Don't over think it. Just take it step-by-step. This exercise goes for pretty much any ocular disease.
1) Always ask: What are you visualizing? What is its "body plan?" How will it appear to the patient? How will it appear to you?
The vitreous is designed (bauplan or body plan - zoology term) to be a transparent and invisible tissue that supports the roundness of the eye, protects the more delicate internal structures of retina/choriod and aids in the transmission of light to the critical tissues. IT IS MEANT TO BE INVISIBLE. In older patients, it gets lumpy. That lumpiness interferes with function because the more dense tissue of the PVD will create a shadow on the retina. If the PVD caused a retinal tear, there may be flashes. Also, that lumpiness (syneresis) makes the vitreous visible to you and the patient. (Although some floaters are subclinical).
The patient should see a shadow. You can also see a shadow. With PVD, you may see the actual tissue of the PVD first, OR the shadow of the PVD on the retina.
PVDs can be tricky. I like to use a 20D lens and BIO and use motion parallax to see if I can visualize a shadow or a distortion in the vitreous tissue. I'll focus the retina in my field and then move myself back and forth (side to side, not in and out). It gives you a good idea as to how transparent the vitreous is. Try it in normal patients first, especially children. You won't see anything. That's because the vitreous is fully functional and doing its job. If you see a wobbly appearance to the retina in an older patient with symptoms, you have a floaters, or a PVD. For me, low mag is almost easier than high mag in the trickier cases.
Actually, a good comparison is to a "wobble" seen in a spectacle lens. Sometimes lens manufacturers have errors in lens blanks called "wobbles." You see them best by motion parallax. They're subtle. Some distortions in the vitreous look the same! It's just optics.
And then sometimes it's obvious when you see that worm-like Weiss ring in front of the optic nerve. In that case, rock the slit lamp forward and back and it'll come into view. PVD, remember, is vitreous detachment ... and they detach in the direction of gravity, top down. The presence of a floater is not necessarily a detachment, OR it can be the aftermath of an old PVD.
The main concern in either case is: is the retina intact 360 degrees? Always check.
Basically, if you mistake a floater for a PVD it's not that big of a deal. The real concern is the retina. When you're in school, they'll want precision in the diagnosis because you're learning, but in clinical practice, the real concern is: has the changes in the vitreous affected the structure or function of the retina?
Anyway, just think about the tissue and its function. Ask yourself if the tissue IS functioning properly (you can get this from history). Then go for it.
You will make mistakes and some professors delight in making you feel like a dufus. But just let it roll off you, learn from it, and move on.
I literally had nightmares about maybe writing down the wrong rx every night and the dry heaves every morning before work when I started practicing optometry on my own. I didn't do a residency. Went straight out of OD school into a commercial setting with no supervision. I realized that in order to function in life, I had to leave work at work, and home at home and not mix the two. I wouldn't even read OD magazines at home. I did make mistakes ... not big ones ... but some. I felt like a dufus a few times by over-referring stuff. (My big thing was optic disk drusen vs papilledema). See a mistake as an opportunity to learn. And if you're not sure about something, get a consult without the fear of being judged by the MD. Believe me, they'll LOVE the opportunity to teach you something AND you might even get a job offer for being an enthusiastic learner!
Good luck!
