PATHOPHYSIOLOGY OF CATARACT

Question 1

What is a definition of a cataract?

Answer 1

Any opacification of the lens, which is only considered significant when impacting visual function

Question 2

What is the classification of a cataract?

Answer 2

Onset - age, congenital & secondary
Location - nuclear, cortical, polar/subcapsular

Question 3

What is the process of the crystalline lens?

Answer 3

• Accounts for almost all of the metabolic activity of the lens

Question 4

What is the structure of the Crystalline lens?

Answer 4

• The anterior lens surface is of a single-layer inverted cuboidal epithelium
• The posterior lens capsule is thinner

Question 5

What happens at the crystalline lens?

Answer 5

• New cells constantly formed during life and laid down externally to older cells
• The epithelial cells are unable to shed due to the thick basement membrane
• The cells proliferate and elongate while becoming compacted inward with advancing age

Question 6

What is age-related cataract?

Answer 6

Most common form of cataract that is encountered by eye care practitioners

Can can be affected by UV toxins , metals, steroids, smoking, drugs and diseases

Question 7

What are the mechanisms of formation of age related cataract?

Answer 7

Compaction and stiffening of the central lens material (nuclear sclerosis) as new layers of cortical (outer lens) fibers continue to proliferate over time

Question 8

What is a nuclear cataract?

Answer 8

• This is an exaggeration of normal ageing change
• Often associated with myopia due to an increase in the refractive index of the nucleus
• Characterised by a yellowing centre

Question 9

What is a cortical cataract?

Answer 9

• This is a wedge shaped cataract that forms around the edges of the nucleus

Question 10

What happens with a cortical cataract?

Answer 10

• Increases lens fibre membrane
• denatured proteins aggregate and form globules
• The shape of the cataract is due to the organisations of the lens fibres

Question 11

What is a posterior Subcapsular Cataract?

Answer 11

It is a opacity adjacent to the lens capsule at the posterior pole right in the path of light

It is the idiopathic degeneration of the posterior capsular lens fibres and can interfere with reading vision

Question 12

What is a congenital cataract?

Answer 12

• It is a chromosomal abnormality and genetic mutation
• It is inherited: autosomal dominant, X linked or autosomal recessive

Question 13

What is a polar cataract?

Answer 13

Polar cataract is associated with an anomaly of the neighbouring tissue

Question 14

What can anterior polar cataract be associated with?

Answer 14

Can be associated with intrauterine keratitis where the lens capsule became adherent to the inflamed cornea

Question 15

What can posterior polar cataract be associated with?

Answer 15

Persistent hyperplastic primary vitreous = interruption of the lens capsule

Question 16

What is the Mittendorf’s dot polar cataract?

Answer 16

Peristing tissue remnants of the hyaloid vessel on the back surface of the lens
central ‘oil’ droplet opacities

Question 17

What is Suture polar cataract?

Answer 17

Dominantly inherited bluish dots or a dense chalky band around the sutures affecting one or both foetal sutures

Question 18

What is punctate cerulean/Fleck cataract?

Answer 18

Bilateral, non progressive, small bluish dots scattered throughout the lens with little effect on vision

Question 19

What is a lamellar polar cataract?

Answer 19

Common, bilateral and symmetrical
round, grey shell of capacity that surrounds a clear nucleus

Question 20

What happens in cataract surgery?

Answer 20

• Application of local anaesthesia
  2-3 corneal incision through to anterior chamber
• manual or laser capsulorhexis
• phacoemulsification and removal of lens cortex
• Insertion of IOL

Question 21

What are post op complications with cataract?

Answer 21

• Trauma induced on cornea, iris, trabecular meshwork, lens, vitreous and retina
• There is also increased levels of interleukins and prostaglandins reported in aqueous humor after intraocular surgery

Question 22

What is a Posterior Capsular Opacification?

Answer 22

This is the most common complication of cataract surgery

Results from proliferation of anterior lens epithelium onto the posterior capsule

Question 23

What is the treatment for posterior capsular opafication?

Answer 23

Creating an opening in the posterior capsule with Nd: YAG laser (capsulotomy)

Question 24

What is Cystoid Macular Oedema?

Answer 24

• post op complication
  Probably occurs due to prostaglandin release at surgery site upsetting the retinal fluid balance

Question 25

What is the treatment for Cystoid Macular Oedema?

Answer 25

Intravitreal steroids or anti-VEGF agents