This question is collecting the relevant percentage required by s 39(6) of the 1971 Act. Section 39(6) provides for compensation for partial loss of sight in one eye proportionate to the percentage of reduction in sight caused by the injury. Any loss of sight in that eye prior to the injury is excluded from the calculation when determining the percentage loss.
Section 39(6) states:
39(6)The compensation payable under this Act in respect of any injury resulting in partial loss of sight of an eye by an employee is such percentage of the amount of compensation that would be payable under this section in respect of an injury resulting in total loss of sight of that eye as is the percentage by which the injury to the employee resulted in the sight of that eye immediately before the injury being reduced.