By Linda Conlin, ABOC, NCLEC
One of the functions of the eye’s ciliary muscle is to control accommodation for viewing objects at varying distances by changing the shape of the crystalline lens. When the ciliary muscles are relaxed, the lens is thinner and flatter for distance viewing. When they contract, the lens becomes rounder for near vision. But what about the in-between of focusing on a computer screen or digital device? The ciliary muscle is neither fully relaxed nor fully contracted. I once heard the condition of the ciliary muscle for intermediate vision described as trying to hold your ankles two inches off the floor while lying down... most of us can’t do it for very long! Still, we spend hours every day staring at screens with a consequence to our eyes.
In addition to focusing strain, use of digital devices for extended periods of time has other effects. Digital eye strain describes a group of eye and vision-related problems that result from prolonged computer, tablet, e-reader and cell phone use. Symptoms include headaches, blurred vision, dry eyes, and neck and shoulder pain. Digital device users may also experience visually induced trigeminal dysphoria, which results from eye misalignments. In an attempt to compensate for the misalignment of the eyes, the visual system becomes overworked and strained with prolonged digital device use, leading to trigeminal nerve overstimulation and the uncomfortable symptoms of digital eye strain.
Tip: Subtle misalignments of the eyes must be detected and measured before they can be effectively treated. The Neurolens Measurement Device uses advanced eye-tracking technology to accurately measure the degree of ocular misalignment. The misalignment can then be treated with Neurolenses, customizable contoured prism lenses that gradually increase the prism from distance to near.
In some cases, individuals who do not require the use of eyeglasses for other daily activities may benefit from glasses prescribed specifically for computer use. Eyecare practitioners are noticing an increased number of consultations for both school age children and pre-presbyopic groups who are emmetropes with normal accommodative amplitude. For children and students, the eye strain, visual fatigue and blurred vision both near and far after near tasks are the most common complaints. This is due to the continued effort to maintain the accommodative state needed for visual device use.
Tip: Lenses that have the distance power for everyday use, or plano for emmetropes and a “boost zone” at the bottom of the lens, are available from major lens manufacturers. This boost zone is an area with an increased amount of relaxing power, which reduces eye strain during prolonged up-close activities such as looking at digital screens, reading or any “near task” activities. The eye muscles relax and focus more easily for better visual comfort.
When viewing electronic devices, defocused blue light results in digital eye strain. Blue light is myopically defocused, creating a blur circle on the retina surrounding the in-focus green component of visible light. This results from longitudinal chromatic aberration (LCA) and can degrade visual quality. Artificial lighting and bright blue-rich digital screens expose eyes to light levels that can disturb the normal sleep cycle by disrupting the circadian rhythm. Blue light is especially problematic for young adults and teens who use their devices in bed, scrolling through social media or just browsing the web.
Certain wavelengths of blue light are beneficial, however. Blue-turquoise light in the wavelength range of roughly 465 to 495 nm has been identified as beneficial in the regulation of our circadian biorhythms. The challenge facing the ophthalmic optics industry is to find the right balance between protecting the eyes from harmful light while allowing the essential light to reach the retina for vision and circadian entrainment.
Tip: Major lens manufacturers have developed technologies that deflect and absorb blue light, using coatings and in-mass technology while allowing beneficial wavelengths. Some manufacturers have new formulations to improve the level of protection and the aesthetic look of blue-filtering lenses.
Digital devices are here to stay. As the research continues, we’ll learn more about the impact of screen time on eyes and vision. As eyecare providers, we may be the front line for awareness of the effects of excessive screen time, so we need to be informed about the resources to address the issue.
