What is the pen top test?
Answer:
The optometrist will ask you to hold your head still while staring at an object such as a pen top. The optometrist will then move the object in different directions and observes whether both eyes are able to follow the target freely.
From his knowledge of the position and range or actions of each of the muscles the optometrist is able to determine whether all are working correctly and if not which muscle or muscles are affected.