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My Own Deck > Lens Disorders > Flashcards

Lens Disorders Flashcards

1
Q

What is the pathophysiology of cataracts?

A

Changes to biochem composition and structure which continues throughout life

Result in loss of lens fibre and elasticity and accommodation

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2
Q

What is oxidative stress?

A

Free radicals cause change in cell structure

This alters proteins that allow lens to have transparency

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3
Q

What cause light scatter?

A

Protein denaturation and intercellular spacing

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4
Q

What increases from birth and age?

A

Nuclear fibres

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5
Q

What is coronal?

A

Equatorial section of lens

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6
Q

What is the lens function?

A

Transmit as much light with minimal optical defocus

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7
Q

What are the primary features of the lens?

A

Absence of BV
Lack of cell organelles
Regular and tight fibres

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8
Q

Where are the epithelial cells located?

A

Anterior surface

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9
Q

What is the primary driver of light scatter?

A

Refractive index b/w adjacent structures

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10
Q

Where is light scatter greater in the lens?

A

Cortical layers

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11
Q

Where does the lens receive its nutrients?

A

Aqueous humour diffusion

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12
Q

What are the fibres shaped to reduce scatter?

A

Hexagonal

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13
Q

What are interdigitation?

A

Form of tongue and groove joint- allows movement but minimises the between fibre spacing

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14
Q

What type of light scatter gives cataracts like sxs?

A

Forward

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15
Q

How is backward light scatter formed?

A

Media opacities

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16
Q

What is the point spread function?

A

Being able to measure degree which ocular media spreads that point function

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17
Q

What 2 factors influence point spread function?

A

Abberation

Light scatter

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18
Q

What is veiling luminance?

A

Scattered components randomly distributed across entire retina?

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19
Q

When is vision greatly decreased?

A

Very bright sunlight
Sun low in the sky
Reflected sun

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20
Q

What are considered lower ordet abberation?

A

Regular astig

Positive and negative defocus

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21
Q

What are considered higher order abberation?

A

Irregular astigmatism

Spherical, coma trefoil

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22
Q

In light of high and low order Aberations, how would this effect vision?

A

Increase in any of these would cause blurred vision sxs

23
Q

With high order aberrations, what sxs could be induced?

A

Night vision, halves, stardust pattern, monocular dip

24
Q

What sxs could be presented with glare?

A

Stars/ halies around light
Pain/disc if close to fixation
Increase proximity

25
Q

How does nuclear cat come about?

A

Age and protein related changes

26
Q

What are chromosomes?

A 
Molecules responsible for visible color 
Absorb visible light 
Reduced retinal illumination 
Absorbs blue end 
Lens appears yellow/brown 
'Washed out'
27
Q

What are the potential sxs in nuclear cat?

A

Blurred vision
Glare
Altered colour vision

28
Q

How does cortical cat come about?

A

New lens fibres grow from epithelial cells and can become over hydrated leading to protein changes and reduced transparency

29
Q

What are the pretensions of cortical cat?

A

C shaped crescents- spoked shaped from periphery, shade type opacities

30
Q

Which type of cat is most common?

A

Cortical 30% >45 yrs old

31
Q

What sxs are presented in cortical cat?

A

Asymptomatic… symptomatic if pupil involvement (blurred vision, monocular dip, glare)

32
Q

Where is the most common location for cortical and why?

A

Interior and infranasal

Uv exposure

33
Q

How is PSC formed?

A

Epithelial take a different path and migrate towards posterior pole… become vacuole shaped

34
Q

What are PSC presentations?

A

Circumscribed, circular at posterior pole

35
Q

What sxs accompany PSC?

A

Blurred vision

Glare

36
Q

What test could be carried out to distinguish glare and blur?

A

Contrast sensitivity measurement

Dilating the pupil

37
Q

Which cat type decrease contrast sensitivity more compared to others?

A

PSC

38
Q

What are the possible causes for congenital cat?

A

Mainly Idiopathic
Metabolic disorders
Sytemic abnormalities
Chromosome abnormalities

39
Q

What are the signs of congenital cat?

A

Bilateral

Symmetrical

40
Q

What is subluxated and what can cause this?

A

Anomoly where lens no longer centred to pupil, AKA: Ectopia lentis

CAUSE: Traumatic displacement
Development anomaly
Genetic disorders- marfans syndrome

41
Q

What is included in a pre op assessment?

A 
Biometry
Refractive goals
Monovision 
Astigmatism 
Accommodation IOLs
multifocal/Accom IOL
42
Q

What are the risk factors of cataracts?

A 
AGE
Smoking 
UV radiation 
Diabetes 
Trauma 
Medications
43
Q

What type of meds may increase risk of cataracts?

A

Corticosteroids (Cortical)

Chlorpromazine (PSC)

44
Q

In terms of refractive goals, what can be a real issue?

A

High pre opp rx

45
Q

How would monovision IOLS work?

A

NV rx IOL 1 eye and emetrope IOL in other eye

46
Q

When should an individual be seen for a sight test post op?

A

3/52

47
Q

What factors should an optom consider for a cat surgery?

A 
Effects vision and quality of life 
One eye or BE effected
Risks and benefits of surgery 
Quality of life if opt NOT to have surgery 
If px WANTS surgery
48
Q

When is cat surgery indicated irrespective of visual performance and sxs?

A

Compromised iris anterior drainage angle= increase risk of IOP elevation

49
Q

What do direct referral schemes involve?

A

Full eye exam- lens assessment and fundoscopy (retinal path with pupil dilation)
Discuss pros and cons
Where px would like to be assessed

50
Q

What can optoms do to manage those with cat?

A 
Correct refractive error 
Dispensing
- Absorptive tints
- UV absorber 
- Anti reflection coatings
Nutrition
51
Q

Who would benefit with a tint?

A

Beneficial for PSC however detrimental for cortical

52
Q

In all cataracts, what should be considered?

A

Pupil size, depth of focus, retinal defocus

53
Q

What is the most popular surgical intervention for cataracts?

A

Phacoemulsification

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