The Eye separation ratio is the ratio of your eyes width relative to your bizygomatic with. For men the ideal is between .46-.48 % setness. Now changing this non surgically obviously isn't possible but here is how to change how your eyes are perceived.

Narrow ESR

In this picture, barrett has a narrow ESR of about .44. This is mostly due to his overly wide zygos in conjunction with high BF%. The way you could fix this is hiding the widest part of your zygos.

Excuse this awfully photoshopped picture but as you can see by hiding the bizygomatic breadth it improved his perceived ESR. This change is minimal but its a giga easy Looksmax.

Narrow ESR

If you have a slightly narrow IPD/ESR, you can hide points that are needed to get an accurate measurement. By covering the zygomatic width its impossible to perceive the ESR, as well as the strands of hair covering parts of the face. This is the best way to go if your IPD is slightly narrow.