Joint Archive of Continuing Education

44580-NO-109481 – Outline

Exploring the Link Between Head Injury, Photophobia and Pupillary Function – Outline

Andrew Hartwick OD, PhD
Ohio State University College of Optometry

  1. Background on TBI
    1. Definition of TBI
    2. Leading causes of TBI
    3. In 2010, it was linked to 50,000 deaths and 2.2 million ED visits
    4. Increased media attention due to prevalence in war-fighters and athletes
  2. Photophobia
    1. Definition of photophobia
    2. Symptom associated with TBI
    3. Treatment options – mostly anecdotal right now (sunglasses, tinted glasses)
  3. Intrinsically photosensitive retinal ganglion cells (ipRGCs)
    1. A photoreceptor in the inner retina – express melanopsin
    2. Play a role in telling brain about ambient light levels
    3. Key role in circadian rhythm entrainment, pupil constriction, sleep/wakefulness
    4. Most sensitive to blue light
    5. Temporal properties
  4. Evidence linking ipRGCs and photophobia?
    1. Projection of ipRGCs to pain centers in thalamus
    2. Effect of light on migraines in visually blind patients
    3. Pharmacological inhibition of ipRGCs in mice prevents light aversion
  5. Looking for direct evidence for link between ipRGCs and TBI-associated photophboia 
    1. Genesis of Head Injury-Associated Photosensitivity and Pupillary Function (HIPP) Study
    2. Hypothesis of study: ipRGCs hypersensitivity associated with photophobia
    3. Pupil responses in humans to red and blue light
  6. Light aversion responses in normal subjects
    1. Grading optometry students reactions to red and blue light
    2. Effect of light color and gender on light aversion gradings
    3. Correlation of pupil responses to observer-graded aversion responses to light
    4. Discussion or results with respect to initial hypothesis
  7. Demographics of TBI subjects tested
    1. 28 subjects enrolled, 24 completed both visits
    2. Age and gender-matched with group of 12 controls
    3. Outline of tests performed
    4. Background on commercial pupillometer used
    5. Responses to survey on photophobia symptoms
  8. HIPP Study findings
    1. Pupil responses to monochrome light stimuli
    2. Pupil responses to alternating light stimuli 
    3. Light exposure findings
    4. Discussion of experience with orange-tinted lenses
  9. Summary
    1. Link between ipRGC dysfunction and photophobia
    2. Implications for optometrists
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