Cataracts Flashcards
What are cataracts?
Clouding of the lens of the eye, reducing visual acuity.
What is the most common cause of preventable blindness worldwide?
Cataracts - there is an effective surgical treatment (250,000 of these are performed in the UK each year)
30% of people over 65 years have visual acuities below that required for driving (Snellen acuity less than 6/12)
What is the aetiology of cataracts?
Congenital
- Maternal infection
- Familial
Age
- Elderly
Metabolic
- Diabetes
- Galactosaemia
- Hypocalcaemia
- Wilson’s disease
Drug-induced
- Corticosteroids
- Phenothiazines
- Miotics
- Amiodarone
Traumatic
- Post-intraocular surgery
Inflammatory
- Uveitis
Disorder-associated
- Down syndrome
- Dystrophia myotonica
- Lowe syndrome
What are the risk factors for cataracts?
- >65yrs
- smoking - changes in crystalline lens proteins leading to the formation of cataract
- long term UV exposure - beta-crystallin protein aggregation
- diabetes mellitus
- eye trauma
- long term corticosteroid use
- FH
- uveitis
other metabolic/hereditary conditions - galactosaemia, Wilson’s disease, Marfan’s syndrome, and myotonic dystrophy (e.g., Christmas tree cataract in people with myotonic dystrophy; sunflower cataract in people with Wilson’s disease
Why does diabetes cause cataracts?
High glucose levels lead to retention of glucose in the lens and its conversion to sorbitol –> osmotic stress
These cataracts often progress very rapidly, especially in young people with poorly controlled diabetes.
What are the signs of cataract on examination?
Red reflex can be reduced due to the clouding - will appear red-orange instead as light cannot reach the retina
What are the symptoms of cataracts?
- Visual impairment
- Glare
- Halos around lights
- Painless
- Problems with night driving
- Early changes in the lens are correctable by spectacles
What investigations would you do for cataracts?
- Ophthalmoscopy: done after pupil dilation. Findings: normal fundus and optic nerve
- Slit-lamp examination. Findings: visible cataract
Clinical diagnosis - decrease in visual acuity not corrected by refractive correction and an eye exam which is otherwise normal apart from opacity in the crystalline lens.
Blood glucose, serum calcium and liver biochemistry should be measured to diagnose metabolic disorders.
Why must you refer infants with cataracts?
Refer to the ophthalmologist in order to minimize the subsequent development of amblyopia.*
*Amblyopia = eye fails to achieve normal visual acuity, even with prescription eyeglasses /lenses. Also called lazy eye, amblyopia begins during infancy and early childhood. In most cases, only one eye is affected.
How are cataracts classified?
- Nuclear: change lens refractive index, common in old age
- Polar: localized, commonly inherited, lie in the visual axis
- Subcapsular: due to steroid use, just deep to the lens capsule, in the visual axis
- Dot opacities: common in normal lenses, also seen in diabetes and myotonic dystrophy
This is in terms of anatomy of the lens.
Which cataract type is most common with old age?
Nuclear
Which cataract type is most common with steroid use?
Subcapsular
What is the management of cataracts?
Conservative/medical:
- Stronger glasses
- Brighter lighting
Surgical:
- Lens replacement surgery - various types of intraocular lenses available
What factors does NICE consider for referral for cataract surgery?
- Visual impairment present
- Impact on quality of life
- Patient choice
What is the success rate of cataract surgery?
85-90% of patients achieve 6/12 corrected vision on Snellen chart post-op
What type of cataract is this?
Cortico-nuclear
