You should discard soft contact lenses when they expire. Soft contact lenses are medical devices that must be sterilized and packaged in sealed containers before being sold to eye doctors and consumers. Since they touch the eye, they have the potential to harm the eye if they are contaminated.
Just as packaged foods display an expiration date, so do packaged medical devices, as a consumer protection measure.
Contact Lens Expiration Date
Though soft lenses are sealed in an airtight container, it's possible that over time the seal of the container can become compromised, possibly leading to contamination of the saline solution and lens inside.
The expiration date on the lens package indicates the last month and year that the container should be considered free from contamination and the lenses inside safe to wear.
It is not unusual for the expiration date of a soft contact lens to be four years from the date the lens was manufactured and packaged.
Generally, the expiration date on contact lens packaging is written in a yyyy/mm format. For example, an expiration date of 2021/08 means the lenses should be considered safe for wear until the end of August 2021.
Soft Contact Lens Packaging
Most soft contacts sold today are packaged individually in small, plastic "flat pack" containers with a sealed foil cover. The containers usually are filled with non-preserved buffered saline (salt water) and a wetting agent to keep the lens fully hydrated.
For cost and weight reasons, these plastic containers are much more common now than the traditional glass vials that once were the predominant packaging method for soft lenses.
The foil cover of soft contact lens containers typically displays the following information:
Contact lens brand name
Lens material name
Name of manufacturer
Base curve of lens
Other information also may be included, such as the CE mark (mandatory for lenses sold in countries of the European Union and European Economic Area) and the location where the lens was made.
Gas Permeable Contact Lens Packaging
Unlike soft contact lenses, rigid gas permeable contacts generally are shipped dry from the manufacturer to the eye doctor. Also, gas permeable (GP) lenses are made-to-order and customized to the wearer's eye shape and prescription with a lathe-cutting process.
For these reasons, there is no risk of GP lenses becoming contaminated from being kept in a fluid-filled container for long periods of time. Therefore, gas permeable contacts typically don't require an expiration date.
Contact Lens Prescription Expiration Date
The expiration date on your contact lens prescription is the last date that your eye doctor has authorized you to purchase new contacts with the prescription.