In my professional practice as a glaucoma specialist, I have found many myths and misconceptions about the definition of this disease. A large portion of my conversations with patients, both formally diagnosed and suspects, circle around what glaucoma really means.
Originally, the root of the word “glaukos” comes from ancient Greek, and refers to the “green-blue-gray” hue that the cornea shows in very advanced and untreated cases of glaucoma (see image 1), which is how this disease was recognized in antiquity. In the modern era, we only very rarely come across such dramatic cases.
Glaucoma is a group of diseases, which have in common the gradual and irreversible damage to the cable that connects the eye to the brain, called optic nerve. Usually, this damage is caused by the increase in the pressure inside the eye, but it is important to mention that there are cases of glaucoma (that is, typical and proven damage to the optic nerve) in which the intraocular pressure is not in “officially high” levels, and is only “higher than what that particular eye is able to stand”. At the same time, there are eyes with “officially high pressure” where no definite nerve damage has been proven.
Let’s go step by step.
The eye is like an inflated balloon with a certain pressure inside it. This pressure is generated by a liquid that is constantly being created, at a more or less constant rate, although there are some fluctuations. We can picture it like a bathroom sink with a constantly open faucet.
To prevent the water in the sink from overflowing, there needs to be a drainage system able to remove the water at the same rate it is being introduced, and in that way, keep the pressure at a stable level. The eye indeed has a drainage structure through which the liquid eventually exits into the veins that are located inside the walls.
In some people, this outflow system very slowly becomes microscopically clogged, like the shower sewage when it captures residues. This is normally due to genetic effects, in about 3-5% of the general population. It happens very very slowly, over decades. The more clogged it becomes, the less liquid it can drain, and the more the eye pressure increases.
This increase in intraocular pressure, when happening in a very slow manner, is a painless process without any noticeable visual changes. Once the increase reaches a certain level, the internal walls of the eye start suffering damage, particularly at the place where the cable leaves toward the brain.
As years go by and the pressure keeps on rising, this nerve stops working irreversibly, and it is the peripheral vision that is lost first. Like a lightbulb that starts dimming progressively, and the edges of the room which it illuminates become darker and darker (see image 2). Given that it is such a slow and painless process, the person is usually not aware of it, until the very end, where the loss of peripheral vision is nearly total.
For me to know whether someone has glaucoma, the first thing to do is ask if there are family members with ocular conditions or blindness (because this increases the risk of suffering from the disease). After, I measure the pressure in the eye, and finally, directly observe the optic nerve to detect if it seems to be damaged.
From this process, usually one of these 3 results emerges:
- Healthy person without suspicion of glaucoma.
2.Definite and usually advanced glaucoma.
- Suspicion for glaucoma, which needs to be confirmed by specific testing and/or future assessments.
This will be the first of many entries in which I will try to pin down the most common and important questions about the diagnosis and treatment of this disease, so as to make it permanently available for people who have been diagnosed or have a family member suffering from glaucoma.
Thank you very much,
Dr. Victor Flores.
Image 1 (Courtesy of the American Academy of Ophthalmology)
Image 2 (Courtesy of myupchar.com)