What test is used to diagnose cataracts?

Diagnosis of Cataracts

Slit-lamp biomicroscopy is the primary diagnostic test used to diagnose cataracts, allowing direct visualization of lens opacities. 1 This examination, performed through a dilated pupil, is the definitive method for identifying and characterizing lens opacities that define cataracts.

Core Diagnostic Approach

The diagnostic process for cataracts involves:

Primary Diagnostic Test

• Slit-lamp biomicroscopy: Allows direct visualization of the lens to identify opacities, their location (nuclear, cortical, posterior subcapsular), and severity 1, 2
  • Examination should be performed through a dilated pupil for optimal visualization
  • Various illumination techniques (direct, indirect, sclerotic scatter, specular reflection) help evaluate different aspects of lens opacity

Supporting Clinical Evaluation

• Comprehensive ophthalmic history: Assess symptoms such as:

  • Gradual, painless vision loss
  • Glare sensitivity (especially with bright lights or night driving)
  • Monocular diplopia
  • Changes in color perception
  • Recent myopic shift 2, 3

• Visual acuity testing:

  • Distance visual acuity with current correction
  • Near visual acuity when appropriate
  • Refraction and measurement of corrected distance visual acuity (CDVA) 1

Supplemental Diagnostic Tests

When visual symptoms are disproportionate to the degree of cataract observed or to assess functional impact:

• Glare testing: Measures visual impairment in the presence of light scatter

  • Particularly useful for patients who report good vision in dim conditions but poor vision in bright light or at night
  • May reveal significant visual disability not apparent on standard acuity testing 1, 4

• Contrast sensitivity testing: Evaluates ability to detect subtle variations in shading

  • More comprehensive assessment of visual function than Snellen acuity alone
  • May demonstrate functional loss not appreciated by standard acuity testing 1, 5

• Potential acuity testing: Attempts to predict visual potential by bypassing anterior segment opacity

  • Options include Potential Acuity Meter or super-illuminated pinhole techniques
  • Most useful in moderate cataracts; less reliable in advanced cases 1, 6

Clinical Pearls and Pitfalls

• Key pitfall: Relying solely on visual acuity to determine cataract impact

  • Standard visual acuity testing alone underestimates functional problems in real-life situations 1
  • Patients may have good Snellen acuity but significant visual disability from glare or contrast loss 5

• Important consideration: Different cataract types cause different symptoms

  • Nuclear cataracts: Often associated with myopic shift
  • Posterior subcapsular cataracts: Typically cause more glare and reading difficulties
  • Cortical cataracts: May have distinctive patterns on autofluorescence testing 2, 7

• Diagnostic challenge: Distinguishing cataract from other causes of vision loss

  • Comprehensive dilated examination is essential to rule out retinal or optic nerve pathology
  • In cases with disproportionate visual symptoms, additional testing for comorbidities is warranted 1

By following this diagnostic approach, clinicians can accurately identify cataracts, assess their functional impact, and determine appropriate timing for intervention to preserve vision and quality of life.