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Medical Forum / General / Vision / July 2005Humphrey's FDT Visual field
I am thinking about purchasing the above for my practice. Can anyone tell me if cataracts will interfere with the results of the feild test more, less or equal when compared to the computerized automated parameter (CAP). I heard from a friend that it is not as good as the CAP if the Px has cataracts. Anybody with experience with this instrument? I would appreciate your comments. Thanks Roland J. Izaac Why do you want it? You cannot follow glaucoma progression. I have an Octopus 123. It has a fast mode that does a central threshold in less than 5 minutes per eye, including an automatic fixation monitor. DrG > Why do you want it? You cannot follow glaucoma progression. I have an > Octopus 123. It has a fast mode that does a central threshold in less > than 5 minutes per eye, including an automatic fixation monitor. > > DrG But the FDT, especially the new version is an excellent screening tool for general visual field defects, including glaucoma. Takes about a 1.5 minutes in screening mode, far faster than the big machines.. Dense cataracts would be an issue, moderate cats no problem. Best do run test with a partially dilated eye. In full threshold mode, I believe you *could* follow glaucomatous field defect progression (there's plenty of data comparing that ability to the big Humphrey's machines), but, as per Dr. G, the Octopus would be better and, of course, HRT or GDx better still. For the patient test time requirements at full threshold, there's no advantage FDT over the big machines. It's so fast and easy, I run it on every patient. More than once in the last two years it has picked up ischemic stroke and pituitary tumors in otherwise asymptomatic patients. --LB, O.D. The Octupus 123 does a quick threshold in 2.5 minutes per eye. I'm thinking about getting a Stratus OCT. Any comments? DrG I like my Synemed. It's priced right and has quick modes as well as full thresholds. Also, it is very reliable. I've had it for over 12 years and did a software and hardware upgrade last year to bring it in alignment with the Humphrey's standards. Never has broken down and there is no maintainence. w.stacy, o.d. > The Octupus 123 does a quick threshold in 2.5 minutes per eye. > > I'm thinking about getting a Stratus OCT. Any comments? > > DrG > The Octupus 123 does a quick threshold in 2.5 minutes per eye. > > I'm thinking about getting a Stratus OCT. Any comments? > > DrG The FDT and Matrix units do screening 45 seconds per eye, BTW. Real life, including set up and instruction to patient, 3 minutes total. Well, well worth the time. Meanwhile, here are two articles of interest relating to retina imaging: http://archopht.ama-assn.org/cgi/content/abstract/122/6/827 http://www.ophthalmologymanagement.com/article.aspx?article=86304 A number of the OMDs around here are leaning toward the OCT these days. Certainly, if I was going to treat and manage glaucoma patients or had a population with numbers of patients with macula holes and such, I would in a heartbeat have a retina imaging system delivered. --LB, O.D. You can also perform pachymetry and anterior segment imaging with the OCT. DrG Thanks for all the comments, I was really concidering the FDT as it is claimed to be more sensitive to field loss due to glaucoma. It targets the M cells which is non linear and the cells do not overlap each other. I also read an abstract from pubmed that says it may fall short in neuro-ophthalmic disorders especialy in "hemianopias because of the presence of scatered abnormal test locations and failure to detect test locations along the vertical lines. the results showed that "FDT testing masked the hemianopia nature of the defect in 15 of 25 patients. Also, test locations along the verticle midline in densely hemianopic areas were seen with FDT testing in some patients with hemianopia, probably due to light scatter across the verticle midline and into the uninvolved hemianopic field." Source PubMed Sensitivity and specificity of frequency doubling perimetry in neuro-ophthalmic disorders: a comparison with conventional automated perimetry. Roland J. Izaac > Why do you want it? You cannot follow glaucoma progression. I have an > Octopus 123. It has a fast mode that does a central threshold in less > than 5 minutes per eye, including an automatic fixation monitor. > > DrG I have used an FDT for several years and don't have much confidence in it. While I'm sure that it picks up early glaucomatous changes easily, it also gives a very high rate of false positives. I would hazard to guess that approximately one-third of my patients show some kind of field defect by FDT. In those patients, follow-up testing with HVF-II and careful fundoscopic exam shows nothing and if the patient returns and is retested the FDT defect is either gone or has moved elsewhere. I have lost patience with FDT and no longer use it. ========== > Thanks for all the comments, > [quoted text clipped - 25 lines] >> >> DrG > fundoscopic exam shows nothing and if the patient returns and is retested > the FDT defect is either gone or has moved elsewhere. I have lost > patience with FDT and no longer use it. I haven't lost patience but it's scary sometimes. The scariest was a textbook bitemporal hemianopsia, clearly defined, dense, and perfectly symmetrical. The patient went for neuro eval and nothing was found. He still has the "defect." The most recent was a radiologist... superior bitemporal field loss that remained on repeated testing. I explained that we get a lot of false positives and he said "that's OK, it's easy for me to get an MRI." -MT > > fundoscopic exam shows nothing and if the patient returns and is retested > > the FDT defect is either gone or has moved elsewhere. I have lost [quoted text clipped - 11 lines] > > -MT I'd much rather a false positive than false negative than no test results at all. It's a tool, that's all. Follow up with the next-in-lline appropriate tool is not a problem. Not doing so is. And how often to we observe something weird on the retina that does not have a corresponding visual effect or is otherwise unidentifiable as a progressive pathology? We send them for angio or other test with no resolution? Or how many people out there get no eye care at all and do fine, or end up with a serious pathology that could have been fixed earlier, or that makes no difference either way? We don't have all the answers or all the tools to find them in one place. But we look the best we can, eh? --LB, O.D. i agree. i find FDT to be so prone to giving false positives that its value in early glaucoma detection, without corroborating additional findings, to be virtually worthless. > I have used an FDT for several years and don't have much confidence in it. > While I'm sure that it picks up early glaucomatous changes easily, it also [quoted text clipped - 4 lines] > the FDT defect is either gone or has moved elsewhere. I have lost patience > with FDT and no longer use it. I had FDT done four times last September, and I knew I had a visual field defect in one eye. The results were so inconsistent from test to test--showing gross defects in one quadrant that on second test was normal but with a defect showing in a different region then on each subsequent test, and in both eyes--that the optometrist gave up and said she could not explain it. The glaucoma specialist looked at the FDT readouts, said that FDT is supposed to detect visual field defects before they show up on the SITA 24-2, but that in my case the results were so wildly inconsistent the tests were meaningless. The 24-2 showed repeatable superior visual field defect in one eye and normal field in the other. Do you think this was a case of user error, the tech perhaps not knowing how to run the test, or just the FDT itself? As a patient it was certainly a waste of money for me. I found it very hard to tell whether I was seeing actual squiggles or just floaters but patients are always told that floaters don't affect visual field tests. -Gudrun |
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