The effects of glaucoma start with blind spots that may not be noticeable, in just the same way that the natural blind spot in your eye is not noticeable and requires you to check your blind spot when changing lanes on the motorway for instance.
Try this interesting experiment below to illustrate your own blind spot.
Close your left eye and stare at the cross mark below with your right eye. Below, you should be able to see the spot. Don’t look directly at it; just notice that it is there. If it’s not, move farther away. You should be able to see the dot if you are a couple of feet away.
Now slowly move toward the screen while still looking at the cross mark. When you’re approximately a foot away from the paper, the spot will disappear. As you move closer, it will reappear.
The point where your optic nerves exit the eye has no light-sensitive cells to detect light rays. This is called your blind spot and is present in all of us.
When the spot disappears, you instead “see” a continuous white field. Here, the brain is filling in the area that’s missing and it appears that there is white area even though in reality there is a spot.
In the example to the right, the yellow dot will disappear and be replaced with a red one as the brain attempts to create the missing area with a similar surrounding.
Patients with glaucoma experience similar symptoms, which is why symptoms may only become obvious when a lot of vision has been affected.
In this example below, the two children and the red car on the right appear to have “disappeared” into the enlarged blind spot. As glaucoma progresses the silver car on the left is also not seen.
The simulation below was taken from the Glaucoma Simulation app (developed by Santen, a pharmaceutical company) and can be downloaded to an Apple or Android device. It is able to simulate how glaucoma affects your vision over time. It works with your phones’ camera and can give you an idea about how glaucoma can effect how you perceive your immediate surroundings.
Normal visual field
Early visual field defects (blue arrow) affecting the right hand side of vision
These visual changes are monitored in a clinic by performing a visual field test. You may have already had one of these done at the opticians. The ones used by ophthalmologists are more detailed and help in the diagnosis and management of glaucoma. It essentially lets you and your ophthalmologist know how much your vision is affected by glaucoma and whether its getting worse. Mr. Pandey will go through the results of this test with you.
