GreenLight is the common name for photoselective vaporisation of the prostate (PVP). It uses a 532 nm KTP laser, delivered through a side-firing fibre inside a cystoscope, to vaporise obstructing prostate tissue.
The laser beam is green because its wavelength is 532 nanometres, which is in the visible green part of the spectrum. The wavelength is generated by passing a 1064 nm infrared beam through a potassium titanyl phosphate (KTP) crystal, which halves the wavelength and doubles the frequency. The resulting 532 nm beam is preferentially absorbed by the red pigment haemoglobin in prostate blood vessels. That selective absorption is why it vaporises vascular tissue efficiently and leaves a well-sealed surface behind.1
Unlike the Holmium laser used for HoLEP, the GreenLight laser does not cut forward from the tip of the fibre. Instead, a small prism inside the fibre tip deflects the beam sideways by about 70 degrees. This "side-firing" design lets the surgeon "paint" the beam back and forth across the inner surface of the prostate, vaporising tissue in a controlled, layer-by-layer fashion.
With a traditional transurethral resection of the prostate (TURP), the surgeon uses a wire loop heated by electrical current to cut strips of prostate tissue. Each strip is then flushed out and sent to pathology.
With GreenLight PVP, the tissue is not cut into strips. Instead the laser vaporises it in place, turning solid tissue into steam that is washed away by the saline irrigation. Because nothing physical is removed, there is no specimen sent to pathology. That is one of the trade-offs with GreenLight: it is typically quicker and bleeds less than a TURP, but if the pre-operative suspicion of prostate cancer is high, an operation that yields a specimen (such as HoLEP) is usually preferred.1
Because the laser vaporises using a clean beam rather than an electrical current, the operation is performed with normal saline irrigation. This removes the risk of "TUR syndrome" (dilutional hyponatraemia from absorption of electrolyte-free irrigant), which was a historical concern with monopolar TURP.
GreenLight is performed entirely through the urethra. There is no external skin incision and no stitch. The scope is passed through the water-carrying channel of a resectoscope, which is introduced through the natural opening of the penis under anaesthetic.
Ask for a second opinion on your symptom score, flow studies and prostate size before committing to a treatment plan.