Visual pathology encompasses various medical conditions affecting the visual system, each with distinct characteristics and implications for vision. A cataract refers to an opaque or cloudy lens that impairs vision by reducing the transparency necessary for light to pass through clearly. This cloudiness obstructs the eye’s ability to focus, leading to blurred or dim vision.
A chalazion is a firm, painless cyst that forms on the eyelid due to blocked oil glands. Unlike infections, this blockage causes swelling without pain. In contrast, a hordeolum or stye is a painful cyst resulting from an infected eyelid gland, often presenting as a tender lump. The key difference lies in the presence of infection, which causes pain in a hordeolum but not in a chalazion.
Strabismus is a condition characterized by misaligned eyes, commonly known as being cross-eyed. It typically arises from weakness in the eye muscles, causing the eyes to deviate inward, outward, upward, or downward. This misalignment is most frequently observed in children and can affect depth perception and binocular vision.
Myopia, or nearsightedness, is a refractive error where distant objects appear blurry while close objects remain clear. This occurs because the eye focuses images in front of the retina rather than directly on it. The term derives from "my," meaning to shut, reflecting the squinting often used to see distant objects more clearly, and "opia," meaning a vision condition.
Retinitis pigmentosa is a chronic, progressive degeneration of the retina, particularly affecting the rod cells responsible for vision in low light and peripheral vision. As these rods perish, individuals experience gradual vision loss, often leading to blindness. This condition impairs the ability to see in dim lighting and reduces gray tone perception, significantly impacting night vision.