There are incandescent,fluorescent and LED lamps whose voltage waveform,principle and spectrum are different.
1.Incandescent lamp brings low frequency flicker light and infrared.
110volt 60 Herts AC sinusoidal voltage is across the incandescent lamp. When sinusoidal voltage reaches peak value, the lamp is brightest; when sinusoidal voltage reaches 0 point, the lamp is darkest. In one second, the brightness of lamp varies 60 cycles.(Hertz(Hz): times in one second for the cycles that voltage starting from peak value, passing 0 volt, reaching valley value and coming back to peak value
Pupils will constrict under bright environment and will dilate under dark environment. Pupils is controlled by Ciliary(eye muscles) to dilate and constrict 60 cycles per second. Long term so frequent dilation and constriction leads to ciliary eye muscles loose and not able to adjust eyes to see distant object. That results in myopia
Poland Wroclaw university of Technology measured the size of pupil under flicker light [1]
China NanTong university hospital found myopia can be induced by low frequency flicker light.[2]
La Trobe University in Australia found low frequency temporal modulation of light promotes a myopic shift[3]
http://en.wikipedia.org/wiki/Power-line_flicker explained how voltage variation in power system caused flicker.
IEEE Par 1789 group summarize research on Biological Effects and Health Hazards From Flicker,Including Flicker That is Too Rapid To See in Table1 showed flicker light impact on vision and health.[4]
The filament of incandescent lamp can reach thousands of degree Celcius and energy created by incandescent bulbs is in the form of infrared radiation (heat). Long term infrared expose can cause damage in ocular lens and retina.
Uppsala University in Sweden found near infrared radiation may cause cumulative damage in the ocular lens.[5]
University of Texas at Austin found the 1300-nm ocular damage data have yielded unusual characteristics where continuous wave retinal damage was observed in rabbit models.[6]
Fluorescent lamp brings high frequency flicker light and ultraviolet.
Ballast is used for Fluorescent lamp to generate high frequency sinusoidal voltage across the Fluorescent lamp.The lamp's brightness varies with the voltage variation at the same frequency.
Fluorescent tube lamp with high frequency flicker light(left);Compact fluorescent lamp with high frequency flicker light(right)
Eye muscles can not adjust pupils with so fast frequency flicker light. Strong peak fickler light shine directly on the retina. In the long term, people will feel eye irritation, headache and decreased vision. Many kids play smart phones, PC tablets and have decreased vision that is related to high frequency flicker.
IEEE Par 1789 group summarize research on Biological Effects and Health Hazards From Flicker, Including Flicker That is Too Rapid To See in Table1 showed flicker light impact on vision and health.[4]
University of Florida found association between severity of light exposure and age-related macular degeneration that is a leading cause of blindness in the western world.[7]
University of Essex; UK,National Research Council Canada and Northeastern University found low-frequency flicker between 3 and 70 Hz can cause seizures; invisible flicker (70 Hz) above can cause malaise, headache and visual impairment.[8]
The electric current (in the gas) excites mercury vapor which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the bulb to fluoresce, producing visible light. So fluorescent lamps emit ultraviolet (UV).
Fordham University, New York City found Ultraviolet(UV) radiation as a risk factor for cataract and macular degeneration. The removal of these wavelengths UV-A and UV-B from ocular exposure will greatly reduce the risk of early cataract and retinal damage.[9]
Answer is No. LED on market brings high frequency ripple flicker light by switching power supply,low frequency ripple by battery, dimming flicker light and unsafe blue light.
There is long wire between battery and LED lamp. Battery voltage=wire voltage+LED lamp voltage, wire voltage=wire resistanceXcurrent, when current pass through wires, wires are heated to cause resistance up, then wire voltage goes up, Battery voltage is constant, so LED lamp voltage goes down, LED lamp becomes darker, LED current goes down, wire current goes down,so wire voltage goes down, now LED lamp voltage goes up, LED lamp becomes brighter, back and forth, LED lamp has low frequency flicker light.
Pupils dilate and constrict with low frequency flicker light. After long term, muscles controlling pupils to dilate and constrict so many times become loose and cannot adjust eyes to see distant object finally leading to myopia.
High frequency flicker light is so fast that the pupils can not keep up with fast brightness variation. So strong light will shine on retina. Long term strong light cyclic stimulation will cause eye irritation, headache and decreased vision.
LED power supply will produce high frequency voltage ripple. The ripple is the small voltage variation around DC output voltage. Because the LED current depends on LED voltage exponentially, small voltage variation will cause dramatic current variation thus dramatic high frequency flicker light is produced.
When operation point moves between point Va and point Vb with a small variation for voltage ripple, the current has a dramatic change from Ia to Ib, the output power at point b is Pb=Ib*Vb, that is much higher than power at point a which is Pa=Ia*Va, the brightness of LED is proportional to output power, so small voltage ripple cause a huge flicker light.
Northrop Grumman Information Technology, San Antonio found that exposure to near-UV/blue wavelength sources induce a veiling glare intense enough to degrade visual performance[10].
University of Texas Southwestern medical center in Texas found strong blue light can cause macular degeneration and other vision problem[11].
As above,
To prevent myopia and minimize eye fatigue, low frequency flicker and high frequency flicker must be removed from the lamp. So low frequency AC sinusoidal voltage, high frequency AC sinusoidal voltage must not be applied across the lamp. The ripple voltage around DC voltage must be removed. To get constant brightness light, constant DC voltage or DC current without ripple or spike should be applied across the lamp;
To prevent cataracts, ultraviolet must be removed from the light spectrum.
To prevent retinal damage, infrared must be removed from the light spectrum.
To prevent macular degeneration, hazard blue light must be removed from the light spectrum.
The vision protection LED desk lamp designed by Bright Quantum LLC, (www.uprlt.com) with US the required features:
No low frequency flicker light;
No high frequency flicker light;
Electromagnetic radiation meet international standard;
Premium LED lamp has no infrared, no ultraviolet, no harmful blue light;
Premium LED lamp has continuous smooth light spectrum simulated to sun light without strong monotonic color light.
Theory is published in international journal of ophthalmology;cited by US National Library of Medicine National Institutes of Health.
US safety company UL approved our power supply.
China national household appliances quality supervision and inspection center inspected the product. Test was passed.
There is long wire between battery and LED lamp. Battery voltage=wire voltage+LED lamp voltage, wire voltage=wire resistanceXcurrent, when current pass through wires, wires are heated to cause resistance up, then wire voltage goes up, Battery voltage is constant, so LED lamp voltage goes down, LED lamp becomes darker, LED current goes down, wire current goes down, so wire voltage goes down, now LED lamp voltage goes up, LED lamp becomes brighter, back and forth, LED lamp has low frequency flicker light.
Pupils dilate and constrict with low frequency flicker light. After long term, muscles controlling pupils to dilate and constrict so many times become loose and cannot adjust eyes to see distant object finally leading to myopia.