Final answer:
A cataract is a clouding of the eye's lens, leading to dispersed or diffused light and impaired vision. Surgery often involves replacing the clouded lens with an intraocular lens (IOL) to restore vision, requiring careful selection of IOL power based on prior refractive errors such as nearsightedness or farsightedness.
Step-by-step explanation:
A cataract is a condition characterized by cloudiness or opacity in the lens of the eye, significantly impacting the ability of the eye to focus light. Over time, cataracts can develop due to multiple factors, including age, UV exposure, and nutritional deficiencies, particularly in vitamins A and C, which are thought to help protect against the formation of cataracts. When cataracts become so severe that they impair vision to a significant extent, they are considered clinically significant. This level of severity often necessitates surgical intervention, where the clouded lens is replaced with an artificial intraocular lens (IOL) to restore clear vision.
When light passes through a cataract-clouded lens, it becomes dispersed or diffused, resulting in blurred or diminished vision. A clear, healthy lens focuses light precisely onto the retina, but cloudiness alters this process. Furthermore, in certain eye surgeries such as fixing a retinal tear with laser spot-welding, it is crucial to use parallel rays of light to ensure precise and controlled delivery of energy to the retina without damaging surrounding tissues.
Patients with cataract removal often require glasses with approximately 16 diopters (D) if an intraocular lens is not implanted, to compensate for the focusing power the natural lens provided. However, with modern advancements, a cataract-clouded lens can be replaced with an IOL tailored to provide good distant vision. The power of the IOL chosen will depend on whether the person was previously nearsighted or farsighted, to ensure the correct refraction is achieved post-surgery.