Prolonged work in front of computers has caused visual fatigue in many people. Nowadays, quite a number of people wear anti-fatigue lenses. However, most overlook a key detail: they assume any frame works for these lenses. In fact, specific rules apply if you want to achieve the optimal anti-fatigue effect. Let’s take a closer look.
Causes of Binocular Visual Fatigue
When the eyes focus on distant or near objects, the ciliary muscles relax and contract to adjust the thickness of the eye lens. The ciliary muscles stay relaxed for distance vision and contract for near vision. Excessive eye use or prolonged close-range viewing keeps the ciliary muscles in a sustained contracted and tense state, which may lead to accommodative spasm — namely visual fatigue.
Working Principle of Anti-Fatigue Lenses
Designed to relieve fatigue caused by continuous ciliary muscle contraction, anti-fatigue lenses adopt a principle similar to progressive lenses. They add a +0.50 D to +0.60 D accommodative power to optimize myopic diopters, restore normal minor diopter fluctuations and rebalance the eye’s accommodation system. This fully eases strain on the eyes.
To put it simply: the lens has a higher power for distance vision and a lower power for near vision, with diopters gradually decreasing from the center to the edge of the lens.
Frame Selection for Anti-Fatigue Lenses
Given the gradual diopter change across the lens surface, frame height is a critical factor. If the frame is too short, the effective visual area will be limited. Both near and distance vision will rely on the same diopter zone, and the anti-fatigue function will be largely ineffective.
For anti-fatigue lenses, the vertical height of the frame should preferably be no less than 30 millimeters. That said, an excessively tall frame is not ideal either. Always pick a suitable frame based on your own diopter.
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