Which of the following disinfectant chemicals is safe to use with soft contact lenses?

Polyquaternium-1 is a safe disinfectant chemical to use with soft contact lenses. It is a type of cationic polymer that is commonly included in multipurpose contact lens solutions due to its effective antimicrobial properties. This compound is gentle on the lenses and does not cause the same level of irritation to the eyes as some other disinfectants. Furthermore, it has been shown to be compatible with the materials commonly used in soft contact lenses, preventing adverse reactions while ensuring adequate disinfection.

In contrast, the other options have been associated with potential issues when used with soft contact lenses. Thimerosal is a mercury-containing compound that can cause allergic reactions and is less commonly used today due to safety concerns. Benzalkonium chloride, while effective, can lead to lens discoloration and irritation as it is more likely to leach out plasticizers present in soft lenses. Benzyl alcohol can also be harsh on lenses and may cause discomfort or damage over time. Therefore, Polyquaternium-1 stands out as a preferred choice for safely disinfecting soft contact lenses.