Types of Cataracts

Nuclear cataract

This form of cataract is the most common in the United States. It begins centrally in the lens and grows outward toward the periphery. As the cataract grows, or becomes more dense, the lens also becomes larger. These changes in the lens directly lead to changes in your glasses prescription, because the changes that occur in your lens cause light to be refracted, or bent, differently. The way in which your eye focuses or bends light determines your individual refraction, or prescription. In the early stages of cataract formation, you may be able to restore normal vision with an updated or new glasses prescription. Some patients will even notice that they have improved ability to read without their glasses. This is because the majority of cataracts cause myopia, or nearsightedness, which allows you to focus close for activities such as reading, sewing, etc. Then, as a cataract progresses, the lens will lose its ability to focus light, and the light rays will actually scatter within the eye. As the cataract becomes more dense, more light will scatter, and vision will become increasingly blurry.

Initially, a nuclear cataract takes on a yellowish hue, whereas advanced cataracts are brown, or sometimes even white. The more advanced brown (brunescent) and white (mature) cataracts are typically associated with significant decreases in vision. They are also more complicated to remove, so it is preferable not to allow your cataract to progress to this point.

Figures 5.1 and 5.2: Illustrations showing a nuclear cataract centrally located within the lens.

Cortical cataract

This type of cataract starts at the periphery and then moves into the center. In the early stages, when the cataract is located peripherally, it tends not to affect vision. As the cataract grows centrally, it will have an increasing impact on vision, and when it encroaches on the central visual axis, it can cause significant drops in vision. Patients with this type of cataract are more likely to suffer from glare, and may notice marked changes in vision in different lighting conditions.

Figures 5.3 and 5.4: Illustrations showing a cortical cataract peripherally located in the lens.

Posterior Subcapsular Cataract

Posterior subcapsular cataracts (PSCs) can be due to age-related changes. They are also frequently seen in the settings of trauma, diabetes, steroid use, inflammation inside the eye (uveitis), and a few other less common medical conditions. This type of cataract most commonly begins centrally, and patients with this type of cataract can be very symptomatic, even in the early stages of its development. PSCs occur in the back layer of the lens.

Figures 5.5 and 5.6: Illustration of a posterior subcapsular cataract centrally located in the back layer of the lens.

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