Gradual loss of vision | Flashcards
What is a cataract?
Any opacity on or within the lens
How does the incidence of cataracts change with age?
Incidence increases with age - by age of 100 years, incidence of cataracts is 100%
What are the main structures of the lens from front to back (5)?
- Anterior lens capsule
- Lens epithelium
- Cortex
- Lens nucleus
- Posterior lens capsule
What are the different causes of cataracts (8)?
- Age
- Trauma
- Metabolic
- Toxic
- Secondary (complicated)
- Maternal infection
- Maternal drug ingestion
- Hereditary
What are the 3 types of age-related cataracts?
- Subcapsular cataracts
- Anterior subcapsular
- Posterior subcapsular - Nuclear sclerotic cataract
- Cortical cataract
How would a patient with a posterior subcapsular cataract typically present? (2)
- Trouble with bright sunlight/oncoming headlights
2. Reading vision affected more than distance vision
How would a patient with a nuclear sclerotic cataract typically present?
Myopic shift up to 3 diopters
What are cortical cataracts?
What configuration do they form?
Opacification of lens cortex
Radial spoke-like configuration
Do all cataract patients need surgery?
No - only if it affects their vision
What are the 2 types of diabetic cataracts?
- Age-related cataract + diabetes (cataract appears earlier)
- True diabetic cataract
In what group of diabetics do age-related cataracts appear earlier?
Non-insulin dependent diabetes
Why does cataract surgery not benefit all patients with diabetes to the same extent?
They may have retinopathy as well
What are the features of a true diabetic cataract?
Osmotic overhydration of the lens - lens epithelium is leaky so fluid flows from anterior chamber into lens itself
Causing posterior or anterior lens opacities - snowflake opacities
What is the role of the lens epithelium?
Controls flow of fluid from anterior chamber into lens
How can you classify cataracts according to stage of development (3 stages)?
- Immature cataract
- Mature cataract
- Hypermature cataract
What is a immature cataract?
Cataract hasn’t involved the whole lens
What is a mature cataract?
When the cortex is totally opaque
What is a hypermature cataract?
A mature cataract, where the lens material has become smaller and lens capsule is wrinkled due to leakage of water out the lens
What are the other metabolic causes of cataract (excluding diabetes)
- 2 common
- 4 rare
Common:
- Galactosaemia
- Hypocalcaemic syndromes
Rare
- Mannosidosis
- Fabry’s disease
- Lowe’s
- Wilson’s disease
Metabolic disease are more common causes of cataracts in what age groups?
Congenital or infantile
What are the 5 types of cataracts caused by trauma?
- Penetrating eye injuries – direct damage to lens
- Blunt injury – iris pigment imprinted onto lens
- Glass Blower’s cataract – infared radiation affects anterior lens capsule
- Electric shock
- Ionising radiation
What are the 3 toxic causes of cataracts?
- Corticosteroids (systemic/topical) – causes posterior subcapsular cataract
- Chlorpromazine – fine yellow deposits anterior lens capsule
- Chemotherapy e.g. busulphan
What are the 4 secondary complicated causes of cataracts?
- Anterior uveitis
- Hereditary retinal degenerations
- Retinitis pigmentosa
- Gyrate atrophy
- Stickler’s syndrome - High myopia
- Glaucomflecken – small grey white anterior subcapsular cataract
What are 3 maternal infections and 2 drug ingestions that cause cataracts?
Maternal infections:
- Rubella
- Toxoplasmosis
- CMV
Drugs:
Thalidomide, corticosteroids
How common are cataracts caused by maternal rubella infection?
50% - of mothers infected during pregnancy in 1st/2nd trimester get cataracts. After 6 weeks gestation, virus can cross lens capsule
What are 4 syndromes associated with cataracts?
- Down’s syndrome
- Alport’s syndrome
- Werner’s syndrome
- Rothmund’s syndrome
What is retinitis pigmentosa (4)?
- Genetic disorder of the eyes that causes loss of vision
- Symptoms include trouble seeing at night and decreased peripheral vision
- Involves the progressive loss of rod photoreceptor cells in the back of the eye. This is generally followed by loss of cone photoreceptor cells
- Eventually leads to tunnel vision
What is gyrate atrophy (5)?
- An inherited disorder characterized by progressive vision loss
- There is an ongoing atrophy in the retina and choroid
- In childhood, they experience myopia, night blindness, resulting in tunnel vision
- Many also develop cataracts
- Eventually leads to blindness by around the age of 50
What is Stickler’s syndrome (2)?
- A group of hereditary conditions characterized by a distinctive facial appearance, eye abnormalities, hearing loss, and joint problems.
- Many have severe nearsightedness (high myopia), abnormal vitreous, glaucoma, cataracts and retinal detachment, which can cause impaired vision or blindness
What is high myopia (2)?
- If the eye requires -6.0 diopters or more of lens correction
- Increases risk of cataract, retinal detachment and glaucoma
What are glaucomflecken?
Small grey-white epithelial and anterior cortical lens opacities that occur followin an episode of markedly elevated IOP, as in acute angle closure glaucoma
In the management of cataracts, what are the 7 things you need to assess in a patient?
- Degree of disability
- Patient’s opinion - do they want it?
- Best corrected visual acuity i.e. after a recent refraction
- Coexisting ocular pathology
- General health, serious cardiac or respiratory disease
- Age of the patient is not a contraindication for cataract surgery
- No need to wait until cataract ‘matures’
What are 4 important aspects to ask about regarding degree of disability with cataracts?
- Does it bother them?
- Affects reading, driving?
- Affects occupation
- Impact on household work, watching TV?
What are the 2 main issues regarding best corrected visual acuity when going into cataract surgery
- You can change the refraction error, so need to know recent spectacle correction
- If you make one eye emmotropic, and the other eye is still myopic, the eye can only tolerate a certain difference in power between the eyes otherwise it will lead to double vision
- could do surgery in one eye, followed by the other eye (not together for safety reasons)
- or if patient doesn’t want surgery in the other eye, balance power in the eye being operated on so they can see without diplopia
What 2 main issues regarding coexisting ocular pathology need to be addressed when a patient undergoes cataract surgery?
- Need to check for e.g. macular degeneration - the patient may not have as good a result following cataract surgery if they have coexisting pathologies, which needs to be explained to patient beforehand
- Check for glaucoma as the high pressures can complicate surgery and lead to expulsive haemorrhage or complete loss of vision
What is the management of cataracts?
- Biometry - calculation of required intraocular lens power
2. Operations - usually phacoemulsification
What are the 3 things that the biometry calculation is based on?
- Corneal dioptric power
- Axial length of the eye
- IOL formula
What refraction are patients usually corrected to with biometry?
Slightly myopic so they can have some reading vision
What is the main type of cataract operation?
Phacoemulsification
How is phacoemulsification done (5)?
- Small incision from 2.5-3.5
- Anterior lens capsule is peeled in a circular fashion, known as capsulorrhexis
- High frequency ultrasound phaco probe is used to fragment and aspirate the lens nucleus
- Lens cortex is aspirated with irrigation and aspiration probe
- Foldable intraocular lens made up of acrylic and silicone is inserted through the wound which then unfolds in the lens capsule bag with anterior opening
What are the 3 advantages of phacoemulsification?
- Small incision, fast recovery - frequently manage to see 6/6 next day - although generally takes 2 weeks
- Good refractive results, very little astigmatism
- Quick operation
What are 4 complications of cataract surgery?
How frequently do they occur?
- Posterior capsule opacification (20-40%) over the next few years
- Vitreous loss (4%)
- Retinal detachment (1%)
- Endophthalmitis (0.1%)
What are the 5 clinical features of acute bacterial endophthalmitis?
- Pain and marked visual loss
- Absent or poor red reflex
- Corneal haze
- Fibrinous exudate
- Hypopyon (inflammatory cells in the anterior chamber of the eye)
What are the 3 common causative organisms of acute bacterial endophthalmitis?
- Staph. epidermidis
- Staph. aureus
- Pseudomonas sp
What is glaucoma?
Term used to describe a number of disorders by which the intraocular pressure (IOP) is elevated to damage the optic nerve and normal visual process
What structure produces aqueous?
Where does it go before it is drained?
Ciliary body
Goes into the posterior chamber, through pupil into anterior chamber, and then is drained
What drains the aqueous humour?
Trabecular meshwork
Then goes into collecting channels, then into venous system of superficial eye
Where is the trabecular meshwork?
On the angle between the cornea and the iris
It is 360 degrees around the eye
What equipment needs to be used to see the trabecular meshwork?
Contact lens with LA
What are the 3 different classifications of glaucoma?
- Primary vs secondary
- Open versus closed
- Congenital vs acquired