LIGHT SENSITIVITY (PHOTOPHOBIA)

WHO ARE YOU GONNA BELIEVE, ME OR YOUR LYING EYES?

CHICO MARX

EXPLAINING LIGHT SENSITIVITY

AND WHAT TO DO ABOUT IT

1. NON-VISUAL FUNCTIONS
  • When people have an aversion to light because of post-concussion syndrome (PCS), they tend to avoid light.
  • While avoiding blue light in the evening can be good for you; avoiding light during the day can affect your health
  • Avoiding daylight, even if you were to keep your eyes closed, can have health implications
  • When light enters your eyes, there are many signals that spread out to the brain
  • Some of those signals are important in mood and immune system regulation, endocrine functioning, and for healthy sleep (Roberts et al., 2000)
  • Sleep is important to clear our system of molecular waste and toxins
  2. VISUAL FUNCTIONS Photophobia is a common symptom following ABI that frequently persists after other symptoms have resolved (Hellerstein et al., 1995). PCS patients have been found to have objective increases in photosensitivity, both within 3  (Waddell et al., 1984) weeks of minor head injury and 6 months following mild head injury (Bohnen et al., 1992) There are many visual issues that can occur in PCS patients with photophobia.
  • Light intolerance (both indoor light and outdoor light; sunlight tends to be the most aggravating) and impaired performance in dim illumination (Zihl et al., 1990).
  • Often seen with headache, nausea and dizziness
  • Perception of waviness and shimmering of the surrounding environment that is greater in bright light (Jackowski et al., 1996)
  • Reading difficulty, even if there is normal binocular vision; this is closely related to visual stress (Wilkins, 2003)
  • Visual stress is a condition that describes a problem with the brain’s ability to process visual information such as patterns, light and movement. In the face of these things, the brain becomes hyperexcitable leading to the symptoms described here, symptoms like eyestrain and headaches provoked by reading, blurring of print, letters changing size or doubling, patterns or illusions of colour appearing on the page, nausea, dizziness, discomfort (Wilkins, 2003)
  • Hypersensitivity to strong patterns & visually busy environments
  • Decreased field of view
  • “Pattern glare” where lines of text can look like geometric patterns that provoke perceptual distortions leading to headaches and eyestrain in susceptible patients (Wilkins, 2003)
  • Increased sensitivity to fluorescent light (many of us don’t notice, but fluorescent lights flicker; PCS patients don’t tolerate that well)
  • Loss of contrast sensitivity

Photosensitivity has been known to adversely affect people in many aspects of their lives:

  1. Reading
  2. Driving
  3. Mobility
  4. Difficulty with performing academically, occupationally, recreationally and activities of daily living
  5. Patients with photosensitivity may also report reading discomfort, loss of visual function in the dark (this is often not recognized by patients in the face of everything else), peripheral visual field reduction, visual distortion, and asthenopia (eye discomfort)
Light sensitivity post-TBI can happen for many reasons; reasons unrelated to the eye, and reasons related to the eye.

 

1. NON-OCULAR REASONS

  • Magnocellular Pathway Disruption
    • You have heard of rods and cones before…Well, these structures in the retina send information to pathways known as the magnocellular and parvocellular pathways. The functioning of these pathways can get disrupted leading to hypersensitivity to light amongst some of the other symptoms mentioned above (see Clinical Presentation)

 

  • Cortical Hyperexcitability
    • More of the brain fires in response to light via many biochemical mechanisms (a.k.a. Cortical hyperexcitability)

 

  • Binocular Vision (BV) Disorders
    • BV and accommodative disorders are common vision disturbances following TBI (Kapoor et al., 2002)
    • Symptoms of BV issues (these can be measured on a physical exam) and visual stress (these can exist without physical exam abnormalities) are hard to differentiate and need optometric assessment
    • There is a lot of evidence for Vision Therapy (VT) for BV and accommodative dysfunction (Gallaway et al., 2016)
    • This sentence is more technical, but for those interested, some patients have signs and symptoms like high exophoria or exotropia, convergence insufficiency, oculomotor dysfunction, accommodative dysfunction, low blink rate, spatial disorientation, diplopia (double vision), headache and photophobia. These patients are often given the diagnosis Post Trauma Vision Syndrome (PTVS), which is synonymous with Post Concussion Vision Syndrome (PCVS)
    • Post trauma vision syndrome has been described as the most common visual sequela following TBI (O’Dell et al., 1998)

 

  • Migraine
    • Light sensitivity does not just occur with the headache; it can occur between headaches too in those with chronic headache (Datta et al., 2013).
      • Those migraineurs with aura also showed significantly more cortical hyperexcitability.

 

2. OCULAR REASONS

  • Mydriasis
    • This means dilation, or widening, of the pupil
    • It can be due to trauma to iris sphincter or cranial nerve III damage
    • It can be a reaction to meds such as amphetamines or antihistamines or many widely prescribed antidepressants
    • It is often treated with tinted lenses/contact lenses; or in extreme cases, artificial pupil contact lenses may be beneficial for reducing excess light

 

  • Dry eye syndrome/Lagophthalmos
    1.  

 

 

3. OTHER MEDICAL CONDITIONS THAT CAN CAUSE LIGHT SENSITIVITY

  • Migraine
    • There are some differences in photophobia with migraine; and some differences in potential treatments too

 

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Many additional things are checked in those with photophobia including refraction, eye health, oculomotor function, accommodation, vergence, colour assessment, contrast sensitivity, visual field, and more. This is important as it’s the only way to see if binocular vision issues are contributing to your photophobia.

1. GLASSES, OVERLAYS, AND CONTACT LENSES

Many people will need glasses as part of their rehabilitation
  • the criteria under which glasses may be dispensed often changes for those who have post-concussion syndrome (See article “Glasses & Rehabilitation“).
  Some patients will find that they are given several pairs of glasses
  • some for near work (e.g., reading), some for intermediate work (e.g., computer work) and some for distance; and then some glasses for indoors, and some for outdoors.
  Most post-concussion syndrome patients with photophobia prefer coloured filters.
  • Specific filters can be incorporated in your spectacles as coloured lenses; some people prefer contact lenses, especially if their pupils are more dilated (i.e., mydriasis).
 
  • There are many ways to find the right colour for you; speak to an optometrist with experience in this area.
    • Generally, in a healthy neurologically normal visual system, gray filters are preferred by patients
    • An Intuitive Colorimeter can be used to help identify the most congenial colours for patients
      • This colour can then be incorporated into a lens for you to “try on” and see how it feels, if you can read faster with it, if there is better contrast sensitivity, etc.
    • There are “ready-made” coloured lenses you can “trial-and-error”, the most common ones being:
      • Corning Photochromic Filters: CPF 450-S (yellow) was the favourite by most patients
      • Other manufacturers have similar products at slightly different wavelengths (e.g., Eschenback Optick released Wellnes Protect eyewear) that cuts out most blue light
        • not all blue light can be cut out…lenses that do that cost over $5000 for a lens the size of a coin!
      • FL-41 lenses can be helpful, especially in those with migraine or spasms of their eyes
        • It is more effective when tinted to a darkness of 50%, and are more cosmetically acceptable than very darkly tinted glasses
 
  • If patients only needed filters when reading, you can put a transparency of a specific colour over your reading material; this is called an overlay.
    • This will not change the colour of the ambient lighting
    • some patients say that the text becomes too dark to comfortably read with the overlay ontop
    • In addition to overlays, the following measures can help with pattern glare (see “Clinical Presentation” section of this article):
      • If font size is 12, spacing size should be about 18
      • Things that can help with this are: increasing line spacing, use a cover mask to cover all lines but the line of interest. Change in classroom placement or modifications to positioning of reading material, etc.
  Progressive lenses are generally not advised because they distort your peripheral vision.
  • If you’re going to get bifocal lenses, flat top or round segment bifocal lenses are generally better tolerated.
  • These are most typically used for near and distance tasks, with another pair of spectacles for intermediate distance (e.g., like computer work).
  Most glasses for those with light sensitivity will also have tints
  • Coloured-lens glasses are usually also tinted so that not all of the light comes through the lenses.
  • Outdoor glasses are generally more tinted (usually providing 85-90% attenuation of light) than indoor lenses.
    • Some people find gray lenses better for the outdoors since they cut down on more light from getting through; although some prefer brown lenses as they cut down more of the blue wavelength of light.
  • Polarizing glasses reduce glare (optimal for water, snow, wet roads) but are less effective in icy conditions, LCD (TVs, etc.) or when the windshield is already polarized.
  Other optometric solutions that can help with photophobia:
  • For some people, using plus lenses and prisms help. For some, occluding your glasses on the inner aspect of the lenses (binasal occlusion) helps.
  • Getting custom made lenses for all the situations in which you may find yourself in a day can help a lot, but it can also be expensive, and it can be challenging to find an optometrist with experience in this area.
    2. BINOCULAR VISION DYSFUNCTION      3. TREATING OTHER RELATED CONDITIONS

Many patients have many glasses, and it’s expensive, and it’s hard to find practitioners who specialize in this. Consider the following to help you cope better with light sensitivity:

  1. Approach vs. Avoidance behaviours
  • There is a fine line between “protecting yourself” from the light, and sensitizing yourself from the light
  • Read more in about this here.
  2. Lightly tinted lenses for indoor use
  • Again, as soon as you can, aim to not use glasses indoors (see point 1).
  3. Darkly tinted lenses or polarizing lenses for outdoors   4. Correct refraction/Update your prescription (for your glasses)
  • You may need different refraction for near, intermediate and far distances
  5. Progressive lenses distort periphery
  • Avoid these if you can
  6. If you go for bifocals…
  • the “old school” (flat top or round segment) ones with the line are better for near/distance;
  • using a separate pair of glasses for intermediate distance
  7. Low power lenses and/or BI prism and/or binasal occlusion can help
  • This will be prescribed usually by an optometrist with a special focus on binocular vision disorders.
  8. Vestibular therapy & VMS habituation
  • This is very helpful for “recalibrating” how your brain coordinates “signals” coming from your inner ear, eyes, and musculoskeletal system.
  • This can help right-size how your eyes are used in your environment.
  • We discuss this a bit more in this video
  9. Those with normal pupillary responses
  • have better reading rate, contrast sensitivity with CPF 450-S (yellow)
  • Gray preferred outdoors (most natural) although brown blocks more blue-light
  10. Those with abnormal pupillary response prefer grey lenses   11. Blue-tinted reduce glare control   12. Blue-blocking (FL-41) reduce light sensitivity and perceived flicker of fluorescent lighting: indoors   13. Outdoor tints are more effective when the tint is 85-90% attenuation   14. polarizing glasses reduce glare
  • optimal for water, snow, wet roads
  • less effective in icy conditions, LCD (TVs etc.) or when windshield is already polarized
  15. If you have access to to an Intuitive Colorimeter
  • use it to decide on the colour of your lenses for indoor use (which may also include plus lenses or base-in prisms)
  • test it out in the office with a distant eye chart and reading material
  16. Computer apps:   17. IRIS e-paper
  • This used technology to replace LCD monitors and can help increase your endurance on a screen
  • https://noviscend.com/the-iris-monitor
  18. “Anti-zoom fatigue” strategies
  • treat dry eyes
  • Behavioural strategies
    • e.g., minimize screen time: there are apps to help you track your screen time
    • Multiple short exposures
    • During meetings, when you don’t need to look at screen, you may be able to cover your screen save for camera, so others can still see you.
    • Check out these articles for more suggestions (Screen Adjustments, Computer Vision Syndrome)
  • Appropriate ergonomics, with special attention on maintaining healthy neck posture, can help a lot improve visual performance and reduce symptoms like headache
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Research & writing: Dr. Taher Chugh

Last update: January 2021