What does the expiration date of a contact lens indicate?

The expiration date of a contact lens is an important indication of the timeline within which the product is safe and effective to use. It specifies the last day the manufacturer guarantees the integrity and performance of the lenses, which is critical for both the safety and health of the wearer. Using contact lenses beyond this date can lead to a breakdown in the materials, increasing the risk of discomfort, reduced vision quality, or eye infections.

The other options address different aspects of contact lens use but do not relate to what the expiration date signifies. For example, the manufacturing date would indicate when the lenses were made but does not indicate whether they are still suitable for use. The duration of lens wear refers to how long the lenses can be worn after they have been opened and does not correlate with the expiration date. The date of first use is relevant to the wearability timeline of the lenses, especially in terms of daily wear or disposal schedules, but it is not what the expiration date describes. Thus, choice A is the most accurate representation of what the expiration date indicates.