Weak eyesight is most often associated with either nearsightedness (called myopia) or farsightedness (called hyperopia). Factors like genetics, poor nutrition, aging and excessive strain on the eyes usually contribute to these conditions. The most common symptoms of weak eyesight are blurry vision, frequent headaches and watery eyes. Be sure to consult your doctor for proper diagnosis and treatment. At times, eye problems can be caused by serious issues like glaucoma, macular degeneration, cataracts and optic neuropathy.