CVI: Impact of Light

Written by: Rachel Bennett

At Perkins, we are a gathering place of ideas. The CVI visual behaviors synthesize current research and build on the work of leading theorists in the field. CVI is a lifelong disability and we want to ensure that all individuals with CVI are fully understood. The CVI visual behaviors are an ongoing need, they can change and they can improve for some, but the need never goes away. No one area is separated from the other—the CVI visual behaviors are highly connected and all can impact the individual with CVI at any time.

What is the Impact of Light?

Light can be both a support and an area of difficulty for people with CVI, where it can either increase or decrease visual attention and recognition.

Some people with CVI require light to establish or maintain visual attention, and visual recognition may also be dependent on light.
Other people with CVI may demonstrate photophobia, avoiding light sources and fatiguing quickly when presented with lighted presentations.
It is speculated that some may be involuntarily drawn to light and can’t control where their brain chooses to attend. These light sources may include primary sources of light (lamps and overhead lights), light from windows or the sun, backlit displays (including iPads), TVs/monitors, phones, and glare on surface areas.

Some people with CVI may

Only be visually attracted to lighted items.
Need objects brightly illuminated.
Need competing light sources removed.
Seek out the brightest target in the room.
Not be able to see an object if others around it are also equally lit.
More easily attend to and recognize visual information presented on a backlit device.

Some people with CVI may demonstrate light sensitivity. They may

Avoid looking at and turn away from sources of light.
Squint excessively.
Have difficulty transitioning from dark to bright environments or vice versa.
Navigate with their heads down.
Become visually fatigued from using lighted materials.
Have significant difficulty traveling outdoors on sunny or snowy days.

There are specific indoor lights that my daughter does not prefer to have on. In her bedroom, she prefers a daylight color temperature bulb to be on as opposed to the overhead ceiling light. She uses this projected light from her desk lamp as a spotlight and does not want it directly on her.
Parent of child with CVI

What are some compensatory strategies related to the Impact of Light?

People with CVI have strategies and workarounds for so much in their daily lives. Light can be used as compensatory support, but some may also use compensatory skills when light is distracting, disorienting, or fatiguing.

Some people with CVI may:

Need a visual break after too much viewing of an iPad.
Increase their use of tactile and auditory skills when in a very bright environment with distracting and disorienting light sources.
Need to spend time in a dark room or a low-lit room when experiencing visual fatigue and overwhelm.
Rely on light to know where to look and/or to support recognition.
Rely on light when navigating an environment. Light may be used as a landmark. For example, if there is difficulty with seeing and recognizing the door to a porch, the light coming through it serves as a compensatory support for orientation.

If there was a bright lamp in a dim room, or if the TV was on with the lights off, that’s what would grab my visual attention. I would find myself staring at it, even if it hurt my eyes.
Nai, adult with CVI

What are some look fors/questions when observing your child with CVI?

Observable behaviors may include: being distracted by light sources, avoiding light sources, increased attention or recognition with backlighting or task lighting, squinting or avoiding light of different spectrums.

To what extent do lighted objects, backlighting, and/or task lighting impact visual attention (increase, decrease, no impact)?
Does your child with CVI show discomfort and/or fatigue in response to lighted materials or light sources in the environment?
Do they become captivated by a lighted target or item and are unable to redirect visual attention?
What type of environmental lighting does your child with CVI prefer—dim or bright lighting? Is there a specific task where they need more or less environmental lighting?
To what extent do they become captivated, distracted, and/or disoriented by certain light sources in the environment: light from windows, overhead lights, lamps, glare on surfaces and materials?
To what extent does backlighting and/or task lighting support visual recognition of 3D and 2D items? Is this only required for new, unknown items or for all no matter the familiarity?
To what extent does the person with CVI rely on light to orient in an environment?

When I read, I need to have a lot of light in the room and have frequent breaks in between, especially when I’m reading school books.”
Dagbjört, an adult with CVI, from Why Music is My Vision

What are some examples of adaptations and accommodations?

All accommodations must be based on individual assessment. The following are meant to inspire and provide a general idea. Accommodations and instructional approaches must be student-specific. Access is individual.

Some environmental considerations may include

Controllable artificial lighting (dimmers, banked lighting, lamps etc.)
Controllable natural lighting (shades or curtains)
Dark rugs to absorb glare
Seating that allows the individual to face away from light sources (side lighting from windows and lamps, overhead lighting from ceiling and skylights)

Some considerations for materials or personal equipment may include

Brimmed hats, wrap-around sunglasses, and/or transition lenses
Options for adjustable task lighting and/or backlighting (i.e., iPad)
Items/toys that are lighted
Materials that use a matte finish instead of a gloss finish

Find more examples from a guide to common CVI IEP accommodations in the CVI Now IEP Guide.

I don’t like dark movie theaters. I can’t tell if someone is coming toward me. I look at all the exits, but I can’t map the space. I can’t tell where people are or where they’re going.
Albie, adult with CVI, from Albie’s CVI Perspective

Following the science

Connecting current research of the brain, our visual system, and CVI to better understand the CVI visual behaviors.

Vision is only possible with light. Light impacts form perception, clarity, depth, color, and contrast. The retinal photoreceptors convert light energy into electrical impulses which are transmitted to the visual cortex where primary processing takes place for visual acuity, color, contrast sensitivity, and visual fields. (Geetha, 2020).
Light-gazing: Some individuals with CVI flick their fingers in front of the light source, blink excessively, gaze at flickering fires, or stare at spinning fans (Jan et al., 1990).
Light sensitivity: Individuals who have eye teaming and/or eye movement may experience light sensitivity. Strabismus and nystagmus are co-existing impairments commonly found in individuals who have CVI (Salati et al., 2002; Fazzi et al., 2007). Photophobia (light sensitivity) is present in a third of children with CVI (Jan et al. 1993). Ocular and visual pathway disorders (e.g., optic nerve and chiasm issues) can cause varying degrees of photophobia, along with neurological disorders (including traumatic brain injury). (Wu & Hallet, 2017).
Light and contrast: “Environmental lighting may be optimized to promote visual functioning, and the size of visual targets coupled with optimal contrast is also important” (Good et al., 2012).

CVI Parent Perspective

“My son really loves his darkroom time. He needs this time to help him recover from visual and physical fatigue. He also has photophobia and never loved using a bright light box or brightly lit toys. On a bright sunny day, he relies more on his blindness skills because the bright sun and all the objects in the environment that reflect the sun can be disorienting. He does love to watch iPad videos but prefers a paper version of his adapted books during reading time. When he’s in the house, he needs medium light for eating and daily living tasks and hates it when he’s trying to do tasks in the complete dark. So light is not a simple notion; it can be both a support and a barrier to access.”

References

Geetha, V. K. P. (2020). Cerebral visual impairment in children. Kerala Journal of Ophthalmology 32(1), 27-35.

Good, W. V., Hou, C., & Norcia, A. M. (2012). Spatial contrast sensitivity vision loss in children with cortical visual impairment. Investigative ophthalmology & visual science, 53(12), 7730–7734. https://doi.org/10.1167/iovs.12-9775

Jan. J. E., Groenveld, M., & Sykanda, A. (1990). Light-gazing by visually impaired children. Dev Med Child Neurology 32(9), 755-759.

Jan, J.E., Groenveld, M. and Anderson, D.P. (1993), PHOTOPHOBIA AND CORTICAL VISUAL IMPAIRMENT. Developmental Medicine & Child Neurology, 35: 473-477. https://doi.org/10.1111/j.1469-8749.1993.tb11677.x

Lueck, A. H., & Dutton, G. N. (2015). “Intervention Methods: Overview and Principles.” A. H. Lueck & G. N. Dutton (eds). Vision and the Brain: Understanding Cerebral Visual Impairment in Children (pp. 497-536). New York, New York: American Foundation for the Blind Press.

Oh BL, Suh SY, Choung HK, Kim SJ. Squinting and photophobia in intermittent exotropia. Optom Vis Sci. 2014 May;91(5):533-9. doi: 10.1097/OPX.0000000000000251. PMID: 24727823.

Roman-Lantzy, C. (2018). Cortical Visual Impairment: An Approach to Assessment and Intervention. 2nd ed., New York, NY: AFB Press.

Salati, R., Borgatti, R., Giammari, G., & Jacobson, L. (2002). Oculomotor dysfunction in cerebral visual impairment following perinatal hypoxia. Developmental Medicine & Child Neurology, 44(8), 542-550. doi:10.1017/S0012162201002535

Wu Y, Hallett M. Photophobia in neurologic disorders. Transl Neurodegener. 2017 Sep 20;6:26. doi: 10.1186/s40035-017-0095-3. PMID: 28932391; PMCID: PMC5606068.