You can roughly correlate to blood sugar. Since you take those heart meds... beta blockers typically block sweating etc so that sign is not there for you to use.

But if you get the vision things, when you get hungry, or just before a meal is due...or first thing in the morning before breakfast, etc, it might be low blood sugar. If it gets better with food, then comes back, that would implicate blood sugar IMO.

The tiny muscles in the eye that change the lens shape, are very sensitive to metabolic changes. Low oxygen, low electrolytes, low sugar, low pressure (results in slow blood flow).

I am thinking the beta blocker. This drug tends to make cold extremities, and constricts the bronchioles of the lungs. The beta blocker might be causing vision issues. If you look up
"beta blockers vision" on Google you will see vision changes listed as a side effect. I was on atenolol for about 13 yrs and all of sudden it started to make me wheeze. Even though I did well otherwise, my doctor took me off and will not let me have it again...I ask each time! So side effects can come much later in therapy and not be paid attention to.