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Contact lenses year 3 > Rigid contact lens complications > Flashcards

Rigid contact lens complications Flashcards

1
Q

which 2 ways are rigid lens complications classified

A
  • by the structure that is affected

- by the aetiology/origin of that complication

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2
Q

list the 4 structures affected by RGP lenses

A 
- Conjunctiva
Bulbar
Palpebral
- Cornea
Epithelium
Stroma
Endothelium
- Tear film
- Lids
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3
Q

which parts of the conjunctiva can be affected by RGP complications

A
  • bulbar

- palpebral

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4
Q

which parts of the cornea can be affected by RGP complications

A
  • epithelium
  • stroma
  • endothelium
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5
Q

list 4 types of RGP complications

A
  • hypoxia
  • drying
  • mechanical
  • toxic/hypersensitivity
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6
Q

what are the 4 signs of hypoxia, produced by RGPs

A
  • Central staining
  • Oedema
    Spectacle blur
    Striae/Folds
    Corneal steepening/Corneal warpage
  • Endothelial Polymegethism
  • Neovascularisation
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7
Q

what are the 6 other related signs along with central staining caused by hypoxia produced by an RGP

A
  • Epithelial stress
  • Softening of the epithelium
  • Breakdown of surface
  • Corneal oedema
    Spectacle blur
    In severe cases can = corneal steepening
    and/or clouding of central cornea
    Sclerotic scatter
  • Corneal exhaustion syndrome
  • Reduced acuity
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8
Q

which type of RGP lens causes corneal oedema due to hypoxia

A
  • More of a PMMA or low Dk material issue

- Esp with tight fitting PMMA/RGP lenses which restricted tear exchange

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9
Q

where is the oedema usually present due to an RGP lens causing hypoxia

A

corneal stroma

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10
Q

what measurement can you take in practise to look for corneal swelling due to hypoxia and why

A
  • the cornea can only swell forwards or backwards hence can cause steepening of the cornea
  • can do K readings as baseline measurement during fitting and take these readings on every aftercare to look for changes and avoid any medico-legal issues
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11
Q

what 2 things may a severe case of corneal oedema cause

A
  • may affect contrast and cause light scattering

- may cause corneal clouding where it affects vision

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12
Q

what can corneal steepening, caused by corneal oedema due to hypoxia from an RGP be associated with

A

a myopic shift

which is noticed during the sight test

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13
Q

when may a patient with corneal oedema due to hypoxia caused by the RGP experience spectacle blur and why does this occur

A
  • experienced following removal of the lens
  • as the RGP causes the eyes to swell, it changes the power of the cornea such as PMMA lenses
  • book a sight test after 1 day of not wearing the lenses
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14
Q

how much of swelling does an RGP or a low dk Hydrogel lens cause during the day

A
  • 1-6%
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15
Q

what are the normal values of corneal swelling over night

A

3-4%

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16
Q

what does any contact lens on the eye do

A

restricts some amount of oxygen reaching the cornea, therefore creates a hypoxic environment

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17
Q

what does the epithelium start to do when it is restricted of oxygen

A
  • it begins to respire anaerobically to conserve energy

- lactate is created as a by product of the anaerobic metabolism which goes into the stroma

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18
Q

when a corneal epithelium that is restricted of oxygen begins to respire anaerobically to conserve energy, what is created as a by product of this, where does this by product move to and what affect does this cause and why

A
  • lactate is created as a by product
  • the concentration increases and moves into the stroma
  • this creates an osmotic effect where by water rushes into the stroma
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19
Q

how does the osmotic effect within the corneal stroma cause corneal/stromal oedema

A

because the endothelial pump cannot remove water from the stroma at the same rate as it is entering the stroma = oedema

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20
Q

as the oedema increases it forms, _______, _______ and at worst _______

A

as the oedema increases it forms, striae, folds and at worst haze

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21
Q

how much of corneal oedema causes striae

A

5%

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22
Q

what is the appearance of corneal striae and where about are they formed, caused by oedema

A
  • Fine, wispy, vertical lines

- in the posterior stroma

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23
Q

Striae __________ as _________ increases

A

Striae increase as oedema increases

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24
Q

vision is __________ with striae produced by corneal oedema

A

vision is unaffected with striae produced by corneal oedema

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25
Q

how much of corneal oedema causes folds

A

8%

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26
Q

what is the appearance of corneal folds and where about are they formed, caused by oedema

A
  • Depressed grooves, raised ridges

- Physical buckling of posterior stroma in response to oedema

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27
Q

vision is __________ with folds produced by corneal oedema

A

vision is unaffected with folds produced by corneal oedema

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28
Q

how much of corneal oedema causes haze

A

15-20%

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29
Q

what is the appearance of corneal haze and where about are they formed, caused by oedema

A
  • Stroma hazy, milky appearance

- Gross separation of collagen fibres throughout stroma

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30
Q

vision is __________ with haze produced by corneal oedema

A

vision is affected by haze produced by corneal oedema

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31
Q

what is the corneal oedema stage of haze down to

A

not just down to the lens alone, but also other effects e.g. mechanical effects or temperature changes

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32
Q

what will be the solutions to oedema caused by contact lenses

A
  • make the lens move more by fitting with a flatter lens
  • change to a higher dk/t material
  • fit lenses with fenestrations so the lens moves more, giving better tear exchange
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33
Q

what can long term hypoxia cause

A

endothelial polymegathism

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34
Q

what is endothelial polymegathism

A
  • Structural damage to endothelial cells

- Changes to shape/size of cells

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35
Q

what is the long term effect of endothelial polymegathism caused by hypoxia

A
  • corneal exhaustion syndrome

= the patient becomes intolerant to contact lenses, they are very sensitive and complain of discomfort

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36
Q

what is the ddx of endothelial polymegathism

A

Fuch’s dystrophy

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37
Q

what can endothelial polymegathism create problems for

A

future surgery
e.g. laser refractive or cataract as it can cause corneal endothelial problems, so it is important to control this by fitting with a better lens

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38
Q

what is the appearance of an advanced stage of endothelial polymegathism

A

1 cell can be up to 20x bigger than other cells

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39
Q

other than contact lenses, what else can cause endothelial polymegathism

A

ageing

but contact lenses speeds this process up

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40
Q

what is the debate about what happens during endothelial polymegathism

A

some think it is due to cells migrating out to the periphery, some say cells stay in the same place but just turn around e.g. one side is larger than the other, or some say the endothelial pump fails and causes an acidic shift

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41
Q

what is corneal neovascularisation (which is caused by hypoxia)

A

Formation of new blood vessels (neo=new) in an area usually

devoid of blood vessels - the avascular cornea

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42
Q

which lenses is there low prevalence of corneal neovascularisation (caused by hypoxia), and which lenses could be more associated and why

A
  • Low prevalence of
    neovascularisation with rigid lenses
  • Could be associated with poor (PMMA) lens fit, chronic irritation,
    poor tear exchange
43
Q

when can corneal neovascularisation affect vision

A

when it crosses the line of sight

44
Q

what is the management for corneal neovascularisation

A
  • refit with a higher Dk/t lens, or stop lens wear until the blood drains out of the shell
    or
  • fit with a better fitting lens with better tear exchange
45
Q

why will you need to monitor a patient with corneal neovascularisation very closely after management

A

because the blood will go out of the vessel, but the shell remains so it can easily be filled back up with blood again

46
Q

what is corneal neovascularisation from an RGP caused by

A

poor fitting of the lens

47
Q

what is neovascularisation from a SCL caused by

A

over wear of the lens

48
Q

what are the two signs of drying caused by RGP complications

A
  • Vascularised limbal keratitis

- 3 and 9 o clock staining (mechanical origin)

49
Q

what is vascularised limbal keratitis, caused by dry eyes

A

A chronic CL induced irritation

(mechanical), inflammatory reaction which produces a Semi-opaque corneal nodule, ‘pseudopterygium’

50
Q

what is vascularised limbal keratitis, caused by dry eyes associated with and therefore what will be the management

A
  • inadequate lubrication and low edge lift

- change the firing of the lens if due to low edge lift

51
Q

what is the ddx of vascularised limbal keratitis, caused by dry eyes

A

pterygium (but this can invade the cornea and affect vision)

52
Q

what is the other positions of 3 and 9 o’clock staining

A

4 and 8 o’clock staining

53
Q

what type of staining is 3 and 9 o’clock staining

A

Coalesced superficial staining

54
Q

as well as 3 and 9 o’clock staining, what other sign does vascularised limbal keratitis as a result of drying produce

A

Localised superficial and stromal

vascularisation

55
Q

what 2 types/categories of 3 and 9 o’clock staining are there

A
  • Mechanical/Drying
    and/or
  • Impression from lens
    edge (= poor fitting of lens)
56
Q

what are the 5 signs of 3 and 9 o’clock staining

A
  • Usually bilateral
  • Staining
  • Dellen
  • Vessel encroachment
  • Opacification of tissue
57
Q

what is dellen (a sign of 3 and 9 o’clock staining)

A

it is a depression at the side of the cornea formed from an impression

58
Q

list the 8 causes of 3 and 9 o’clock staining

A
  • Poor or incomplete blinking
  • Poor tear film
  • Large eye (wide palpebral
    aperture)
  • RGP material
  • Excessive edge clearance
  • Edges to thick
  • Total diameter too large
  • Total diameter too small
59
Q

list 9 solutions/managements of 3 and 9 o’clock staining

A
  • Break from lens wear- (esp if moderate)
  • Correct blinking
  • Change care regime, ocular lubricants
  • Refit with different material (e.g. soft lens as has a wider diameter)
  • Refit with a soft lens
  • Refit with lid attachment design
  • Different TD
  • Different peripheral design
  • lots of lubrication so the eye doesn’t dry out
60
Q

why do RGP lenses cause mechanical effects to the eye

A

because they’re a rigid/hard material

61
Q

what 7 things can mechanical changes from RGP lenses to the eye cause

A
  • Corneal shape changes
    Corneal topography changes and corneal warpage
    Fischer-Schweitzer pattern
  • Lens binding
  • Dimple staining
  • Foreign body tracks
  • Ptosis
  • Contact lens associated palpebral changes (mechanical or allergic)
  • 3 & 9 o clock staining (mechanical origin)
62
Q

what is the main lens associated with corneal shape changes/warpage

A

ill fitting PMMA lenses

63
Q

what is useful for monitoring corneal shape changes/warpage

A

corneal topography

should be done before and after contact lens fitting

64
Q

what may be contraindicated with corneal shape changes/warpage

A

refractive surgery

65
Q

what is the wrinkling of bowman’s membrane called

A

Fischer-Schweitzer pattern

66
Q

what is the appearance of Fischer-Schweitzer pattern

A

polygonal mosaic

67
Q

what is Fischer-Schweitzer pattern caused by

A

it is a stress indicator, caused by stress of a rigid lens rubbing on the cornea and also caused by rubbing the eye

68
Q

how far can a Fischer-Schweitzer pattern extend over the cornea

A

it can be localised or can cover the whole cornea

69
Q

when does Fischer-Schweitzer pattern disappear and how

A
  • on lens removal

- as the cornea bounces back into shape

70
Q

what is the ddx of Fischer-Schweitzer pattern

A

epithelial wrinkling

71
Q

describe the association, appearance and symptoms of epithelial wrinkling (which makes it different to Fischer-Schweitzer pattern)

A
  • Rare
  • Associated with soft CL
  • Small lines or furrows, at any
    angle
  • Very painful
  • Vision affected
72
Q

what causes lens binding

A

an immobile, decenetred lens

due to eyelid pressure, forming an indentation of the cornea by lens edge

73
Q

what can be noted inside from lens binding due to the indentation of the cornea by lens edge

A

superficial punctate keratitis

74
Q

what type of effect does lens binding have on the eye

A

suction effect

75
Q

what may a patient experience with lens binding

A

difficulty in removing their lens due to the suction effect

76
Q

what may be seen on removal of a lens with lens binding

A

indentation staining

77
Q

what is the management of lens binding

A
  • alter the lens fit and aim to increase mobility

- cease lens wear temporarily

78
Q

what is simple staining/veiling

A

small bubbles which become mechanically compressed between the lens and the eye, causing indentations in the corneal epithelium

79
Q

what is the cause of dimple staining/veiling

A

poor lens fit relationship between cornea and posterior

lens surface

80
Q

what is the management of dimple staining/veiling

A
  • Remove lens (to let the eye recover)

- Modify fit

81
Q

when can dimple staining/veiling disturb vision

A

if its in the middle of the visual axis

82
Q

with which lenses are foreign body tracks more common

A

in PMMA lenses and RGP lenses rather than soft

83
Q

what type of appearance does foreign body tracks have and why

A

Linear staining-indicates path taken by FB = scratched cornea

84
Q

what are the symptoms of a foreign body track

A

– Lacrimation

– Discomfort

85
Q

what must you assess with foreign body tracks and how

A

the depth and extent by doing an optic section on slit lamp

86
Q

what is the management for foreign body tracks

A

Remove lens (search for the FB), address cause, maybe replace lens

87
Q

why should you know which FB is causing the FB track

A

to know if it is a dangerous particle or a sterile substance e.g. if from the soil, it can be fungal which can lead to dangerous conditions

88
Q

what can cause ptosis

A
  • Long-term wearers of PMMA or RGP lenses
  • Possibly due to lens removal procedure of pulling laterally on
    the eyelids followed by a harsh blink
  • Other causes may be the constant rubbing of the lens edge
    against the palpebral conjunctiva
89
Q

what will you want to exclude when assessing contact lens related ptosis

A

other serious neurological causes

90
Q

what can be the management for ptosis

A
  • could try soft lenses or cease wear

- or explain to patient not to be so aggressive with RGP lenses

91
Q

where is CL associated palpebral changes located and what appearance does it have

A
  • Towards the lash margin (underside of eyelid)
  • Crater-like form
  • Often appear as round light reflexes, giving an irregular specular reflection
92
Q

how can you tell if someone with contact lens associated palpebral changes has it due to mechanical reaction

A

they will have a delayed reaction

93
Q

what is the aetiology of someone who has immediate contact lens associated palpebral changes

A

if it is allergic

94
Q

what can be a allergic cause for a patient who has contact lens associated palpebral changes

A

lens solution toxicity

95
Q

contact lens associated palpebral changes is caused by continual interaction with the __________ ___________

A

contact lens associated palpebral changes is caused by continual interaction with the tarsal surface

96
Q

the cause of contact lens associated palpebral changes can be ___________ or _________

A

the cause of contact lens associated palpebral changes can be mechanical or allergic

97
Q

what are more numerous in allergic contact lens associated palpebral changes

A

the papillae

98
Q

where are the papillae located with allergic contact lens associated palpebral changes

A

closer to the fold of the eyelid

99
Q

what is the appearance of the papillae in allergic contact lens associated palpebral changes

A

the apex of the papillae take on a rounded, flatter form

100
Q

what is the management of allergic contact lens associated palpebral changes

A

frequent replacement

101
Q

what is the main cause of solution toxicity

A

sensitivity to the preservative

102
Q

what are the signs and symptoms or solution reaction

A
  • Localised epithelial reaction
    (Superficial punctate keratitis)
  • Conjunctival hyperaemia
  • Burning sensation
103
Q

what can be a management of a solution reaction

A

switch to daily lens to avoid solutions all together

Contact lenses year 3 (15 decks)

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