This opens a slightly larger question: is fundus camera FAF as good a tool as Spectralis FAF?  I am more interested in diagnostic ability than aesthetics.   Open the flamethrowers!  

Marty Rothenberg

Angiographics, Inc

The retina doc at a practice I work with just found out that they own a Canon CR-2 Plus in one of their remote offices.  Can anyone comment on the FAF (autofluorescence) on this camera?  I could only find a few images online.    I realize this is designed as a non-myd, but we would probably take the images dilated.  

This opens a slightly larger question: is fundus camera FAF as good a tool as Spectralis FAF?  I am more interested in diagnostic ability than aesthetics.   Open the flamethrowers!  

Marty Rothenberg

Angiographics, Inc

Hi Marty,

Good questions. I've played with the Canon CR-2 in FAF mode at a recent meeting. Looks promising. We were working in non-myd mode & shot just an image or two of someone there who happened to have some pigmentary changes that showed up well in FAF. The contrast was lower than I liked, but the software had controls to change that. We'll be testing the camera here in our clinic in the next couple weeks, so I'll add more info to this thread after we've tried in a clinical setting. I would highly recommend that any patient for FAF imaging be pharmacologically dilated. The low levels of fluorescence make this a necessity.

As to the second question, I think the answer is yes. We use both the Spectralis and fundus camera FAF here and find them pretty interchangeable in terms of the clinical or diagnostic info they provide. We often pick & chose which device based on convenience to the patient or whichever instrument is available at that time. If they are having another procedure on the fundus camera, we do FAF on that. If they are having Spectralis OCT, we use that. The wavelengths employed are significantly different so intuitively, you'd think the diagnostic appearance would be quite different but surprisingly that's not the case here.

I've attached a few slides from the recent OPS webinar on FAF just last week. They compare Spectralis with 1st & 2nd generation filter sets. The published specs on the Canon filter set looks like they are in the same range as the Topcon Spaide filters. Take a look at the slides & see for yourself. From an imaging standpoint both devices have advantages & disadvantage in terms of ease of use, patient tolerance, etc. Both provide valuable (and quite similar) information in several retinal conditions.

Hope this helps,

ps. I have no financial interest in any of these devices or companies.

MHO ( my humble opinion)

Denice

May I please transfer this conversation to the OPS general membership forum and continue to encourage everyone to do so as well as we transition over to a one stop shop for all things OPS.

Denice

Thanks for the info.  As usual, you did the superb work of running a comparison test (although it is very un-internet of you to mess up a good discussion with actual objective observations). I am  surprised how similar the images are.

Now, could you comment on the issue of "oversampling" FAF images on the Spectralis?  How many frames do you recommend be set for normalization?  Do you have similar recommendations for FA, ICGA and redfree images, too?  Does one size fit all?

 Is the OPS putting the webinar on-line for those of us who missed it?  And if not, why not?

Marty Rothenberg

The OPS is exploring the possibility of recording these webinars and offering them at future times/dates.

The OPS recognizes the need for multiple offering of these events but some details need to be worked out before we can proceed with this.

The OPS very much wants to do this and we will publish details once these details have been resolved.

bob 

Tim,

Thanks for the info.  As usual, you did the superb work of running a comparison test (although it is very un-internet of you to mess up a good discussion with actual objective observations). I am  surprised how similar the images are.

Now, could you comment on the issue of "oversampling" FAF images on the Spectralis?  How many frames do you recommend be set for normalization?  Do you have similar recommendations for FA, ICGA and redfree images, too?  Does one size fit all?

 Is the OPS putting the webinar on-line for those of us who missed it?  And if not, why not?

Marty Rothenberg

Good one Marty!

Yeah, I've been surprised at how similar the two image types can appear. In a normal patient, the biggest differences are in the optic nerve head, blood vessels, and fovea, which all appear darker in SLO images. That could be due to the wavelength difference, but the confocal nature of the instrument plays a role as well. In patients with RPE pathology, the difference in appearance is minimal.

Great question about oversampling on the Spectralis. Denice asked about that in the webinar as well. Intuitively, more sampling should result in a better, smoother image. In practice however, you can get some movement artifacts that can soften or degrade the overall image. You can start to see what I call a "plastic" look to some images as sampling is increased. It could be a result of eye movement just as you lock on the eye. Could also be from changes in the tear film during extended sampling. It's more prominent in the IR & red free images. Noise from eye movement during sampling is often noticeable close to the edge of the frame. We keep the ART set for 100 frames and capture an image whenever we think it looks "good". That could be anywhere between 10 frames and 100. The good thing is that you can capture an image at multiple points during the buildup to 100 frames and select the best image afterwards. This is a case where a skilled, experienced imager has an advantage in knowing when it looks "good".

Bottom line is that we have no set formula for how many frames to sample. The patient's cooperation level has as much to do with it as anything else. Some (many) patients can't tolerate the constant brightness of the excitation light and image quality goes south in a hurry. You can set the sampling to a specific number for consistency, but that won't deliver the best image on a good portion of the eyes you'll see. We try to get the best looking images we can and ignore the numbers.

For more info on this subject, check out the short article in the tutorial section of the website:
http://www.opsweb.org/?page=Autofluorescence

Also there was a previous discussion on this forum with a few image comparisons a while back:
http://www.opsweb.org/forums/posts.asp?topic=428509&

The OPS Board of Education is working through some details to do another webinar or make it available on-demand. There will likely be news on that very soon.

Again, I have no financial interest in the instruments mentioned here.

Hope this helps,

Marty-  I hope you can make it!

Sarah