Glaucoma: The Leading Cause of Permanent Blindness in Thailand and Worldwide
Glaucoma is a group of eye diseases characterized by abnormalities at the optic nerve head (Image 1) and is related to intraocular pressure, which may be high or normal. Generally, an intraocular pressure above 21 millimeters of mercury is considered abnormal.
Characteristics of Glaucoma Development
The progression of glaucoma is a degenerative process that gradually damages the optic nerve head and the optic nerve fibers inside the eye (Image 2) resulting in a narrowing of the visual field and blurred vision. The visual field loss in glaucoma has a specific pattern, usually starting from the side or outer edges of vision and gradually expanding inward.
Because of this, most patients are unaware they have glaucoma until the damage approaches or reaches the center of their vision. However, some types of glaucoma begin by damaging the central vision first, which may lead patients to seek medical attention earlier due to noticing abnormalities themselves.
Although glaucoma is commonly found in the elderly, it can actually occur at any age, including from birth. If left untreated, treated late, or detected but not continuously managed, including poor disease control, it can lead to vision loss, visual impairment, and ultimately permanent blindness.
Image 1
Left image shows the optic disc of a normal person
which is the starting point of the optic nerve, located at the back and inside of the eye. It appears round or oval, pinkish-orange in color, with a small central depression or cup that appears paler than the surrounding neural tissue.
Right image shows the optic disc of a glaucoma patient with a wider and deeper central cup along with reduced neural tissue due to degenerative processes of the disease and a thinner rim on the sides.
Image 2
The left image shows a special lens used with a slit lamp microscope to diagnose and monitor changes in the optic nerve head located at the back of the eye through the pupil, as shown in the right image.
Types of Glaucoma
Glaucoma can be subdivided into several types, each with different symptoms, characteristics, severity, progression, treatment approaches, and prognosis. This results in treatment methods being tailored to each individual.
Considering the anatomy of the anterior chamber angle (Image 3), which is a structure in the front chamber of the eye responsible for draining aqueous humor continuously from inside the eye to the outside, glaucoma can be divided into two main types:
- Open-angle glaucoma is the most common type, caused by gradually increased intraocular pressure over time without symptoms. Symptoms usually appear only after about 40-50% of the optic nerve fibers have been damaged.
- Angle-closure glaucoma is less common and occurs when the angle between the iris and cornea is narrow, causing blockage of aqueous humor drainage, leading to increased intraocular pressure. Chronic cases often have no symptoms, but acute cases cause a rapid and severe increase in pressure, resulting in intense eye pain. Other common symptoms include headache, blurred vision, nausea, vomiting, and seeing rainbow-colored halos around lights. This is an emergency requiring immediate ophthalmologist consultation.
Causes of Glaucoma and Risk Groups
The cause of glaucoma is generally unknown. When known, it is often due to other eye diseases such as intraocular inflammation, tumors or cancers inside the eye, or following certain eye procedures. Risk groups more likely to develop glaucoma include:
- Age 40 years and older
- Family history or close relatives with glaucoma
- High intraocular pressure
- Severe nearsightedness or farsightedness
- Diabetes, heart disease, or hypertension
- Blood or vascular abnormalities that impair blood supply to the optic nerve head
- Long-term use of steroids in any form such as eye drops, oral medication, injections, ointments, or inhalers without medical supervision or exceeding prescribed doses
- History of eye surgery, laser treatment, or severe eye injury
- Occupations or activities that increase pressure in the neck and face, potentially raising intraocular pressure and making glaucoma control difficult, such as wind instrument musicians, opera singers, weightlifters, or sports requiring head-down positions like yoga
- Obstructive sleep apnea, such as in overweight individuals with thick neck tissues narrowing the airway, or nasal obstruction from sinusitis or allergic rhinitis
Glaucoma Treatment Methods
The goal of treating all types of glaucoma is to reduce or control intraocular pressure, the only controllable factor, to normal levels and/or slow disease progression. There are three main methods to lower intraocular pressure:
- Medication, including topical eye drops, oral tablets or liquids, and injections used in some cases only
- Laser treatment, with several types available, such as:
- Laser iridotomy used to treat or prevent acute angle-closure glaucoma in patients with narrow angles, often combined with pressure-lowering medications
- Laser trabeculoplasty used in some types of glaucoma to improve aqueous humor outflow and reduce intraocular pressure
- Surgery to create drainage pathways for aqueous humor from the anterior chamber to outside the eye, or angle surgery to enhance natural outflow. Special implants may also be used to help drain fluid inside or out of the eye. The fluid drains under the conjunctiva, appearing as a fluid-filled bleb on the outer surface of the eye.
Since glaucoma involves both the eye and brain, as well as systemic diseases, and the optic nerve abnormalities have specific structural and functional characteristics, in addition to eye examinations by ophthalmologists, various instruments (Images 4 and 5) and special devices such as contact lenses (Image 3) placed on the cornea to examine the anterior chamber angle are used to aid diagnosis and monitor treatment. Early detection and treatment of conditions like narrow angles may help prevent acute angle-closure glaucoma. Currently, there is no cure or method to improve glaucoma, as the disease is either stable or progressive.
It is true that even with good vision, hidden eye diseases may exist. Therefore, regular eye health check-ups are important not only to receive correct and timely treatment but also to help prevent and preserve our valuable vision for as long as possible.
Image 3
The left image shows a gonioscopy lens used with a slit lamp microscope to assess the width of the structures at the front and inside of the eye, which are important for the outflow of aqueous humor produced inside the eye, as shown in the right image.
Image 4
The left image shows an optical coherence tomography (OCT) device that analyzes the optic nerve head, macula, and retinal layers by scanning cross-sectional images with laser light to view the retinal layers and optic nerve head depth, as shown in the right image. This device is important for diagnosing and monitoring glaucoma long-term.
Image 5
The left image shows a visual field analyzer computer, which assesses the function of the optic nerve and the visual field of each eye, including the central (macula) and peripheral areas. The results are displayed as shown in the right image.
