Where BioEye could help
improve health outcomes

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Brain health

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Head trauma

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Cognitive decline

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Drug and alcohol
impairment

Why the Eye?

The problem

  1. Conventional neurological examination is limited and subjective,
    evaluating ~10% of brain
  2. Neuropsychological examination is costly/not readily accessible

The solution

  • Assessment of the visual-ocular motor system
  • Evaluates >50% of the brain (direct connections)
  • Affordable, accessible
  • Damage at any point = measurable abnormalities in eye movement

Current in-app tests

Eye movement test app

Smooth Pursuit (SMP)

Light reflex test app

Pupillary Light Reflex (PLR)

Application within a broader
brain health context

Application within a broader brain health context

Given the breadth of the circuitry involved in the control of vision and eye movements it is perhaps not surprising that SMP and PLR changes are seen in many neurological conditions.

Smooth Pursuit (SMP)

Although non-specific, SMP eye movement abnormalities are evident in a large number of patient populations/neuropathologies consistent with the extent of the system supporting their integrity. Using different types of stimuli (circular horizontal, vertical, sinusoidal, step ramp), velocities and stimuli sizes/shapes, SMP changes include:

  • Multiple sclerosis – reduced gain, increased latencies, high amplitude saccades [1]
  • Parkinson’s disease – reduced gain, inadequate catch up saccades [2]
  • Multiple System Atrophy – reduced gain, catch up and/or anticipatory saccades [3]
  • Progressive Supranuclear Palsy – reduced range vertically, many catch up saccades vertically [3]
  • Alzheimer’s disease – reduced peak velocities, increased number and amplitude of anticipatory saccades [4]
  • Cerebellar ataxias (not SCA7 or 2) – saccadic pursuit [5]
  • Amyotrophic Lateral Sclerosis – square wave jerk, saccadic pursuit [6]
Outline of woman's brain
Outline of woman's brain

Smooth Pursuit (SMP)

SMP eye movements implicate a complex neural system with long ranging brain connections spanning the visual pathways from retina to cortex, brainstem, cerebellum, basal ganglia and multiple visual, temporal, parietal and frontal cortical regions. Given the complexity of the system, it is perhaps unsurprising that a range of SMP metrics distinguish concussed from non-concussed individuals. Although studies have used several types of stimuli (circular horizontal, vertical, sinusoidal, step ramp), many different velocities and stimuli sizes/shapes, results variously demonstrate that following a concussion, SMP eye movements may:

  • be inaccurate (e.g. lag behind a moving target with reduced velocity) [50-56]
  • be dysconjugate (eyes movements are asymmetrical) [52, 57, 58]
  • have increased initiation latencies [53]
  • be interrupted by saccades (or feature many catch up saccades) [54, 55]
  • show greater intra-individual variability in accuracy [56]
Man having his eyes checked

Pupillary Light Reflex (PLR)

PLR changes may be found in a myriad of contexts including:

  • Optic nerve injury
  • Oculomotor nerve damage
  • Brain stem lesions, such as tumours
  • Concussion
  • Medications that dilate the pupil (mydriasis) → sympathomimetics (e.g. phenylephrine, adrenaline) and antimuscarinics (e.g. cyclopentolate, tropicamide, atropine), tricyclic antidepressants, amphetamines and ecstasy [7]
  • Medications that constrict the pupil (miosis) → muscarinic agonists (e.g. pilocarpine) and opiates (e.g. morphine) [7]
  • PLR changes have also been recently taken into consideration as potential markers of Alzheimer’s disease → decreased maximum velocity of constriction and maximum constriction acceleration [8]

Published evidence

*A/Prof Joanne Fielding (Chief Scientific Officer, BioEye) & Prof Owen White (Chief Medical Officer, BioEye)

Sports industry spotlight

Why better concussion diagnosis and management is critical

Around 50% of concussions go unreported or undiagnosed [44]

Concussions can lead to acute brain swelling with mortality rate close to 50% and morbidity rate almost 100% [45]

The utility of eye movements in
measuring concussion

Close-up of eyeball

Pupillary Light Reflex (PLR)

Pupil abnormalities are common immediately following a concussion and while they often resolve over a short period of time, can persist indefinitely. Notably, pupillary size, shape, and reactivity to light are regulated by the autonomic nervous system – central autonomic control nuclei and pathways are mainly integrated within the brainstem, shown in histopathological studies to be an important site of axonal injury following concussion. Although studies have tested subjects with different stimulus conditions, at various ages, at various time points following concussion, results variously demonstrate that following a concussion, pupillary changes to:

  • Steady-state pupil size [46-48]
  • Pupil size following constriction in response to a light stimulus [46-48]
  • Latencies (time to maximum constriction in response to a light stimulus) [48]
  • Peak and average constriction velocities [46-49]
  • Peak and average dilation velocities [46, 48, 49]
  • T75 (time to 75% pupillary redilation) [49]
  • Constriction amplitudes [46]

Smooth Pursuit (SMP)

SMP eye movements implicate a complex neural system with long ranging brain connections spanning the visual pathways from retina to cortex, brainstem, cerebellum, basal ganglia and multiple visual, temporal, parietal and frontal cortical regions. Given the complexity of the system, it is perhaps unsurprising that a range of SMP metrics distinguish concussed from non-concussed individuals. Although studies have used several types of stimuli (circular horizontal, vertical, sinusoidal, step ramp), many different velocities and stimuli sizes/shapes, results variously demonstrate that following a concussion, SMP eye movements may:

  • be inaccurate (e.g. lag behind a moving target with reduced velocity) [50-56]
  • be dysconjugate (eyes movements are asymmetrical) [52, 57, 58]
  • have increased initiation latencies [53]
  • be interrupted by saccades (or feature many catch up saccades) [54, 55]
  • show greater intra-individual variability in accuracy [56]
Woman's eyeball

Smooth Pursuit Eye movements (SMP)

Although non-specific, SMP eye movement abnormalities are evident in a large number of patient populations/neuropathologies consistent with the extent of the system supporting their integrity. Using different types of stimuli (circular horizontal, vertical, sinusoidal, step ramp), velocities and stimuli sizes/shapes, SMP changes include:

  • Multiple sclerosis – reduced gain, increased latencies, high amplitude saccades [1]
  • Parkinson’s disease – reduced gain, inadequate catch up saccades [2]
  • Multiple System Atrophy – reduced gain, catch up and/or anticipatory saccades [3]
  • Progressive Supranuclear Palsy – reduced range vertically, many catch up saccades vertically [3]
  • Alzheimer’s disease – reduced peak velocities, increased number and amplitude of anticipatory saccades [4]
  • Cerebellar ataxias (not SCA7 or 2) – saccadic pursuit [5]
  • Amyotrophic Lateral Sclerosis – square wave jerk, saccadic pursuit [6]

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References

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