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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
How does nuclear cat come about?
Age and protein related changes
26
What are chromosomes?
``` Molecules responsible for visible color Absorb visible light Reduced retinal illumination Absorbs blue end Lens appears yellow/brown 'Washed out' ```
27
What are the potential sxs in nuclear cat?
Blurred vision Glare Altered colour vision
28
How does cortical cat come about?
New lens fibres grow from epithelial cells and can become over hydrated leading to protein changes and reduced transparency
29
What are the pretensions of cortical cat?
C shaped crescents- spoked shaped from periphery, shade type opacities
30
Which type of cat is most common?
Cortical 30% >45 yrs old
31
What sxs are presented in cortical cat?
Asymptomatic... symptomatic if pupil involvement (blurred vision, monocular dip, glare)
32
Where is the most common location for cortical and why?
Interior and infranasal Uv exposure
33
How is PSC formed?
Epithelial take a different path and migrate towards posterior pole... become vacuole shaped
34
What are PSC presentations?
Circumscribed, circular at posterior pole
35
What sxs accompany PSC?
Blurred vision | Glare
36
What test could be carried out to distinguish glare and blur?
Contrast sensitivity measurement | Dilating the pupil
37
Which cat type decrease contrast sensitivity more compared to others?
PSC
38
What are the possible causes for congenital cat?
Mainly Idiopathic Metabolic disorders Sytemic abnormalities Chromosome abnormalities
39
What are the signs of congenital cat?
Bilateral | Symmetrical
40
What is subluxated and what can cause this?
Anomoly where lens no longer centred to pupil, AKA: Ectopia lentis CAUSE: Traumatic displacement Development anomaly Genetic disorders- marfans syndrome
41
What is included in a pre op assessment?
``` Biometry Refractive goals Monovision Astigmatism Accommodation IOLs multifocal/Accom IOL ```
42
What are the risk factors of cataracts?
``` AGE Smoking UV radiation Diabetes Trauma Medications ```
43
What type of meds may increase risk of cataracts?
Corticosteroids (Cortical) | Chlorpromazine (PSC)
44
In terms of refractive goals, what can be a real issue?
High pre opp rx
45
How would monovision IOLS work?
NV rx IOL 1 eye and emetrope IOL in other eye
46
When should an individual be seen for a sight test post op?
3/52
47
What factors should an optom consider for a cat surgery?
``` 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
When is cat surgery indicated irrespective of visual performance and sxs?
Compromised iris anterior drainage angle= increase risk of IOP elevation
49
What do direct referral schemes involve?
Full eye exam- lens assessment and fundoscopy (retinal path with pupil dilation) Discuss pros and cons Where px would like to be assessed
50
What can optoms do to manage those with cat?
``` Correct refractive error Dispensing - Absorptive tints - UV absorber - Anti reflection coatings Nutrition ```
51
Who would benefit with a tint?
Beneficial for PSC however detrimental for cortical
52
In all cataracts, what should be considered?
Pupil size, depth of focus, retinal defocus
53
What is the most popular surgical intervention for cataracts?
Phacoemulsification

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