What is a Cataract?
A cataract is a progressive opacification of the crystalline lens inside the eye. The lens, normally transparent, is composed of water and precisely arranged protein fibers (crystallins) that allow light to pass through and focus on the retina. With age or due to other factors, these proteins begin to clump together and denature, creating cloudy areas that scatter light and reduce the clarity of the image reaching the retina. Cataracts can affect one or both eyes and typically develop slowly over months to years. The three main types based on their location within the lens are nuclear sclerotic cataracts (most common, affecting the center), cortical cataracts (affecting the periphery with spoke-like opacities), and posterior subcapsular cataracts (forming at the back of the lens, often progressing more quickly). Cataract surgery, in which the clouded lens is replaced with an artificial intraocular lens (IOL), is one of the most commonly performed and successful surgical procedures in the world.
Symptoms
- Gradual blurring or dimming of vision
- Increased sensitivity to glare, especially from headlights at night
- Fading or yellowing of colors
- Frequent changes in eyeglass or contact lens prescription
- Double vision in one eye (monocular diplopia)
- Difficulty reading or performing fine tasks in low light
- A halo effect around lights
- Temporary improvement in near vision ("second sight") in early nuclear cataracts
Causes and Risk Factors
The most common cause of cataracts is age-related degeneration of the lens proteins. By age 80, more than half of all people either have a cataract or have undergone cataract surgery. Additional risk factors include:
- Prolonged exposure to ultraviolet (UV) radiation
- Diabetes mellitus
- Smoking and excessive alcohol consumption
- Long-term use of corticosteroid medications
- Previous eye injury or surgery
- Family history of early cataracts
- High myopia
- Exposure to ionizing radiation
Diagnosis
Cataracts are diagnosed through a comprehensive eye examination. A visual acuity test measures how well you see at various distances. Slit-lamp biomicroscopy allows the ophthalmologist to examine the lens under high magnification and identify the type and extent of opacification. A dilated fundus examination is performed to rule out other causes of vision loss such as macular degeneration or diabetic retinopathy. Biometry (measuring the eye's length and corneal curvature) is performed preoperatively to calculate the appropriate power of the intraocular lens implant.
Treatment
The only definitive treatment for cataracts is surgical removal. In the early stages, updated eyeglass prescriptions, magnifying lenses, and improved lighting can help manage symptoms. When cataracts significantly impair daily activities, surgery is recommended:
- Phacoemulsification — the most common technique, using ultrasound energy to break up the clouded lens through a small incision, followed by aspiration and IOL implantation
- Femtosecond laser-assisted cataract surgery — uses a laser for key steps of the procedure, offering added precision
- Extracapsular cataract extraction (ECCE) — used in very advanced or dense cataracts requiring a larger incision
- Choice of IOL — monofocal, multifocal, extended depth of focus (EDOF), or toric lenses for astigmatism correction
Surgery is typically performed under local anesthesia on an outpatient basis, and most patients experience significant visual improvement within days.
Prevention and Recommendations
- Wear sunglasses with 100% UV protection when outdoors
- Stop smoking and limit alcohol consumption
- Maintain good control of diabetes and other systemic conditions
- Eat a diet rich in antioxidants — leafy greens, fruits, and colorful vegetables
- Have regular eye examinations, especially after age 50
- Discuss the risks of long-term corticosteroid use with your physician
- Protect your eyes from injury with appropriate safety eyewear