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OD3 S1 > CL - Extended Wear - Week -3 > Flashcards

CL - Extended Wear - Week -3 Flashcards

1
Q

Define Extended Wear (EW) and Continuous Wear (CW)

A

EW: CLs worn continuously for a period of up to 7 days (6 nights)

CW: CLs worn continuously for up to 30 days

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2
Q

What is adequate oxygen supply to the cornea essential for? (2)

A

Normal epithelial aerobic metabolism
Elimination of waste products

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3
Q

How can the wearing of low oxygen transmissible contact lenses affect the cornea? (1)

A

Corneal hypoxia and oedema.

Oxygen-deficient corneal metabolism leads to an accumulation of lactate, which lowers the rate of fluid pumped out of the cornea. This leads to oedema/swelling.

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4
Q

How does sleep (eyelid closure) affect: corneal oxygen levels, lens temperature, tear pH, and tear osmolarity

A

Corneal oxygen: reduces by 4%
Lens temperature: up by 2 degrees (C)
Tear pH: more acidic
Tear osmolarity: reduces (hypotonic shift)

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5
Q

By how much does the cornea swell during sleep?

A

4% on average

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6
Q

By how much does oedema reduce during the day in: hydrogel EWs, and RGP EWs?

A

Hydrogel: 8% reduction in oedema
RGP: 10% reduction in oedema

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7
Q

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

A

Daily: 24
Overnight: 87

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8
Q

What revision to the Holden-Mertz criteria is being considered and why?

A

EW critical Dk/t set to 125 to prevent stromal anoxia

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9
Q

Is corneal swelling uniform? Explain

A

No it isn’t
Peripheral > central

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10
Q

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

A

Adapted contact lens wearers are more resistant to corneal swelling

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11
Q

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

A

~10%

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12
Q

List 6 possible indications for EW contact lenses

A

Convenience
Aphakes (absence of lens in eye)
Anisometropic infants
Therapeutic
Occupation
Pre-refractive surgery

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13
Q

List 4 therapeutic uses for EW contact lenses

A

Bullous keratopathy
Dry eye disease
Post corneal surgery
RCEs

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14
Q

List 8 lifestyle considerations for EW contact lenses

A

Strong hx of CL non-compliance
Smoking
Regular Swimming
Chronic bleph or MGD
Severe drye eye
Previous corneal inflammatory events
Immunocompromise

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15
Q

Why do we not use hydrogel soft contact lenses?

A

They do not meet Holden-Mertz criteria

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16
Q

Do RGP lenses meet the Holden-Mertz criteria?

A

yes

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17
Q

What ocular effect of hydrogel extended wear lenses is evident after a few hours of wear?

A

Limbal hyperaemia

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18
Q

List 6 ocular effects of hydrogel EW wear

A

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

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19
Q

What are epithelial microcysts, and when do they occur in a hydrogel EW lens patient?

A

5-30um inclusions composed of necrotic cells/debris that occur after more than 2 months of corneal hypoxia

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20
Q

Where do epithelial microcysts originate?

A

originate deep in the epithelium and migrate anteriorly over time

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21
Q

How can you examine epithelial microcysts?

A

reversed illumination with retroillumination

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22
Q

Is stromal oedema from Hydrogel EWs acute or chronic? Is it reversible?

A

Acute and reversible

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23
Q

How can you resolve stromal neovascularisation in a hydrogel lens wearer? How long does this take?

A

Vascular response regresses after 1 month of re-fitting to a higher Dk/t lens

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24
Q

What are endothelial blebs? How long do they last after lens removal?

A

Short term oedematous cells that disappear within ten minutes of lens removal

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25
Q

Describe endothelial polymegathism. Why does it occur and what can it lead to?

A

a permanent increase in variability in the size of corneal endothelial cells in response to chronic hypoxia. Contact lens intolerance is likely with time

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26
Q

Describe Corneal Exhaustion Syndrome. What symptoms are involved? (6)

A

a syndrome characterised by lens intolerance, endothelial polymegathism, and ongoing change in corneal refraction and astigmatism
Symptoms include:
redness, photophobia, lacrimation, stinging, blur, discomfort

27
Q

Who is indicated for rgp extended wear lenses?

A

daily wearers of RGPs with hyper-DK lenses

28
Q

List 5 advantages of RGP EW lenses

A

reduced hypoxic effects
reduced inflammatory responses
enhanced lens durability
enhanced optical clarity
reduced sensation of ‘dryness’

29
Q

List 3 ocular side effects of RGP EWs

A

Lens adherence (immobile upon waking)
3+9 o’clock staining (sign of peripheral corneal dessication)
Superior eyelid ptosis

30
Q

Describe the incidence of lens adherence in rgp extended wear patients. What does it lead to?

A

10-22% of patients. Leads to corneal distortion

31
Q

What are 3 risk factors for lens adherence?

A

Thinner corneas
Tight eyelids
Low amounts of corneal cyl

32
Q

What may 3+9 o’clock staining lead to? (2)

A

Vascularised limbal keratitis
Corneal thinning

33
Q

What are 3 risk factors for 3+9 o’clock staining? (3)

A

Higher baseline conj hyperaemia
Viscous tear film
Poor lens centration

34
Q

How are silicone hydrogels able to have much more oxygen permeability (Dk) than hydrogels?

A

Hydrogel lens transports oxygen mainly by the water in the lens, therefore, high water content means high oxygen permeability. Even when the water content of the lens is as high as 99%, the oxygen permeability would not go over the theoretical value, which is 40. As for the silicone hydrogel lens, although it also contains water, oxygen is not transported by water; instead, it is delivered by the polymer which consists of silicon molecule chains. The theoretical value of silicon molecule’s oxygen permeability can be more than 100; therefore, silicone hydrogel lens’ oxygen permeability is much higher than hydrogel lens’, which depends on water to transport oxygen.

35
Q

Is oxygen transmissiblity linked to water content in silicone hydrogels? How does this differ from regular hydrogels? Explain

A

no. While oxygen transmissibility is permeability divided by lens thickness. The permeability in Si-Hy is determined by the silicone polymer and not by water (unlike hydrogels)

36
Q

What is the maximum extended wear time for the following Si-Hy EW lens options? (6)
Alcon focus
Alcon air optix
B&L purevision
B&L purevision 2
Coopervision biofinity
J&J acuvue oasys

A

Alcon focus night and day: 30 nights
Alcon air optix aqua: 6 nights
B&L purevision: 30 nights
B&L purevision2: 30 nights
Coopervision biofinity: 6 nights
J&J acuvue oasys: 6 nights

37
Q

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

A

Daily wear with normal adaptation schedule for minimum of 2 weeks and gradually increase wear time.
Aftercare at 2 weeks before commencing overnight wear.

38
Q

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

A

Aftercare after first night of overnight wear
Aftercare after 6 nights of extended wear
Aftercare before lens replacement (for monthly disposable)
Aftercare after 3 months
Minimum routine after-cares every 6 months

39
Q

What advice can be given to contact lens patients?

A

If in doubt, take it out

40
Q

What does RSVP mean for contact lenses?

A

A patient should remove contact lenses if they notice: Redness, Soreness, Vision change, Photophobia

41
Q

How do silicones compare to hydrogels for extended wear in terms of: Hypoxia, risk of MK, rate of mechanical prob lems, rate of sterile infiltrates?

A

Hypoxia: greatly reduced
Risk of MK: unchanged
Rate of mechanical problems: unchanged or slightly greater
Rate of sterile infiltrates: higher (double)

42
Q

What are mucin balls and where can they be found?

A

pearly, transluscent, spherical particles found between the back surface of the lens and the cornea

43
Q

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

A

accumulation of post-lens debris: shearing of tear film rolling of debris into balls. Consist of mucin and lipid. When lens removed, transient depressions are seen in the epithelium

44
Q

List two mechanical effects of Si-Hy EW

A
  1. Superior epithelial arcuate lesions (SEALs) [full thickness epithtelial split, with jagged edges)
  2. Conjunctival Flaps (separation of conj epithelium)
45
Q

Where do SEALS occur? What about conjunctival flaps? Are they symptomatic?

A

SEALS: usually ~1mm from superior limbus
Conj. flaps: up to 1mm away from lens ege

Usually both are symptomatic

46
Q

Following epithelial repair in superior epithelial arcuate leions, what is indicated? How about for conjunctival flaps?

A

Refit indicated for both

47
Q

What is giant papillary conjunctivitis?

A

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

48
Q

What is giant papillary conjunctivitis typically associated with?

A

Contact lens deposits

49
Q

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

A

Mast cells and basophils infiltrate into the superior tarsus

50
Q

Define corneal infiltrate.

A

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

51
Q

Describe the two kinds of corneal infiltrates and primary cause.

A

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

52
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

53
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

54
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

55
Q

Does infiltrative keratitis have symptoms?

A

Mimimal to no patient symptoms

56
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

57
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

58
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

59
Q

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

A

Recurrences likely
Recommend ceasing extended wear
Consider daily disposables

60
Q

What is microbial keratitis characterised by (2)?

A

Corneal excavation and necrosis

61
Q

What is a common bacteria for microbial keratitis?

A

Pseudomonas spp.

62
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

63
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 (25 decks)

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