Cataract Etiology
Primary Risk Factors
Cataracts develop primarily due to aging, with approximately 50% of adults aged 75 years or older affected, making age the single most important risk factor for cataract formation. 1
Age-Related Mechanisms
- The crystalline lens undergoes progressive opacification with aging, involving marked insolubilization of crystallin proteins and extensive oxidative damage to lens constituents 2
- Risk increases with each decade of life starting around age 40, with prevalence reaching approximately two-thirds of the population older than 80 years 1, 3
- The number of people with cataracts in the US is forecasted to double from 24.4 million to about 50 million by 2050 1
Medication-Induced Cataracts
Corticosteroids
- Long-term users of oral or inhaled corticosteroids are at significantly higher risk of cataract formation, particularly posterior subcapsular cataracts 1, 4, 3
- Both systemic and topical steroids demonstrate strong association with posterior subcapsular cataract development, with high relative risk despite low population attributable risk 5
- Intranasal corticosteroids are not associated with significant cataract risk based on recent systematic reviews 4
Other Medications
- Phenothiazines are associated with anterior subcapsular opacities 4
- Systemic α1-adrenergic antagonists (such as tamsulosin) increase risk of surgical complications during cataract surgery 3
Systemic Medical Conditions
Diabetes Mellitus
- Diabetes is strongly associated with increased cataract risk through multiple mechanisms including sorbitol accumulation and increased oxidative stress 4
- Uncontrolled diabetes represents a significant risk factor for cataract development 3
Metabolic and Cardiovascular Factors
- Metabolic syndrome (combination of diabetes, hypertension, obesity, and dyslipidemia) significantly increases cataract risk 4
- Hypertension is an independent risk factor for cataract development 4
- Obesity is associated with increased risk of cataract formation 4
Environmental and Lifestyle Factors
Smoking
- Smoking is a well-established independent risk factor for cataract development, with dose-response relationships demonstrated, particularly for nuclear sclerosis 1, 4, 5
- Smoking cessation reduces risk of cataract development and progression 4
Ultraviolet Radiation
- UV-B radiation exposure is strongly associated with lens opacities, especially cortical cataracts, with demonstrated dose-response relationships 1, 4, 5
- UV protection through brimmed hats and UV-B blocking sunglasses reduces cataract risk 4
Ionizing Radiation
- Ionizing radiation is a proven cause of cataracts, with risk present even at relatively low exposures 4
- Radiation protective shields and lead glasses are recommended for occupational exposure 4
Alcohol
- Alcohol use is identified as a risk factor for cataract development 1
Trauma and Ocular Factors
- Ocular trauma, both blunt and penetrating, significantly increases risk of cataract formation 4, 3
- Intraocular inflammation is an important cataract risk 5
- Safety glasses are recommended for high-risk recreational or work activities to prevent traumatic cataracts 4
Genetic and Hereditary Factors
- Hereditary or genetic predisposition contributes to cataract risk 3
- Positive family history strongly correlates with certain types of cataracts 1
Other Medical Conditions
- Retinitis pigmentosa, Down syndrome, and congenital rubella are associated with increased cataract risk 3
Nutritional Factors
- Undernutrition represents an important modifiable risk factor, though specific nutrient deficiencies require further clarification 5
- Diet low in green leafy vegetables is thought to increase risk 1
- Elevated cholesterol levels may contribute to cataract development 1