressure in your eye. However, the optic nerve could get damaged even though your eye pressure is within the normal range. Therefore there are different types of glaucoma. Open-angle glaucoma develops slowly over time and there is no pain. Closed-angle glaucoma can present gradually or suddenly. The sudden presentation may involve severe eye pain, headache, nausea, blurred vision, redness of the eye, and a dilated pupil.
In normal tension glaucoma the optic nerve may be very sensitive, or the blood supply to your optic nerve may be decreased. This limited blood flow could be caused by different cardiovascular diseases (conditions that impair blood circulation, e.g. diabetes, high or low blood pressure, atherosclerosis etc.) Mostly the damage to the optic nerve progresses very slowly and creepingly and affects the central vision only in the final stage. Because of this lack of symptoms (no pain, no prompt vision loss), glaucoma has been called the „silent thief of sight“. Vision loss due to glaucoma can’t be recovered. The progression can be stopped, though. It is important to have regular exams that include measurements of your optic nerve and eye pressure so a diagnosis can be made in its early stages and treated appropriately. If glaucoma is recognized early, vision loss can be prevented. Worldwide, glaucoma is the second-leading cause of blindness!
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The space between the clear front surface of the eye (the cornea) and the lens inside the eye is filled with a clear fluid called the aqueous humor. This fluid nourishes the inside of the anterior part of the eye. It also maintains the shape of the eye by keeping the eyeball properly pressurized. The aqueous humor is constantly being produced by a structure called the ciliary body that surrounds the lens, and drains from the eye through a mesh-like channel called the trabecular meshwork that’s located in the angle formed inside the eye where the cornea and iris meet.
If something causes this „drainage angle“ to close down or the trabecular meshwork to become clogged, the aqueous humor cannot drain from the eye fast enough, and pressure inside the eye (IOP) increases. Normal range of intraocular pressure is 9 – 21 mmHg. As mentioned before, patients may develop glaucoma with normal intraocular pressure. Therefore measuring the IOP is not evident for diagnosing glaucoma. Advanced diagnostic must be done.
Types of Glaucoma
Primary open-angle glaucoma
This is the most common type of glaucoma. The increased pressure is caused by trabecular meshwork blockage. Because the microscopic passageways are blocked, the pressure builds up in the eye and causes imperceptible very gradual damage to the optic nerve, thus leads to gradual vision loss. Peripheral vision is affected first, but eventually the entire vision will be lost if not treated.
Some children are born with a defect in the drainage angle that prevents the aqueous fluid from exiting the eye normally. Usually there are obvious symptoms, such as dilated pupil, cloudy corneas and light sensitivity.
This type happens when someone’s iris is very close to the drainage angle in their eye. The iris can end up blocking the drainage angle. You can think of it like a piece of paper sliding over a sink drain. When the drainage angle gets completely blocked, eye pressure rises very quickly. This is called an acute attack. It is a true eye emergency, and you should call your ophthalmologist right away or you might go blind. Many people with angle-closure glaucoma develop it slowly. This is called chronic angle-closure glaucoma. There are no symptoms at first, so they don’t know they have it until the damage is severe or they have an attack. Angle-closure glaucoma can cause blindness if not treated right away.
This type of glaucoma develops due to complications of certain medical conditions (including diabetes and high blood pressure) or because of other eye conditions (such as cataracts and infection of anatomical structures in the eye), side effects of medications, or trauma to the eye.
- abnormal intraocular pressure
- genetical (positiv family history of glaucoma)
- skin color (statistically, people with dark skin pigmentation are more prone to glaucoma)
- cardiovascular diseases
- age (40 years old an above)
- taking corticosteroid medications
- being extremely nearsighted or farsighted
How is glaucoma diagnosed?
Screening for glaucoma is usually performed as part of a standard eye examination. Eye drops to dilate the pupil may be needed to examine your optic nerve. Testing for glaucoma should include measurements of the intraocular pressure, a formal visual field test should be performed and the retinal nerve fiber layer should be assessed with imaging techniques such as optical coherence tomography (OCT). Some health insurances do not cover all of the glaucoma measurements needed for appropriate diagnosis. Ask your eye doctor for further information.
OCT (Optical Coherence Tomography)
The most specific technique to diagnose a glaucoma in early stage is the measurement of the retinal nerve fiber layer with an OCT. Regular check-ups with an OCT also provide treatment guidance for glaucoma. It is a non-contact, non-invasive and completely painless eye exam, which provides a detailed, 3D scan of the tissue lining at the back of the eye (retina). OCT eye tests are quick to perform, last around 2-3 minutes and work in a similar way to an ultrasound.
Visual field (perimetry)
The examination of the visual field (perimetry) provides information on neurological deficits of the optic nerve fibers, which may have already occurred due to glaucoma. The patient looks straight ahead and is asked to indicate when light passes the patient’s peripheral field of vision. This allows the examiner to map the patient’s field of vision.
Intraocular pressure can be controlled and decreased with eye drops. Used every day, these eye drops lower eye pressure. Some do this by reducing the amount of aqueous fluid, others reduce pressure by helping fluid flow better through the drainage angle. Glaucoma medications can help you keep your vision, but they may also produce side effects. Some eye drops may cause:
- dry eyes (stinging, itching sensation, blurred vision)
- red eyes or red/ purple discoloration around the eye
- changes in your pulse and heartbeat
- changes in your energy level
- changes in breathing (especially if you have asthma or breathing problems)
- dry mouth
- eyelash growth
There are two main types of laser surgery to treat glaucoma. They help aqueous drain from the eye. These procedures are usually done in the ophthalmologist’s office.
- Trabeculoplasty – is used to make the drainage angle work better. In this process, pigment particles are removed from the drainage channels. That way fluid flows out properly and eye pressure is reduced. Low energy is used here, so it can be repeated several times.
- Iridotomy – this is for people who have angle-closure glaucoma. The ophthalmologist uses a laser to create a tiny hole in the iris. This hole helps fluid flow to the drainage angle.
Combining trabeculoplasty with the intake of micronutrients (containing the ingredient resveratrol) is stimulating the metabolism of the optic nerve fibers and can lead to the best therapy result (see https://paulig-eye-clinic.com/no-blindness-in-low-tension-glaucoma/). Regular OCT check ups which follow the therapy showed significant improvement of the retinal nerve fiber layer over years.
Other glaucoma surgeries include canaloplasty, trabeculectomy and other glaucoma drainage implants. Most of these surgeries have certain side effects and risks. In severe cases however, an operation should always be considered to preserve the optic nerve.