cataract Flashcards
what is cataract?
. any opacity of the crystalline lens or its capsule
what is a normal crystalline lens?
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
what happens in cataract?
. loss of transparency due to disorganisation of
- lens fibre membrane
- lens protein
what is the cataract prevalence ?
. leading cause of visual impairment worldwide
- 47.9%
. prevalence increases with age
- 2 out of 3 cases diagnosed
- 70 years
what is the prevalence of cataract in uk?
. 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
what are the modifiable risk factors of cataract?
. diabetes . steroids . sunlight . nutrition and socio-economic status . smoking . alcohol . dehydration
what are non-modifiable risk factors of cataract ?
. age . female gender . genetics . diabetes . cardiovascular disease
explain the classification of cataract ?
- acquired
- age-related
- pre-senile
- traumatic
- drug induced
- secondary to another condition - congenital
- without systemic association
- with systemic association
. theses can be classified into
1.morphology - which part of lens is affected
- maturity
- immature
- mature
- hypermature
- morgagnian
explain the difference in cataract maturity ?
- immature
- partially opaque - mature
- completely opaque
- mature lens can take in water
- risk of 2 closed angle glaucoma (CAG) - hypermature
- cataract shrunken, anterior capsule wrinkles water leaks out
- proteins can leak out of hypermature lens
- = risk of phacolytic gluacome
- morgagnian
- total liquefaction of cortex
- nucleus sinks
what are the types of age-related cataract ?
- subcapsular
- anterior
- posterior - nuclear
- cortical ( cuneiform )
- christmas tree
what is anterior subcapsular cataract ?
- age related cataract
- lens opacity directly below anterior lens capsule
- fibrous metaplasia of lens epithelium
what is posterior subcapsular cataract?
- 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
how does posterior subcapsular cataract ( PSC)?
- 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 ‘
what does PSC cause?
. 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
why does PSC affect px vision so severly?
- location of cataract
- X-section of posterior lens surface covers 75% pupil area
- scattered light from PSC cause more veiling glare - difficulty detecting the cataract
- difficulty with slit lamp
- difficult with direct ophthalmoscope - not related to position of cataract close to eye’s nodal point
what in nuclear sclerosis?
- 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
what is cortical cataract?
- 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
what does cortical cataract cause?
. gradual painless progressive loss of VA
. VA tends to be better in bright light
. increase in astigmatism
what is christmas tree cataract?
- polychromatic
- may co-exist with other types
- looks like christmas tree light
what is pre-senile cataract ?
. type of acquired cataract
. before age related
e.g. diabetic cataract - also known as snowflake cataract
what is traumatic cataract?
. 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
what is drug induced cataract?
- steroid induced PSC cataract
- following long-term use of steroids
- topical or systemic - chlorpromazine
- antipsychotic drug
- pigmented deposits in the lens - amiodarone
- cardiac arrhythmia
- anterior subcaspsular cataract
what is the prevalence of congenital cataract ?
. prevalence 0.63 to 9.74 per 10,000
what is the signs of congenital cataract?
. 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
what are the two types of congenital cataract?
1- without systemic association
. genetic mutation
. most are idiopathic
2- with systemic association
. metabolic disorders e.g. rubella
. chromosomal abnormalities
e.g. down’s
what is anterior polar congenital cataract ?
. 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
what is posterior polar congenital cataract?
. symptoms similar to PSC
. often associated with posterior hyaloid remnant
what is mittendorf’s dot ?
. small , circular opacity on the posterior lens capsule
. often nasal in location
. due to anterior attachment of the hyaloid artery
what is hyaloid artery ?
- 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
what is cause congenital cataract ?
. usually autosomal dominant (AD) but maybe autosomal recessive (AR) or X-linked
what are the types of congenital cataract?
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
what is an example of congenital cataract: idiopathic ?
- 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
what is another example of congenital cataract: idiopathic?
- 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
what is rubella cataract?
- 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
what are the signs of rubella cataract?
- strabismus
- microphthalmus
- retinopathy
what are other systemic signs of rubella cataract?
- severe learning difficulties
- deafness
- heart defects
