"Glaucoma," a condition that causes damage to the optic nerve.
Glaucoma is a condition in which the intraocular pressure (water pressure inside the eye) increases, causing pressure on and eventual loss of the optic nerve. While, together with cataracts, this is a condition the name of which is generally known as a disease affecting the eyes, there are probably only a few people with a correct understanding of the phenomenon. Indeed, there are people who, upon hearing the word "glaucoma," go into a panic believing that they will lose their eyesight the following day.
The truth is that, in almost all cases of glaucoma, there are absolutely no subjective symptoms at the onset, the condition slowly developing over a period ten to twenty years, and as long as treatment is properly controlled, there is very little chance of loss of sight. Let's start by improving our understanding of glaucoma.
1. Why does glaucoma occur?
Although the eyeball is shaped rather like a rubber ball, it contains various internal components and a uniform hardness (intraocular pressure) is maintained.
The most important factor in the maintenance of intraocular pressure is the flow of "aqueous humor," a fluid found in the eye. As you can see in the illustration, this aqueous humor is produced by the ciliary body and flows along its main route from the Schlemm's canal located in the angulus iridocornealis, or corner angle (water outlet) to the venous duct, being completely transposed every 100 minutes or so.
Poor water flow from the corner angle results in accumulation of aqueous humor in the anterior chamber and a consequent increase in intraocular pressure. If this phenomenon persists and affects the optic nerve, the condition is referred to as "glaucoma."
2. Types of Glaucoma
While there are several types of glaucoma including those caused by congenital anomalies or aging and types occurring due to other diseases and conditions, glaucoma can be broadly divided into two categories, depending on whether the corner angle is wide and open (open-angle glaucoma) or narrow and blocked (closed-angle glaucoma). Anatomically speaking, there are people born with wide or narrow corner angles and congenital narrowing of the corner angle may also occur for a wide variety of reasons including swelling of the crystalline body and the appearance of new veins.
Blocked corner angles may cause acute glaucoma
The idea that glaucoma is a disease that quickly results in loss of vision came about due to acute glaucoma. An attack of acute glaucoma causes obstruction of the flow of aqueous humor for some reason, resulting in a sudden increase in intraocular pressure, producing symptoms such as severe headaches or nausea. While such attacks may also produce symptoms including pain in the eyes, dim eyesight or iridopsia (the glare of lights will appears to be surrounded by rainbow colors), concerned about other symptoms, patients suffering from acute glaucoma may first tend to go to an internist or brain specialist, with the result that, by the time the condition has been accurately diagnosed, loss of sight may already have set in. It seems that the name "glaucoma" came into use due to observation in olden times that the pupils of sufferers of the condition became cloudy and greenish in appearance. The vast majority of cases of acute glaucoma are caused by a blocked corner angle. In addition, during the process of production of new veins in people with diabetic retinopathy or other retinal vascular disorders, a time may come when an open corner angle gradually becomes closed or blocked. This is an ophthalmological condition requiring emergency treatment or surgical procedures to quickly lower the intraocular pressure.
In addition, surgical procedures that use lasers, for example, to open a minute hole in the iris, or surgery on the crystalline body (Surgery to remedy cataracts: This procedure widens the corner angle and is, therefore, sometimes selected for people with a narrow corner angle, even in cases where cataracts have not yet advanced to a problematic stage) are among the measures available to prevent the occurrence of this kind of acute glaucoma in people with congenitally narrow corner angles.
It should be born in mind that medication or various other drugs used during endoscopic examinations may bring on attacks of glaucoma in people with narrow corner angles, and this is why patients are often asked if they suffer from glaucoma during medical examinations.
The majority of cases of glaucoma are "open-angle glaucoma"
In patients suffering from open-angle glaucoma, the corner angle that serves as the channel for water is open, but the drainage channel (Schlemm's canal) becomes blocked, preventing the outward flow of fluid, resulting in increased intraocular pressure. While this differs depending on the individual visual field sensitivity and normally deteriorates slowly, this means that the condition may not be identified until has it has advanced to a considerable extent. For this reason, in many cases, the optic nerve has already been weakened by the time the person concerned becomes aware of the condition, with the result that many patients are already suffering the effects of considerably advanced visual field defects.
Moreover, it has been discovered that, in patients suffering with open-angle glaucoma, there is a very high incidence of "normal tension glaucoma," a condition in which the intraocular pressure (Normal value: 10 - 20 mmHg) is no higher than 12 mmHg. Although accompanied by visual field defects, like open-angle glaucoma, normal tension glaucoma has become the focus of attention as a disease caused not only by intraocular pressure, but related to a great many other factors such as cardiovascular abnormalities and environmental factors.
3. How is glaucoma detected?
Open-angle glaucoma is not such a terrible affliction as long as it is detected and brought under control in the early stages. That being said, open-angle glaucoma is characterized by a total absence of subjective symptoms in the early stages and this means that sufferers are unable to detect the condition themselves. People with this type of glaucoma do not become aware of problems with the visual field until the condition has already advanced to a considerable degree, by which time progress of the condition cannot easily be arrested, even with treatment. Excessive myopia is also one of the risk factors for glaucoma, and it is advisable to be on the lookout for this telltale sign. So, what can we do to spot glaucoma? First of all, once you pass the age of 40, it is advisable to take advantage of regional health checks and thorough physical examinations.
4. The importance of second opinions
Diagnosis of glaucoma based on typical or advanced cases is simple, but the opinions of physicians on early stage cases are widely divided. In addition, since, once diagnosed, this is a condition that requires continued, lifelong treatment and continued visits to an ophthalmologist, initial diagnosis requires great care.