If you have already used a voucher towards the cost of your glasses or lenses you cannot get a refund (unless it was only a complex lens voucher).
Os ydych chi eisoes wedi defnyddio taleb tuag at gost eich sbectol neu lensys, ni allwch chi gael ad-daliad (oni bai mai taleb ar gyfer lensys cymhleth yn unig oedd honno).