## Basic introduction:

  • Cataract is a congenital or degenerative opacity of the lens with the major symptoms being gradual, painless and blurring of vision.
  • It is the leading cause of blindness worldwide.

## Classes of cataract:

  • Nuclear cataract (the central lens nucleus is affected).
  • Posterior subcapsular cataract (beneath the posterior lens capsule).
  • Cortical cataract (on the side of the lens).

Also, cataracts can be classified into:

  • Congenital cataract
  • Senile cataract

## Risk factors for cataract

  • Aging (majority of cases)
  • Diabetes (and other systemic diseases)
  • Trauma of the eye(s)
  • Alcoholism
  • Smoking
  • Corticosteroids (and other systemic drugs)
  • Undernutrition
  • Uveitis
  • Acute dehydrating illnesses
  • Exposure to X-rays, infrared light, and chronic UV light

## Pathogenesis

  • Cataract is caused by the deposition of aggregated proteins in the lens that leads to clouding, light scattering and obstruction of vision.
  • Ageing also causes accumulation of yellow-brown pigment in the lens affecting color vision and contrast thus hampering reading

## Statistics:

  • It is responsible for 47.9% of total cases of blindness globally (the leading cause of blindness globally, affecting about 20 million people).
  • In Kenya, 43% of blindness is caused by cataract.
  • In the USA, about 50% of old people >75 years old are affected by cataract in one way or another.
  • Cataracts are more common in women
  • Progressive painless visual loss or blurring of vision of either one or both eyes
  • Clouding of pupil
  • Halos and starbursts around lights
  • Requiring more light to see
  • Challenges in distinguishing dark blue from black
  • In congenital cataract, there is loss of or irregular red reflex
  • Sometimes, it can cause glaucoma
  • Clinical review
  • Ophthalmoscopy
  • Slit-lamp examination.
  • Red reflex test
  • Glaucoma
  • Refractive error
  • Refractive error
  • Age-related macular degeneration
  • Optic neuritis
  • Macular edema
  • Epiretinal membrane
  • Dry eye
  • Ultraviolet-coated eyeglasses or sunglasses
  • Reducing risk factors as highlighted above

a. Allen D, Vasavada A; Cataract and Surgery for Cataract: BMJ. 2006 Jul 15; 333(7559): 128–132.

b. Kenyan Ministry of Health. Clinical guidelines for management and referral of common conditions at levels 4-6. Hospitals. 2009; 3:259-261.

c. Ministry of Health, Kenya. Kenya Essential Medicine List (2016).

d. Prevention of Blindness and Visual Impairment: Priority Eye Diseases - Cataract Factsheet; World Health Organization, 2015

  • Surgical removal and placement of intraocular lens.
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