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    Types of cataracts and their underlying conditions

    Causes and treatment

    CataractFigure 1. Lens anatomyA cataract is a clouding of the crystalline lens, resulting in vision loss. There are different types of cataracts, and they may be associated with underlying conditions. Understanding the differences among types of cataracts will improve clinical management of your patients.

    Cataract overview

    The crystalline lens has a biconvex shape with a central nucleus, an outer cortex, and a shell, called the capsule. The outmost layer is composed of epithelium. It is held in place by lens zonules that anchor the lens to the ciliary body. As we age, the lens grows around the nucleus, forming the cortex (Figure 1). The lens increases in size with age as the lens continues to produce lens fibers, and it is the only part of the eye that continues to grow in adulthood. The crystalline lens is made of water and protein. The protein fibers are precisely arranged in parallel such that the lens is clear, allowing light to pass through and land on the retina. As we age, degradation of proteins disrupts the array, causing a clouding of the lens. 

    Increased risk of cataract development is associated with ultraviolet light (UV) exposure, steroid use, diabetes, and smoking. This process cannot be reversed, but a healthy lifestyle may slow the progression. Avoiding UV is important, so UV protection in the form of sunglasses and hats is recommended. Not smoking or drinking excessive alcohol is also recommended, as well as maintaining tight blood sugar levels if diabetic. Antioxidant supplements have not been found conclusively to alter the progression of cataracts.  

    Symptoms associated with cataracts include cloudy or blurry vision, glare particularly at night, double vision, fading color vision, and a shift in the refractive error. As the proteins age, the refractive power of the lens changes, which may lead to a myopic shift even in the absence of other visual symptoms. This is often the first sign of cataracts.

    Nuclear sclerosis initially presents as central yellowing with opacification. Figure 2. Nuclear sclerosis initially presents as central yellowing with opacification. Cataracts are diagnosed based upon their anatomical location and appearance. If the clouding is limited to the center of the lens, it is termed nuclear sclerosis (Figure 2).

     

     

     

     

     

     

     Peripheral cortical changes do not effect vision and are simply monitored over time. Figure 3. Peripheral cortical changes do not effect vision and are simply monitored over time. If the clouding is located in the cortex, it is called a cortical cataract (Figure 3).

     

     

     

     

     

     

     

    Note the yellowing of the nucleus (nuclear sclerosis) and cortical spoking (cortical cataract) in this combined cataract.Figure 4. Note the yellowing of the nucleus (nuclear sclerosis) and cortical spoking (cortical cataract) in this combined cataract. Cataracts may occur together, and they are then called a combined cataract (Figure 4). Cataracts adjacent to the capsule are called subcapsular cataracts. Anterior and posterior subcapsular cataracts may occur in younger people because they are associated with diabetes and steroid use.

     

     

     

     

     

     

    Congential cataracts may be small opacities along the Y suture of the nucleus.Figure 5A. Congential cataracts may be small opacities along the Y suture of the nucleus. Patients may develop cataracts as babies (congenital), as children or young adults (presenile), or with typical aging (senile) (Figure 5). Cataracts may be secondary to trauma, or related to a systemic condition (see Table 1).

     

     

     

     

     

    Congenital cataractFigure 5B. Or larger, more visually significant opacification.

     

     

     

     

     

     

     

     

    Next: Diabetes and cataracts

    Tracy Schroeder Swartz, OD, MS, FAAO
    Tracy Schroeder Swartz currently practices at Madison Eye Care Center in Madison, Alabama. She serves as Education Chair for the ...

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