DISORDERS OF THE CRYSTALLINE LENS

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DISORDERS OF THE CRYSTALLINE LENS

  1. 1. DISORDERS OF THE CRYSTALLINE LENS Dr Russell J Watkins
  2. 2. Disorders of Lens Shape & Position  Coloboma  Congenital  Zonules absent also → lens rim relaxation  Affects lower quadrants  Associated with iris, choroidal, & optic nerve colobomata  Associated with giant retinal tears
  3. 3. Disorders of Lens Shape & Position  Lenticonus  Anterior or posterior coning of lens surface  ‘Oil drop sign’ against red reflex  Irregular myopic lenticular astigmatism  Anterior & posterior lenticonus are associated with cataract  Lentiglobus  Generalised hemispherical deformity
  4. 4. Disorders of Lens Shape & Position  Microphakia  Small lens due to arrested lens development  Microspherophakia  Small spherical lens, usually bilateral  Zonule visible on pupil dilatation  Iridodonesis & sometimes pupil block glaucoma  Zonular rupture common  Isolated/familial or associated with Marfan’s syndrome
  5. 5. Disorders of Lens Shape & Position  Ectopia lentis  Subluxation or dislocation of the lens due to zonular rupture  → Loss of accommodation  → Refractive error • Myopia or astigmatism if subluxation (lens tilt) • Hypermetropia if dislocated  Can → glaucoma & uveitis
  6. 6. Disorders of Lens Shape & Position  Causes of a dislocated lens  Can be hereditary (Marfan’s, homocysteinuria, familial et al)  Can be acquired (trauma, couching, buphthalmos, anterior uveal tumours, spontaneous [hypermature cataract], high myopia, chronic anterior uveitis)
  7. 7. Lens-induced Disorders  Glaucoma  Phakomorphic (caused by lens shape/size)  Phakolytic (capsular leakage)  Lens displacement  Uveitis  Phakoanaphylactic (AI sensitivity to lens protein)  Phakotoxic (toxic reaction to lens protein)
  8. 8. Cataract  Lens opacity or cataract?  WHO estimates worldwide there are 15 million blind (<3/60) from cataract  CATARACT IS THUS THE MOST COMMON CAUSE OF BLINDNESS WORLDWIDE
  9. 9. Cataract Classification  According to age  Congenital  Infantile  Juvenile  Presenile  Senile
  10. 10. Cataract Classification  According to stage  Immature  Stationary  Progressive  Mature  Intumescent  Hypermature (morgagnian)
  11. 11. Cataract Classification  According to morphology  Capsular • Congenital - anterior polar; pyramidal • Acquired - infrared, mercury (grey), chlorpromazine (white star)  Subcapsular • Posterior - senile or 2° e.g. myotonic dystrophy or corticosteroid use • Anterior - glaukomflecken, miotics, Wilson’s disease (green sunflower)
  12. 12. Cataract Classification  According to morphology  Cortical • Congenital - blue/brown dot; coronary • Acquired - senile cuneiform, Christmas tree  Nuclear • Congenital - embryonal; lamellar [± riders] (genetic, metabolic, infective causes) • Acquired - senile nuclear sclerosis
  13. 13. Cataract Classification  According to aetiology  Not associated with ocular or systemic disease  Associated with ocular disease  Associated with systemic disease
  14. 14. Causes Of Congenital Cataract  Idiopathic (largest group - 40%)  Hereditary (25%) - usually AD  Remaining 35%  Maternal infection, drug ingestion, malnutrition  Inborn errors of metabolism  Chromosomal abnormalities  Uveitis  Prematurity  50% are associated with other ocular anomalies
  15. 15. Cataract not Associated with Ocular or Systemic Disease  Senile cataract - 90% of >70yr age group  Type  Anterior subcapsular (fibrous metaplasia)  Posterior subcapsular (epithelial migration)  Cortical  Nuclear cataract (exaggerated aging process)
  16. 16. Cataract not Associated with Ocular or Systemic Disease  Risk factors for senile cataract  Smoking  Dehydration (e.g. diarrhoeal illness)  UV light exposure  ?↓ by NSAIDs
  17. 17. Pathology of Cataract  Changes in crystallins by deamination, glycosylation, carbamoylation, accelerated by RFs, cause  Protein unfolding  Disulphide cross-links  Removal of positive charge from cells  Exposure of hydrophobic sites  Protein aggregation & ↑ insoluble protein  These pathological changes produce opacification by  Altering refractive index, especially at interfaces  Forming large protein aggregates
  18. 18. Cataract Associated with Ocular Disease  Congenital disorders  Aniridia  Hyperplastic primary vitreous  Hereditary retinal & vitreoretinal disease
  19. 19. Cataract Associated with Ocular Disease  Acquired disorders  Uveitis  Glaucoma (glaukomflecken)  Myopia  Retinal detachment  Neoplasia  Drug Rx e.g. miotics, corticosteroids  Trauma [contusion → Vossius’ ring; lens rupture; retained IOFB; electric shock; radiation; alkali burns]
  20. 20. Cataract Associated with Systemic Disease  Intrauterine factors  Maternal rubella - fetal risk 80% in 1st trimester • General features - stillbirth; deafness (90%); CVS defects; small babies; psychomotor retardation; chest infection • Ocular features - 30-60%; cataract in 50%, uni- or bilateral, nuclear or diffuse; microphthalmos (15%); ‘salt & pepper’ retinopathy; glaucoma (10%); strabismus; nystagmus; refractive errors; optic atrophy
  21. 21. Cataract Associated with Systemic Disease  Intrauterine factors (continued)  CMV • General features - low birth weight; jaundice; enlarged spleen & liver; chest infection; deafness; fits; psychomotor retardation • Ocular features - cataract; uveitis; microphthalmos; optic nerve hypoplasia; optic nerve coloboma; optic atrophy; chorioretinitis  Drug ingestion  Radiation exposure
  22. 22. Cataract Associated with Systemic Disease  Chromosomal abnormalities e.g.  Down’s syndrome (snowflake cataract)  Hereditary disorders  E.g. Marfan’s syndrome  Retinitis pigmentosa syndromes  Systemic drugs  E.g. corticosteroids, antimitotics, chlorpromazine
  23. 23. Cataract Associated with Systemic Disease  Cutaneous disorders  E.g. Atopic dermatitis → anterior or posterior stellate cataract; also associated with keratoconjunctivitis & keratoconus  Muscular disorders  Myotonic dystrophy (AD) → ptosis; Christmas tree cataract [cortical polychromatic dusting]; light near dissociation; pigmentary retinal changes
  24. 24. Cataract Associated with Systemic Disease  Metabolic disease (there are many associated with cataract. The important ones are:)  Diabetes mellitus → bilateral white snowflake cataract - may progress rapidly. Also accelerated senile cataract  Wilson’s disease (hepatolenticular degeneration) - green sunflower cataract. Also causes Kayser-Fleischer ring at level of Descemet’s membrane

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