Ophthalmology > Cataract > Flashcards

Cataract Flashcards

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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
How can cataracts be described and categorised?
By the part of the lens that is affected
26
What are the three broad types of cataract?
- Nuclear sclerosis - Cortical - Posterior subcapsular
27
What forms a nuclear sclerosis cataract?
New layers of fibres added with ageing causing compression of the nucleus of the lens
28
What are the typical symptoms of nuclear sclerosis cataract?
- Gradually reduced contrast - Reduced colour intensity - Reading which may be surprisingly good for acuity level - Difficulty recognising faces
29
What causes cortical cataract?
New fibres added to the outside which cause cortical spokes with age
30
When may cortical cataract not cause symptoms?
If the cataract is not on the visual axis or the entire cortex isn't affected
31
What symptoms may present with a cortical cataract?
- Light scatter - Problems with glare when driving at night - Difficulty reading - Daytime activity relatively unaffected
32
What is a posterior subcapsular cataract?
Opacity in the central posterior cortex
33
When do posterior subcapsular cataracts cause the most problem?
In good lighting
34
When are posterior subcapsular cataracts less trouble?
In low light levels when the pupil is dilated
35
What problems can be caused by a posterior subcapsular cataract?
- Difficulty in daytime driving | - Difficulty in reading
36
What may be seen on examination in cataract?
- Opacities seen as a defect in the red reflex | - Lens may appear brown or white under bright light
37
How is cataract diagnosed?
Clinically
38
What investigations can be done to rule out other causes when suspecting a cataract?
- Dilated fundus examination - Measurement of intra-ocular pressure - Glare vision test - Slit lamp examination of the anterior chamber
39
What should be seen in examination of the fundus in cataract?
Normal (unless other pathologies)
40
What should be seen on measurement of intra-ocular pressure in cataract?
Normal (unless associated glaucoma)
41
What is seen on glare vision test in significant cataract?
Reduced visual acuity
42
What should be visible on slit lamp examination in cataract?
Cataract
43
What are the differentials for cataract?
- Macular degeneration - Presbyopia - Retinal disease
44
What is the only proven therapy for cataract?
Surgery
45
What is involved in modern cataract surgery?
Lens extraction and replacement
46
What is it called when a patient has a replacement lens?
Pseudophakia
47
What are the two types of procedures to remove the cataract lens?
Intracapsular and extracapsular
48
Which form of cataract removal is more commonly performed?
Extracapsular
49
When is surgery given in cataract?
No set threshold, consider risk of surgery against patient's quality of life impact
50
What does extracapsular lens extraction involve?
Removal of the anterior capsule and extraction of the lens nucleus and cortex with the posterior capsule left to support the implanted lens
51
How can the lens be removed in extracapsular lens extraction?
- Via a large incision at the limbus OR - After phacoemulsification of the lens with ultrasound via a smaller incision
52
How are cataract surgeries performed in terms of anaesthetics?
Under local injection or anaesthetic eye-drops
53
How are cataract surgeries usually performed in terms of length of stay
Day-case
54
What post-operative care is required with cataract surgery?
Use of topical antibiotics and steroids and avoiding strenuous activity
55
What does intracapsular lens extraction involve?
Removing the entire lens and replacing with a plastic lens
56
What can cause poor visions after cataract surgery?
- Inadequate correction of refractive error post-op - Failure to detect pre-existing eye conditions - Surgical complications
57
What are the early surgical complications of cataract surgery?
- Posterior capsule rupture with or without loss of vitreous - Protruding or broken sutures - Trauma to iris - Endophthalmitis
58
What is endophthalmitis?
A rare but devastating infection caused by Staph. epidermidis
59
In what percent of post-cataract surgery cases does endophthalmitis occur?
0.05-0.1%
60
What are the late complications of cataract surgery?
- Posterior capsule opacification - Cystoid macular oedema - Uveitis - Retinal detachment - Open or closed angle glaucoma
61
What percentage of post-cataract surgery cases does posterior capsule opacification occur in?
Around 40%
62
What advice should be given to patients with severe bilateral cataracts or failed extractions?
Not to drive and contact the DVLA
63
What are the potential complications of cataracts?
- Falling - Depression - Blindness
Ophthalmology
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