Getting The Most Out Of OphthalmicEdge

All students are encouraged to view the images multiple times by clicking the “again” icon found at the end of each movie. Note the probe position and the consequent registration of the screen. Ask yourself, what does the top, bottom, left and right portions of the screen represent? Are recti muscles seen on the screen within the orbital tissue and, if so, are the images of the muscle cross-sections or sagital views? How thick is the muscle image and how close is it to the globe wall?  Answers to these question help enormously in registering the position of the images. Also, is the optic nerve visible or not? Should the nerve be visible from the probe position depicted and, if not, why not?

 

Once oriented, observe for any motion of the probe or the globe. Decide what type of motion is noted in the movie segment and be sure to observe for after-movements. What is moving and how do the movements relate to the ocular wall movement? Is movement rapid, slow, undulating, tethered, etc.?

 

Then, how strong are the reflections from the areas in question?The strength of returning echoes may be based upon gain settings or simultaneous A-scans. Be sure intensity is judged from the most perpendicular portions of the area in question to the passage of sound from the B-scan probe (usually the center portion of the B-scan image).

 

If a simultaneous A-scan is presented, every attempt will be made to show a perpendicular image to the area being evaluated. Are the reflections strong, medium or weak in gray scale? Do they disappear quickly as the gain is reduced or do they remain on the screen? In simultaneous A-scan, compare the amplitude of the echoes from the area in question to known strong reflectors such as retina or sclera. Often, reduction of the gain is required to levels that allow comparison of the strong reflectors to weaker reflectors. By now, most students recognize that minimal A-scan amplitudes should appear as weak intensity dots in B-scan and high A-scan amplitudes should appear as intense dots in B-scan.

 

Finally, try to create a 3-D image or map of the globe or orbit from the cross sections presented.  Often this portion will be limited due to the constraints of movie time and memory storage capacity. Practice 3-D thinking by asking yourself: if I changed my probe position to a different site how would the screen image be affected? Where would the abnormality be represented on the screen or would it be seen at all?