The first lecture slot the day after the conference dinner can be tough, but Evan ripped into it with an outstanding lecture titled ‘Anxiety, distress and the visual process’. The statistic that 16.6-28% of the population suffer from anxiety was a wake-up call. Not surprisingly, females outnumber males in this statistic 23.4% to 14.3%.
Evan then tackled the neuro-endocrinology of anxiety and the stress response, reminding us of the neuroanatomy of anxiety in which the parasympathetic nervous system helps us self-regulate, communicate through voice or gesture and show and read emotion by accessing the social engagement system. The stress response is a neural and hormonal pattern of behaviour that for humans and other mammals maximises the availability of energy in the skeletal muscles and brain and activates the immune system to battle stations. Distress is when, under adverse conditions, the active coping response is unavailable and we tend to engage a vigilance response involving the sympathetic nervous system, accompanied by inhibition of movement and shunting blood away from the periphery. In other words, the behaviour of anxiety is both a neurological and a chemical reaction resulting in a stress response reaction. Personality determines the type, strength, and length of reaction. Aggressive personalities associate with norepinephrine release and may show unusual aggression, whereas anxious personalities associate with epinephrine release which may result in a flight behavioural disposition with dysfunctional adaptations, such as selective mutism withdrawal or freeze mode.
Many visual abilities are important to the developmental learning of the social engagement system including the magnocellular processing of motion and the dorsal stream control of fixation, binocularity and oculomotor control. Evan quoted Arnold Gesell, who in 1950 wrote “the visual system is more than a dioptric lens and a retinal film. It embraces enormous areas of the cerebrum; it is deeply involved in the autonomic nervous system; it is identified reflexively and directively with the skeletal musculature from head and hand to foot.” Likely clinical findings for anxious patients are accommodation dysfunction, near esophoria, high AC/A ratio, restricted divergent ranges with early blur points, convergence insufficiency and early fatigue.
Unilateral spatial neglect
Unilateral spatial neglect (USN) is not a subject frequently talked about. This is a common consequence of stroke and other traumatic brain injury incidents. Cathy Stern, who has experience in several rehabilitation settings in the USA, gave a very comprehensive overview on how to distinguish USN from hemianopia, the problem of agnosognosia or lack of awareness of the defect, and rehabilitation strategies. As with any brain injury, there is no one size fits all method to alleviate the problem and no quick fix, but Cathy outlined the technique of multiple sessions of Prism Adaptation Therapy using a 20-40 dioptre prism and ballistically-fast reaching hand movements with the patient’s hand shielded from their view. The effect can last from hours to, eventually, months after the prism is removed. Fascinating stuff they didn’t teach us at optometry school!