A behavioural optometrist will assess the health of the eye and the ability of the eyes to see to the bottom line on the letter chart but they will also assess the ability of the focus or accommodation, convergence and directed eye movements. These mechanical movements must be able to work together easily and efficiently throughout the school or working day and are referred to as the Visual Skills. If too much effort is going into these visual skills then it will detract from a person’s performance and can lead to a lack of attention, poor schoolwork, fatigue, frustration, and avoidance behaviours.