scan angles

Darrin Landry

unread,

Dec 11, 2014, 9:25:18 AM12/11/14

to Spectralis Users

Can someone explain something to me as if I were a 10 year old?

When I do an initial scan on a patient, whether a cross hair and/or volume, I set it as a reference. When they return and I use that reference as a follow up, the scan pattern is tilted approximately 10 degrees. Even the patient notes the angle change.

However, this tilting is there when I am actively scanning, and is there in the "preview" thumbnail of the scans, but when I open the scans, the scan lines are straight.

I know there is a reasonable explanation, but frankly I am brain fried and all my synapses are not firing.

Thanks for the help

Darrin

Darrin A. Landry, CRA, OCT-C

Ophthalmic Consultant

Bryson Taylor Inc.

www.brysontaylorpublishing.com

Sandor Ferenczy

unread,

Dec 11, 2014, 9:30:22 AM12/11/14

to spectralis...@googlegroups.com

Darrin,

I have noted that the patient's head position seems to affect this.

If their forehead is drifting left or right, or their head is slightly turned, the followup scans seem to adjust for the differing positions from visit to visit.

I find it very rare that a patient re-enters the chin rest in the precise position they were in prior.

sandor

> --
> --
> You received this message because you are subscribed to the Google
> Groups "Spectralis/HD OCT User Group" group.
> To post to this group, send email to
> spectralis...@googlegroups.com
> To unsubscribe from this group, send email to
> spectralis-user-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/spectralis-user-group?hl=en?hl=en
>
> ---
> You received this message because you are subscribed to the Google Groups "Spectralis/HD OCT User Group" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to spectralis-user-...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.

Darrin Landry

unread,

Dec 11, 2014, 9:33:53 AM12/11/14

to spectralis...@googlegroups.com

that thought crossed my mind, but as I paid closer attention, the patient's head is centered and their eye is in the same relative position. I would believe that if it wasn't happening on every patient; and the same degree of angle.

Darrin A. Landry, CRA, OCT-C

Ophthalmic Consultant

Bryson Taylor Inc.

www.brysontaylorpublishing.com

From: "Sandor Ferenczy" <sandorf...@gmail.com>
Sent: Thursday, December 11, 2014 9:30 AM
To: spectralis...@googlegroups.com
Subject: Re: [spectralis-user-group] scan angles

Sandor Ferenczy

unread,

Dec 11, 2014, 9:39:09 AM12/11/14

to spectralis...@googlegroups.com

Intersting.

Not being in front of the camera right now, i cannot verify it, but i seem to remember the scan position being variable when i have seen it shift. I think the first patient i remember noting it in had muscle disinsertion during surgery, so i didnt think twice about it.

> On Dec 11, 2014, at 9:33 AM, Darrin Landry <dar...@brysontaylor.com> wrote:
>
> that thought crossed my mind, but as I paid closer attention, the patient's head is centered and their eye is in the same relative position. I would believe that if it wasn't happening on every patient; and the same degree of angle.
>
>
> Darrin A. Landry, CRA, OCT-C
>
> Ophthalmic Consultant
>
> Bryson Taylor Inc.
>
> www.brysontaylorpublishing.com
>
>

Strong, Jim

unread,

Dec 11, 2014, 9:40:50 AM12/11/14

to spectralis...@googlegroups.com

Darrin

I can’t speak to your specific circumstances, which do sound unusual. The fact that it’s consistent both in degree of offset and frequency (of occurrence) make it sound more systemic. Are you on a boat at varying tidal flow times?

Can you scan a co-worker and complete scanning, set the reference, and then re-scan in a new “folder” and see if it happens while the pt stays in the chin rest?

I will, however +1 Sandor’s explanation as that is also what we experience here.

j-

Darrin Landry

unread,

Dec 11, 2014, 9:57:53 AM12/11/14

to spectralis...@googlegroups.com

so running it through some exercises, it does appear that the eye position is the issue. I assume H'berg algorithm is adjusting for this, as when looked at side by side, the scans are in the same anatomical position, but the fundus image shows that the eye is not in the same exact location.

It's funny - I've been using Spectralis since 07, and it takes fresh eyes to point these things out to me. Must be age....

Thanks, all

Darrin

Darrin A. Landry, CRA, OCT-C

Ophthalmic Consultant

Bryson Taylor Inc.

www.brysontaylorpublishing.com

From: "Strong, Jim" <jstr...@hmc.psu.edu>
Sent: Thursday, December 11, 2014 9:41 AM
To: "spectralis...@googlegroups.com" <spectralis...@googlegroups.com>
Subject: RE: [spectralis-user-group] scan angles

John M Head

unread,

Dec 11, 2014, 1:35:32 PM12/11/14

to spectralis...@googlegroups.com

my observations...

I've seen the "scan angle" change during a single scanning session. I've noticed as the "green box" which outlines where the fundus initially at the start of the scan will "drift," and "slant," but the fundus image remains locked. I've noticed this more pronounced on pt's who may try to move in the headrest to get a "better view" of the fixation target. Or as they get tired, they can "drift" too, when the pt's have trouble fixating and the scans drag out.

I've noticed it too. and mainly I've seen it relate to the pt's head position. when the follow up is selected, the scan box can be tilted, then depending on how the pt is lined up at the time, the lines will re-shift. I use it to amuse me, just to see how the pt will line up this time.

-John