Hello, my name is Dr. David Richardson. I’m a cataract and glaucoma surgeon in Southern California. Today’s commute was actually pre-dawn. So I’m here in the parking lot today. So it’ll be a parking lot video.
What I’d like to discuss is the first of a series of videos going over Visual Field Testing. Essentially why we do it, what it is and some of the other nuances.
Today I’m going to focus on, “Why We Do It”.
Almost universally patients hate the visual field testing. It’s tedious and it’s boring and so I find that if I explain why we do it and provide some information that that can be motivating for the individual who needs to sit through the field testing. It was kind of like me and working out at the gym. I would never work out at a gym on my own, if it wasn’t for the knowledge about the potential benefits to me.
I just don’t like to work out. I’m just not one of those athletic types.
So my hope is that by having information about why visual field testing is important, that if you have glaucoma or have been recommended visual field testing that you will also be motivated by this.
So first, I want to get something out of the way, why doctors recommend visual field testing. It is not because this is a test that is profitable for the individual doctor. Visual field testing is equipment intensive, space intensive, staff intensive and time intensive for the doctor. It’s not easy to interpret and it can be quite frustrating to interpret for the doctor just as it is to take for the patient with modern insurance eimbursements. Many practices they’re lucky to even break to break even on it.
So if this test is disliked almost universally by both patients and doctors why do we do it? Well the reason we do it is that most visual field defects can’t be recognized by the individual person who has them not at least until the very end stages of disease at which point it’s it’s really too late. We want to find these defects before the individual who has glaucoma is even aware of them.
Now, it might seem odd that you’d lose vision and not be aware of it. But there are a couple of reasons for that one is that early visual field defects can be on the small side and we just don’t recognize small visual field defects. If you need proof of this look for your own blind spot, everyone’s got one. One in each eye just off to the side so off to the side of center left side of center in the left eye right side of center in the right eye.
Now, people assume that visual field defects are either areas of blackness or gray or just an area where there’s nothing there.
But that’s not how we see them. And the reason why we don’t see visual field defects is because our brains play a clever, clever trick on us. If you’ve ever played around with Photoshop you’re aware of this trick. It’s called the “pattern fill tool”. You can take any area and select a pattern a complex pattern not just a color and fill that in. And indeed that’s what our own brains do with our blind spots. It takes the pattern surrounding the blind spot and fills in that blind spot where the optic nerve comes into the eye and there’s no retinal cell to actually detect light.
The reason we don’t see visual field defects is that our brains actually camouflage them. So our brains are actually making it impossible for us to see them unless we use techniques to actually find them. And perhaps I’ll linked to this video, some of the techniques that you can use to find your blind spot and it’s pretty awe-inspiring.
Now the other thing that goes on is that we’re just not aware of really the extent of our visual field so in terms of the edges of our visual field. People who lose field on the edge and start to get constriction generally aren’t aware that they’ve lost the visual field until they start bumping into things.
If you think about it, it’s not that surprising that we’re not aware of what we don’t see. Just like we’re not aware of what we don’t hear until we don’t hear something important.
Now the other reason why we tend not to be aware of visual field loss is usually it’s not a complete loss, so early changes in the visual field tend to be more a reduction of what we call the “threshold of field”. So in other words in order to see something light has to be brighter colors have to be more saturated contrast has to be greater so it’s not that we can’t see anything at all it’s that it we see less in that area. This is very subtle and most people are not aware of this. Sometimes those who are visually quite sensitive to their environment so artists engineers hunters may be able to state that there’s something that’s not right but it’s rare that they can…it’s rare that they can describe it in great detail.
So these are reasons why we can’t detect them on our own. So because we’re pretty much incapable of detecting this change on our own, it’s important that we use a test that’s designed to find these very early changes.
Now in addition to finding these early changes, once glaucoma is detected and treated–often with lowering interactive pressure–although I’ve talked about and we’ll talk about other methods to treat glaucoma as well–we have to monitor to make sure that the treatment is being effective. If visual field loss is progressive–so continues, then more aggressive treatment needs to be recommended.
So visual field testing is critical not only for detection but also for monitoring for progression of the disease itself.
So in summary why do we do visual field testing when almost everybody doctors and patients pretty much universally hates doing this testing? It’s because we are incapable of a pretty much incapable of detecting loss or reduction on our own until it’s really too late in the disease. And because once it is detected it’s an important component of monitoring for progression to make sure that the treatment is actually adequate, right. So that’s pretty much it for why we do it at least in a short video. My next video I’ll be discussing a bit more what a visual field testing is. Again with the idea that my sense is the more you know about the test the more likely it is that you will be willing to sit for this very important test if you have glaucoma or are a, what we call, a glaucoma suspect. Alright, thank you.
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David Richardson, MD
Medical Director, San Marino Eye
David Richardson, M.D. is recognized as one of the top cataract and glaucoma surgeons in the US and is among an elite group of glaucoma surgeons in the country performing the highly specialized canaloplasty procedure. Morever, Dr. Richardson is one of only a few surgeons in the greater Los Angeles area that performs MicroPulse P3™ "Cyclophotocoagulation" (MP3) glaucoma laser surgery. Dr. Richardson graduated Magna Cum Laude from the University of Southern California and earned his Medical Degree from Harvard Medical School. He completed his ophthalmology residency at the LAC+USC Medical Center/ Doheny Eye Institute.