Consider this late night situation: an older surgical patient is trying to sleep when suddenly the darkness is thrown back and bright lights flood the room. A drowsy patient will immediately exhibit a startled reflexive reaction which triggers the eyes to spring open bringing about a neurochemical cascade which initiates two stress-related reactions, neither of which are desirable for a recovering patient: 1) a disruption to the sleep process that may take hours to stabilize resulting in an increase for sleep meds, and 2) an ocular glare reaction that for the elderly patient is not only stressful, but in most cases, downright painful. And the sad part is that this scenario can be prevented with a bit of nursing staff education5 and an epigenetic design approach.

For once we begin to understand how the body and brain are directly affected by our design specifications; we will only then begin to create a truly human-centered healing facility. To further increase our understanding of the stress-induced ocular reaction brought about by sudden light intrusion in darkened conditions, consider this:

Many of the negative effects of light are identified as “glare”. As experienced by the aging eye, glare is a sensation of blinding whiteness, blackness, and/or physical irritation. Physiologically it is a metabolic failure of the retinal surface to quickly remove cellular waste in response to changing light conditions. When light strikes a photoreceptor, the retinal cell generates a unit of work which produces a waste by-product that dissipates swiftly in the younger eye. As the eye ages, the rate of removal slows and the waste by-products build up thus causing the temporary “blinding” and sometimes painful effects we identify as glare. With the increasing use of bright blue-shifted fluorescent and blue rich LED overhead lighting we can expect the glare reaction to be accelerated. Because short wavelength (blue) light “peaks” strike the retina closer together, it causes the cellular “work” to occur up to 2 trillion times faster than longer wavelengths thus causing the cellular waste to build up faster than can be processed. This in turn exacerbates the sensation of glare in a manner that increases with age.2, 3, 9, 10

I believe that the detrimental effect of these new light sources will be most noticeable in older people because their vision is adversely affected due in part to two degrading anatomical characteristics. The first is a measurable size decrease of the pupil correlated directly with advancing age. This occurs when tissue of the iris swells thus preventing the pupil from adapting by opening to its full extent in dim light. In total darkness, the pupil diameter of a 45 year old is 6.2mm and decreases to 5.2mm by age 80, while in the light adapted state, it is further reduced to only 3.4mm. Coupled with the normal 2mm shift of pupil size which occurs when attention shifts between center and peripheral focus in the presence of bright light, the older pupil will have dramatically less ability to admit and shield light at night. Because pupil dilation is influenced by the circadian clock targeted iPRGC response, an increased expression of a stress related neurotransmitter known to control pupil activity can also be expected as the percentage of short wavelength light at night increases.1, 4, 9, 13, 14


1. Boyce, Peter LIGHTING for DRIVING, CRC Press

2.Kitchel, Elaine EFFECTS OF BLUE LIGHT on HEALTH pages 81–83 article VISION REHABILITATION: Assessment, Intervention and Outcome by Cynthia Steven

3.Kitchel, Elaine THE EFFECTS OF FLUORESCENT LIGHT on the OCULAR HEALTH of PERSONS with EXISTING EYE PATHOLOGIES American Printing House for the Blind

4. Rabbetts R.B. CLINICAL VISUAL OPTICS, Edinburgh: Butterworth Heinemann Elsevier 2007

5. Bartick M., Solet, J. et. al. Decrease in As Needed Sedative Use by Limiting Nighttime Sleep Disruptions from Hospital Staff (2009) Journal of Hospital Medicine Cambridge Health Alliance

6. Crowley, Kate The Effect of Blinks and Saccadic Eye Movements on Visual Reaction Times (2009) Atten Percept Psychophys 71: 783-788

7. Einhauser Wolfgang et. al Pupil Dilation Reflects Perceptual Selection and Predicts Subsequent Stability in Perceptual Rivalry (2008) Proceedings of the National Academy of Sciences February 5 Vol.105 No.5 1704-1709

8. Grimm C, et al. Rhodopsin_Mediated Blue Light Damage to the Rat Retina; Effects of Photoreversal of Bleaching (2004) Invest Ophtalmol Vis Sci Feb. 42 (2): 497-59

9. Hattar, S. Melanopsin-containing Retinal Ganglion Cells: Architecture, Projections, and intrinsic Photosensitivity (2003) Science 295: 1065-1070

10. Noell, W.K. et. al Irreversible Effects of Visible Light on the Retina: Role of Vitamin A (1971) Science April 2 Vol.172. no.3978. pp.76-780 DOI:10.1126/science.172.3978.76

11. Pelli, Dennis and Tillman, Katherine THE UNCROWED WINDOW OF OBJECT RECOGNITION (2008) NATURE NEUROSCIENCE Vol.11 no.10: 1129 – 1137

12. Taylor H.R., et al. Visible Light and the Risk of Age-Related macular Degeneration (1990) Trans Am Ophthalmol Soc. 88: 163 – 178

13. Wang JS, An Alternative Pathway Mediates the Mouse and Human Cone Visual Cycle (2009) Current Biology ; 19 ( 19 ): 1665 DOI: 1016/j.cub.2009.07.054

14. Wang JS, Intra-retinal Visual Cycle Required for Rapid and complete Cone Dark Adaption (2009) Nature Neuroscience; 12 (3): 295 DOI: 10.1038/nm.2258