What are the pathophysiology, clinical manifestations, and treatments of cataracts?

Cataracts: Pathophysiology, Clinical Manifestations, and Treatment

Cataract is defined as an opacity within the clear lens of the eye that interferes with visual function, and surgery is the only definitive treatment with approximately 90% of patients reporting improved functional status and satisfaction with vision after the procedure. 1

Pathophysiology

Definition and Mechanism

• Cataract is characterized by progressive opacification or clouding of the eye's natural lens 2
• Pathophysiological changes include:
  • Progressive loss of lens transparency 3
  • Accumulation of molecules that absorb in the UV-visible spectrum 4
  • Formation of fluid-filled vacuoles, particularly in diabetics 4

Risk Factors

• Age is the primary risk factor, with risk increasing after age 40 1
• Other significant risk factors include:
  • Smoking
  • Trauma
  • Radiation exposure
  • Medications (particularly corticosteroids)
  • Genetic predisposition
  • Uncontrolled diabetes
  • Retinitis pigmentosa
  • Down syndrome
  • Congenital rubella 1, 2

Nutritional Factors

• Protective factors:
  • Balanced diet
  • Vegetarian diet
  • Dairy products
  • Vegetables
  • Antioxidants (β-carotene, lutein, zeaxanthin)
• Risk-increasing factors:
  • High-sodium diet
  • High carbohydrate intake
  • High polyunsaturated fatty acid intake 5

Oxidative Mechanisms

• Oxidative stress plays a crucial role in cataract development
• Associated with changes in antioxidative enzymes and biomarkers:
  • Glutathione (GSH)
  • Superoxide dismutase (SOD)
  • Malondialdehyde (MDA)
  • 4-hydroxynonenal (4-HNE) 5
• Photodynamic effects from endogenous compounds absorbing UV-A-visible light contribute to oxidative damage 4

Clinical Manifestations

Symptoms

• Painless, progressive blurring of vision 2
• Visual glare, especially at night 2
• Other symptoms vary based on anatomical distribution of opacities:
  • Photophobia
  • Monocular diplopia
  • Myopic shift
  • Changes in color vision 3

Clinical Classification

• Based on anatomical distribution of opacities:
  • Nuclear cataracts
  • Posterior subcapsular cataracts
  • Cortical cataracts 3

Diagnostic Approach

• Comprehensive eye examination by an ophthalmologist or optometrist 1
• Slit-lamp examination after pupillary dilation to classify opacities 1, 3
• Assessment of visual function decline that interferes with daily activities 1

Treatment Approaches

Non-Surgical Management

• Refractive correction (glasses or contact lenses) for early cataracts 1
• Low-vision devices for temporary visual support 1
• Nutritional considerations:
  • Increased intake of antioxidants
  • Balanced diet with adequate protein intake 5

Surgical Management

• Phacoemulsification with intraocular lens (IOL) implantation is the gold standard procedure worldwide 1
• Surgical indications:
  • Visual function decline that interferes with daily activities
  • Reasonable likelihood of improvement with surgery
  • Clinically significant glare disability 1

Preoperative Considerations

• Detailed assessment required:
  • Visual acuity
  • Refraction
  • Intraocular pressure
  • Ocular comorbidities
  • Biometry and IOL power calculation 1
• Ocular surface disease management:
  • Surgery should be postponed if visually significant ocular surface disease is detected
  • Treatment should be initiated at a higher step for preoperative visually significant ocular surface disease 6

Surgical Procedure

• Most commonly performed with topical anesthesia 2
• No need for preoperative general medical testing (bloodwork, ECG) 2
• Anticoagulants typically do not need to be discontinued 2
• Special consideration for patients on α1-adrenergic antagonists (e.g., tamsulosin) due to increased risk of complications 2

Postoperative Care

• Topical antibiotics and anti-inflammatory medications 1
• Regular follow-up to monitor for complications 1
• Management of residual refractive error 1
• Treatment of posterior capsule opacification if it develops 1

Complications

• Common complications include:
  • Posterior capsule opacification
  • Increased intraocular pressure
  • Corneal edema
  • Cystoid macular edema
  • Endophthalmitis (risk reduced with intraocular antibiotics from 0.07% to 0.02%) 1, 2

Nursing Considerations

• Patient education about the surgical procedure and expected outcomes 7
• Support during pre- and post-operative phases 7
• Monitoring for potential complications 7

Outcomes and Benefits

• Approximately 90% of patients report improved functional status and satisfaction with vision 1
• Benefits beyond vision improvement:
  • Reduced rates of falls (>30%)
  • Reduced rates of dementia (20%-30%) 2
• Advanced technology IOLs can reduce dependence on eyeglasses, though these have additional costs not covered by insurance 2

Special Considerations

• Patients with narrow, occludable angles may benefit from lens extraction to widen the anterior chamber angle and lower intraocular pressure 1
• Patients should be informed that surgery can exacerbate existing ocular surface diseases 6
• Risk stratification for dry eye disease should be performed for all cataract surgery candidates 6