How effective are this contact lens?

Probably OK: Contact lenses are released after careful design and clinical trials. They should be comfortable, stable and give good vision. Most succeed in this and can be considered in this case to be effective. If you have discomfort or poor vision, then you need a refit.

For what?: Contact lenses are often used to help people see better. They are also used as a bandage over the eye to promote comfort and healing. They usually work well in both instances. To give you more information, we would need to know more details.