A different prescription is often needed for computer glasses because standard distance or reading prescriptions are not optimized for screen use. Prolonged work at a computer screen frequently leads to Digital Eye Strain (DES) or Computer Vision Syndrome (CVS). This discomfort results from the specific distance at which people view their monitors, a range poorly corrected by general-purpose eyewear.
Understanding the Intermediate Working Distance
The human visual system focuses across three zones: distance, near, and intermediate. Standard prescriptions are optimized for far vision (driving) or near vision (reading, typically 14 to 16 inches). The computer screen distance falls into the intermediate zone, which is distinctly different from the other two.
Most monitors are positioned between 20 and 28 inches away, requiring specific focusing power. Wearing a standard distance prescription forces the eyes to strain their focusing mechanism, called accommodation, to achieve sharp focus. Conversely, using standard reading glasses at this greater distance causes the screen to appear blurry, often leading to awkward posture.
This uncorrected strain causes the fatigue associated with DES. To correct this, the prescription power must be calculated based on the individual’s habitual working distance. An optometrist measures the distance between the user’s eye and the monitor to determine the precise lens power needed for clear, effortless vision. Correcting this intermediate zone is the fundamental purpose of computer glasses.
Specialized Lens Designs for Digital Screens
Once the correct intermediate power is determined, several specialized lens designs are available to deliver that correction.
Single Vision Computer Glasses
These lenses are ground with one power tailored specifically for the intermediate screen distance. They provide the widest, clearest field of view for the monitor. However, objects at near reading distances and far distances will appear blurry, requiring the glasses to be removed when the user looks away from the screen.
Occupational Progressive Lenses
Often called computer progressives, these are multifocal lenses that prioritize the intermediate and near zones with a very wide corridor for screen viewing. They are ideal for users who need to see the screen and reference documents or interact with people nearby. Unlike standard progressive lenses, which prioritize distance vision, occupational progressives offer a much larger intermediate viewing area, often sacrificing clear distance vision at the top.
Bifocals or Trifocals Optimized for Computer Use
These designs place the intermediate correction in the main or upper segment of the lens. In a computer bifocal, the upper segment is adjusted to correct for the screen distance, unlike traditional bifocals where the top is for distance. If a trifocal is used, the intermediate power may occupy the large middle section, with a small reading segment placed below it. This offers a structured solution for users who prefer distinct focal zones.
Enhancing Comfort with Lens Coatings and Filters
Non-prescription additions can enhance visual comfort for extended screen use.
Anti-Reflective (AR) Coating
An AR Coating is a thin, multi-layered treatment applied to the lens surfaces. This coating reduces glare and reflections from the computer screen and overhead lighting, which cause visual distractions and increase eye fatigue. By eliminating reflections, AR coatings allow more light to pass through the lens, improving visual clarity and contrast, making fine text easier to read.
Blue Light Filter
A Blue Light Filter is often integrated into the AR coating or the lens material. Digital screens emit high-energy visible (HEV) blue light, and filtering a portion of this light can reduce perceived eye strain and fatigue. Although scientific consensus is still developing regarding the long-term retinal effects of blue light, many users report subjective improvements in comfort when using these filters.