My mom had been operated for cataract on her left eye. after 5 months of surgery her eye is irritated since she put eye drops for dilation today. why?

Irritation: It's not uncommon to experience mild ocular surface irritation following an eye exam, especially when diagnostic eye drops are instilled. Infrequently corneal abrasions can occur after iop checks. Dilating drops are also culprits for chemical irritation, that can be more noticeable in folks with dry eye or surface diseases. Her symptoms should fade quickly. Try preservative free eye drops/call md.

Dry eye: The most common cause of this issue is dry eye. Try using artificial tears during the day, ointment before bedtime, warm compresses, and fish oil supplements orally. If persistent symptoms, go see an eye doctor for further evaluation and treatment.

Eye irritation: May be related to her dilating drops. Because it's been so long since her cataract surgery, it's most likely not related to that. For now, she should try using some artificial tears to see if her symptoms improve. If they persist, then she should see her eye doctor.