Cataracts in Adults

A cataract is a condition defined as painless clouding or opacity of the lens. It causes visual impairment, as the lens provides part of the eye’s refractive power. Although all age groups can be affected, the age-related or senile type of cataract is the most common. Aside from age, there are multiple risk factors, including systemic diseases, medications, or trauma. Patients present with blurry vision, glare sensitivity, and color vision change. Ophthalmologic inspection often shows darkening of or opacities in the red reflex. Slit-lamp examination will show the extent and location of the cataract. The treatment is surgery, which is indicated when loss of vision function interferes with daily function.

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Overview

Definition

A cataract is a painless opacity of the lens that disrupts the light projecting onto the retina, resulting in a clouding of vision. It can cause partial or total blindness.

Epidemiology

  • Leading cause of blindness worldwide
  • Affects all age groups 
  • Age-related cataract: most common type
  • Prevalence in persons aged > 80 years: approximately 70% 
  • More common in women than men

Anatomy

  • The lens is part of the eye’s refractive media.
  • It is a transparent structure made of fibers.
    • Lens fibers:
      • Cortex: outer part; made of younger fibers
      • Nucleus: deep part; made of older fibers
    • Lens epithelium: between fibers and the anterior capsule 
    • Lens capsule: outermost layer (anterior and posterior)
Essential anatomy of the eye diagram

This image displays the essential anatomy of the eye. In cataracts, there is clouding of the lens, which opacifies the light as it projects to the retina; this leads to reduced vision, particularly at night when light levels are low.

Image by Lecturio.

Etiology and Pathophysiology

  • Age:
    • The primary risk factor
    • Aging increases the thickness of the lens.
    • Cortical layers are added → cells become compressed in the center → loss of transparency + stiffening of lens
    • Epithelial cell changes lead to altered lens fiber formation and homeostasis → affects transport of nutrients and antioxidants
    • Oxidative damage contributes to cataract formation.
  • Other risk factors:
    • Toxins
      • Smoking
      • Excessive alcohol use
    • UV light exposure
    • Infrared radiation (especially common in glass workers)
    • Electric shock (exposure to high-voltage current)
    • Trauma
      • Perforation of the eye
      • Blunt injuries (direct blows to the eye)
    • Medications:
      • Corticosteroids
      • Miotics (cholinesterase inhibitors)
    • Other medical conditions:
      • Infections of the eye
      • Chronic dialysis in patients with renal insufficiency
      • Wilson’s disease
        • Error in copper metabolism causing accumulation in cornea
        • “Sunflower cataract”: greenish central disc with spoke-like radial opacities
      • Diabetes
        • Glucose is processed by aldose reductase to sorbitol in the lens.
        • ↑ glucose → ↑ sorbitol → ↑ osmolarity and fluid accumulation in the lens → cataracts
      • HIV/AIDS: Patients undergo cataract surgery at a younger age than usual.

Clinical Presentation

Symptoms

  • Decreased or blurry vision:  
    • Can be unilateral or bilateral
    • Often gradual and painless
  • Diplopia or polyopia: Cataracts create multiple refractions (through clear areas and opacities).
  • Glare sensitivity: to sunlight or headlights (at night)
  • Color vision change: fading of objects
  • Colored halos around the light: scattering of light by collection of water drops in lens
  • Changes in refractive glasses
    • Temporary myopic shift: increase in near vision
    • Frequent changes in near and/or distant vision

Signs

  • Visual acuity diminished unilaterally or bilaterally
  • Nondilated funduscopic examination
    • Darkening of red reflex
    • Opacities within red reflex
    • Fundus obscured

Diagnosis

Ophthalmologic examination

  • Slit-lamp examination: examines the extent and type of lens opacity and other ocular structures
  • Dilated funduscopic examination: examines the posterior pole, to rule out other pathology

Classification of diagnostic findings

  • Types of cataracts based on maturity 
    • Immature: 
      • Variable amount of opacification
      • Still allows for visualization of retina and has red reflex
    • Mature: Cataract is opaque and there is no red reflex
    • Hypermature: 
      • Dense opacity obscures the red reflex and the cortex has liquefied
      • Morgagnian cataract: hypermature cataract with nucleus sinking inferiorly
  • Types of cataracts based on the portion of the lens affected (often overlap)
    • Posterior subcapsular
      • Posterior portion of the lens 
      • Most common in metabolic disorders (diabetes and galactosemia)
    • Nuclear
      • Nucleus or central portion of lens
    • Cortical
      • Cortex of the lens (lens fibers surrounding the nucleus)
      • Most common type of acquired cataracts
Posterior subcapsular cataractsNuclear cataractsCortical cataracts
Causes
  • Aging
  • Steroids
    • High doses
    • Chronic use
  • Chronic intraocular inflammation
  • Trauma (UV exposure)
  • Metabolic conditions
    • Diabetes
    • Galactosemia
Aging
  • Aging: most common type of senile cataracts
  • Diabetes
Symptoms
  • Rapid onset (months)
  • Glare
  • Decreased distance and near vision (more pronounced in bright light)
  • Gradual onset
  • Decrease in distance vision
  • Colors less vibrant
  • Variable onset
  • Glare (most common)
  • Decreased near and distant vision
  • Night blindness
  • Depth-perception problems
  • Diplopia
DiagnosisGranular opacity in the posterior pole of cortex adjacent to the posterior capsule
  • Opacification of the central nucleus
  • Sclerosis and yellowing of the lens nucleus
  • Opacities in the cortical layer
  • Spoke-shaped peripheral opacities progressing circumferentially

Management

  • Surgery:
    • Indicated when severe visual disturbances interfere with daily living
    • Outpatient procedure, often under local anesthesia 
  • Surgical techniques:
    • Standard extracapsular cataract extraction:
      • For removal of advanced cataracts 
      • Removal of lens nucleus in 1 piece, leaving capsule
      • Intraocular lens (IOL) placed in the capsular bag
    • Phacoemulsification:
      • Most common surgery in developed countries
      • Small-incision surgery
      • Phaco probe fragments hard central part of lens (with ultrasonic energy) 
      • IOL placed in lens capsule
    • Intracapsular cataract extraction
      • Rarely used, older technique
      • Increased complications
  • Complications:
    • Endophthalmitis (infection within the eye)
    • Intraocular malposition
    • Retinal detachment
    • Macular degeneration

Differential Diagnosis

  • Diabetes mellitus: a heterogeneous group of metabolic diseases characterized by hyperglycemia resulting from insulin resistance and deficiency. Diabetes mellitus can lead to a number of complications including transient error of refraction (from fluctuating glucose levels) and chronic retinopathy, which manifests as visual floaters and blurred vision. 
  • Glaucoma: an optic neuropathy with distinctive changes in the optic cup and visual field defect. Glaucoma is often associated with increased pressure within the eyeball (commonly within the anterior and posterior chambers), which results in gradual vision loss. This vision loss can occur acutely due to a blockage of the aqueous humor drainage (acute angle-closure glaucoma), which is a medical emergency. The majority of cases are due to open-angle glaucoma. 
  • Macular degeneration: degenerative disorder of the central portion of the retina. Primarily presents with loss of central vision. Patients rarely lose their peripheral vision. Diagnosis is by characteristic findings on slit-lamp examination (drusen, subretinal hemorrhage).
  • Refractive errors: These occur when the eye is unable to focus light on the retina. Factors affecting this include eye size and shape of the cornea. The main types of refractive errors are myopia (nearsightedness), hyperopia (farsightedness), and astigmatism.
  • Uveitis: acute inflammation of the uvea (middle layer of the eyeball) and the ciliary body. Uveitis can be caused by infections (herpes, syphilis) or can be related to systemic inflammatory disease (inflammatory bowel disease, rheumatoid arthritis). Symptoms include blurry vision, red-eye with pain (anterior uveitis) or without pain (intermediate and posterior uveitis), and visual floaters (intermediate uveitis).

References

  1. Folberg, R.(2020). The Eye  in Kumar, V., Abbas, A., Aster, J. (Eds.), Robbins and Cotran Pathologic Basis of Disease (10th ed., pp. 1305-1328). Elsevier, Inc.
  2. Jacobs, D., Gardiner, M.; Givens, J. (2020). Cataract in adults. UpToDate. Retrieved September 12, 2020, from https://www.uptodate.com/contents/cataract-in-adults
  3. Nizami, A., Gulani, A. (2020) Cataract. Retrieved September 12, 2020, from https://www.ncbi.nlm.nih.gov/books/NBK539699/
  4. Ocampo, V., Foster, C.S., Dahl, A. (Ed.). (2018).Senile cataract. Medscape. Retrieved September 12, 2020, from https://emedicine.medscape.com/article/1210914-overview
  5. Pollreisz, A., Schmidth-Erfurth, U. (2010). Diabetic Cataract-Pathogenesis, Epidemiology and Treatment. J Ophthalmol. https://pubmed.ncbi.nlm.nih.gov/20634936/ 

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