Hi Keith,
I too have been hunting around for data on light adaptation, primarily photopic. I will be piloting a study on lighting tolerances in children who are neurodiverse (with photophobia), observing their responses to different lighting conditions of illumination and temperature. So, clearly I want to understand how long a period is necessary before introducing a new condition.
The attached chapter from Lamb and Kefalov (2025) seems to indicate that photopic adaptation (such as you described with retinal exposure to varying levels of light) is just a few seconds. This probably does not account for changes in the aging eye. However, dark adaption (rods to bleaching cones to full color/contrast adaptation) may take up to an hour. So, for my study, I will not be introducing a totally dark environment at the onset. For you, I would think you are still addressing a photopic response but perhaps longer since less light is being filtered through the lens.
Not sure if the attached is helpful.....the article has some great information on Wells curve adaptation and goes into a LOT of detail on phototransduction in salamanders! (at which point it lost my interest:-)
If you find any more information, would love to learn! I will be sure to forward any other readings that might be relevant.
Reference:
Trevor D. Lamb, T.D., & Kefalov, V.J. (2025). Light adaptation in photoreceptors. In Adler's Physiology of the Eye (12th ed). Elsevier, ch 20, pp 451-463 Best,
Marcy
Martha Sanders PhD, MSOSH, OTR/L, CPE, LS, FAOTA
Professor of Occupational Therapy
Quinnipiac University
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Sent: 12/9/2025 4:36:00 PM
From: Keith Karn
Subject: Dark adaptation in older person wearing photochromic lenses
Fellow Technical Group Members (cross-posting to multiple TGs - I'm sorry for those in multiple groups),
I am writing to ask for your thoughts and / or suggested reading / references on the following.
The scenario:
- An older person (80s) is wearing prescription lenses with photochromic lenses (sometimes referred to as "Transitions Lenses," though I'm not sure they were this specific brand).
- The person is outside in bright sunlight long enough for the lenses to darken.
- The person then walks into a portico area that is shaded from direct sunlight but that is still relatively bright due to reflected sunlight from windows and open doorways as well as significant artificial overhead lighting.
My questions:
- How would we expect the photochromic lenses to affect the wearer's dark adaptation when walking from the direct sunlight into the shaded area? Note that we are not talking about dark adaptation to the level of scotopic vision since it is still relatively bright.
- Presumably the darkened lenses prevent some of the pigment bleaching that would occur in the viewer's cones if no filters were worn in the bright sunlight. How does this impact the person's ability to see when walking into the less bright area?
- Is there data that would be relevant to this situation that could describe the time-course of adaptation of the entire system (human visual adaptation + the lens transmission change) in such circumstances?
I've begun a lit search but not coming up with much so far. I would appreciate any guidance that you can provide. Feel free to post to the group and / or contact me directly at my work email address <
Keith@HumanFactorsInContext.com>.
Keith
Keith S. Karn, PhD
Principal
Human Factors in Context LLC
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Keith Karn PhD
Principal Consultant
Narberth PA
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