Brief Answer: Around one month. Detailed Answer: Hello, Thanks for trusting us with your health concern. When you first start with trifocal non progressive lenses there will be a short period of time where your judgements of distance will be effected. You may feel a little disoriented and off balance. This should resolve completely within the first month if you wear the lenses consistently. It is recommended that you wear your new lenses full time until you make the adjustment. Please feel free to discuss further. I will be glad to answer the follow up queries that you have. Wishing you good health. Regards. Dr. Rakhi Tayal. For future query, you can directly approach me through my profile URL http://bit.ly/Dr-Rakhi-Tayal

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