What is the range of light levels the human visual system can process?
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About 10^12 to 1.
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What is the range of light levels the human visual system can process?
About 10^12 to 1.
What is spectral sensitivity?
The relative efficiency of light detection as a function of the wavelength of light.
What does the internal circadian body clock synchronize to?
The local daily light-dark pattern.
What are humans, like other animals and plants, born to live under?
Exposure to solar radiation.
What type of variations do humans have complex physiological responses to?
Daily and seasonal variations of UV, visible, and IR light.
What do the cone receptors in the human eye respond to?
A wide range of wavelengths of the visible spectrum.
What causes color blindness?
A fault in the development of one or more sets of retinal cones.
What are the names of the four photoreceptor types?
Rods, L-cones, M-cones, and S-cones.
How are photoreceptors distributed across the retina?
They are distributed in different areas across the retina.
What are the three states of sensitivity in the visual system related to?
Different retinal illuminance.
What is the maximum luminance ratio the human visual system can handle at one moment?
1000 to 1.
What is color blindness?
The inability or decreased ability to see color or perceive color differences under normal lighting conditions.
How many cone photopigments do most human visual systems have?
Three cone photopigments (L-, M-, and S-cones).
What do color blind correction glasses use to improve color distinction?
A filter to cut out overlapping wavelengths.
What is a common sleep disorder experienced by young people?
Delayed sleep phase.
What is a key characteristic of the different photoreceptor types?
They have different spectral sensitivity.
How does light impact mood?
It can positively or negatively affect it.
What effect does IR exposure have on the skin?
It raises the temperature, which can lead to burns if elevated sufficiently.
What is the luminance range for neural adaptation?
1000:1.
What medical condition can be treated with phototherapy involving short-wavelength visible radiation?
Jaundice.
What happens to light when it reaches the retina?
It is absorbed and converted into signals.
What is the function of photoreceptors in the retina?
They convert optical radiation to neural signals.
Which photoreceptors are active during photopic vision?
Cones.
Which colors are particularly affected by color blindness that correction glasses aim to improve?
Red and green.
What sleep disorder is often seen in the elderly?
Advanced sleep phase.
Are circadian rhythms self-sustained?
Yes, but they are adjusted by external cues.
What is an example of harmful IR exposure to the eyes?
Looking directly at the sun for a prolonged period.
What is mesopic vision?
An intermediate state where both cones and rods are active.
What is Bright Light Therapy?
A treatment method that uses bright light to influence mood and behavior.
What is the circular opening in the eye that admits light called?
The pupil.
What occurs when the eyes are diverted to a white space after an afterimage?
Overstimulated cells send weak signals, causing affected colors to appear muted.
Why does the brain perceive opposite colors during an afterimage?
Surrounding fresh cells send strong signals, contrasting with the muted signals from overstimulated cells.
What type of vision occurs at higher luminances?
Photopic vision.
What effects does melatonin have on the body?
It causes drowsiness and lowers body temperature.
What is presbyopia?
Difficulty in focusing at near-working distances.
What can happen if the temperature of the retina is elevated sufficiently?
It can damage the tissue.
How does pupil size change with age?
There is a reduction in adaptation ability due to limits in pupil size.
What is the primary function of cones?
Responsible for color vision and perceiving fine details.
What is an example of a media that caused seizures in sensitive individuals?
'Pokémon Shock' from the episode 'Dennō Senshi Porygon'.
What is essential for the visual system to operate?
Light.
What inhibits the production of melatonin?
Light to the retina.
When is the production of melatonin permitted?
During darkness.
What is a challenge when describing colors to blind people?
Finding ways to convey color concepts without visual references.
What is Seasonal Affective Disorder (SAD)?
A type of depression related to the time of year, causing serious mood changes with seasonal changes.
What type of light do cones function under?
Bright light.
How can excessive brightness contrast contribute to eyestrain?
It creates discomfort and strain on the eyes.
How does adaptation affect the spectral sensitivity of the visual system?
It changes the spectral sensitivity by activating different combinations of retinal photoreceptors.
What process allows the visual system to cope with varying luminance levels?
Adaptation.
How does light affect circadian rhythms?
Light entering the eye regulates or modifies the phase and amplitude of the circadian system.
What can UV radiation purify?
Air, liquids, and granular materials.
What is the melatonin cycle sensitive to?
Light.
How does light affect human biological systems apart from vision?
It affects them positively and negatively.
What daily human rhythms are governed by optical radiation?
Daily rhythms, endocrine systems, sleep cycles, and mood.
What is photophobia?
Sensitivity to light, often resulting in discomfort.
What type of hormone is melatonin?
A stress hormone.
What is photochemical adaptation?
Change in sensitivity due to the percentage of unbleached pigment in photoreceptors.
What is a possible cause of eyestrain related to lighting?
Inadequate lighting level for the task.
What is a medical benefit of UV radiation?
It is important for the production of vitamin D in the skin.
How does the eye encode information about the image?
As neural signals.
How are the neural signals transmitted to the brain?
Through neural pathways.
What are circadian rhythms?
Daily rhythms that repeat approximately every 24 hours, driven by an internal biological clock.
What is perceived during photopic vision?
Color.
What happens to photons when they arrive at the retina due to IR exposure?
Some photons are absorbed in the pigment, increasing its temperature.
Who else, besides young people and the elderly, experiences sleep disorders related to circadian rhythms?
Night-shift workers and travelers across several time zones.
What is the perception of color during scotopic vision?
There is no perception of color.
What is the impact of cell loss in aging eyes?
It leads to reduced visual acuity and reduced contrast sensitivity.
What effect can lamp flicker have on eyestrain?
It can cause eyestrain even when it is not visible.
What are the extreme luminance levels in terms of cd/m² that the human visual system can adapt to?
From 10^-6 cd/m² to 10^6 cd/m².
What is the effect called when we experience a visual phenomenon after staring at a color?
Afterimage.
What can improper use of light lead to?
Injuries to health.
Why is UV radiation important for human health?
It can destroy microorganisms that may damage human health.
What are some symptoms of eyestrain?
Irritation, inflammation of the eyes and lids, blurring or double vision, headaches, indigestion, giddiness.
What happens to the lens as it ages?
It becomes yellow, reducing short wavelength radiation reaching the retina.
What is fluorescence in the context of aging eyes?
Light generation that reduces the quality of the image.
What is neural adaptation?
Change in sensitivity due to neural processes, fast and operative at moderate light levels.
What causes an afterimage?
Overstimulation and fatigue of cone cells in the eyes.
What role does the lens play in the eye?
It focuses the image by changing its shape.
What does the eye produce?
An image of the external world on a layer of photoreceptive cells in the retina.
What type of color vision do humans have?
Trichromatic color vision.
How many types of cones are sensitive to different spectra in humans?
Three types.
What issue do people with more overlap between green and red regions face?
Difficulty differentiating certain shades.
What is a common example of an afterimage?
The bright glow that seems to float before one's eyes after looking into a light source.
What is eyestrain?
Discomfort resulting from prolonged exposure to certain lighting conditions.
What type of vision occurs at low luminance?
Scotopic vision.
Which photoreceptors are active during scotopic vision?
Rods.
How many cones are present in the human eye?
Approximately 8 million.
Where are cones concentrated in the retina?
In the fovea, a small area on the visual axis of the eye.
What colors do S-cones, M-cones, and L-cones absorb?
S-cones absorb blue, M-cones absorb green, and L-cones absorb red.
What can trigger seizures in individuals with photoepilepsy?
Fluctuating light covering a large area with high percentage modulation.
What happens to cone cells when they become overstimulated?
They lose sensitivity.
Why is vitamin D important for the human body?
It is required for the absorption of calcium.
Where does light reach after passing through the lens?
The retina.
What conditions can be helped by exposure to sunlight?
Rickets and osteomalacia.
What type of radiation is capable of destroying many viruses and bacteria?
UV radiation.
What happens when we stare at a particular color for too long?
It leads to exhaustion of the cone cells that respond to that color.
How many types of photoreceptors are in the retina?
Four types: rods, L-cones, M-cones, and S-cones.
What is the primary role of light for humans?
To see.
What types of microorganisms can UV radiation destroy?
Viruses, bacteria, molds, and yeasts.
What is an example of a circadian rhythm in humans?
The sleep-wake cycle.
What percentage of females have some form of abnormal color vision?
0.2%.
How do plants exhibit circadian rhythms?
They raise and lower their leaves from day to night.
Why is color blindness more common in males than in females?
Because many genes involved in color vision are on the X chromosome, and males have only one X chromosome while females have two.
What adjusts circadian rhythms to the local environment?
External cues, with daylight being the most important.
What happens to melanin levels with excessive solar radiation exposure?
The body releases more melanin, darkening the skin color.
What does 100% UV protection refer to?
Complete shielding from ultraviolet radiation.
What treatment is shown to be effective for sleep disorders related to circadian rhythms?
Exposure to light.
What happens to the iris in response to changes in retinal illuminance?
The iris constricts and dilates.
What is important about the timing of light exposure for treatment?
Using high light levels at appropriate times.
How can lighting affect individuals with Alzheimer's disease?
It can influence their abilities and behavior.
What type of light do rods require to function?
They require less light and function under low light conditions.
How long may the photochemical reaction take?
Several minutes.
Which skin conditions can be treated with UV radiation?
Psoriasis and eczema.
What does exposure to light help reset in the human body?
The internal circadian body clock.
What hormone is associated with the sleep-wake cycle?
Melatonin.
What are the effects of UV radiation on the skin?
Reddening, sun tan, edema, pain, blistering, peeling, and sunburn.
How does melanin protect the body from solar radiation?
By absorbing solar radiation.
What are the types of photoreceptive cells in the eye?
Rods and cones (S-cones, M-cones, L-cones).
What does clouding of the lens refer to?
A decrease in transparency in the lens.
What type of therapy is used to treat Seasonal Affective Disorder?
Light therapy with sunlight or bright lights.
Where are rods concentrated in the retina?
In the outer edges of the retina.
What is the primary function of rods?
Responsible for night vision.
What is the human body's response to the light-dark cycle?
It secretes hormones that synchronize the body clock to a 24-hour cycle.
What percentage of males have some form of abnormal color vision?
About 8%.
What types of electromagnetic radiation affect human health?
UV, visible, and IR spectrum.
What are some effects of UV exposure on the eye?
Clouding of cornea, reddening of the eye, tearing, photophobia, twitching of the eyelids, and a feeling of grit in the eye.
Why is melatonin important?
It is important for a normal sleep-wake cycle.
How many rods are present in the human eye?
Approximately 120 million.
What is the luminance range for pupil size change?
16 to 1.
What happens to pigment during changes in retinal illuminance?
Pigment is bleached and regenerated to re-establish equilibrium.
What systems are influenced by optical radiation entering the eye?
Endocrine systems and sleep cycles.
What are the long-term effects of frequent UV radiation exposure?
Skin aging and increased risk of certain types of skin cancer.
What is the recommended light intensity for effective light therapy?
2,500 – 10,000 lux at the eye.
What is the trend in retinal disease prevalence with age?
There is an increased prevalence of retinal disease.
