filtering load_resource results in CanCan

The CanCan documents state that the :index method, of necessity, ignores any hash of conditions when checking a class and returns true, as in:

  can :read, MedicalRecord, :patient_id => user.id
  can? :read, MedicalRecord # returns true

So if I want MedicalRecordsController#index to ONLY return medical records for the current user, what's the right technique?  What I've done -- and it appears to work -- is to exploit the fact that load_resource sets @medical_records to a relation, and do further filtering on that:

    class MedicalRecordsController
      load_and_authorize_resource
      def index
        @medical_records = @medical_records.where(:patient_id => current_user.id)
      end
      ...
    end

Is this the approved technique?

- ff