Uveal melanoma (UM) is the second most common major tumour of the eye globally after childhood retinoblastoma and is the primary fatal intraocular disorder in adults. UM occurs in melanocytes found within the three different regions of the uveal tract: choroid, iris and ciliary body.
It can be diagnosed at any age. However, it is much more common in middle age and later life. It has a median onset age of 55–60 years. It is comparatively rare.
It is related with especially high mortality, majorly due to a high level of metastatic liver disorder. Once liver metastasis is diagnosed, prognosis is poor. It has median survival duration between 2.2 to 12.5 months.
UM might have no early symptoms. As the tumor (cancer) grows it may cause symptoms including:
• Blurred vision
• Change in vision
• Floaters (spots that drift in your field of vision)
• Flashes of light
• Dark spot on the iris
• Variation in the shape or size of the pupil
• Variation in the position of the eyeball in the eye socket
In this article we will discuss the association between the development of uveal melanoma and blue light. To understand that link completely we will discuss:
• What is blue light?
• Can blue light promote the development of uveal melanoma?
• Role of blue light in the development of uveal melanoma
• Conclusion
• What is blue light?
Blue light is the visible light spectrum having the shortest wavelength and highest energy. Sunlight is the major source of blue light. But flat-screen televisions and LED lighting are among the man-made sources of this light.
Especially, the display screens of computers, electronic devices, smartphones and other digital devices emit considerable amounts of this light.
Almost all visible blue light passes through the cornea and lens and arrives at the retina. Studies suggest that excess exposure to blue light can damage light-sensitive cells in the retina.
This results in the changes, which look like those of macular degeneration that can lead to permanent vision loss.
As the short-wavelength, high energy blue light scatters more easily than the other visible light; therefore it is not easily focused. Looking at computer screens and other digital devices, which emit its considerable amounts can contribute to digital eye strain.
Studies have revealed that lenses, which inhibit the blue light with wavelengths less than 450 nm augment contrast extensively. So, computer glasses having yellow-tinted lenses might enhance the comfort while watching digital devices for a long period of time.
Blue light protection might be even more vital following cataract surgery. Following cataract surgery eyeglasses having lenses with a special blue light filter will be beneficial if you have a long screen time in front of digital devices.
• Can blue light promote the development of uveal melanoma?
It has been found that the lack of ocular pigmentation can be a risk factor for UM and the light iris color is connected to poor prognosis in UM patients.
An association between ultraviolet exposure and UM is seen with cutaneous melanoma. It is known from years that ultraviolet exposure attached with particular skin pigment gene polymorphisms, is an important factor in the growth of cutaneous melanoma.
However, there is no link established in UM patients. Sunlight exposures do not reveal any strong relationship with UM. While arc welding, which is a source of ultraviolet or blue light show such connection.
Arc welding generates considerable amounts of strong short-wave light. Unlike ultraviolet radiation, short-wave, supposed as blue light can contact the posterior uveal tract while holding enough energy to be deleterious to biological structures.
A considerable number of articles have reported the blue-light-mediated injury to cells derived from the retinal ganglion cell layer, retinal pigment epithelium, and other epithelia, particularly the light ranging from (425–475 nm).
Blue light can also produce the reactive oxygen species (ROS) in mitochondria, which generally causes the cell dysfunction or death.
• Role of blue light in the development of uveal melanoma
Studies have demonstrated that blue light has a mitotic effect on human UM cell lines. The cultured human UM cells exposed to this light (maximum 475 nm) considerably augmented their mitotic division rate comparative to blue-light-shielded controls. It has been revealed that shorter wavelengths of this light can encourage the retinal pigment epithelial cell death by mitochondrial-derived ROS production.
Blue light has been revealed to stimulate nuclear DNA lesions, which suggested that there is a possible mechanism for tumorigenesis. Particular nuclear DNA lesions consequential from this light have been recognized in the presence of lipofuscin, which is a photoinduced intracellular generator of ROS.
Additionally, no study has demonstrated the DNA mutations in uveal melanocytes in the blue light, in the 365–436 nm. Blue light is not directly absorbed by DNA but rather shows its effect through a photochemical interaction with melanin.
A possible scenario related to blue-light-triggered ROS-induced melanocyte mutation can be assumed as an impulsive factor resulting from UM.
Blue light might also have a role in neovascularization, which is a primary episode in the growth of solid tumors and in addition UM. A vital performer in this development is vascular endothelial growth factor (VEGF), which is a signaling protein that promotes both angiogenesis and vasculogenesis.
Hypoxia is identified to stimulate VEGF generation by UM cells and higher levels of VEGF have been seen in both the vitreous and aqueous humors of UM patients.
In addition, VEGF is a related biomarker of UM metastasis. According to study, VEGF generation in response to white light exposure can be blocked directly by inhibiting the blue light component.
• Conclusion
The experimental and epidemiological supports show that blue light is a probable risk factor for UM development. However, further studies are needed to explain the risk linked with this light and the defending potential of blue-filtering intraocular lenses after cataract surgery. As life expectancy increases people are expected to live longer following cataract surgical procedure.
Protecting your eyes from the harmful effects of blue light with the use of blue-filtering intraocular lenses is of clinical benefit as a preventive measure against the development of UM.