Diagnostic Procedures for MGD
Dr David Kading elaborates on the diagnostic criteria for MGD and provides insights into his interpretation of meibography and meibomian gland expression results.
Well I think these couple of cases here brought up some really interesting points and some conversations that we were able to have and some things that I think I would encourage you to be thinking about with regards to your MGD [meibomian gland dysfunction] treatment. First of all is when does a patient have meibomian gland dysfunction? And when do they have dry eye disease? What is it that makes those 2 things stand apart? And I think the key component here is that meibomian gland dysfunction is occurring when the meibomian glands are dysfunctional. So in order to understand that, let’s talk first about what function is.
When the tarsal plate gets pressed by the orbicularis muscle in that blinking sequence, it squeezes the acini and the central duct to start to release oil through the tip of the meibomian gland, but a muscle called Riolan’s muscle is there, which keeps the oil from just “geysering” out to the surface. So it requires us to have a certain amount of pressure with our blink in order to get oil to come out. And that pressure is 1.25 g per millimeter squared of pressure. That amount of pressure is synonymous to about the amount of pressure when you push on the tip of your finger to get it to indent. That’s it. That’s all the pressure it is as of a forceful blink. So when we push on the oil-secreting glands and push hard,…that isn’t diagnostic for MGD. What we really need to be doing is pressing with very light pressure, and if you see a liquid secretion coming out, then that gland is functional in its normal everyday life. What Korb and Blackie showed us is that if we evaluate with our finger 5, 5, 5 glands, which is about how big one of your fingers is, and 15 glands are flowing, that means the patient does not have dysfunction. In fact, they say 10 to 15 indicates no MGD. Six glands or fewer indicates yes, the patient has MGD. And then there [are] a couple numbers in there that are kind of like the ocular hypertension numbers; [in other words,] is it a yes or is it a no.
So when we’re thinking about dysfunction, if a patient does have dysfunctional meibomian glands, that means that downstream the oil secretions are going to be less robust. There’s going to be more desiccating stress and the patient’s ocular surface is going to start to suffer and the patient will then develop dry eye. They could have a cause of dry eye other than MGD, but we just know that it’s so present in so many people that it’s oftentimes the first thing that we recommend treating.
So what tests do we need to have? Well, number 1, we need to be looking at the number of meibomian glands yielding liquid secretions. [If there are] 6 or fewer, they must have treatment. Otherwise, when we do meibography, we expect over time for their glands to show atrophy. Meibography tells us what has happened. Meibomian gland expression tells us what is happening. So somebody could have fully flowing glands because they’ve done treatment, but in the past their glands were clogged and they have atrophy. Meibography doesn’t signal treatment. Meibomian gland expression signals treatment. So when we think about [whether] somebody should be treated or not, it’s very simple. If the number of meibomian glands yielding liquid secretion is 6 or fewer, that signals they have MGD. If they have…symptoms of other dry eye issues, corneal staining, a reduc[tion] or increase in tear flow, if they have…hyperosmolarity, if they have…inflammation in the surface of their eye and they have 7, 8 or 9 glands that are flowing, I’m going to do treatment on their meibomian glands. If they have none of those other symptoms, the ocular surface is pristine and beautiful, and they’ve got 8 or 9 glands, I’m going to monitor them. But if they’ve got 6 or fewer, regardless of their symptomatic [status] or any other things going on, we need to treat them just like we would treat a patient who has elevated pressures but no visual field loss and no OCT [optical coherence tomography]. We know what’s going to happen in those cases.
Transcript is AI-generated and edited for clarity and readability.
