一般目前时与一般过去时的混用

As the system makes the assessments, the facial regions that were mosthelpful in the determination are highlighted and made available for doctors toview.

这句话的are为何不需要were?

As the system makes its assessments, the facial regions that were most helpful in the determination are highlighted and made available for doctors to view. 

若是之前发生的事，当然要用were。