Upshot

So...I did it. In spite of the last-minute second opinion curveball.

Here's why:

• Yes, my limbal stem cells are at risk, but...
• Apparently limbal stem cell damage is not super common, and Dr. Shields likes to deal with it if it arises, rather than act proactively with something like a pre-emptive limbal stem cell transplant
• The dosage is a bit lower than the other doctor had predicted

The main things I wanted to make sure of were that:

1. My age was being taken into account
2. A plaque covering my entire cornea was deemed necessary

I am reassured on both counts. Here's why:

Even with a full plaque, patients tend to tolerate the radiation well, and irreparable cornea damage is not too common

The reason we went with a full plaque is due to the type of melanoma we seem to be dealing with. My iris melanoma is diffuse (as opposed to nodular), meaning that cells can easily shed to other parts of the iris. This means that it's not necessarily easy to tell whether a slightly darker area of my eye is just darker, or is the result of cells that have shed from the main affected area. It's especially tricky to deal with these shed cells in what's called the angle, or the part of the eye where the cornea meets the iris (see images below if you're having trouble picturing this). Having a 15 mm plaque means we're irradiating that edge (since a typical iris / cornea is 12 mm), giving us a better chance of catching it all.

So yeah, I went through with it! And I'm uncomfortable :(

The angle is where the cornea meets the iris.

Maybe easier to see in this less-cluttered diagram.