Peter’s diagnosis

Saccades eye movements

Saccades eye movements are fast conjugate eye movements. They are rapid refixation movements and ensure that individuals maintain clear vision when undertaking significant changes of eye position. They can be initiated both voluntarily and involuntarily and are a response to visual, auditory or tactile stimuli. They are the fast component of optokinetic nystagmus and are also demonstrated during the sleep ‘rapid eye movement’. Defective saccades can result in difficulty with everyday activities such as reading. This may be demonstrated by people losing their place regularly when reading and using a finger to locate the word being read.

Smooth pursuit eye movements

Smooth pursuit eye movements enable individuals to view slowly moving objects. They ensure that a clear image is viewed by the eyes and they are the slow component of optokinetic eye movement. Defective smooth pursuits can result in difficulty with everyday activities such as watching or participating in sporting activities i.e. following an object.

Vergence eye movements

Vergence eye movements enable individuals to maintain binocular single vision. Effective vergences are required to appreciate single vision and have good depth perception (stereopsis/stereoacuity). Defective vergence eye movements can result in asthenopic symptoms (e.g. eyestrain, frontal headache) or double vision (diplopia). This can have a significantly detrimental effect upon an individual’s everyday function.

The vestibular and optokinetic eye movement

The vestibular and optokinetic eye movement systems are interlinked. The vestibular system is co-ordinated from within both the central ear and the brainstem. The optokinetic system is a network of brain areas known as ‘eye fields’ located in the frontal, parietal and temporal lobes and the brain stem. The vestibular and optokinetic systems work together to ensure that individuals maintain a stable image during head movement. They react by ensuring that the eyes produce movements that are equal and opposite to those of the head, ensuring that a clear image continues to be appreciated whist maintaining physical balance. Defect vestibular or optokinetic systems can result in significant balance disturbance and perceived visual instability.