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First of all, we have to take care of itching and watering, and for that, you have to start Moxifloxacin eye drop four times a day for five days and Refresh Liquigel eye drop (Carboxymethylcellulose sodium) six to eight times a day. It can be continued for a long time as it has no side effects.
Now coming to the blinking part, blinking is a response that is to be carried out by both conscious and unconscious mind. You are saying that unconscious blinking has reduced. For diagnosing the problem, we have to conduct a cotton wisp test by an ophthalmologist by which we can check the child's corneal sensation because if the corneal sensation is reduced, it can lead to reduced blinking.
Also, while you are at the doctor's, you can have him rechecked for glasses to see whether the prescription for glasses has changed or not because that can lead to watering. Spending more time on mobiles and laptop can cause reduced blinking. So, please look into it.
For more information consult an eye care ophthalmologist online --> https://www.icliniq.com/ask-a-doctor-online/eye-care-ophthalmologist