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Clinical Opthalmology > Lens > Flashcards

Lens Flashcards

1
Q

3 Layers of the Lens

A
  • Capsule
  • Cortex
  • Nucleus
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2
Q

2 Types of Lens Pathology

A
  • Cataract - opacification/cloudiness of lens that impairs vision (light does not get through media)
  • Phacomorphic glaucoma
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3
Q

What is an age related cataract

A
  • most common cause of impairment and blindness worldwide
  • incidence increases with age
  • 30% of people >65 have visually significant cataract
  • no preventative measures
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4
Q

Nuclear Cataract

A
  • Exaggeration of normal ageing process
  • Often associated with myopia due to an increase in refractive index of nucleus, hence why some elderly px’s are able to read without their glasses again
    • Emmetrope - DV deteriorates
    • Myope - DV deteriorates
    • Hyperope - DV improves
  • Characterised by a yellowish hue
  • If advanced - nucleus appears brown
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5
Q

Nuclear Cataract - Symptoms

A
  • Slowly developing, gradually progressive
  • Bilateral, but often asymmetrical
  • Painless blurring of vision
  • Improvement in unaided NV
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6
Q

Cortical Cataract

A
  • Opacification of lens cortex
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7
Q

Cortical Cataract - Symptoms

A
  • Gradual onset, slowly progressive
  • Bilateral, but may be asymmetrical
  • May be less effect on central vision - clear nucleus
  • VA can be normal
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8
Q

Cortical Cataract - Symptoms (Glare & Diplopia)

A
  • 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
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9
Q

Cortical Cataract - Signs

A
  • 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
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10
Q

Cortical Cataract - How to View

A
  • Retro-illumination
  • Use SL to create red reflex
  • Healthy - uniform red glow
  • Light reflected from retina
  • Cortical opacities - black shadows
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11
Q

Posterior Subcapsular Cataract

A
  • Opacity develops at posterior aspect of lens
  • Between lens fibres and posterior capsule
  • Centre of posterior capsule close to visual axis
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12
Q

Posterior Subcapsular Cataract - Symptoms

A
  • Profound effect on vision often disproportionate to clinical signs
  • Central location of opacity
  • Close to nodal point
  • NV typically affected more than DV
    • Fine resolution for reading
    • Miosis at near
  • Symptoms increased by miosis (e.g. NV and bright lights)
  • Glare (e.g. from headlights of cars)
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13
Q

Posterior Subcapsular Cataract - Signs

A
  • Direct view - white-yellow opacity, centre of pupil
  • High mag - rough, granular texture
  • Advanced - Dense plaques
  • Retro-illumination - central, dark plaque like appearance, black and vacuolated
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14
Q

Anterior Subcapsular Cataract

A
  • Opacity develops at anterior aspect of lens
  • Associated with fibrous metaplasia of lens epithelium
  • Change in lens epithelial cells (anterior)
  • Reduced transparency - opacity
  • Opacity close to visual axis
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15
Q

Anterior Subcapsular Cataract - Symptoms

A
  • Profound effect on vision
  • Central location of opacity
  • Poor vision in bright light - miosis
  • NV more affected - miosis
  • Glare
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16
Q

Anterior Subcapsular Cataract - Signs

A
  • Direct view - central opacity
  • High mag - rough, granular texture
  • Advanced - dense plaques
  • Retro-illumination - reduced transparency
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17
Q

Christmas Tree Cataract

A
  • Uncommon
  • Needle like formation in the deep cortex and nucleus
  • Sparkle (multi-coloured) with reflections
  • May be asymptomatic
18
Q

Traumatic Cataract

A
  • Blunt trauma (punch, elbow, tennis/squash ball injury) - can cause a characteristic flower shaped opacity
  • Electric shock - rare cause, patterns including diffuse milky, white opacification and multiple snowflake-like opacities, sometimes in a stellate subcapsular distribution
  • Infrared radiation - may rarely cause true exfoliation of anterior lens capsule
  • Ionising radiation - exposure for ocular tumour treatment can cause PSC, may not manifest for months/years
  • Risk of retinal detachment
  • Emergency referral
19
Q

Stages of Cataract Maturity

A
  • Immature - lens partially opaque
  • Mature - lens completely opaque
  • Hypermature - shrunken and wrinkled anterior capsule due to leakage of water out the lens
  • Morgagnian - hypermature in which liquefication of cortex has allowed nucleus to sink inferiorly
20
Q

Cataract - Risk Factors

A
  • Develops during life-span (i.e. not born with it)
  • Increasing age
  • Smoking - nuclear cataract
  • UV light exposure - cortical cataract
  • Positive FH - early development
21
Q

Cataract - Systemic Disease (Diabetes)

A
  • Early development of nuclear cataract
  • Matures and progresses rapidly, requires referral earlier (e.g. 50 yrs old)
  • Classic Diabetic Cataract- rare
  • Young adults, suggests sub-optimal control of diabetes
  • Consists of snowflake opacities in cortex
  • May resolve spontaneously, may develop quickly and require surgical extraction
22
Q

Cataract - Systemic Disease (Myotonic Dystrophy)

A
  • 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 PSC (severely impair VA)
  • often causes Christmas tree cataract
23
Q

Cataract - Systemic Disease (Atopic Dermatitis)

A
  • Atopic eczema
    • Itchy, red, inflamed skin
  • ASC
  • Shield cataract
  • PSC
  • Severe atopic dermatitis - bilateral and rapidly maturing cataracts
24
Q

Secondary Cataract - Chronic Anterior Uveitis

A
  • Most common cause of secondary cataract
  • Incidence related to the duration and intensity of inflammation
  • Steroids used in treatment also causative
  • Earliest finding often polychromatic lustre at posterior pole of lens
  • If inflammation persists - posterior and anterior opacities develop
  • Cataract progresses more rapidly in presence of posterior synechiae
25
Q

Secondary Cataract - Acute Congestive Angle Closure

A
  • May cause small anterior grey-white subcapsular or capsular opacities to form within the pupillary area
  • Represent focal infarcts of lens epithelium, sign of previous acute ACG
26
Q

Secondary Cataract - High Myopia

A
  • Associated with PSC opacities and early onset NS (which ironically may increase refractive error)
27
Q

Secondary Cataract - Hereditary Fundus Dystrophies

A
  • Retinitis pigmentosa, Leber congenital amaurosis, gyrate atrophy and Stickler syndrome - associated with PSC and less commonly ASC cataract
  • Cataract surgery may improve visual function even in presence of severe retinal changes
28
Q

When to refer for surgery?

A
  • Negative impact on QoL
  • Px elects to have surgery
  • Delay has no effect on the final outcome
  • Complex decision made on case-by-case basis
    • Driving
    • Occupation
    • Hobbies
29
Q

Should we refer all px’s?

A
  • Don’t refer px’s who don’t want the surgery (some may say “I’d rather put up with the blurry vision than have surgery”)
  • Don’t refer asymptomatic px’s
  • Very successful operation but can still have complications
    • Retinal detachment
    • Severe ocular infection
    • Need for further surgery
  • Risks must outweigh benefits
  • Don’t deny px’s opportunity to be considered for surgery
30
Q

Cataract Surgery Procedure

A
  • Day-case procedure, 15-20 minutes
  • Topical anaesthesia
    • Anaesthetic eye-drops (e.g. proxymetacaine)
    • Intraocular injection of anaesthetic under Tenon’s capsule
  • Corneal incision for access
  • Tear open anterior lens capsule
  • Ultrasound probe to break-up cataract lens - phacoemulsification
  • Suction for debris
  • Implant plastic IOL in remaining capsule
31
Q

Cataract Surgery - Intra-operative Surgical Complications

A
  • Problems with corneal incision (poor wound reconstruction requiring suturing)
  • Capsular tear leading to vitreous loss and inability to implant an IOL
  • Drop nucleus (lens falls in the vitreous cavity)
  • Intra-ocular haemorrhage (supra-choroidal or expulsive)
32
Q

Cataract Surgery - Immediate-early Post Operative Complications

A
  • Wound leaks
  • Vitreous outside of the wound
  • Raised IOP
  • Lens dislocation
  • Endophthalmitis
  • Incorrect lens power (refractive surprise)
33
Q

Cataract Surgery - Late Complications

A
  • Chronic inflammation/infection
  • Posterior capsular opacification
  • Capsular shrinkage and lens dislocation (capsule phimosis)
  • Retinal detachment (high myopia with axial lens of over 25.5mm) - uncommon
  • Secondary OAG may develop in up to 2/3 of eyes 10 yrs after surgery
    • Angle closure may occur in the immediate post-op period secondary to pupillary block, especially in microphthalmic eyes
34
Q

First visit after referral

A
  • Discussion with Ophthalmologist on benefits/risks
  • Px gives consent
  • Ocular biometry:
    • Axial length
    • Keratometry
  • The px is added to waiting list for cataract surgery
35
Q

What is lens biometry

A
  • Calculate IOL power
  • Measures axial length of eye and curvature of cornea
  • Hyperopic eye will need bigger lens and myopic eye will need smaller lens (dioptric power)
  • Aim to leave eye emmetropic after operation
  • Can be done with ultrasound machine or an optical system
36
Q

Post-operation Review and Medication

A
  • A combination of topical steroid and antibiotic drops are given for 2-4 weeks
  • There is no need for day 1 review
  • Examined by optometrist within 7 days of surgery and then 4 weeks after for refraction
  • Post operative spectacle correction is usually required
37
Q

Congenital Cataract

A
  • Cataract surgery required urgently as infant can develop dense sensory deprivation amblyopia within days
  • Choice of IOL or aphakia
  • Long term problem with glaucoma
  • Irreversible damage develops quickly (Approx. 6-10 weeks of life)
  • Emergency referral to paediatric ophthalmologist
  • Surgery to remove lens
  • CL/Spectacles are temporarily given for lost 20D+ of lens power
  • IOL implantation at later date (18-24 months)
38
Q

Congenital Cataract - Management

A
  • Requirement for surgery balanced with the fact that the earlier it takes place, especially before 1/12 of age, higher the chance of developing glaucoma during juvenile years
  • Bilateral dense cataracts - surgery within 4-10 weeks of age to prevent development of stimulus deprivation amblyopia
  • Bilateral partial - may not need surgery till later or not at all, if doubtful it is wise to defer surgery in favour of careful monitoring
  • Unilateral dense - merits more urgent surgery
  • Partial unilateral - can be observed or treated non-surgically with pupil dilation and possibly part time contralateral occlusion
39
Q

Lens Coloboma

A
  • Congenital indentation of lens periphery
  • Due to localised zonular deficiency
  • Not a true coloboma as no focal absence of a tissue layer due to failure of closure of optic fissure
  • Occasionally a lens coloboma is associated with a coloboma of the iris or fundus
40
Q

Ectopia Lentis

A
  • Hereditary/acquired displacement of lens from normal position
  • May be completely dislocated leaving eye aphakic (luxated), or dislocated leaving eye partially displaced remaining partly within the pupillary area (subluxated)
  • Early stages of subluxation - phacodenesis (lens wobble on rapid return of the eye to the eye position)
41
Q

Ectopia Lentis - Causes

A
  • Trauma
  • Pseudoexfoliation
  • Inflammation
  • Hypermature cataract
  • Large eye (e.g. myopia)
  • Anterior uveal tumours
  • Aniridia (absence of iris?)
42
Q

Ectopia Lentis - Management

A
  • Main complications - refractive error depending on lens position, glaucoma, lens induced uveitis (rare)
  • Spectacle correction may correct astigmatism induced by lens tilt or edge effect with mild subluxation
  • Surgical removal

Clinical Opthalmology (7 decks)

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