The Crystalline lens

Question 1

Lens anatomy:

Answer 1

• 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

Question 2

Describe Nuclear Cataract:

Answer 2

• Inevitable part of ageing process
• Develops in nucleus (core)
• Nuclear Sclerotic Cataract
• Sclerosis = hardening

Question 3

Nuclear Cataract: Symptoms

Answer 3

• 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

Question 4

Is index myopia the only cause of blurred vision?

Answer 4

• 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

Question 5

Nuclear Cataract: Signs

Answer 5

• 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

Question 6

Cortical cataract : Describe and symptoms

Answer 6

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

Question 7

Cortical cataract : Signs

Answer 7

• 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

Question 8

Cortical cataract : Signs during retro illumination

Answer 8

• Retro-illumination
• Use slit lamp to create red reflex
• Healthy: uniform red glow
• Light reflected from retina
• Cortical opacities: black shadows

Question 9

Mixed cataract:

Answer 9

Age-related cataract often includes both nuclear and cortical opacities (i.e. Mixed)

Question 10

Describe Posterior sub-capsular Cataract

Answer 10

• Opacity develops at posterior aspect of lens
• Between lens fires and posterior capsule
• Centre of posterior capsule
• Opacity close to visual axis

Question 11

Posterior sub-capsular Cataract: Symptoms

Answer 11

• 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

Question 12

Posterior sub-capsular Cataract: Signs

Answer 12

• Direct view: white-yellow opacity, centre of pupil
• High mag: rough, granular texture
• Advanced: Dense plaques
• Retro-illumination: central, dark, reduced transparency

Question 13

Describe Anterior sub-capsular Cataract:

Answer 13

• 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

Question 14

Anterior sub-capsular Cataract: Symptoms

Answer 14

• Profound effect on vision
• Central location of opacity
• Poor vision in bright light- miosis
• Near vision more affected- miosis
• Glare

Question 15

Anterior sub-capsular Cataract: Signs

Answer 15

• Direct view: central opacity
• High mag: rough, granular texture
• Advanced: dense plaques
• Retro-illumination: reduced transparency

Question 16

Describe Christmas Tree cataract:

Answer 16

• Uncommon
• Nucleus and/or Cortex
• Branches (or needles) protrude from central zone
• Sparkle (multi-coloured) with reflections
• May be asymptomatic

Question 17

Acquired Cataract: Risk Factors

Answer 17

• 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

Question 18

Acquired Cataract: Systemic Disease; Diabetes

Answer 18

• 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

Question 19

Acquired Cataract: Systemic Disease; Myotonic Dystrophy

Answer 19

• 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)

Question 20

Acquired Cataract: Systemic Disease; Atopic Dermatitis

Answer 20

• Itchy, red, inflamed skin
• Anterior subcapsular cataract
• Shield cataract
• Posterior subcapsular cataract
• Severe atopic dermatitis: bilateral and rapidly maturing cataracts

Question 21

Acquired Cataract: Systemic Disease; Steroid Use

Answer 21

• 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

Question 22

Traumatic Cataract:

Answer 22

• 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

Question 23

Acquired Cataract Management:

Answer 23

• 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

Question 24

Risks of cataract surgery:

Answer 24

• 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

Question 25

How is cataract surgery done?

Answer 25

• Day-case procedure, 15-20 minutes

• Topical anaesthesia
- Anaesthetic eye-drops (e.g. proxymetacaine)
- Intraocular injection of anaesthetic

• Corneal incision for access
• Tear open anterior lens capsule
• Ultrasound probe to break-up cataract lens: phacoemulsification
• Suction for debris
• Implant plastic intra-ocular lens (IOL) in remaining capsule

Question 26

What is done first visit following referral?

Answer 26

• Discussion with Ophthalmologist on benefits/risks

• Patient gives consent

• Ocular biometry:
- Axial length, Keratometry

• Calculate intra-ocular lens (IOL) power

• Aim to leave emmetropic (or slightly myopic)

• Added to waiting list for surgery

Question 27

Describe congenital cataract:

Answer 27

• Congenital: present from birth
• UK: 200-300 births each year
• Newborn Physical Examination within 72 hours
• Red reflex check (fundus retro-illumination)
• Congenital cataract: dark, less transparent regions

Question 28

congenital cataract: Risks and treatment

Answer 28

• Risk of amblyopia
• Sensory deprivation
• Irreversible damage develops quickly
- Estimated 6-10 weeks of life

• Emergency referral to pediatric ophthalmologist
• Surgery to removal crystalline lens
• Contact lenses/Spectacles for lost 20D+ of lens power
• Intra-ocular lens implantation at later date (18-24 months)