Having trouble seeing things clearly? Is it difficult to watch TV, scroll on your phone, look at your computer, read a book or complete close-up tasks such as cross-stitching? Does it make you dizzy when you try to do any of these things? Have you been told you have a lazy eye? Does it seem like your glasses aren’t working well? Has your eye doctor told you there’s nothing wrong with your current glasses prescription?
If you’ve answered yes to any of these questions, you may have a problem with your visual or vestibular system, such as a condition of convergence insufficiency or unilateral or bilateral vestibular hypofunction.
The visual sensory system consists of the receptors in our eyes that detect light and the colors of objects, and the ability to have fine discrimination and visual acuity through the pupil. In other words, it helps us see things clearly.
The oculomotor system is a motor component of the eye function. It helps bring targets onto the fovea, found in the pupil, and keeps the targets on the fovea. This system uses six muscles that we have in each eye to move the eye in all positions. The eye movements perform two functions. First, it holds the image on the retina, and second, it allows the gaze or focus to be shifted.
One of the two functions of the eye movements is that it holds the images in the retina. There are three ways that oculomotor control works with eye movements to hold images onto the retina.
- Visual Fixation: Where the retina holds the image of a stationary object on the fovea while your head is stationary, for example, reading a posted sign while standing to look at it.
- Vestibular Ocular Reflex: Where images of the seen world are held steady on the retina during brief head rotations, for example, following a flying insect or animal.
- Optokinetic Reflex: Where images of what we see in the world are held steady on the retina during sustained low frequency head rotation, such as driving and looking out the window at passing objects or reading.
The second function of the eye movement allows your gaze to be shifted. There are three types of gaze shifting.
- Smooth pursuit: Holds the image of a moving target on our eyes
- Saccades: Where there is rapid movements of the eyes, for example, when we’re watching a tennis match
- Vergence: Moving the eyes in opposite directions to provide depth perception such as when reading a book or looking at your computer or phone.
Vestibular hypofunction occurs when the vestibular nerve is not responding to movement at an accurate rate. The person experiencing this can feel “off,” dizzy, unbalanced and may have trouble focusing. Vestibular therapy and exercises can help with these conditions.
Occupational Therapist Dawn Wylie, O.T.R.L., is a vestibular and balance specialist and part of MidMichigan Health’s Rehabilitation Services team. She sees patients in Alma.