by Stacy Kramer OT Reg. (Ont) & Lizette Alexander OT Reg. (Ont)
Vision is a strong sense that provides input to the brain, at times; this sense can even impact other areas of development such as posture and mobility. For example, with your eyes closed, standing can be difficult. Most people think that if you have 20/20 vision, the fact that you can see clearly at a specific distance, means that vision is fine. However, there are other components of vision that are not routinely evaluated during a regular eye check-up. Good vision also requires the ability to see efficiently, therefore, the skills required in addition to 20/20 vision are called vision efficiency.
Children may not have developed these skills despite having “good” eyesight, which can result into learning difficulties. Children rarely report difficulties with vision because they believe that this is how everyone sees. Difficulty with vision can lead to difficulties the ability to perceive spatial relations, experience visual discomfort when reading, limited attention to visual detail. Many children might even appear to be easily distracted.
Visual efficiency skills consist of three general categories of skill: binocular function, ocular-motility, and oculo-motility.
Binocular function is the ability for both eyes to coordinate so that the visual field in both eyes merge into one distinct image. Two common aspects of binocular function are accommodation and convergence. Accommodation involves the eyes shifting focus from near point to far point or vice versa. is the ability to change the focus of the eye so that objects at different distances can be seen clearly. Accommodation problems are common – up to 6% of children aged 6-18 are affected. These problems are more common in individuals with development and learning disabilities. Convergence involves the ability of both eyes to team and focus on the same object.
Some difficulties that may occur when experiencing difficulty with binocular function:
- Difficulty going down stairs
- Poor eye-hand coordination
- Inability to read without losing place
- Headaches after work
- Difficulty copying from the board
- Poor 3D perception
- Difficulty sustaining eye contact
The oculo-motor system is the system that controls eye movements. Difficulties in this area can be classified into three different areas: fixation, saccades, and pursuits. Fixation simply refers to the ability to stay visually focused on a stationary object without any eye movement. A child with weak fixation skills may look away from a task more often than other children, often appearing ‘off task’. Saccades are small, rapid eye movements which move our eyes from one fixed point to the next. Coordinated saccadic movement is necessary for smooth reading. Finally, pursuits refer to the ability to accurately follow a moving object such as an airplane as it moves in the visual field. This is a very important skill for reading and writing.
Common difficulties that occur with difficulties with ocular motility include:
- Inability to hold head still while tracking
- Eye movement that is jerky when tracking
- Eyes stop tracking an object as it continues to move
- Overflow movements to the other parts of the face or body when attempting to track
As a parent you may ask how do I have my child’s vision efficiency assessed?
Your Occupational Therapist is able to screen for vision efficiency and advise as to whether your child would benefit from a thorough assessment with an OD. Following an assessment with an OD intervention specific to vision efficiency may be offered through the OD’s clinic with a vision therapist. In many circumstances, your Occupational Therapist may be able to collaborate with the OD in order to provide intervention in the above areas concurrent with treatment of other skills such as sensory regulation or printing. The role of occupational therapy involves the integration of visual skills with other sensory systems and functional skills.
Please note that not all optometrists are trained in vision therapy. If you have concerns regarding your child’s vision “efficiency” please speak with your occupational therapist. She will be able to screen your child and refer you to your locally trained optometrist.
Vision stress indicators:
- Avoiding tasks by doing as little as possible
- Experiencing pain, headaches, stomach aches
- Falling asleep while reading
- Sensitivity to light
- Attention and concentration difficulties