Okay, let's tackle this question about primary open-angle glaucoma in diabetics. The question is asking about the cause of decreased aqueous outflow. First, I need to recall the pathophysiology of primary open-angle glaucoma (POAG). POAG is typically due to increased intraocular pressure (IOP) from impaired drainage of aqueous humor, usually through the trabecular meshwork. In diabetics, there might be specific mechanisms at play.

I remember that diabetes can affect the trabecular meshwork. Maybe there's some sort of accumulation in the trabecular meshwork that blocks the outflow. Diabetic patients often have glycation end products (AGEs), which are formed when glucose binds to proteins non-enzymatically over time. These AGEs can accumulate in tissues, leading to structural changes. If the trabecular meshwork is infiltrated by AGEs, it might become less elastic or more rigid, thus reducing the outflow of aqueous humor.

Another possibility is that diabetes leads to microvascular changes, like in the retina, but I'm not sure if that's directly related to the trabecular meshwork. Alternatively, maybe there's some sort of endothelial dysfunction or increased matrix deposition in the trabecular meshwork. I should also consider other options like neovascular glaucoma, which can occur in diabetics due to retinal ischemia leading to new blood vessel growth in the iris, blocking the angle. But the question specifies primary open-angle, not neovascular, so that's probably not it.

Wait, neovascular glaucoma is a secondary glaucoma, not primary. So the question is about primary open-angle. The key here is that in diabetics, the trabecular meshwork is affected by AGEs, leading to outflow resistance. So the answer is likely the accumulation of AGEs in the trabecular meshwork causing decreased outflow.

Now, looking at the options. The correct answer would be the one mentioning AGEs or extracellular matrix accumulation. The other options might be about other causes like cataract, uveitis, or other factors. But since the user didn't provide the options, I have to infer based on common distractors. For example, if an option says "Increased production of aqueous humor," that's incorrect because POAG is about outflow, not production. Another wrong option might be "Angle closure due to lens swelling," but that's not open-angle. Another could be "Inflammation from uveitis," but that's a different type of glaucoma.

The clinical pearl here is that diabetics are at higher risk for POAG due to AGEs in the trabecular meshwork. So the key point is the role of AGEs in trabecular meshwork dysfunction in diabetic patients with POAG.

**Core Concept**
Primary open-angle glaucoma (POAG) involves impaired aqueous humor outflow through the trabecular meshwork, leading to elevated intraocular pressure (IOP). In diabetic patients, non-enzymatic glycation of proteins forms advanced glycation end products (AGEs), which accumulate in the trabecular meshwork, reducing its elasticity and increasing outflow resistance.

**Why the Correct Answer is Right**
In diabetic POAG, AGEs deposit in the trabecular meshwork,

✓ Correct Answer: C. Block in trabecular meshwork