The Crystalline lens Flashcards
Lens anatomy:
• Lens capsule
- Capsular bag, outer envelope surrounds lens
• Lens epithelium (anterior)
- layer of epithelial cells between capsule and fibres, anterior surface only
• Lens fibres
- Long, thin fibres tightly packed together
- Fibres stretch from posterior to anterior, in Y-Shape (y-suture)
• Lens nucleus : central core
• Lens cortex: surrounding area
• Equator: imaginary band from top to bottom
• Zonules hold lens in position
- Attach to lens capsule and ciliary body
Describe Nuclear Cataract:
• Inevitable part of ageing process
• Develops in nucleus (core)
• Nuclear Sclerotic Cataract
• Sclerosis = hardening
Nuclear Cataract: Symptoms
• Slowly developing, gradually progressive
• Bilateral, but often asymmetrical
• Painless blurring of vision
• Improvement in unaided near vision
• Second Sight of the Aged
• Increase in refractive index of crystalline lens
Is index myopia the only cause of blurred vision?
• Degraded transmission of light through crystalline lens
• Reduced retinal image quality
• Changes in refractive correction may not ameliorate blurred vision
• Confirm with pinhole
• If blurred vision cannot be addressed with refractive correction, consider surgery
Nuclear Cataract: Signs
• Dilated pupils
• Slit lamp, 5-30° illumination angle
• Range of magnifications
• Opacity most dense in centre (nucleus) of lens
• Yellow discoloration- brunescence
• Progresses to deeper brown as cataract develops
• Reduced Visual Acuity
Cortical cataract : Describe and symptoms
Lens cortex- surrounds nuclear, mid-peripheral
Symptoms:
• Gradual onset, slowly progressive
• Bilateral, but may be asymmetrical
• May be less effect on central vision- clear nucleus
• Visual Acuity might be normal
• Glare
- Incoming light scattered by cortical opacities, Scattered light reduces retinal image contrast, veiling glare
• Monocular Diplopia
- Ghost image created due to light scatter
- Diplopia persists when fellow eye closed
- Second image fainter
Cortical cataract : Signs
• Mid-peripheral opacities, clear nucleus (good VA)
• Cortical Spokes: Straight lines or wedge-shaped opacities
• Direct viewing: cloudy-white
• Radial pattern of cortical spokes
• Advanced: bicycle wheel
Cortical cataract : Signs during retro illumination
• Retro-illumination
• Use slit lamp to create red reflex
• Healthy: uniform red glow
• Light reflected from retina
• Cortical opacities: black shadows
Mixed cataract:
Age-related cataract often includes both nuclear and cortical opacities (i.e. Mixed)
Describe Posterior sub-capsular Cataract
• Opacity develops at posterior aspect of lens
• Between lens fires and posterior capsule
• Centre of posterior capsule
• Opacity close to visual axis
Posterior sub-capsular Cataract: Symptoms
• Profound effect on vision
• Disproportionate to clinical signs
• Central location of opacity
• Close to nodal point
•Near vision typically affected more than distance vision
> Fine resolution for reading
> Miosis at near
• Poor vision in bright light- miosis
• Glare
Posterior sub-capsular Cataract: Signs
• Direct view: white-yellow opacity, centre of pupil
• High mag: rough, granular texture
• Advanced: Dense plaques
• Retro-illumination: central, dark, reduced transparency
Describe Anterior sub-capsular Cataract:
• Opacity develops at anterior aspect of lens
• Change in lens epithelial cells (anterior)
• Fibrous metaplasia: cells become fibrous tissue
• Reduced transparency - Opacity
• Opacity close to visual axis
Anterior sub-capsular Cataract: Symptoms
• Profound effect on vision
• Central location of opacity
• Poor vision in bright light- miosis
• Near vision more affected- miosis
• Glare
Anterior sub-capsular Cataract: Signs
• Direct view: central opacity
• High mag: rough, granular texture
• Advanced: dense plaques
• Retro-illumination: reduced transparency
Describe Christmas Tree cataract:
• Uncommon
• Nucleus and/or Cortex
• Branches (or needles) protrude from central zone
• Sparkle (multi-coloured) with reflections
• May be asymptomatic
Acquired Cataract: Risk Factors
• Develops during life-span (i.e. not born with it)
• Increasing age
• Smoking- nuclear cataract
• Ultraviolet light exposure- cortical cataract
. Positive family history- early development
Acquired Cataract: Systemic Disease; Diabetes
• Early development of nuclear cataract
• Cataract matures and requires referral earlier (e.g. 50 years old)
• Classic Diabetic Cataract
• Rare
• Young adults, suggests sub-optimal control
• Snowflake opacities in cortex
• May resolve spontaneously, may develop quickly and require surgical extraction
Acquired Cataract: Systemic Disease; Myotonic Dystrophy
• Muscular dystrophy: progressive muscle weakening
• Voluntary muscle control of arms + breathing
• Can develop at any age, most common in young adulthood
• 20-30 years old: Reflective cortical opacities (minimal effect on VA)
• 40-50 years old: Wedge-shaped cortical opacities
• Star-shape posterior subcapsular cataract (severely impair VA)
Acquired Cataract: Systemic Disease; Atopic Dermatitis
• Itchy, red, inflamed skin
• Anterior subcapsular cataract
• Shield cataract
• Posterior subcapsular cataract
• Severe atopic dermatitis: bilateral and rapidly maturing cataracts
Acquired Cataract: Systemic Disease; Steroid Use
• Posterior subcapsular cataract
• Topical (ocular): anterior uveitis, scleritis
• Inhaled: asthma
• Systemic (oral): inflammatory bowel disease (e.g. Crohn’s disease)
• Topical (skin cream): systemic lupus erythematosus
Traumatic Cataract:
• Blunt trauma (punch, elbow, tennis/squash ball injury)
• Penetrating trauma (glass, knife)
• Opacification: trauma disrupts organisation of lens fibres (and
• Typical flower or star shape
• Risk of retinal detachment
• Dislocated lens
• Emergency referral
Acquired Cataract Management:
• Direct, routine referral to Ophthalmologist for consideration for surgery
• Negative impact on quality of life
• Patient elects to have surgery
• No effect of delay on final outcome
• Complex decision made on case-by-case basis: Driving, occupation, hobbies
Risks of cataract surgery:
• Don’t refer asymptomatic patients
• Highly successful operation (>95% success rate) but no operation is free from risk of complications:
• Retinal detachment
• Severe ocular infection
• Need for further surgery
