When it comes to minimally or micro-invasive glaucoma surgery (MIGS) it is really all about the angle. In order to effectively perform the MIGS surgery, it is essential to establish the fundamentals of surgical gonioscopy. Below, I will share my top five surgical gonioscopy pearls.
Follow along with the video: 5 Key Steps to Mastering Surgical Gonioscopy in MIGS
1. Tilt the head
This might appear to be a simple step, but it is very important. In order to obtain a favorable view, one must tilt the head appropriately. Typically for angle surgery, we sit temporally, which makes it good to begin by tilting the patient's head 30 to 45 degrees away from where you will be sitting. (See Fig 1)
Fig 1. Sitting at a microscope tilted towards the surgeon, and the patient's head turned away from the surgeon.
It is important to position the patient’s head this way before the surgical start for two reasons:
- To ensure that the head can be tilted to that degree
- To communicate with the patient that you are placing their head in the position in which you want them to stay for the duration of the surgery
Sometimes patients may shift and forget the original head placement by the time you are ready to begin that part of the surgery. Therefore, it is best to take the time to discuss this with the patient before you begin the surgery. Communicate to them that once you have positioned their head, this is where you need it to stay in order for you to do this surgery well.
2. Tilt the microscope
Tilting the microscope is another key step. As you tilt the patient’s head away to procure a good view of the angle, you also have to tilt the microscope toward you in order to achieve finer visualization. Again, this should be about a 30 to 45 degree angle. (See Fig 1) What I also have found to be very helpful is to mark the microscope with a black marker once I have established a nice angle for my routine MIGS surgery. .
This allows me to easily find the angle, as I am often going from a position where the microscope is straight for the cataract portion of surgery to tilted for the MIGS part of the surgery. It also allows for quick setup of the surgical microscope when working with different operating room nurses. (See Fig 2)
Another important strategy is to always ensure your microscope focus and starting XY position are centered prior to starting the surgery. MIGS angle surgery is done under high magnification, so completing this step will help to ensure you have enough range to achieve high magnification. Oversight of this step may lead to the inability to increase the magnification for greater visualization of important angle structures during surgery, as you have exhausted the range of ability for any more magnification.