Treatment of contact lenses with aqueous solution comprising a biguanide disinfectant and a complementary phosphate-borate buffer system

A method of disinfecting or cleaning and disinfecting a soft contact lens with a multi-purpose solution or effective multipurpose solution, which method comprises the steps of:

• (a) treating the lens by soaking said lens in an ophthalmically safe solution, such that acceptable disinfection of the contact lens is obtained within a minimum recommended soaking period, the solution having a pH of 5 to 8 and comprising, in formulation, the following components:
• (i) a germicidally effective amount of at least one biguanide germicide, and
• (ii) a buffering system comprising 0.004 M to 0.2 M of a first buffer component selected from the group consisting of phosphoric acid, salts thereof, and mixtures thereof, in combination with 0.02 M to 0.8 M of a second buffer component selected from the group consisting of boric acid, salts thereof;
• and mixtures thereof, such that the combination of the first and second buffer component provides a buffering capacity of 0.01 to 0.5 mM of 0.01 N of HCl or 0.01 to 0.3 mM of 0.01 N of NaOH to change one liter of solution one pH unit,
• (iii) an effective cleaning amount of a non-ionic surfactant;
• and
• (b) directly placing the treated lens on an eye of a wearer, such that (i) rinsing with a different solution prior to placement on the eye is not required, and (ii) no other solution is required for daily cleaning of the lens.