Final answer:
The exact percentage of individuals aged 50 and older in the contact lens market cannot be determined based on the provided information.
Step-by-step explanation:
The question asks about the percentage of contact lens (CL) wearers who are 50 years old and older. According to the provided information, the prospective US contact lens market is expected to increase to 34 million over the next decade.
The single largest age component of this group will be individuals aged 50 and older. However, the precise percentage of this group out of all contact lens wearers by 2018 is not specified. Therefore, we cannot determine the exact percentage based on the given information.