Weak eyesight can occur due to refractive error (needing glasses), eye strain, dry eyes, vitamin deficiencies, diabetes, cataract, or retinal problems. Treatment depends on the exact cause, and there is no single medicine that permanently improves eyesight in all cases. Doctors may sometimes advise supplements such as Vitamin A, Lutein, or multivitamins if deficiencies are present. Limit screen strain, maintain good lighting, control blood sugar/BP, and get adequate sleep. Please consult an ophthalmologist for an eye examination and vision testing, especially if vision is worsening, associated with headaches, redness, pain, or difficulty seeing at night.