Vitreous biopsies may be:
i. Vitreous-cutter Biopsy
ii. Fine Needle Aspiration Biopsy
A vitreous sample should be obtained without diluting/contaminating it with BSS® infusion.
Set up for a standard three port pars plana vitrectomy but do not open the infusion line. 25 or 27 gauge cannulas with beveled insertion is preferable for self-sealing wounds. If there is poor view, consider using a 6 mm length infusion cannula to ensure the infusion is in the vitreous cavity, especially if there is coexisting choroidal or retinal detachment detected on preoperative B-scan ultrasound.
This ensures that any sample will not be diluted by BSS® coming from the infusion. If using the Alcon CONSTELLATION® vision system: The "Setup" screen is divided into 6 boxes. The top middle box says "Probe." In this box it says "Skip Prime". Push the button next to this and it will place a green check next to it. When everything on the machine is set up and ready to prime, just select "Start Prime" as normal. The whole system will prime like normal except there will be no fluid in the cutter line, allowing for a pure sample to be taken.
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