Weaker vision in one eye should not be treated with eye drops without knowing the cause, because it may be due to refractive error (glasses number difference), cataract, lazy eye, retinal problems, optic nerve issues, infection, or glaucoma. Most causes of reduced vision are not corrected by routine eye drops. Lubricating drops such as Carboxymethylcellulose may help only if dryness or irritation is present. Please consult an ophthalmologist for proper vision testing and eye examination, especially if the weakness is increasing, sudden, associated with pain, redness, headache, flashes, or floaters.