This useful occluder effectively prevents the patient from seeing through whilst at the same time allowing the observer to study eye movements behind it. In addition, the following scales feature on the handle: 

·          Rule in mm (0 to 110) 

·          Rule in inches (0 to 4.5) 

·          Corneal diameter (5 to 14 mm) 

·          Pupil diameter (3 to 10 mm).