May LEDs have a negative effect on the eyesight?

Considering potential photobiologic damages deriving from LED it is important to demarcate white color LED provided for the general lighting aims from LED with clearly identified lighting color or strict spectral distribution of optical radiation. In the last case, can be obtained LED emitting in purposeful way UV radiation, IR or also blue, which in case of unappropriate usage can result in significant threats for the human eyesight or skin. It is the same problem for the usage of other types of radiators on the basis of discharge lamps or incandescent lamps, when it is crucial to go by the manufacturer’s instructions.

Evaluating potential threats obtained from white color LED, for the general lighting goals, it is necessary to look at it as in case of other light sources, either incandescent or discharge. Criterions for photobiologic safety evaluation of all light sources types are indicated in the European Standard EN 62471 based on the IEC standard with the same number and CIE Publication S009.

The basic types of photobiologic threats obtained from the radiation of light sources may be grouped in such way:

  • UV radiation threat (actinic and close) harmful for cornea and lens of the eye;
  • Blue light threat resulting in photochemical damage to the retina of the eye;
  • Thermal radiation threat resulting in thermal damage to the retina of the eye;
  • IR radiation threat harmful for cornea and lens of the eye.
  • In practice, the level of risk for each group depends on radiation power in the indicated spectrum range and time of its influence on the human eye. Additionally, in case of damage to the retina not only the radiation power but also the angle in which this radiation is being sent is important. The slighter the solid angle is the higher is the risk level. In the Standard named above, the maximum values are indicated, as well as, the intensity of radiation or energetic illumination, which are the basis for light sources classification to three fundamental groups of damages: without risk, low level or medium level. It is crucial to notice that set fixed requirements are based on the assumption of appropriate usage of light sources what means the avoidance by the user of the long-​time contact with light source in conditions of clear risk for the human eye, for example, looking at filament or other shining element or excessive impending of the light source to the human eye.

    Evaluating white LED light according to the foregoing criterions, it is worth to verify that the majority of literature data classify it similarly as the other light sources for the general lighting aims, to the group with no threats to the human eye. Some LEDs can be exceptions, mainly those of cold-​white color, which refer to the group of potential threat by blue light as to the group two, what means with significant risk. Comparing LED parameters with other light sources, for example, halogen bulb or metal halide lamps, it may be obvious to claim that those last groups significantly more often exceed the levels of threats considered as safe.

    It is worth mentioning that radiation resulting from the light sources, is ranked as threats included in the basic safety requirements indicated in Voltage Directive, compliance with which is the condition for legal implementation of product to the market. It means, that manufacturers of lighting equipments on the basis of LED indicating their products with CE symbol, ensuring the completion of basic safety requirements, also have to take into consideration threats connected with optical LED radiation. Their evaluations may be based on the information coming from LED manufacturer. For this reason, LED manufacturers have to evaluate and classify their products to indicated group of photobiologic threats, and valuable information may be included on the label of the product. In case of threat occurrence, recommended precautions or required actions in order to eliminate or limit threats should be proposed. Tips for manufacturers working in this field are mentioned in Technical Report IEC/​TR 624712.

    Summing up contemplations, it is worth to mention that the way of light projection while using LED differs from other light sources, well analized technologies, admitted as traditional. Further actions aiming at detailed examination of photobiologic threat resulting from LED and possible establishment of safety usage conditions for this type of products.

    In the foregoing analysis, some issues were consciously skipped: the ones considering typical for light sources-​dazzle effect related to the high illumination of shining sources or light pulsation related to charging with low voltage considering that experiences of traditional bulbs usage are enough for appropriate application and usafe of LED.