Specsavers is typically a hierarchical structure, where the business owners are the top of the hierarchy. These people then delegate roles and responsibilities to people further down the structure.
The directors are the next layer down, with Retail Directors and Optometrist, which are in control of mangers and assistants within the that area (Optometrist). The Store managers and individual Optometrists are responsible for the Directors above, with store managers have a slightly larger span of control when working in bigger stores with support teams and assistants for when there is customer contact. There could be 50-60 staff members that report to Store Managers, this would be more common in large stores