I am going to link “Vernier acuity” to your ability to sink putts.
In short, the brain does its best to interpret the alignment information it’s getting from the eyes, but it’s not easy. Many putts don’t even start on the intended line.
To get better, and sink more putts, we need to achieve a level of ’hyperacuity’. We need to help the eyes and brain work better together. Then you can notice even smaller changes in angles of target line vs the putter head.
Make sure of your eyeline
There are other ways of giving your eyes and brain a better chance of working together. The perfect putting setup helps too. In 30 minutes you’ll notice a difference in the number of putts you’re sinking.