Final answer:
Chloroquine is the drug associated with turning the sclera blue as a side effect. Cyclospora cayetanensis appears with a blue halo under UV microscopy, which is unrelated to the effect of chloroquine.
Step-by-step explanation:
The question asks which drug can cause the sclera of the eye to turn blue as a side effect. The correct answer is Chloroquine, an antimalarial drug that can have such a side effect with long-term use. Although not as common, Tamoxifen, which is used for treating and preventing breast cancer, has also been reported to cause ocular side effects, but turning the sclera blue is not typically one of them.
In the context provided by the reference information, Cyclospora cayetanensis is the protozoan that has a unique appearance with a blue halo when viewed using ultraviolet fluorescence microscopy. Acanthamoeba infections, relevant to the reference information, are typically acquired through contact with contaminated water and can cause Acanthamoeba keratitis. This eye infection is treated with a combination of chlorhexidine and polyhexamethylene biguanide. None of these points directly pertain to the original question regarding drugs that turn the sclera blue.