Antimicrobial resistance in frequent lens user is due to-
(Refer: AK Khurana Comprehensive Ophthalmology, 6th edition, pg no. 50)

The contaminated contact lens provides Psuedomonas aeruginosa an idea site for attachment and biofilm production
Continuous contact of the eye to the biofilm-infested lens can lead to serious ocular diseases, such as keratitis (corneal ulcers)
The biofilm also prevent effective penetration of the antibiotics, which increase the chances of antibiotic resistance
Biofilm formation
Improper handling
Unhygienic formation
Low potency of antibiotics