How so you convert power of glasses to contacts?

To convert glasses prescription power to contact lens power, you need to consider the vertex distance, which is the distance from the back of the glasses lens to the eye. For prescriptions with a power of -4.00 D or greater, the contact lens power is typically less than the glasses prescription due to this distance. Generally, you can use a conversion formula or consult with an eye care professional for precise adjustments. Additionally, factors like the shape of the eye and the type of contact lens will also influence the final prescription.