Cataract types
Cataracts come in three types: nuclear sclerotic, cortical, and posterior subcapsular. You may have just one of these types, or a combination of them.
Nuclear sclerotic cataracts. These are the age-related type of cataract that ophthalmologists see most often. They cloud the nucleus, or center of the lens, turning it yellow and then eventually brown. As the cataract darkens, it hardens. (“Sclerosis” is a medical term for hardening.)
Because nuclear sclerotic cataracts grow very slowly, several years might pass before you notice any changes to your vision. Distance vision is typically the first to fade. Close-up vision may improve temporarily because of myopic shift, a phenomenon sometimes referred to as “second sight.” Eventually, the darkening of the lens will reduce your ability to distinguish details and colors.
Cortical cataracts. This type is characterized by areas of clouding of the cortex, or outer layers, of the lens. The cloudy areas look like white spokes on a wheel. The spokes first appear at the edges of the lens under the iris and then extend into the center of the pupil. These white spokes scatter light.
Diabetes increases the risk for cataracts (especially cortical cataracts) up to fivefold, particularly among people who have lived with the disease for a long period of time and in those with poor blood sugar control. The clouding also appears at an earlier age than usual. When blood glucose is high, sugar accumulates on the lens, damaging and changing the structure of the lens over time, leading to the cortical spoking pattern of cloudiness.
The main cortical cataract symptoms are glare, which can make it hard to drive at night, and blurred vision. Glare may interfere with depth perception, making it hard for you to discern your distance from objects and people.
Posterior subcapsular cataracts. This type of cataract begins as a small spot on the back surface (posterior) of the lens, just underneath the lens capsule, a clear membrane that surrounds the lens. A posterior subcapsular cataract causes halo effects and glare in bright sunlight or around lights in the dark. It progresses much more quickly than the other cataract types—over a period of months rather than years. It may degrade vision drastically in some situations, but not in others. You’re more likely to have this type of cataract if you have diabetes or take steroid medicines.