Hello I’m Dr. David Richardson. I’m a cataract and glaucoma surgeon in Southern California. And on my morning commute, I like to discuss those topics that there’s simply not enough time to discuss in a typical exam room situation.
So, today I’d like to discuss the topic of how frequently visual field should be performed.
Now, visual field testing—as we have discussed in the past, is something that neither doctors nor patients really enjoy and so we both like to do it as infrequently as possible. But what’s an appropriate frequency? Let’s take a look at that together as we take off.
Alright…So the appropriate frequency really depends on one’s diagnosis. And although there are no hard and fast rules for how frequent visual field should be performed, there are some guidelines that we can discuss depending on where one is in the glaucoma diagnosis.
So is one just a glaucoma suspect? Does one have chronic controlled glaucoma? Uncontrolled glaucoma? Early diagnosis? Advanced glaucoma? So you see, there’s a whole bunch of things that we need to consider in determining the answer to this question.
So we’ll start with suspicion of glaucoma, someone who is simply a glaucoma suspect may not need frequent visual fields once the level of suspicion has been determined. So for example, someone who is only a mildly (as in exam that’s only mildly) suspicious for glaucoma. So there’s some soft evidence but no hard evidence. They may be able to get away with visual field testing only once or twice a year. Whereas, somebody who is highly suspected of glaucoma by their eye doctor may need more frequent visual field testing.
How about somebody who is who has just been diagnosed with glaucoma. Well this is interesting. There’s some evidence—and I agree with this, that at initial diagnosis is when the most frequent visual field testing really needs to be done. And the reason for that is that when someone is first diagnosed with glaucoma, what we don’t know is how aggressive the glaucoma is. So in other word,s what is the rate of loss. And the only way to discover a rate of loss—as we all remember from our early math classes and in middle school or high school—is you need to plot that out. So you need to get multiple points, multiple tests over time, and plot out a rate of loss. So clearly, the more frequent the testing, the faster you’re going to be able to get multiple points to plot that out. So I actually recommend at initial diagnosis that visual field testing to be performed every two to three months in order to get to that rate. Once I see what the rate is, then I think it’s perfectly appropriate for somebody who has a slow rate of loss to lengthen the time between visual fields. There is a caveat to that, though and we’ll get to that in the next couple of topics here.
So let’s talk about somebody with a chronic but controlled glaucoma. So somebody who’s being treated for glaucoma. So a known glaucoma. Not a suspect but by all evidence—visual field testing, evaluation of the optic nerve both by examination by the doctor, as well scanning—someone like that, is well controlled, with no evidence of…no strong evidence of progression, can be monitored with visual field testing usually about twice a year. Some will extend it a little bit further out than that…I’m personally not comfortable with going beyond once a year… Somebody has to have, you know, essentially years of evidence of stabilization with excellently controlled intraocular pressures.
And the reason why my preference is twice a year testing—if not visual field tests (you know) at least optic nerve scanning, is (but that’s a separate topic) that glaucoma is not always so well behaved. So, you can have what appears to be well controlled glaucoma, hop along just fine…and you know, suddenly for reasons we don’t understand, the intraocular pressure can escape control and given that glaucoma is a symptom-free condition for the most part—that’s something that we wouldn’t detect unless there were multiple visits, multiple visual fields each year.
How about uncontrolled glaucoma? Well somebody whose glaucoma is not under good control needs more frequent testing because in someone like that, we’re really trying to establish how low the pressure needs to be, as well as how aggressive the glaucoma is. So, in those not controlled I will often recommend visual field testing every few months, every three to four months. Sometimes even more frequently.
Advanced glaucoma is another situation where a visual field testing really should be done more frequently. And the reason for that is that (unfortunately) the more advanced glaucoma, the more visual field loss there is, the more aggressive the glaucoma tends to be. So, in other words, the rate of loss increases. In that case, you really do need more frequent visual field tests in order to detect the rate of loss and see whether it’s increasing or stabilizing.
Now, the other thing that makes it necessary to test those with advanced glaucoma more frequently is that: the more advanced the visual field loss, the more field to field fluctuation there tends to be. So, in other words, you can have what appears to be visual field loss or even improvement and really not know for sure that that’s a true loss or ** unlikely improvement so many times when visual field loss is detected it really needs to be repeated in order to confirm that is an actual loss.
This gets to other reasons—that are unrelated to diagnosis or not directly related to diagnosis—why visual field testing may need to be repeated or performed more frequently.
So we’ve also (have already, rather) talked about test to test variability Now although that is more likely to occur in advance glaucoma it does occur to some extent with all forms of glaucoma. So, in other words, every test is going to be a bit different from the past test even if you were to repeat it the following day. So if a test is worse a day after an initial test and the pressures are fine, there’s no reason to believe that glaucoma is worse, but it appears to be worse on the second testing, is it really worse? Probably not, but because of tests-to-test variability, one may need to test the visual fields more frequently than one would otherwise wish to do. And then there’s just the the need to confirm: is this really worse or not? So whenever there’s a suggested change but not a definite change, often, we’ll need to repeat that.
The other thing is poor quality testing. There’s so many things that can affect the quality of the visual field…if someone has not slept well the night before, if someone is concerned or anxious about something potentially completely unrelated to their glaucoma or the visual field testing, if someone is otherwise distracted, has dry eyes…there’s so many things…it just forgets to focus on the fixation spot… these things can all result in a poor quality visual field. And poor quality visual field is not a useful field in terms of determining loss from glaucoma. So in that case the field needs to be repeated.
Other things— surgery. So for example any time someone has surgery that could change the vision or impact the treatment of glaucoma, we need to get new baseline field. So cataract surgery, which tends to improve the vision—we need to get a new baseline after cataract surgery. Glaucoma surgery—we should get a new baseline after glaucoma surgery, once somebody’s healed up and the vision is cleared up. This actually gets back to something I should have talked about earlier, which is “baseline visual field testing”. The very first visual field performed is usually not that great because there’s what we call a, “learning artifact” which means that that really should be repeated within a couple of months in order to see what the true baseline is. After one its’ we just kind of figure out how to go perform the visual field testing.
Then there’s the need to occasionally zoom in on the center of the vision so the standard visual field testing is what we call 24 – 2 or 30 – 2 essentially 24 to 30 degrees in visual field around fixation. But it’s known that when there is depression of the central field that glaucoma can be more aggressive. So it’s important to occasionally check just the central visual field – the central 10 degrees of field. That central 10 degrees is incredibly important because not only as I alluded to does glaucoma tend to be more aggressive when the central field is impacted but the central field is what we use for reading, for recognizing faces, for recognizing emotions…so it’s critical for person-to-person interaction. It’s also important for using computers tablets, watching videos…all of these things. So we really want to protect that 10 degrees of field as it’s so important. So that really requires zooming in once in a while, which means an extra visual field.
In summary, although we really don’t like to do visual field testing. It turns out that we really should probably be doing it more frequently. One would prefer not to do it but given that the alternative is to potentially miss progressive loss of vision, the question one really needs to ask us, “which does one prefer (more or less as the case maybe): frequent visual field testing or permanent and progressive loss of vision that would otherwise be undetected?”. My sense is that we should have more frequent visible field testing, pretty much as frequent as we can bear because we really don’t want to miss that loss of vision.
My next video will be how visual field testing fits in with other testing. I alluded to OCT (optical coherence tomography) or what are called, “optic nerve scans”. And so I’ll be discussing how that can be used alongside a visual field testing, rarely instead of visual field testing. And I hope you’ll find that interesting and I hope you found this one to be interesting and helpful as well.
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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. Dr. Richardson is also an Ambassador of Glaucoma Research Foundation.