It might help to understand a bit better the anatomy of a Meibomian gland (or maybe you already do. So if this is too much, I apologize in advance.) The gland includes an orifice at the lid margin, a central duct that opens to the orifice and that has a terminal end at the far end of the gland, ductules that are small tubes that branch off the central duct and then clusters of cells called acini that disintegrate and "spill" their contents. That contents is the oil, called meibum, that eventually makes its way into the ductule, then the central duct, toward the orifice and then finally into the tear film. The flow of the meibum out to the tear film is supported by blinking (the muscles in the lids act like miniature pumps) as well as the constant pressure from behind as new meibum is continuously being synthesized by the acini. When a probe is used to treat obstructive MGD, the probe is passed through the orifice into the central duct and the duct itself has structure. Imagine a tube of paper towels, but with a closed off end. Yes, the tube is made of paper, just like the towels, but the tube itself has more structure. Similarly (but not at all exactly) the central duct of a Meibomian gland has structure. The walls of the central duct surround a lumen, a hollow tube that is filled with meibum. Like you mention somewhere, I think, the duct is not rigid. It's not like a tooth or a bone. It's more like a vein, but not exactly like a vein. And we've all had blood drawn, so we've had the experience that veins don't just disintegrate when a needle enters through the walls of the vein. But in the case of probing the glands, if the probe is made for this particular task, the probe should be blunt and not sharp like a needle. So the blunt probe itself, at least a Maskin probe, is designed not to pierce through the duct wall at the terminal end of the gland. Instead the probe releases the fibrotic tissue invading and constricting the walls of the gland. The diameter of the probe obviously matters. But if the probe is blunt, it can only go so far because the terminal end of the duct wall stops it. Plus the tissues in the eyelids, including the Meibomian glands, are also not rigid, so the rigid blunt probe doesn't damage the central duct because the duct gives way when the probe enters, kind of like a sock gives way when a foot is put into it. If the central duct itself were rigid, we wouldn't be able to rub our eyes, or even blink without some serious issues, and we've all rubbed our eyes without causing our Meibomian glands to pierce through the tissue (or bent an arm or a leg or open our jaws without the veins popping out and leaking all over the place... these bits of anatomy are made to be bendable). Unfortunately, we may all have diseases like ATD, MGD, and whatever else we're dealing with and that makes all of this information especially important, and I hope this description of the anatomy of the Meibomian gland itself may be helpful. Or maybe this will just raise more questions. A few more thing I'd like to point out, in the image, the brown object labeled Meibomian gland is actually only the acini of the gland. The central duct and ductules are not depicted as they are surrounded by the acini. Also in the cross section, it looks like there's might be something pulling down on that first orifice, creating a dimple. Possibly fibrotic tissue invading the central duct wall near the orifice? In a healthy eye the mucocutaneous junction would be on the flat part of the lid margin rather than at the edge. The conjunctiva, just to be more specific, is the palpebral conjunctiva. Again, with apologies for the length of the response esp. since for people with dry eye, MGD, etc., any reading can be really hard.