Cataract

Definition

Cataract is the opacification of the lens of the eye, leading to progressive visual impairment. It can be age-related, congenital, traumatic, or secondary to systemic diseases or medications.

Epidemiology

• Leading cause of reversible blindness worldwide
• Incidence increases with age; most common in individuals over 60 years
• No significant gender predilection, though some studies show slightly higher prevalence in women
• Risk factors include age, diabetes, smoking, UV exposure, corticosteroid use, and ocular trauma
• Congenital cataracts are rare but significant cause of childhood blindness

Etiology

• Age-related (senile) cataracts most common
• Congenital: genetic mutations, intrauterine infections, metabolic disorders
• Traumatic cataracts due to blunt or penetrating injury
• Secondary cataracts from diabetes mellitus, uveitis, prolonged corticosteroid use
• Radiation or chemical exposure

Pathophysiology

• Lens epithelial cell damage leads to protein aggregation and lens fiber opacification
• Oxidative stress contributes to lens protein denaturation and cataract formation
• Disruption of lens transparency results in light scattering and decreased visual acuity
• Age-related changes include lens sclerosis and yellowing
• Diabetic cataract involves osmotic stress from sorbitol accumulation in lens fibers
• Trauma induces lens fiber disruption and lens capsule rupture leading to opacification