DISORDERS OF THE CRYSTALLINE LENS

Dr Russell J Watkins

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

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

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

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

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)

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)

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

Cataract Classification

According to age Congenital Infantile Juvenile Presenile Senile

Cataract Classification

According to stage Immature Stationary Progressive Mature Intumescent Hypermature (morgagnian)

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)

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

Cataract Classification According to aetiology

Not associated with ocular or systemic disease Associated with ocular disease Associated with systemic disease

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

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)

Cataract not Associated with Ocular or Systemic Disease

Risk factors for senile cataract Smoking Dehydration (e.g. diarrhoeal illness) UV light exposure ?↓ by NSAIDs

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

Cataract Associated with Ocular Disease

Congenital disorders Aniridia Hyperplastic primary vitreous Hereditary retinal & vitreoretinal disease

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]

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

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

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

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

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