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Minimum edge thickness (MET) is the thinnest measurement allowed at the edge of a spectacle lens. This standard is set by safety regulations to make sure the lens has enough strength to resist impact and prevent cracking when it is inserted into a frame.
read more about minimum edge thickness in lenses ...Safety standards mandate a minimum thickness because the thin edge of a lens is its most fragile part. If the edge is too thin, the lens could shatter when a screw is tightened, or it could easily chip during normal wear. MET makes sure the lens is safe and durable.
For nearsighted patients (minus prescriptions), the lens is thickest at the edge. Opticians control the final edge thickness by choosing high-index materials and selecting smaller frames. This control helps reduce the visible thickness, which improves the aesthetic appearance of the glasses.
The required minimum thickness can change based on the frame type. Lenses in rimless frames (which use drill holes) or semi-rimless frames (which use nylon cord) need a slightly greater minimum thickness than lenses in full-rim plastic frames for added structural integrity.
The control of edge thickness affects the comfort of your backup glasses. A thinner lens means a lighter frame. This lightness helps make sure your backup pair is comfortable and provides relief when your eyes need a break from contact lenses.
Yes, the minimum thickness requirement for safety is generally the same across different lens materials like plastic and polycarbonate.
For standard plastic lenses, the minimum thickness is usually around 1.0 mm, but this measurement can change based on the country's specific safety guidelines.
No, for farsighted prescriptions, the center of the lens is the thickest part, and the edge is thin. MET is mainly a concern for nearsighted prescriptions.
If you have a high "minus" prescription, ask your optician about Minimum Edge Thickness (MET). If the edge is ground too thin, the lens becomes brittle and may shatter upon impact. Professionals ensure your lenses meet ANSI standards to protect your eyes from shards.
ANSI. Z80.1 Prescription Ophthalmic Lenses (ansi.org). 2024.
The Vision Council. Lens Thickness and Safety Standards (thevisioncouncil.org). 2024.
ABDO. Ophthalmic Lens Properties (abdo.org.uk). 2023.
Review of Optometry. Dispensing High-Index Lenses (reviewofoptometry.com). 2024.