Cataracts can be classified according to their cause or the area of opacity in the crystalline lens.
Senile cataracts are the most common and they are age-related.
Metabolic cataracts are associated with metabolic illnesses. The most common is diabetes mellitus.
Congenital cataracts exist from birth or develop over the first few months of life. They may be associated with genetic conditions or a disease suffered by the mother during pregnancy like rubella or toxoplasmosis.
Traumatic cataracts occur after experiencing eye trauma.
Toxic cataracts are associated with chronic use or abuse of some drugs or toxic substances, corticoids being the most common causal element.
Furthermore, depending on the area affected by the opacified crystalline lens, we can distinguish between:
Nuclear cataracts, in which the nucleus or centre of the crystalline lens in particular becomes opaque. A nuclear cataract usually evolves slowly and affects farsight more than nearsight. They are the most common and are usually associated with age.
Cortical cataracts are cataracts where the cortex or lens cover becomes opacified. They are less common than nuclear cataracts and affect nearsightedness.
Posterior subcapsule cataracts
Posterior subcapsule cataracts, which develop in the outermost layer of the crystalline lens: the posterior lens capsule. This type usually progresses quite quickly and a common symptom is glare.
Careful observation and description of cataracts in a slit-lamp exam is key in drawing up an ophthalmic clinical history for each patient. On one hand, it enables the progression of the cataract from one visit to the next to be evaluated. On the other hand, the type and grade of the cataract determine the most appropriate choice of surgical technique used to remove it, and warn of the possible intraoperative risks inherent to each type.