A cataract is a clouding of the eye’s natural lens, which is typically clear and helps focus light to create sharp images. When cataracts form, proteins within the lens break down and clump together, causing the lens to become opaque. This condition is a common cause of vision impairment, particularly with increasing age. While often associated with aging, cataracts can develop in various forms and due to a range of factors.
The Diverse Types of Cataracts
Cataracts manifest in several distinct forms, characterized by the location and appearance of the clouding within the eye’s lens. The most common type is age-related, which further subdivides based on the specific part of the lens affected.
Nuclear sclerotic cataracts involve the central part of the lens, the nucleus, causing it to harden and often yellow or brown over time. This type can lead to a gradual increase in nearsightedness and may cause colors to appear less vibrant. Cortical cataracts begin as wedge-shaped opacities or streaks at the edge of the lens, in the outer layer called the cortex. These opacities often resemble spokes radiating towards the center. They can scatter light, leading to glare and light sensitivity, and may affect color and depth perception. Posterior subcapsular cataracts form as a small, opaque area at the back surface of the lens, beneath its capsule. This type progresses rapidly, significantly impacting near vision and vision in bright light, often causing glare and halos.
Beyond age-related forms, congenital cataracts are present from birth. These can range in severity and may affect one or both eyes, potentially impacting a child’s visual development. Secondary cataracts can arise from other medical conditions or the use of certain medications, such as diabetes or long-term steroid use. Traumatic cataracts occur following an eye injury, like a blunt force impact or a penetrating wound. The clouding can appear immediately or develop over time. Radiation cataracts, though less common, result from exposure to certain types of radiation, including ultraviolet light or medical radiation therapy.
Factors Contributing to Cataract Development
Aging is the primary and most common factor contributing to cataract development, as proteins within the eye’s lens naturally break down and clump together, leading to cloudiness. This process typically starts around age 40, though symptoms may not become noticeable until much later. The lens also becomes less flexible and thicker with age, further contributing to vision changes.
Certain medical conditions significantly increase the risk of cataract formation. Diabetes, for example, can lead to cataracts at an earlier age due to high blood sugar levels causing structural changes in the lens. Elevated glucose levels can lead to sorbitol accumulation within lens cells, altering lens protein structure and promoting clouding. Other conditions like eczema and certain genetic disorders, such as neurofibromatosis type 2 and myotonic dystrophy, are also associated with an increased risk.
Medications, particularly long-term use of corticosteroids, contribute to cataract development. Eye injuries, whether blunt trauma, penetrating trauma, or chemical burns, can directly damage lens fibers and lead to traumatic cataracts. The injury’s severity often dictates how quickly the cataract forms.
Exposure to radiation, including prolonged ultraviolet (UV) light from the sun, can also accelerate cataract formation. Genetic factors play a role, with a family history of cataracts increasing an individual’s risk. In cases of congenital cataracts, genetic mutations are often the underlying cause. Lifestyle choices, such as smoking and excessive alcohol consumption, are also identified as risk factors.
Recognizing the Indications of Cataracts
Recognizing the signs of cataracts involves observing various changes in vision that can impact daily life. One common indication is vision that appears cloudy, blurry, foggy, or filmy, making it feel as though one is looking through a dirty or frosted window.
Difficulty seeing clearly at night is another frequent symptom, often manifesting as trouble with night driving. Individuals may notice halos or streaks around lights, such as streetlights or oncoming headlights. Increased sensitivity to light and glare can also occur, making bright sunlight or indoor lighting uncomfortable.
Cataracts can cause colors to appear faded, dull, or yellowed, impacting the vibrancy of the visual world. Frequent changes in eyeglass or contact lens prescriptions may also signal the development of cataracts, as vision steadily worsens. In some instances, people with cataracts may experience double vision in one eye.