Provide a valuable resource to your clients or customers by linking to this resource page. Just place the following link on your website.
Stress cracks are tiny fractures that appear on the edge of a spectacle lens and move inward from the perimeter. These cracks are usually caused by excessive pressure placed on the lens when it is mounted into a frame.
read more about eyeglass lens stress cracks ...The main cause is concentrated mechanical tension. This happens when the frame is assembled too tightly, or when the lens is cut to a size that is slightly too large for the frame. The constant inward pressure forces the lens material to break.
Stress cracks are most common in rimless (drill-mount) and semi-rimless (nylor groove) frames, as these styles involve direct contact and tension on the lens edge. Full-rim frames are less susceptible because the rim supports the lens circumference evenly.
Prevention involves precision. Technicians must cut the lens to the perfect size (not too tight), use cushioning material (like rubber bushings) in drill mounts, and use only the specified tension of the nylor cord in semi-rimless frames.
Stress cracks significantly compromise the lens's integrity, making it fragile and susceptible to catastrophic failure. Once a crack starts, it will slowly grow inward until the lens breaks completely, requiring immediate replacement.
No, once a stress crack begins, the lens must be replaced, as the structural integrity is compromised.
Yes, rimless frames are highly prone to stress cracks due to the direct pressure applied at the drill holes.
No, a hard coat prevents surface scratches. Stress cracks are caused by internal pressure at the edge of the lens.
If you see tiny "feathers" or cracks near the screws of your rimless glasses, the lens is under too much "hoop stress." This is a safety hazard. An optician should replace the lens and use specialized "bushings" to prevent the hardware from touching the lens material directly.
AAO. Eye Safety and Protective Eyewear (aao.org). 2024.
Review of Optometry. Stress in Ophthalmic Lenses (reviewofoptometry.com). 2023.
The Vision Council. Rimless Mounting Procedures (thevisioncouncil.org). 2024.
ABDO. Glazing Rimless Frames (abdo.org.uk). 2024.