Pars Plana Vitrectomy Defined
Pars plana vitrectomy is the most commonly performed surgical procedure for a retina surgeon. A great deal of understanding about the surgery can be derived from the name of the procedure itself. The vitreous is the gelatinous tissue that fills the largest cavity in the back of the eye, and the suffix –ectomy confers its surgical removal. Pars plana comes from a Latin translation for “the flat part,” fitting for the eye’s anatomic location it represents – the flattest part of the ciliary body, located 3.5 to 4 millimeters back from the limbus, or the outside border of the colored part of the eye.
Why do we perform vitrectomy through the pars plana? In order to reach the vitreous, retina, and other structures in the back of the eye; we insert microscopic ports through which instruments can be introduced and exchanged as needed, depending on the stage of the surgery. These instruments include but are not limited to light sources, the cutter/vacuum apparatus (vitrector), ultrasound, lasers, forceps, scrapers, and syringe tips for injecting for various dyes and stains.
The only safe place to insert the ports for instrument exchange is the pars plana, because anywhere else would damage the eye’s other vital structures. For example, just one millimeter closer to the limbus, and you’re no longer in the pars plana; but rather, the pars plicata, or “the folded part” in Latin. This area of the ciliary body is much thicker than the pars plana, its inner lining is responsible for production of the aqueous humor that helps us maintain normal eye pressure, and its tips serve as insertions for a ring of microscopic suspension cables called zonules that keep our natural lens in proper position; ie, not an area we want damaged. Meanwhile, the ports also cannot be inserted two millimeters in the other direction, where the peripheral border of the retina begins.
Long story short, placement of the vitrectomy ports must be precise, as must all other steps of retina surgery. For a better understanding of specific surgical maneuvers within pars plana vitrectomy required for specific eye conditions, you can find out more in the “conditions” section above.