This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Pharmacology), Subject name: Pharmacology
A patient, diagnosed with rheumatoid arthritis, was on medications. After 2 years, developed blurring of vision and was found to have corneal opacity. Which of the following drug most likely causes that? 
Select and explain. 
A. Sulfasalazine, B. Chloroquine, C. Methotrexate, D. Leflunomide
B: Chloroquine
Answer: B: Chloroquine 
Explanation: Salient Adverse Effects of DMARD's:DrugAdverse effectsGold* Diarrhea* Taste disturbances* Alopecia* DermatitisLeflunomide* Diarrhea* Hypokalemia* Weight loss* Alopecia* Increased incidence of respiratory infections* Raised liver enzymesNatalizumab* Progressive multifocal leukoencephalopathyMethotrexate* Bone marrow depression* Mucositis* Hepatotoxicity* Increased incidence of respiratory infectionsSulfasalazine* Neutropenia* Thrombocytopenia* Hepatitis* Reversible infertility in maleChloroquine* Bull's eye retinopathy* (Less with hydroxychloroquine)* Rash* Greying of hair* Irritable bowel syndrome* Myopathy and Neuropathy