Lens Flashcards
1
Q
3 Layers of the Lens
A
- Capsule
- Cortex
- Nucleus
2
Q
2 Types of Lens Pathology
A
- Cataract - opacification/cloudiness of lens that impairs vision (light does not get through media)
- Phacomorphic glaucoma
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
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
5
Q
Nuclear Cataract - Symptoms
A
- Slowly developing, gradually progressive
- Bilateral, but often asymmetrical
- Painless blurring of vision
- Improvement in unaided NV
6
Q
Cortical Cataract
A
- Opacification of lens cortex
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
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
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
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
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
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)
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
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
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
16
Q
Anterior Subcapsular Cataract - Signs
A
- Direct view - central opacity
- High mag - rough, granular texture
- Advanced - dense plaques
- Retro-illumination - reduced transparency
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
Secondary Cataract - Acute Congestive Angle Closure
- 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
Secondary Cataract - High Myopia
- Associated with PSC opacities and early onset NS (which ironically may increase refractive error)
27
Secondary Cataract - Hereditary Fundus Dystrophies
- 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
When to refer for surgery?
- 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
Should we refer all px's?
- 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
Cataract Surgery Procedure
- 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
Cataract Surgery - Intra-operative Surgical Complications
- 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
Cataract Surgery - Immediate-early Post Operative Complications
- Wound leaks
- Vitreous outside of the wound
- Raised IOP
- Lens dislocation
- Endophthalmitis
- Incorrect lens power (refractive surprise)
33
Cataract Surgery - Late Complications
- 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
First visit after referral
- 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
What is lens biometry
- 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
Post-operation Review and Medication
- 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
Congenital Cataract
- 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
Congenital Cataract - Management
- 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
Lens Coloboma
- 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
Ectopia Lentis
- 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
Ectopia Lentis - Causes
- Trauma
- Pseudoexfoliation
- Inflammation
- Hypermature cataract
- Large eye (e.g. myopia)
- Anterior uveal tumours
- Aniridia (absence of iris?)
42
Ectopia Lentis - Management
- 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
