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OD3 (S1&2) > CLM - Extended Wear - PAP Week 1 > Flashcards

CLM - Extended Wear - PAP Week 1 Flashcards

1
Q

By what percentage does the cornea swell overnight with eyelid closure?

A

~4%

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2
Q

By what percentage does corneal oxygen concentration decrease to with eyelid closure?

A

Decreases to 4%

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3
Q

What is the minimum concentration for oxygen for no reduction in physiological function?

A

~10%

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4
Q

What happens to lens temperature, tear pH, and tear osmolarity with lid closure (overnight)?

A

Temperature increases (~2C)
Tear pH decreases
Tear osmolarity decreases

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5
Q

What is the minimum Dk/t set by the Holden-Mertz Criteria for daily and overnight contact lens wear?

A

Daily - 24
Overnight - 87

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6
Q

What revision to the Holden-Mertz Criteria is being considered, and to prevent what?

A

Critical Dk/t should be revised to at least 125 to prevent stromal anoxia

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7
Q

Is corneal swelling uniform? Explain.

A

No it isnt
Peripheral > central

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8
Q

Are adapted contact lens wearers more resistant to swelling than non-contact lens wearers or vice versa?

A

Adapted contact lens wearers are more resistant

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9
Q

List 6 possible indications for extended wear contact lenses.

A

Convenience
Aphakes
Anisometropic infants
Therapeutic
Occupation
Pre-refractive surgery

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10
Q

List four therapeutic uses for extended wear contact lenses.

A

Bullous keratopathy
Dry eye disease
Post-corneal surgery
Recurrent erosions

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11
Q

List 8 lifestyle considerations for extended wear contact lenses.

A

History of CL non-compliance
Smoking
Regular swimming
Chronic blepharitis or MGD
Severe dry eye disease
History of previous corneal inflammatory events
Delayed wound healing
Immunocomprised

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12
Q

Are hydrogel soft contact lenses physiologically acceptable for extended wear? Explain?

A

No, they do not meet the Holden-Mertz Criteria

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13
Q

What ocular effect is evident after a few hours of wearing hydrogel soft contact lenses?

A

Limbal hyperaemia

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14
Q

What is the major factor for limbal hyperaemia? What is tis directly related to?

A

Hypoxia, directly related to lens oxygen transmissibility

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15
Q

List 6 ocular pathologies that can occur as a result of hydrogel soft contact lenses.

A

Limbal hyperaemia
Epithelial microcysts
Stromal oedema
Stromal neovascularisation
Endothelial blebs
Endothelial polymegathism

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16
Q

What size are epithelial microcysts and what are they composed of?

A

4-30μm
Composed of necrotic cells/debris

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17
Q

What technique can be used to see epithelial microcysts on a slit-lamp?

A

Characteristic reversed illumination with retroillumination

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18
Q

After how long do epithelial microcysts occur (for extended wear in hydrogel) and after what condition specifically?

A

Typically occurs after >2 months of hypoxia

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19
Q

Where do epithelial microcysts originate and how do they move?

A

Originate deep in the epithelium and migrate anteriorly

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20
Q

Is stromal oedema with extended wear hydrogel lenses acute or chronic? Is it reversible? What is the occurence of striae and folds (percentage)?

A

Striae >5%
Folds >10%
Acute and reversible

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21
Q

Define stromal neovascularisation. In what proportion of patients using hydrogel extended wear lenses will this occur?

A

Formation and extension of new capillaries into the previously avascular corneal stroma
Occurs in ~67% of patients using extended wear hydrogel lenses

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22
Q

Does the vascular response in stromal neovascularisation regress over time after fitting to a higher Dk/t lens or is it completely irreversible?

A

Does eventually regress after 1 month somewhat

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23
Q

What are endothelial blebs and are they a short or long term response to extended wear hydrogel lenses?

A

Oedematous cells (blebs) creating dark spots on the endothelial mosaic
Short term response to contact lens wear

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24
Q

Do endothelial blebs persist for long after lens removal?

A

Disappears within 10 minites of lens removal

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25
Q

What is the aetiology of endothelial blebs?

A

Altered stromal pH

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26
Q

What is endothelial polymegathism? Is it permanent or reversible? What does it occur in response to?

A

Increased variability in the size of corneal endothelial cells
It is a permanent change
It occurs in response to chronic hypoxia

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27
Q

Is endothelial polymegathism initially symptomatic or asymptomatic? What is more likely to occur with time with this condition?

A

Initially asymptomatic
Contact lens intolerance is likely with time

28
Q

List 6 ocular effects of hydrogel extended wear lenses.

A

Reduced corneal sensitivity
Reduced epithelial thickness
Corneal distortion
Corneal staining
Stromal thinning
Reversible myopic shift

29
Q

Define corneal exhaustion syndrome, including what it is characterised by (3) and symptoms (6).

A

Syndrome characterised by lens intolerancem endothelial polymegathism, and ongoing changes in corneal refraction/astigmatism
Symptoms of intolerance include:
-redness
-photophobia
-lacrimation
-stinging
-blur
-discomfort

30
Q

Do RGPs cause change to endothelial morphology even after 12 months of extended wear?

A

No

31
Q

What is meant by lens adherence in RGPs and when does it occur in extended wear? In what percentage of patients? What does it lead to?

A

Immobile lens upon waking, occurring in 10-20% of patients
Leads to corneal distortion

32
Q

What are three risk factors of lens adherence in extended wear RGPs?

A

Thinner corneas
Tight eyelids
Low amounts of corneal cyl

33
Q

Aside from lens adherence, list 2 ocular effects of extended wear RGPs.

A

3 & 9 o’clock staining
Superior eyelid ptosis

34
Q

What can corneal staining due to extended wear RGPs increase the risk of (2) and what is it a sign of?

A

Sign of peripheral corneal dessication
Risk of vascularised limbal keratitis or corneal thinning

35
Q

Consider superior eyelid ptosis due to extended wear RGPs. Is it benign or does it have a sinister cause? Does it resolve after discontinuing RGPs or is it permanent?

A

Benign but resolves with discontinuation

36
Q

Is oxygen transmissibility linked to water content?

A

No

37
Q

Where does the oxygen permeability of SiHy lenses come from?

A

Through the silicon component

38
Q

What is the water and ion transport in SiHy lenses achieved with?

A

Hydrogel component

39
Q

What is the extended wear adaptation schedule for a patient with no contact lens experience?

A

Daily wear with normal adaptation schedule for a minimum of two weeks and gradually increase wear time
Aftercare at two weeks before commencing overnight wear

40
Q

What is the extended wear adaptation schedule for an experienced contact lens wearer (5)?

A

Aftercare after first night of overnight wear
Aftercare after six nights of extended wear
Aftercare before lens replacement
Aftercare after three months
Minimum routine aftercare every 6 months

41
Q

What adivce can be given to patients concerning contact lenses?

A

If in doubt, take it out

42
Q

What is meant by the RSVP acronym for contact lenses?

A

Patients should remove their contact lenses if they feel:
-redness
-soreness
-vision change
-photophobia

43
Q

Is the risk of microbial keratitis higher, the same, or lower with SiHy lenses compared to extended wear hydrogel lenses? Wha about mechanical problems? What about sterile infiltrates (by how much)?

A

The same for microbial keratitis
The same for mechanical problems
Rate of sterile infiltrates is approximately double

44
Q

What are mucin balls and where can they be found?

A

Pearly, translucent, spherical particles found between the lens and cornea

45
Q

What are mucin balls composed of, how do they form, and when the lens is removed, what is seen?

A

Accumulation of the post-lens debris, shearing of the tear film rolling debris into balls
It consists of mucin and lipids
When the lens is removed, transient depressions are seen in the epithelium

46
Q

List two mechanical effects of SiHy lenses.

A

Superior epithelial arcuate lesions
Conjunctival flap

47
Q

Describe superior epithelial arcuate lesions, including appearance and size. Are they typucally asymptomatic? Why do they occur? In what eyes are they more common?

A

Full thickness epithelial split with jagged edges ~1mm from the limbus
Asymptomatic or mild FB sensation
Usually due to the stiff nature of SiHy
More common in steep corneas

48
Q

Following epithelial repair in superior epithelial arcuate leions, what is indicated?

A

Refit

49
Q

What are conjunctival flaps, where can they be found, are they symptomatic, and do they indicate a refit?

A

Separation of conjunctival epithelium, occurring up to 1mm away from the lens edge
Usually asymptomatic
Refit recommended

50
Q

What is giant papillary conjunctivitis?

A

Immunological response to lens deposit and/or mechanical irritation from the superior eyelid to the lens surface

51
Q

What is giant papillary conjunctivitis typically associated with?

A

Contact lens deposits

52
Q

What cells infiltrate (2) into the eyelid (layer specifically) in giant papillary conjunctivitis?

A

Mast cells and basophils infiltrate into the superior tarsus

53
Q

Define corneal infiltrate.

A

Local or diffuse areas characterised by the infiltration of inflammatory leucocytes into the corneal stroma

54
Q

Describe the two kinds of corneal infiltrates and primary cause.

A

Non-infectious/sterile (primary inflammatory reaction)
Infective (primary bacterial infection)

55
Q

List 8 risk factors for infiltrates with SiHy extended wear lenses.

A

Corneal neovascularisation
Working outdoors
Microbial contamination of lenses
Tight-fitting lenses
Younger age (<25)
Ametropia >5D
Smoking
Male gender

56
Q

Describe CLARE, when it typically occurs, and what it is associated with.

A

Contact lens acute red eye
Sudden morning onset
Associated with colonisation of gram + or - bacteria on the contact lens

57
Q

List 4 symptoms of CLARE. What kind of disease is it? Can stromal infiltrates be found? Explain (2).

A

Pain, photophobia, epiphora, irritation
Non-ulcerative, sterile keratitis
Anteiror stromal infiltrates near the limbus
No overlying staining

58
Q

Does infiltrative keratitis have symptoms?

A

Nimimal to no patient symptoms

59
Q

How does infiltrative keratitis appear? List 5 possible causes.

A

Small focal infiltrates in the peripheral cornea, which pick up staining
Due to chemical toxicity, cellular debris, denatured protein, exo/endotoxins

60
Q

Define CLPU. What is it a variant of? Describe what it looks like.

A

Contact lens peripheral ulcer
Variant of infiltrative keratitis specifically associated with contact lens wear
Circular, well circumscribed focal infiltrate <2mm

61
Q

Is the overlying epithelium lost in a contact lens peripheral ulcer? What is it caused by?

A

Yesd
Inflammatory reaction due to bacterial adherence or toxins

62
Q

Are recurrences likely with contact lens peripheral ulcers? What is the recommendation (2)?

A

Recurrences likely
Recommend ceasing extended wear
Consider daily disposables

63
Q

What does microbial keratitis involve?

A

Microbial invasion of the corneal stroma

64
Q

What is microbial keratitis characterised by (2)?

A

Corneal excavation and necrosis

65
Q

What is a common bacteria for microbial keratitis?

A

Pseudomonas spp.

66
Q

Describe the PEDALS acronym for differentiating an infectious vs non-infectious inflammatory infiltrate.

A

Infectious
Pain - yes
Epithelial defect - full thickness
Discharge - possible
Anterior chamber - cells/flare
Location - central/mid-peripheral
Size - >1mm
Non-infectious
Pain - some
Epithelial defect - partial/intact
Discharge - unlikely
Anterior chamber - no cells
Location - peripheral
Size - <1mm

67
Q

How does fluorescein stain an infectious vs non-infectious infiltrate?

A

Infectious - pools, fills area of tissue excavation
Non-infectious - patchy, incomplete staining pattern

OD3 (S1&2) (114 decks)

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