Final answer:
A severely clouded lens causes a condition called cataracts, where light entering the eye is improperly focused, leading to impaired vision. Vitamins A and C may help prevent cataracts, and precise parallel laser light is used in surgeries to repair retinal tears.
Step-by-step explanation:
A severely clouded lens causes a chronic eye condition known as cataracts. This cloudiness in the lens of the eye disperses or diffuses light, preventing sufficient light from reaching the retina and leading to vision impairment or blindness. Vitamins A and C may help protect against cataract formation. A cataract causes light to be focused in front of the retina, which is a symptom of another common vision problem known as myopia (nearsightedness). Conversely, hyperopia (farsightedness) occurs when light is focused behind the retina due to insufficient power in the lens or when the eye is too short. When repairing a tear in the retina with laser surgery, it is necessary for the laser light to enter the eye as parallel rays to ensure precise focusing and effective spot-welding of the retina.