Hi. I'm online and happy to answer your question today.
I am a retina specialist and I have to agree with you: The comment that your history of thyroid ablation with radioactive iodine as a cause of this vague "you have fewer capillaries" makes absolutely no sense to me either.
If he wants to evaluate the statues of blood flow and capillary function in your retina then the test to do would be a fluorescein angiogram, not a visual field test.
That being said, if you do not have diabetes yourself, your family history of diabetes would not have any impact on your current issues.
Concerning your color vision changes I am not exactly clear on what is going on. You state that the colors are more bright but then also say they are washed out......
Can you tell me if the doctor found any evidence of refractive change, relative afferent pupillary defect (RAPD), corneal abnormalities, lens changes/cataract, posterior vitreous detachment or macular abnormalities? If you could upload his notes, that would be great :)
I see that you are offline. I will switch to Q&A format. This format works a lot like 'text messaging' but an email is sent to each of us anytime something is posted to this thread. We can continue to work on your question there..... :)