There is no direct relation with cough and cataract....but when you put drops it enter in throat via nasolacrimal duct....which some time leads to coughing in pateint
Next Steps
when putting drops press on nasal side (lower puncta) this will prevent medication coming in throat leading to cough
Health Tips
Search on" punctual occlusion" after adding drops on Google....will help you clear your doubts more clearly