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6 CU MCQ REVISION > CL effect and complication > Flashcards

CL effect and complication Flashcards

1
Q

what is the ideal CL

A
  • allow unlimited CL wear
  • able to avoid ocular complication
  • provide sufficient oxygen for normal corneal metabolism
  • allow safe and comfortable CL wear
  • provide normal vision
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2
Q

Cl effect on ocular physiology

A
  1. hypoxia
  2. hypercapnia
  3. disrupted tear film
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3
Q

what is hypoxia

A
  • Anaerobic, less energy in the form of ATP
  • Generate lactic acid and carbon dioxide in stroma
  • Stromal acidosis – uptake of water into stroma
  • Conrela oedema and potential cell damage
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4
Q

cause of corneal oedema

A
  • hypoxia
  • cl induced
  • during sleep cornea naturally thickened by 4-5 percent due to low tear osmolarity
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5
Q

ssx of corneal oedema

A
  • hazy tissue,
  • central cornea more affected than periphery
  • generally asymptomatic (unless significant corneal swelling)
  • reduced vision
  • haziness
  • haloes
  • spectacle is blur
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6
Q

calculating oedema and grades of oedema

A

thickness diff/ original thickness x 100

  • 8 percent – cornea striae
  • 10-15 percent – folds (physical buckling of posterior stroma horizontal an vertical grey line )
  • > 15 percent – stroma haze
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7
Q

management of corneal oedema

A
  • increase dk/t
  • reduce wearing time
  • monitoring
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8
Q

dk level to avoid eodema and anoxia

A

To avoid odema:
DW/EW -24
Overnight – 87

Avoid anoxia:
Open eye- 35 close eye 125
Extended cl wear – prescribe scl with dk/t >90

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9
Q

types of cornea oedema

A 
striae 
fold 
microcysts and vacuoles 
endothelial polymegathism 
corneal neovascularization
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10
Q

what is cornea neovas and how to manage

A

extending limbal BV to cornea usually superiorly or correspond to lens thicker area (no symptom)
Mx: switch to SiHy, strictly daily wear only

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11
Q

what is endothelium polymegathism and management

A

slow progressive and asymptomatic condition. Caused by chronic hypoxia that is due to long term CL wear

  • increase dk/t
  • reduce wearing time
  • monitor
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12
Q

types of cl complication

A

corneal oedema
infection and inflammation
lens and lens fit related

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13
Q

waht is cl induced papillary conjunctivitis (GPC)

A

due to allergy towards lens deposit

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14
Q

SSX of GPC

A

Enlarged papillae
Lens awareness
Palpebral redness
Discharge in the morning
Itch after removing lens
Blurry vision if the lens is deposited heavily
Stinging/ burning sensation upon sensation

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15
Q

Mx of GPC

A
  • Mast cell stabilizer eye drop for symptoms
  • Crease lens wear if GPC grade 3 / 4
  • Schedule review to check recovery
  • Switch to daily disposable or RGP or add enzymatic cleaner into the cleaning regiment
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16
Q

What is microbial keratitis

A

corneal infection cause by inflammation of cornea tissue through a direct infection by an microbial agent (e.g fungus, bacteria, acanthamoeba etc)

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17
Q

ssx of microbial keratitis

A 
lid swollen 
corneal ulcer with staining and hyperaemia 
severe pain 
photophobia 
tearing
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18
Q

cause of microbial keratitis

A

Caused by: PA – pseudomonas aeruginosa (immunodeficiency, immune suppressed, patient treated for cancer)

  • Contaminated CL/lens case/ solutions
  • Soft extended wear
  • Poor hygiene
  • Non-compliance
  • Cornea hypoxia
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19
Q

risk factor of microbial keratitis

A
  • Exposure to organism
  • Smoking
  • Cornea trauma
  • Online purchasing of contact lens
  • Swimming
  • Contact lens wear
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20
Q

what is contact lens peripheral ulcer

A

non infectious/ sterile inflammatory response to bacteria toxin often seen in patients sleeping with soft contact lens

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21
Q

ssx of contact lens periphery ulcer

A
  • small round peripheral cornea epithelial defects
  • some limbal and conjunctiva hyperaemia near ulcer
  • some redness
  • some tearing
  • may be pain
  • unable to wear lens
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22
Q

Mx of contact lens peripheral ulcer

A

assume its infection refer to GP, review next day , crease lens wear until fully recovered switch to daily disposable or RGP , review compliance

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23
Q

diff between MK and CLPU

A

MK CLPU
Aetiology infection infection Inflammation
Pain Moderate to severe Slight the moderate
Ephiphora Intense Slight
Lacrimation Severe and progressive Slight
Palpebral swelling Common No
Hyperaemia Moderate to severe Slight to moderate
Localization Central to paracentral Peripheral/ semi peripheral
Size >1mm 0.1 – 1mm
Shape Irregular Circular
Depth Anterior and mid stroma Anterior stroma
Anterior chamber reaction Yes hypopyon Medium to none

24
Q

what is contact lens acute red eye

A

immune response to toxin or lens deposit during overnight lens wear

25
Q

ssx of contact lens acute red eye

A 
Moderate to severe ocular redness	
Painful red eye upon waking up with CL
Punctate cornea staining with infiltrates (accumulation of WBC) @ periphery or mid periphery
Teary 
Some discharge
26
Q

mx of contact lens acute red eye

A
  • Cease lens wear, assume infectious immediate refer
  • Review next day if seeing GP
  • Switch to RGP if Daily wear is not feasible
  • Review lens care routines
27
Q

what is infiltrative keratitis (corneal infiltrative events) cause by

A

hypoxia , lens fitting, lens care issue, bacteria toxins trapped beneath contact lens and poor patient compliance

28
Q

ssx of infiltrative keratits

A
  • Small diffuse infiltrates, usually found near periphery or cornea
  • At layer of epithelial, sub-epithelial or stromal staining is absents
    Asymptomatic
29
Q

management of infiltrative keratitis:

A

change types of lenses (e.g increase Dk/t ), patient compliance

30
Q

types of staining

A 
arcuate 
central 
punctate 
foreign body 
irregular staining
31
Q

what is smile staining

A

a type of arcuate staining at lower third of cornea, caused by lens dehydration or poor/ incomplete blinking / dry eyes

32
Q

ssx and mx of smile

A

• if staining is greater than G2.5 some Px will have discomfort complaints prescribe eye drops and review px in 2 weeks to 1 month

33
Q

what is superior epithelial arcuate lesion

A

a type of arcuate staining

due to eye lid pressure + high modulus +high minus power(peripheral thick)

34
Q

ssx of and mx of superior epithelial arcuate lesion

A

• Asymptomatic/ some lens awareness during blinking
• Sign : arcuate corneal staining under the lids
Mx: crease lens wear, schedule review to check on recovery, switch to third generation SiHy /check for published modulus value before fitting

35
Q

what is arcuate staining cause by

A

due to lens edges, tight fitting , deposits on posterior lens surface

36
Q

what is central staining cause by

A

due to poorly fitted lens, solution or material allergy , toxic reaction

37
Q

what is punctate staining caused by

A

corneal desiccation , poor blinking , solution / toxic reaction

38
Q

what is irregular staining caused by

A

poorly fitted lens, damaged lens , poor insertion and removal technique

39
Q

what is solution induced corneal staining

A

toxicity from disinfectants in solution when combining SiHy with PHMB

40
Q

ssx and mx solution induced corneal staining

A
  • Ssx: redness and foreign body sensation/ stinging upon insertion, get better in the afternoon
  • Mx: stop lens wear until full recovery, schedule review, switch to H2O2 or non PHMB solution
41
Q

what is 3 and 9 oclock staining

A

desiccation of corneal and conjunctival surface (tear not distributed to the area)
Cornea and conjunctive staining at 3 and 9 oclock

42
Q

ssx and mx of 3 and 9 oclock staining

A

Ssx: discomfort or dryness complaints, conjunctiva redness and inferior decentred RGP
Mx: improve rgp centration – flatten bc
switch to SCL for last option

43
Q

function of tear film

A
  • Provide optically regular/smooth surface between air and cornea.
  • Removal of debris and waste (carbon dioxide and latic acid)
  • Mucin and lipids to lubricate/wet ocular surface
  • Defense against infection (Tear proteins is antimicrobial , mucin layers prevent microbe from adhering to cornea epithelial. )
  • Supply O2 and nutrients (glucose, amino acids and vitamins) to cornea
44
Q

tear film composition

A

Lipid layer right on top, aqueous component
Electrolyte: they are salts in aqueous component
Protein in aqueous and mucin
Glycocalyx a type of mucin, attached to bottom of tear film to epithelial cell
SCL is a giant structure sitting on to of the cornea, tear layer is then split into two, prelens and post lens. Highly disruptive and cause px to have dry eye complain

45
Q

tear composition of CL wearer

A
  1. Thinner lipid layer
  2. Thinner mucin layer
  3. Increased inflammatory mediators
46
Q

what is contact lens induced dry eyes

A

tear film in cl - structural reorganisation(disrupt tear structure = unstable tear film)

47
Q

3 types of dry eyes

A
  1. Evaporative (meibomian gland)
  2. Aqueous deficient dry eye (lacrimal gland)
  3. Mix
48
Q

what is SCL dehydration

A
  • evaporation and losing of water content while being worn

- after evaporation will cause cl shape change and increase friction

49
Q

factors that increase evaporation rate

A
  1. Lower humidity
  2. Higher air temperature
  3. Higher water content
  4. Thinner SCL
50
Q

events that leads to cl induced dry eyes

A
    1. Unstable tear film (due to compartmentalizing of tear and tear composition change)
    1. Stagnant post lens tear film
    1. SCL dehydration
  • detailed

unstable tearfilm leads to:

Evaporation increase while wearing CL as water molecules leave prelens tear film. The water molecule are then drawn from post lens. So the whole tear film is pulled to the air due to evaporation.

  • Less tear component have lesser volume in ocular surface and lead to tear hyperosmolarity.
  • Tear hyperosmolarity: Less tear volume but salt everything remains, more concentration of all other things besides water
  • PoLTF: post lens tear film, stagnant cause increased friction
51
Q

dry eyes symptoms

A
  • stinging / burning
  • excessive tearing
  • sandy / gritty sensation
  • episode of blur vision
  • redness
  • end day discomfort
  • eyes/ cl dry
  • less wettable surface
52
Q

clinical sign of dry eyes

A
  1. sluggish movement of tear debris
  2. lens surface haziness
  3. reduced tbut
  4. nafl staining of ocular surface - cornea , tarsal, bulbar conj
  5. hyperosmolarity of tear lens
53
Q

mx of dry eyes

A
  • Rewetting drops always consider the latest and preservative free
  • Omega 3 supplement (healthy diet): anti-inflammatory effect
  • Refit with looser SCL, look into changing the material
  • SiHy (lower modulus/new generation), Proclear1-day , Low WC hydrogel
  • Daily Disposable instead of reusables (prevent deposits on lens)
  • Daily Wear instead of Extended Wear, as ocular defense is lower for a person with dry eyes
  • Reduce wearing hours, reduce digital device usage
  • monthly prefer hydrogen peroxide for preservative free disinfection
  • RGP as it have less dryness issue compared to SCL (last option)
54
Q

how to prevent cl complication

A
  • Patient selection – motivated, health, complaint
  • Patient education – Cl care, handling and hygiene
  • Lens wearing regime relection
  • After care is important
  • Careful questioning of patient
  • Meticulous ocular examination
  • Cl induced complication knowledge
55
Q

external eye examination look out for:

A

Cornea and limbus – neovas, staining, scarring, pterygium
Bulbar – injection, staining, naevus / pinguecula
Lid – style/ cysts/ blepharitis , concretion, general condition of papillary conjunctiva and tarsal
Blinking – frequency and completeness

6 CU MCQ REVISION (6 decks)

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