Extralube eye drops and Moxigram eye drops are very different medicines and are not interchangeable. Moxigram contains moxifloxacin, which is an antibiotic used to prevent or treat infection after eye surgery. Extralube contains sodium carboxymethylcellulose, which is a lubricating drop used to relieve dryness and irritation. After lens surgery, antibiotic eye drops are important because the eye is more vulnerable to germs while it heals. Using only lubricating eye drops instead of the prescribed antibiotic may increase the risk of infection and delay recovery. If you have accidentally bought Extralube, it may still be used if your father feels dryness in his eyes, but it should not replace the prescribed Moxigram drops. Please continue the antibiotic drops exactly as advised by your father?s eye surgeon. If there is any confusion or missed doses, consult his doctor or pharmacist promptly.