Differential Diagnosis 
of 
Physical Signs in Lens
In the clinical examination, cataract is often encountered but it is unlikely to be the only physical sign. It is either coincidental or related to the underlying main condition that the examiner expect you to detect (for example; penetrating eye injuries, Fuch's heterochromic cylitis and diabetic mellitus). The lens should be examined with retroillumination (to detect anterior and posterior subcapsular opacities) and direct focal slit illumination (to detect opacity in different zones of the lens).
The only lens condition that may present as the main case is lens subluxation and usually the patient has signs of Marfan's syndrome.

 
Cataract
(Cataract can be classified according to the aetiology or to the zones involved. The following is a list of cataract according to aetiology following by a list for causes for posterior subcapsular cataract)
 
  • Congenital
      • hereditary
      associated with ocular disease such as PHPV
      associated with systemic disease such as congenital rubella or galactosaemia
  • Developmental defects
      • lens colobomas
      ectopia lentis
      lenticonus
      lentiglobus
  • Age-related cataracts
  • Metabolic and toxic cataract
      • diabetes mellitus
      drugs such as chlorpromazine and steroids
  • Radiation
  • Traumatic cataracts
  • Following ocular inflammation
  • Other: myotonic dystrophy
Causes of posterior subcapsular cataract (posterior subcapsular cataract may be easily missed if you do not examine the lens carefully with direct focal slit-lamp illumination)
 
  • drug-induced such as steroids
  • chronic inflammation
  • posterior segment diseases such as retinitis pigmentosa or high myopia
  • neurofibromatosis type II
  • diabetes mellitus
  • age-related


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    Lens subluxation
    (In cases of lens subluxation, the eyes are often dilated for easy examination. In undilated eye, the presence of iridodonosis, phacodonesis, deep anterior chamber and presence of vitreous in the anterior chamber should raise your suspicion. The most common case in the examination is Marfan's syndrome and you may be asked to look for associated physical signs. The other common case is pseudoexfoliation syndrome.
    Always mention to the examiner the direction of the subluxation as one of the favourite questions amongst the examiners  is the differences between Marfan's syndrome and homocystinuria. )
     

    • Congenital
        • congenital glaucoma
        aniridia
    • Systemic syndromes
        • Marfan
        Weill-Marchesani's syndrome
        Ehlers-Danlos syndrome
        Osteogenesis imperfecta
    • Metabolic disorders
        • homocystineuria
        hyperlysinaemia
    • Trauma


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