Over the last 15-20 years, lighting sources and technology have been experiencing a revolution. The primary sources of blue light are the sun and artificial light sources, including LED light bulbs (light-emitting diode) and fluorescent light tubes, emitting the amount of blue light approaching the international exposure limit. [2]
We have seen over the past 10 years with the increased use of compact fluorescent lamps (CFLs) and high-intensity light-emitting diodes (LEDs) in both commercial and domestic purposes.[3] The increasing popularity of blue-rich LED backlight display devices such as mobile smartphones, ultra-portable tablets, and computer screens, our eyes are more exposed to blue light. [2]
Blue light is electromagnetic radiation of short wavelength (400–500 nm) in the visible spectrum (400–780 nm) that carries the highest amount of energy per photon that can cause phototoxic damage to the retina.[3] A sufficient level of optical radiation can damage the retina in one of three ways Mechanical damage caused by intense laser pulsation. Thermal damage caused by elevated temperature in the retina due to absorption and photochemical damage caused by a light chemical retinal reaction. [4]
This blue light exposure is associated with age-related macular degeneration (ARMD), the world's third leading cause of blindness. [2] Significant, progressive visual impairment is associated with advanced age-related macular degeneration, including neovascular age-related macular degeneration (wet) and geographic atrophy (late dry). Cigarette smoking, dietary factors, cardiovascular disorders, and genetic markers are the primary risk factors. [5]
Natural eye absorbance features to limit the amount of potentially harmful radiation that can penetrate the retina. The cornea absorbs ultraviolet radiation below 300 nm and the crystal lens observes the propagation of most wavelengths from 300 to 400 nm, especially up to 360 nm. [6] Short-wavelength light is essential for cardiac rhythms and alertness but excessive exposure of light has cause eye strain and leads to eye fatigue. Long term usage of short-wavelength light-emitting gadgets may result in a group of side effects presently recognized as Visual Display Terminal (VDT) Syndrome and Computer Vision Syndrome (CVS). [7]
Cataract surgery tends to improve sleep-wake cycles due to the increased luminosity that may reach the retina. It was believed that the Blue Light Filter could interrupt circadian rhythms by blocking photosensitive retinal ganglion cells with a maximum light sensitivity of approximately 480 nm. [8] With the help of these RGCs, melatonin synthesis is controlled and inhibited by light exposure in the evening and overnight. The action spectrum of melatonin suppression has been previously defined as the maximum suppression of melatonin is induced in the blue light spectrum by the light of 446 nm. [9]
There is a rush of new ophthalmic aids like intraocular lenses and spectacle lenses to protect the eye from the chemical damage. [2] The lenses are designing to reduce the spectral transmission of short-wavelength blue light by using filtering material and surface coating. These lenses have to effectively reduce the blue light hazards without disturbing the visual function of daily life. [2]
There is a study conducted between young and middle-aged adult participants were wearing three different lenses. The study suggests that there was no significant difference in sleep quality among middle-aged participants. They prefer a blue filer lens compared to the anti-reflection coating lens and brown tinted lens. Among the young participants, there were not satisfied with the brown lens due to the lens appearance and color difference compared to the anti-reflection and blue filter lens. [2]
Figure 1: Young and middle aged adult participants lens preference.
Blue-blocking spectacle lenses have obtained relatively little scientific attention. In standard spectacle lenses offer protection against UV up to 380nm and blue light transmission is reduced or eliminated by using a yellow chromophore additionally. Alternatively, applying anti-reflection interference coating for the anterior and posterior surface of the lens reduces the range of 415nm to 455nm wavelength of the blue light spectrum. This lens stays transparent to other wavelengths of visible light. Blue-blocking spectacle lenses improve sleep quality; reduce eye fatigue and symptoms of eye strain during intensive computer work. [3]
Possible drawbacks of blocking the visible light transmission of short-wavelength include disruptions of color perception and reduced scotopic tolerance which leads to poorer performance under dim lighting conditions and interruption of circadian process timing. [3] In Bipolar disorder patients, the conservation of melatonin production was proven by using blue-blockers in white-light conditions or light during the night without wavelengths below 530 nm. [10]
Light treatment has been used in clinical practice as one of the methods for relieving depression in patients with seasonal affective disorder. There are few reports that the light spectrum band affects depression. Compared with blue-filtered intraocular lens, conventional intraocular lens that produces more blue light has been shown to improve sleep and quality of life and to relieve depression in elders. Such findings indicated that blue light may have beneficial effects on depression. [11]
As an additional treatment for bipolar mania, BB glasses are successful and feasible. [10] An experiment in animals shows that deprivation in blue light exposure causes depression. It indicates an improvement in immobility time following a lack of blue light for 8 weeks. [11]
Figure 2: Effect of blue light deprivation in immobility time.
Finally, the aim is to analyze the knowledge of optical salesperson regarding blue light filter lenses. The objective is to analyze the knowledge of the salesperson about the blue light filter. Also helps to know the customer is satisfied with the explanation of the coating from the optical salesperson.
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