Which preservative is noted for being the least likely to cause discoloration in contact lenses?

The least likely preservative to cause discoloration in contact lenses is Trimethoprim. This preservative is often utilized because it has a relatively low potential to interact with the materials that comprise various types of lenses, thus minimizing any risk of staining or color change.

In contrast, substances like Thimerosal can lead to discoloration; this is often due to its chemical composition, which can react with the lens material. Similarly, Hydrogen peroxide, while effective as a disinfectant, can also affect certain lens materials and lead to undesirable color changes if not neutralized properly. Sorbic acid, although effective as a preservative in many applications, can also have a negative impact on lens materials, particularly if the concentration is not carefully managed.

Trimethoprim stands out in this context because of its compatibility with contact lens materials, making it a safer choice for preserving lens integrity and appearance over time.