D - Cataracts 1 - Week -3 Flashcards
State the 3 components of the lens
Capsule
Cortex with endothelium
Nucleus
What two cell types exist within the lens?
Cuboidal cells
Bow cells
Describe the composition of the lens
40-70% water
2-3% salt
30-70% protein
Which lens crystalin is formed foetally?
Gamma
What is the proposed role of alpha and beta crystalin?
Protective
Which crystalline clumps in association with nucleus hardening?
Gamma
Describe the metabolism of the lens
Anaerobic glycolysis in epithelium.
What is produced from lens metabolism and why?
Energy: for Ion pumps, protein synthesis
Glutathione: an antioxidant
How does fluid flux occur through the lens?
Water enters lens via thin posterior capsule
Pumped out of anterior epithelium with NA/K/ATPase
Where do lens fibres meet?
At suture lines
What are lens fibres made up of?
Bow cells which have elongated and lost their nucleus
What does the lens suture look like anteriorly? And posteriorly?
Anteriorly: a Y
Posteiorly: an upside down Y
What causes the yellowing of the lens with age?
Accumulation of chromophores
How does ageing affect the lens? (Other than yellowing) What does this result in?
Posterior capsule thinning. Leads to increased fluid uptake and cataract formation
What are the 4 general types of cataracts?
Artefacts
Congenital
Acquired
Senile
What types of congenital cataracts are there? (2) Which is most common?
Sight debilitating
Non-sight debilitating = most common
What 3 types of anterior cateractous artefacts are there?
Epicapsular stars
Persistant pupillary membrane
Lenticonus
What secondary conditions is lenticonus associated with?
High myopia
Alport’s syndrome
What are the 2 types of posterior cateractous artifacts?
Mittendorf dot (break off of posterior hyaloid artery)
Nets or whorls (vitreous condensations)
What systemic disorders can be associated with congenital cataract? (2). What should you do in these cases?
Rubella
Galactosemia
Need GP or paediatrician for blood work up
What is a general rule for the association between cataract position and vision?
Generally, the closer the cataract is to the posterior of the lens, the greater the effect on vision
How does a posterior polar cataract present in anterior examination? (2)
Large mittendorf dots (remnant mesodermal vascular tissue)
Small-large obstruction close to nodal point
How does a cataract associated with Galactosemia present in anterior examination? How about in blood test?
Oil droplet cataract
Blood test reveals reduction in galactokinase (GL-1 kinase)
What percentage of rubella cataracts are sight debilitating if <1/12 gestation at time of inoculation? What about <3/12?
<1/12: 60%
<3/12: 20%
Name 5 types of non-debilitating congenital cataracts
Axial
Sutural
Cerulean
Coronary
Pulverulent
Describe a cerulean cataract
Blue dots/opacities in deep lens cortex (near nucleus)
Describe a coronary cataract
Is a zonular/lamellar cataract that has “riders” (i.e. radial wedges of opacity) going into the cortex
Describe a pulverulent cataract
A dense cataract located in embryonic nucleus
How do axial or sutural cataracts present on anterior eye examination?
Chalky white clusters on/near the suture line. May be polychromatic/sparkling (crystals)
What are zonular cataracts?
cataracts where only a region or “zone” of the lens is opaque. i.e. an opacity localized in a specific lenticular region [from webvision, so I know it’s legit]
What kind of cataracts can be zonular?
Any. Providing they only affect one particular region of the lens
What is the most common type of zonular cataract?
Lamellar cataract. Hence why often used interchangeably with zonular despite being a subtype.
What are Zonular/Lamellar cataracts?
A congenital cataract in which opacity is limited to layers of the lens external to the nucleus. Aka “perinuclear” (next to the nucleus). Aka lens cortex for instance.
Name the most common causes of acquired cataracts (6)
Corticosteroids (PSC)
Tranquillisers/antipsychotics (phonothiazine)
Some Cholesterol reducing drugs (Tiparanol)
Miotics
Pesticides
Many other drugs
Give an example of a common corticosteroid that can cause acquired cataract. Where would the cataract form?
Prednisolone. Cataract forms at the back by the nodall point
List the 6 most important causes of secondary/metabolic cataracts
Diabetes - the only one we’ll really see
Galactosemiai
Myotonic dystrophy
Atopic dermatitis
Various syndromes (down’s, marfan’s, alports)
Assoc. with eye disease (RP, uveitis, glaucom)
List 4 causes of traumatic cataract
Blunt injury (most common. Sports)
Explosive injury
Penetrating injury (e.g. nail gun)
Radiating heat/electrical shock
What might happen to the lens with severe trauma? What does this involve?
Subluxation of the lens with tearing of zonules
How can a cataract affect a patient subjectively? (3)
Poor vision: low contrast, facial recognition, reading
Glare sensitivity
Diplopia/polyopia
What forms the red reflex? How might opacities affect this?
light reflected from RPE/choroid. Opacities block the light to form shadows
How do you check the location of an opacity when looking at the red reflex?
Using an ophthalmoscope:
If with movement: opacity behind nodal point (in vitreous)
If against movement: opacity in front of nodal point (i.e. in lens or AC)
How can you get an idea of opacity depth in a slit lamp?
view with a slit/narrow beam. Slit gives cross section of the tissue
