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0V2022 Introduction to eye diseases > cataract > Flashcards

cataract Flashcards

1
Q

what is cataract?

A

. any opacity of the crystalline lens or its capsule

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2
Q

what is a normal crystalline lens?

A 
contains 
- 65% water
- 35% protein 
. insoluble albuminoid ( denatured protein that increases with age)
. soluble protein
  • we have nucleus at centre of lens
  • nucleus surrounded by cortex
  • encased within a capsule

. lens is avascular and transparent

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3
Q

what happens in cataract?

A

. loss of transparency due to disorganisation of

  • lens fibre membrane
  • lens protein
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4
Q

what is the cataract prevalence ?

A

. leading cause of visual impairment worldwide
- 47.9%

. prevalence increases with age

  • 2 out of 3 cases diagnosed
  • 70 years
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5
Q

what is the prevalence of cataract in uk?

A

. 30% of people 65+ years have visually impairing cataract
(VA<6/12 ) in at least one eye
. further 10% have already had surgery

. 71% 85+years

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6
Q

what are the modifiable risk factors of cataract?

A 
. diabetes
. steroids
. sunlight
. nutrition and socio-economic status
. smoking
. alcohol
. dehydration
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7
Q

what are non-modifiable risk factors of cataract ?

A 
. age
. female gender
. genetics 
. diabetes 
. cardiovascular disease
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8
Q

explain the classification of cataract ?

A
  1. acquired
    - age-related
    - pre-senile
    - traumatic
    - drug induced
    - secondary to another condition
  2. congenital
    - without systemic association
    - with systemic association

. theses can be classified into
1.morphology - which part of lens is affected

  1. maturity
  • immature
  • mature
  • hypermature
  • morgagnian
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9
Q

explain the difference in cataract maturity ?

A
  1. immature
    - partially opaque
  2. mature
    - completely opaque
    - mature lens can take in water
    - risk of 2 closed angle glaucoma (CAG)
  3. hypermature
    - cataract shrunken, anterior capsule wrinkles water leaks out
    - proteins can leak out of hypermature lens
  • = risk of phacolytic gluacome
  1. morgagnian
    - total liquefaction of cortex
    - nucleus sinks
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10
Q

what are the types of age-related cataract ?

A
  1. subcapsular
    - anterior
    - posterior
  2. nuclear
  3. cortical ( cuneiform )
  4. christmas tree
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11
Q

what is anterior subcapsular cataract ?

A
  • age related cataract
  • lens opacity directly below anterior lens capsule
  • fibrous metaplasia of lens epithelium
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12
Q

what is posterior subcapsular cataract?

A
  • age related cataract
  • lens opacity directly below posterior lens capsule
  • easily missed with direct ophthalmoscopy
  • can be a side effect of steroid therapy
  • increased risk of PSC in diabetes
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13
Q

how does posterior subcapsular cataract ( PSC)?

A
  • epithelial cells migrate to posterior pole
    . link with lens fibres
    . breakdown of posterior cortex to form ‘globules’
    . epithelial cells coalesce to form larger ‘bladder cells ‘
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14
Q

what does PSC cause?

A

. painless progressive loss of vision
- pinhole does not improve visual acuity
. can have a devastating impact on vision
- minimum opacification causes maximum fall in acuity

. VA will be wore in bright light

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15
Q

why does PSC affect px vision so severly?

A
  1. location of cataract
    - X-section of posterior lens surface covers 75% pupil area
    - scattered light from PSC cause more veiling glare
  2. difficulty detecting the cataract
    - difficulty with slit lamp
    - difficult with direct ophthalmoscope
  3. not related to position of cataract close to eye’s nodal point
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16
Q

what in nuclear sclerosis?

A
  • progressive hardening, yellowing and opacification of lens nucleus
  • vision loss due to light scatter and absorption
    . short (blue light) absorbed
    . gives nucleus a yellow appearance
  • lens colour changes from yellow to brown as cataract progresses
  • significant myopic shift (-0.50D)
  • causes colour vision impaired
    . where nucleus acts as a yellow filter and transmission of blues is reduced
17
Q

what is cortical cataract?

A
  • affects cortex of lens
  • called cuneiform
  • opacification due to scattering of light between regions of different refractive index
  • affect 50-60 year age group
    . earlier may indicate a metabolic disorder
  • two thirds start in the lower nasal quadrant
    . may implicate UV in aetiology
  • rate of progression varies
  • symptoms only noticed once cataract encroaches on pupil
  • px will complain of monocular diplopia
18
Q

what does cortical cataract cause?

A

. gradual painless progressive loss of VA
. VA tends to be better in bright light
. increase in astigmatism

19
Q

what is christmas tree cataract?

A
  • polychromatic
  • may co-exist with other types
  • looks like christmas tree light
20
Q

what is pre-senile cataract ?

A

. type of acquired cataract
. before age related
e.g. diabetic cataract - also known as snowflake cataract

21
Q

what is traumatic cataract?

A

. direct penetrating injury to the lens

. concussion
- imprint of iris pigment on anterior lens

. cataract is often star shaped

. effects very variable
- denser cataract , higher effect on VA

22
Q

what is drug induced cataract?

A
  1. steroid induced PSC cataract
    - following long-term use of steroids
    - topical or systemic
  2. chlorpromazine
    - antipsychotic drug
    - pigmented deposits in the lens
  3. amiodarone
    - cardiac arrhythmia
    - anterior subcaspsular cataract
23
Q

what is the prevalence of congenital cataract ?

A

. prevalence 0.63 to 9.74 per 10,000

24
Q

what is the signs of congenital cataract?

A

. often bilateral

. as well as reduced vision cataracts can cause

. babies eye are screened within 72 hours of birth and again at 6 weeks - look for white pupil which indicates a cataract

25
Q

what are the two types of congenital cataract?

A

1- without systemic association
. genetic mutation
. most are idiopathic

2- with systemic association
. metabolic disorders e.g. rubella
. chromosomal abnormalities
e.g. down’s

26
Q

what is anterior polar congenital cataract ?

A

. white cone shaped opacity called pyramidal
- looks like a stack of plates

. usually no symptoms
- no effect on VA

. often associated with a persistent pupillary membrane
- pupillary membrane supplies blood to lens in utero

27
Q

what is posterior polar congenital cataract?

A

. symptoms similar to PSC

. often associated with posterior hyaloid remnant

28
Q

what is mittendorf’s dot ?

A

. small , circular opacity on the posterior lens capsule
. often nasal in location
. due to anterior attachment of the hyaloid artery

29
Q

what is hyaloid artery ?

A
  • hyaloid artery is present during gestation and typically regresses completely
  • failure to do so can lead to:
    . mittendorf dot
    . bergmeister’s papilla
    both are benign findings
30
Q

what is cause congenital cataract ?

A

. usually autosomal dominant (AD) but maybe autosomal recessive (AR) or X-linked

31
Q

what are the types of congenital cataract?

A

1- zonular
. subcapsular (polar)

2- lamellar

  • affects one lamella surrounding nucleus
  • may have radial extension
  • affect VA depends on density of opacity

3-sutural

  • rarely cause symptoms
  • opacities may increase in size during development of the lens and then remain static
32
Q

what is an example of congenital cataract: idiopathic ?

A
  • blue dot cataract
  • also known as cerulean
  • punctate - dot spot
  • no symptoms
  • punctate spots can be blue or brown coloured
  • very common
  • can be congenital or developmental
  • often bilateral
33
Q

what is another example of congenital cataract: idiopathic?

A
  • coronary
  • forms a crown around nucleus
  • distributed radially with a rounded club or petal-shaped appearance
  • usually appears around puberty then stays stable

. no symptoms
- peripheral in the lens

34
Q

what is rubella cataract?

A
  • congenital cataract with systemic association
  • if virus acquired during the first 6 weeks of pregnancy there is a risk of cataract
  • prevalence declining through immunisation and termination
  • lens may be totally opaque with fluid cortex at birth or may only show a nuclear cataract
35
Q

what are the signs of rubella cataract?

A
  • strabismus
  • microphthalmus
  • retinopathy
36
Q

what are other systemic signs of rubella cataract?

A
  • severe learning difficulties
  • deafness
  • heart defects

0V2022 Introduction to eye diseases (22 decks)

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