PATHOPHYSIOLOGY OF CATARACT Flashcards
What is a definition of a cataract?
Any opacification of the lens, which is only considered significant when impacting visual function
What is the classification of a cataract?
Onset - age, congenital & secondary
Location - nuclear, cortical, polar/subcapsular
What is the process of the crystalline lens?
- Accounts for almost all of the metabolic activity of the lens
What is the structure of the Crystalline lens?
- The anterior lens surface is of a single-layer inverted cuboidal epithelium
- The posterior lens capsule is thinner
What happens at the crystalline lens?
- 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
What is age-related cataract?
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
What are the mechanisms of formation of age related cataract?
Compaction and stiffening of the central lens material (nuclear sclerosis) as new layers of cortical (outer lens) fibers continue to proliferate over time
What is a nuclear cataract?
- 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
What is a cortical cataract?
- This is a wedge shaped cataract that forms around the edges of the nucleus
What happens with a cortical cataract?
- Increases lens fibre membrane
- denatured proteins aggregate and form globules
- The shape of the cataract is due to the organisations of the lens fibres
What is a posterior Subcapsular Cataract?
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
What is a congenital cataract?
- It is a chromosomal abnormality and genetic mutation
- It is inherited: autosomal dominant, X linked or autosomal recessive
What is a polar cataract?
Polar cataract is associated with an anomaly of the neighbouring tissue
What can anterior polar cataract be associated with?
Can be associated with intrauterine keratitis where the lens capsule became adherent to the inflamed cornea
What can posterior polar cataract be associated with?
Persistent hyperplastic primary vitreous = interruption of the lens capsule
What is the Mittendorf’s dot polar cataract?
Peristing tissue remnants of the hyaloid vessel on the back surface of the lens
central ‘oil’ droplet opacities
What is Suture polar cataract?
Dominantly inherited bluish dots or a dense chalky band around the sutures affecting one or both foetal sutures
What is punctate cerulean/Fleck cataract?
Bilateral, non progressive, small bluish dots scattered throughout the lens with little effect on vision
What is a lamellar polar cataract?
Common, bilateral and symmetrical
round, grey shell of capacity that surrounds a clear nucleus
What happens in cataract surgery?
- 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
What are post op complications with cataract?
- 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
What is a Posterior Capsular Opacification?
This is the most common complication of cataract surgery
Results from proliferation of anterior lens epithelium onto the posterior capsule
What is the treatment for posterior capsular opafication?
Creating an opening in the posterior capsule with Nd: YAG laser (capsulotomy)
What is Cystoid Macular Oedema?
- post op complication
Probably occurs due to prostaglandin release at surgery site upsetting the retinal fluid balance
What is the treatment for Cystoid Macular Oedema?
Intravitreal steroids or anti-VEGF agents
