 Immersion biometry for axial length measurements is the standard of care all over the world. I'm happy to see it back as it went away for a while with contact A-scan being used, but we all know that immersion is the most accurate because nothing touches the cornea except fluid, and we really want a pure, precise, and accurate axial length measurements. So we use a scleral shell, and that scleral shell rests on the sclera, and it's filled with fluid. They come in a variety of sizes. There are also several different designs where the probe is actually mounted and fixed to the shell. That's called a fixed standoff immersion shell. In this case, I'm just using a traditional A-scan probe and the traditional immersion shells. They come in a variety of sizes, shown here are three, they are larger and smaller. I'm going to choose the smallest one that works comfortably for the patient, which in this case is an 18, and I normally have the patient just in primary gaze, which is where she is, and I spread the lids, making sure I can see a little sclera above and below, and I just place that cup into the lids, under the lids, making sure that it's fitting perfectly. Keep this up, tell the patient to keep the other eye open. I add a little bit of genteel or gel into the bottom just to add an extra seal. If you have a patient with a hearing aid, for sure, start off right away with a tissue at the lateral canthus. Do not let saline get to the hearing aid. I now finish filling this with saline, and then I place the tip of my probe into the fluid, holding it close, and there I am getting an axiolink scan, perfect. What I'm seeing on the screen is anterior-posterior cornea of equal height, and anterior-posterior lens retina and sclera. I'd like a sharper echo on the retina, there we go. I'm working with a slightly lower gain because I really would like to obtain tall echoes because I was perpendicular to the tissue, not just because I turned up the gain. To remove the shell, I just hold the tissue at the lateral canthus, pull the lower lid, the patient naturally closes their eyes, squeezes the fluid out, and I catch it in a tissue.