You can notice vision improvement immediately after wearing Ortho-k lenses. You may notice it within a few minutes. It is very significant within two hours. Some patients see clearly in as little as one night of wearing OrthoK retainer lenses. Vision is normally good during all waking hours within the first week. In some patients with higher prescriptions, it can take two to four weeks to achieve good vision. Because children's eyes are more easily molded, vision improvement generally takes effect more rapidly than it does for adults. At times the eye will not respond to the original design as expected and your doctor will need to change the design to achieve optimal results.
You can feel noticeable improvement after after the first night of wearing ortho-k lenses. But to maintain stable vision, you still to need wear them for years. Once you stop wearing them, your vision may decrease. But you don't need wear them every night, one or two nights in a week is enough to give you good vision in the day.
Ortho-k contact lenses are designed to wear at night during sleep. And you should remove them the next morning when you get up. How long should you wear them depending on the degree of your nearsightedness or astigmatism and other factors. Some people will get a significant improvement after the first night of wearing them. However, they should continue to wear them to maintain the good vision. Some people may get stable 20/20 vision after a few weeks of wearing the ortho-k lenses at night.