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Ophthalmology > Cataract > Flashcards

Cataract Flashcards

1
Q

What is a cataract?

A

A clouding of the lens of the eye leading to decreased vision

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2
Q

How is lens transparency normally maintained?

A

By multiple factors including microscopic structure and chemistry

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3
Q

What are the 3 main parts of the lens?

A
  • Capsule
  • Epithelium
  • Fibres
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4
Q

Describe the capsule of the lens

A

Elastic

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5
Q

What is the capsule of the lens made of?

A

Collagen

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6
Q

Where is the epithelium of the lens situated?

A

At the anterior portion between the capsule and fibres

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7
Q

What is the role of the epithelium of the lens?

A

It regulates the homeostasis and constantly lays down new fibres

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8
Q

What forms the bulk of the lens?

A

The fibres

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9
Q

What are the fibres of the lens?

A

Long, thin transparent cells arranged lengthwise from the posterior to anterior poles

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10
Q

How are the lens fibres organised?

A

In concentric layers

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11
Q

How does the lens fibre structure maintain transparency?

A
  • Arrangement of fibres
  • Lack of nuclei and other intracellular bodies
  • Cytoskeletons retaining architecture
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12
Q

What can disruption of the lens fibres do?

A

Affect the integrity of the structure and lead to protein deposition

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13
Q

How do cataracts form?

A

From the deposition of aggregated proteins in the lens

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14
Q

What does protein aggregation in the lens do to vision?

A
  • Clouding
  • Light scattering
  • Obstruction
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15
Q

What (other that protein aggregate deposition) contributes to the development of cataracts?

A

Accumulation of yellow-brown pigment in the lens that occurs with ageing

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16
Q

What aspects of vision are affected by the deposition of yellow-brown pigment in the lens?

A
  • Colour vision

- Contrast

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17
Q

What can be made difficult as a result of the yellow-brown pigment deposition in the lens?

A

Reading

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18
Q

What are the causes of cataract?

A
  • Age
  • Trauma
  • Metabolic disorders
  • Medications
  • Congenital problems
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19
Q

What are the main risk factors for cataract in the developed world?

A
  • Age
  • Smoking
  • Diabetes mellitus
  • Systemic corticosteroids
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20
Q

What are the risk factors for cataract in the developing world?

A
  • Malnutrition
  • Acute dehydrating diseases
  • Cumulative exposure to sunlight
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21
Q

What are the less common risk factors for cataract?

A
  • Female gender
  • Uveitis
  • UV exposure
  • Poor nutrition
  • Alcohol
  • Inflammatory and metabolic eye diseases
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22
Q

What do the symptoms of cataract depend on?

A

The size, location and number of eyes affected by the opacity

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23
Q

What are the most common presenting symptoms of a patient with a cataract?

A
  • Gradual, painless loss of vision
  • Difficulty reading
  • Failure to recognise faces
  • Diplopia in one eye
  • Haloes
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24
Q

How are most cataracts detected?

A

Noticed on a routine eye check before they are symptomatic

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25
Q

How can cataracts be described and categorised?

A

By the part of the lens that is affected

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26
Q

What are the three broad types of cataract?

A
  • Nuclear sclerosis
  • Cortical
  • Posterior subcapsular
27
Q

What forms a nuclear sclerosis cataract?

A

New layers of fibres added with ageing causing compression of the nucleus of the lens

28
Q

What are the typical symptoms of nuclear sclerosis cataract?

A
  • Gradually reduced contrast
  • Reduced colour intensity
  • Reading which may be surprisingly good for acuity level
  • Difficulty recognising faces
29
Q

What causes cortical cataract?

A

New fibres added to the outside which cause cortical spokes with age

30
Q

When may cortical cataract not cause symptoms?

A

If the cataract is not on the visual axis or the entire cortex isn’t affected

31
Q

What symptoms may present with a cortical cataract?

A
  • Light scatter
  • Problems with glare when driving at night
  • Difficulty reading
  • Daytime activity relatively unaffected
32
Q

What is a posterior subcapsular cataract?

A

Opacity in the central posterior cortex

33
Q

When do posterior subcapsular cataracts cause the most problem?

A

In good lighting

34
Q

When are posterior subcapsular cataracts less trouble?

A

In low light levels when the pupil is dilated

35
Q

What problems can be caused by a posterior subcapsular cataract?

A
  • Difficulty in daytime driving

- Difficulty in reading

36
Q

What may be seen on examination in cataract?

A
  • Opacities seen as a defect in the red reflex

- Lens may appear brown or white under bright light

37
Q

How is cataract diagnosed?

A

Clinically

38
Q

What investigations can be done to rule out other causes when suspecting a cataract?

A
  • Dilated fundus examination
  • Measurement of intra-ocular pressure
  • Glare vision test
  • Slit lamp examination of the anterior chamber
39
Q

What should be seen in examination of the fundus in cataract?

A

Normal (unless other pathologies)

40
Q

What should be seen on measurement of intra-ocular pressure in cataract?

A

Normal (unless associated glaucoma)

41
Q

What is seen on glare vision test in significant cataract?

A

Reduced visual acuity

42
Q

What should be visible on slit lamp examination in cataract?

A

Cataract

43
Q

What are the differentials for cataract?

A
  • Macular degeneration
  • Presbyopia
  • Retinal disease
44
Q

What is the only proven therapy for cataract?

A

Surgery

45
Q

What is involved in modern cataract surgery?

A

Lens extraction and replacement

46
Q

What is it called when a patient has a replacement lens?

A

Pseudophakia

47
Q

What are the two types of procedures to remove the cataract lens?

A

Intracapsular and extracapsular

48
Q

Which form of cataract removal is more commonly performed?

A

Extracapsular

49
Q

When is surgery given in cataract?

A

No set threshold, consider risk of surgery against patient’s quality of life impact

50
Q

What does extracapsular lens extraction involve?

A

Removal of the anterior capsule and extraction of the lens nucleus and cortex with the posterior capsule left to support the implanted lens

51
Q

How can the lens be removed in extracapsular lens extraction?

A
  • Via a large incision at the limbus

OR

  • After phacoemulsification of the lens with ultrasound via a smaller incision
52
Q

How are cataract surgeries performed in terms of anaesthetics?

A

Under local injection or anaesthetic eye-drops

53
Q

How are cataract surgeries usually performed in terms of length of stay

A

Day-case

54
Q

What post-operative care is required with cataract surgery?

A

Use of topical antibiotics and steroids and avoiding strenuous activity

55
Q

What does intracapsular lens extraction involve?

A

Removing the entire lens and replacing with a plastic lens

56
Q

What can cause poor visions after cataract surgery?

A
  • Inadequate correction of refractive error post-op
  • Failure to detect pre-existing eye conditions
  • Surgical complications
57
Q

What are the early surgical complications of cataract surgery?

A
  • Posterior capsule rupture with or without loss of vitreous
  • Protruding or broken sutures
  • Trauma to iris
  • Endophthalmitis
58
Q

What is endophthalmitis?

A

A rare but devastating infection caused by Staph. epidermidis

59
Q

In what percent of post-cataract surgery cases does endophthalmitis occur?

A

0.05-0.1%

60
Q

What are the late complications of cataract surgery?

A
  • Posterior capsule opacification
  • Cystoid macular oedema
  • Uveitis
  • Retinal detachment
  • Open or closed angle glaucoma
61
Q

What percentage of post-cataract surgery cases does posterior capsule opacification occur in?

A

Around 40%

62
Q

What advice should be given to patients with severe bilateral cataracts or failed extractions?

A

Not to drive and contact the DVLA

63
Q

What are the potential complications of cataracts?

A
  • Falling
  • Depression
  • Blindness

Ophthalmology (16 decks)

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