cataracts

introduction

cataracts occur when the proteins in the lens of the eye undergo changes resulting in opacification of the lens and are the leading cause of blindness in Western cultures
crystallins are the major soluble structural proteins in the lens and in humans comprise 3 major classes encoded by multiple genes: the α-, β-, and γ-crystallins.
as the β and γ crystallins denature, they precipitate and then form complexes with α crystallins which initially help to keep them soluble but eventually may become overwhelmed with the size of the complexes resulting in opacity
congenital cataracts can lead to permanent blindness by interfering with the sharp focus of light on the retina and resulting in failure to establish appropriate visual cortical synaptic connections with the retina.
- prompt diagnosis and treatment can prevent this, although not all affect vision
cataracts can be grouped by anatomic location:
- nuclear cataracts involve the centre of the lens and tends to initially cause some short-sightedness or improve reading vision but later clouds vision
- cortical cataracts involve the periphery of the lens and usually cause issues with glare
- posterior subcapsular cataracts involve the posterior part of the lens and thus often affects reading vision, vision in bright light, as well as causing halos around lights at night

affect 1 to 6 children per 10,000 live births in industrialised countries and up to 3 times that in poorer countries
hereditary cataracts are estimated to account for 8%-25% of congenital cataracts and perhaps up to 50% ¹⁾
aetiology:
- “isolated”
  - tend to be highly penetrant mendelian traits, and usually AD
- in association with metabolic disease or syndromes
  - galactosaemia
  - myotonic dystrophy
  - congenital rubella syndrome
  - Down's syndrome
  - Wilson's disease
  - perinatal-postnatal problems, such as hyperglycaemia and hypocalcaemia

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