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OV2006 contact lenses > indications for contact lenses and use of slit lamp > Flashcards

indications for contact lenses and use of slit lamp Flashcards

1
Q

why are contact lenses fitted ?

A

. to improve visual acuity
. for cosmetic reason
. convenience

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2
Q

what are types of contact lenses?

A
  1. rigid gas permeable (RGP; or rigid corneal lenses)
  2. soft lenses
  3. hybrids
  4. silicone rubber ( SRCL)
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3
Q

what are RGPs fitted for?

A

. they are fitted for spherical prescriptions, toric , multifocal

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4
Q

what are other forms of rigid lenses?

A

. scleral lenses

. ortho-k

  • theses lenses are significantly larger
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5
Q

what are ortho-k lenses?

A

. made to wear at night when the lens re-shapes the cornea after which the patient takes the lenses out in the morning and doesn’t need to wear any visual correction during the day

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6
Q

what are soft lenses fitted for ?

A

. fitted for spherical, toric and multifocal design

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7
Q

what are hybrids made off?

A

they are made of a combination of soft and rigid materials

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8
Q

what is silicone rubber ( SRCL ) used for ?

A

this is used as a therapeutic lens

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9
Q

what are the materials do RGP come in ?

A

. PMMA

. gas permeable materials

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10
Q

what are the 3 categories of rigid contact lenses in terms of size ?

A
  • smaller than corneal diameter (+/- 9.5 mm)
  • semi-scleral( +/- 14 mm)
  • scleral( +/- 18mm)
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11
Q

what materials do soft lenses come in ?

A

1- hydrogel
. hydrophilic, different water contents
2- silicone hydrogel
. mixture of silicone rubber and hydrophilic materials to create much more oxygen transmissibility
. this material lets through more oxygen and we can use it for extended wear- can sleep in these material- mixture of hydrophobic and hydrophilic

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12
Q

what size are soft lenses?

A
  • larger than cornea diameter ( +/- 14mm)
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13
Q

what is hybrid lens made off?

A

. made of a combination of rigid and soft lens material
. rigid centre which provides good vision like a rigid lens
. soft skirt attached which provides comfort like a soft lens

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14
Q

what is good about hybrid lenses ?

A

. they have a rigid lens which has good visual performance

. soft lens is mainly known for comfort §

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15
Q

what are silicone rubber lenses made off?

A

. hydrophobic ( made hydrophilic )

. extreme high oxygen permeability

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16
Q

when are SRCL mostly used ?

A

for therapeutic use due to high oxygen permeability

such as aphakia, corneal irregularities , dry eye

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17
Q

where are SRCL mostly fitted?

A

. mostly fitted in children who have aphakia which is the absence of crystalline lens within the eye

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18
Q

what are the motivations for cls?

A

. refractive, pathological
. cosmetic
. convenience

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19
Q

what are the indications for cls?

A

. refractive, pathological
. cosmetic ( plano colour)
. sports
. occupational

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20
Q

explain the refractive indication for cls use ?

A
  1. myopia - improves acuity, greater FoV, normal eye size, myopia control
  2. hyperopia - greater FoV, normal eye size, possibility of reduced acuity because there is less magnification which can cause fluctuating accommodation
  3. astigmatism - greater success in myopic eye
    . if DC is larger than DS you will notice more lens rotation when px blinks , this causes lower /poorer vision
  4. anisometropia - when the difference is large between the eyes
  5. binocular vision problems- only vertical prism in 1 eye possible
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21
Q

explain the pathological indications for cls?

A
  1. cranio-facial anomalies
  2. allergies ( spectacles; metal, rubber)
  3. irregular cornea
  4. keratoconus
  5. aphakia
  6. bandage
  7. protection
  8. cosmetic
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22
Q

what are contra-indications for cls?

A

1 . occupational -dust, chemical vapours, pc use ( cls will be dry ), poor ventilation

  1. allegies - hay fever, eczema around eyelids , sinusitis
  2. poor hygiene - recurrent conjunctivitis, blepharitis , herpes zoster, smoker
  3. ill health- conditions that have implications on tear film quality ( DM, hyper or hypothyroidism, arthritis, menopause)
  4. age - ability to handle cl
    e. g. infants? student? presbyope?
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23
Q

why would RGP be fitted?

A 
. vision - main reason for fitting RGP
. corneal irregularity 
. handling - easier to put in 
. dry eyes
. compliance - less chance of a corneal infection with RGP
. SCL failure
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24
Q

why would soft contact lenses ( SCL) be fitted?

A

. comfort
. infrequent wear ( e.g sports )
. environment
. RGP failure including fitting problems

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25
Q

when do we use slip lamp in CL practice?

A

. new CL fitting ( baseline measurements)
. Re-fit
. after care ( lens fit, surface condition, ocular integrity )- px regularly comes back and check vision, ocular surface health, comfort.

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26
Q

what magnification to use when examining cl using a slit lamp?

A

. low 6-10x for general eye
. medium 16x for structures
. high 25-40x for detail

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27
Q

when do we use low mag ?

A

. for general eye

  • lids/lashes
  • cornea
  • conjunctiva
  • sclera
28
Q

when do we use medium mag?

A

. for structures

  • blepharitis
  • meibomian gland dysfunction
  • concretions
  • corneal staining
29
Q

when do we use high mag?

A

. for details
- epithelial changes

  • stroma striae and folds caused by corneal oedema which is lack of oxygen
  • endothelial folds, blebs and polymegathism
30
Q

when do you see stoma striae ?

A

. when there is corneal swelling

31
Q

what happens when you see folds in the cornea?

A

. you know you have more than 10% swelling

32
Q

what is the cobalt blue filter in the slit lamp used for ?

A

. excites fluorescein dye

33
Q

what is the purpose of green ( red-free) filter?

A

. enhances contrast of blood vessels and rose bengal staining
. helps differentiate pigment lesions so they appear dark before the filter is applied compared to blood vessels which appear dark after the filter is applied

34
Q

what is the purpose of diffuser?

A

. this gives soft light which enables capture of low magnification images of the anterior eye and the adnexa
. the diffuser scatters the light from the illumination system which enables uniform illumination over the eye

35
Q

what is the purpose of neutral density filter?

A

. modifies all wavelengths of light and avoids under and over exposure
. reduces beam brightness, increases patient comfort

36
Q

what is the purpose of wratten 12 filter?

A

. enhances NaFl staining when used with blue light
. used to enhance staining
. improves contrast with fluorescein

37
Q

what is sodium fluorescein function ?

A

. permeates into the intercellular space associated with any epithelial cellular disruptions
. highlights epithelial defects and stains areas of missing cells
. used for dry eye assessments including the tear breakup time and visualisation of the tear prism height

38
Q

what do we use when using sodium fluorescein ?

A

. use cobalt blue filter at high illumination

39
Q

how long does sodium fluorescein dye last?

A

.dye may disappear after 2-4 minutes?

40
Q

what is lissamine green dye ?

A

.stains dead and degenerative cells
. used for diagnosis of dry eye diseases
. mainly used to check the bulbar conjunctiva and cornea and superior lid margin

41
Q

how to enhance the view with lissamine green dye?

A

.use the red ( wratten 25) filter to enhance staining

42
Q

how long does lassamine green dye last for ?

A

.between 1-4 minutes

43
Q

what is rose bengal dye?

A

. binds to epithelial cells which are uncoated by certain proteins
. stains dead cells and those unprotected by intact mucin layer
. no filter required and use high illumination
. used to observe the conjunctiva during dry eye investigation

44
Q

how do we view the eye during contact lens fitting?

A

. direct illumination - within the beam
. indirect illumination - outside the beam
. retro illumination - when using the back reflected light

45
Q

what technique to use when using slit lamp to assess cl?

A
  1. diffuse - general overview, see whole of cl
  2. parallelepiped- scan the cornea, conjunctiva, and cl
  3. optic section - assess depth ( increase mag)
  4. specular reflection - assess tear film and endothelium ( high mag)
  5. retro illumination - back light from iris or fundus
46
Q

why is retro illumination often used with cls?

A

. the complications we often observe are very small and difficult to see with direct light

47
Q

what are vacuoles ?

A

. found on the epithelial layer of an oxygen deprived cornea

. filled with a gas or with a fluid that has refractive index lower compared to its surrounding

. this means that when light travels through a vacuole using retro illumination, the light will divert

48
Q

what happens when viewing a vacuole using direct illumination ?

A

. when viewing a vacuole using direct illumination , the bubbles light up on the same site where the illumination system from your slit lamp is coming from , while the shadow within the bubble is seen on the other side

49
Q

what is a microcyst ?

A

. filled with dead cell material

. has a higher refractive index than its surrounding which means its refracts against the light

50
Q

how to spot the difference between a vacuole and a microcyst?

A

. vacuole - refraction with light

. microcyst - refraction against light

51
Q

what do we use the slit lamp for ?

A 
. to observe the cornea 5 segments
. tear film 
. lid margin ( superior and inferior )
. lashes ( inferior and superior)
. bulbar conjunctiva 4 segments
. palpebral conjunctiva ( inferior and superior
52
Q

what is the slit lamp routine when looking at cl?

A
  1. start with white light
    - general look at ocular adnexa , low mag, whole eye
    - sclerotic scatter, low mag
  2. increase mag, parallelepiped scan for
    - lashes and lid margins
    - tear prism height and continuity
    - conjunctiva
    - cornea ( from temp to nasal )
  3. change to optic section on high mag to assess depth of anything unusual
    - scan the cornea using direct and indirect
    - investigate the limbus separately
  4. use blue light and fluorescein ( with cl off)
    - we are looking for corneal staining
    examine
    . conjunctiva - 4 segments
    . cornea
    . tear break up time
    . tear prism
    . lid margin
5. back to white light 
examine 
-  lower lid eversion 
-  meibomian gland 
-  upper lid eversion
53
Q

what is the slit lamp routine for lens fit and condition?

A

. diffuse, direct or indirection for centration and movement
. direct for fit and surface conditions ( dryness, broken/chipped, deposits )

54
Q

what is the clinical grading system we use when record keeping?

A
  1. CCLRU - cornea and contact lens research unit
    . grading system that goes from 1 to 4
  2. efron grading scale
    . grading system that goes from 0 to 4
55
Q

what are the advantages of CCLRU ?

A

. uses real eyes

56
Q

what are disadvantages of CCLRU?

A

. uses different eyes

. uses different illumination which makes it hard to compare to your px

57
Q

what are the advantages of efron grading scale?

A

. precise severity shown

. image constancy

58
Q

what are the disadvantages of efron grading scale?

A

. not real eyes

59
Q

how do we grade ?

A

. we grade to the nearest 0.5
. rating of mild will be grade 2 or less which is considered normal limits
. a change of one grade or more at a follow-up visit is considered clinically significant

60
Q

why do we need to record keep?

A

record is a legal document

61
Q

what must you do when record keeping?

A

. accurate record of presenting signs and symptoms
. respond to complaints
. proof that standard of care was met

62
Q

what is important when record keeping?

A 
. monitoring progression
. record across time, within and between practitioners
. impact new therapies or management 
. patient communication 
. medico-legal requirements
63
Q

why are scale used ?

A

. standardized grading scale uses common language and reduces intra/inter observe variability

64
Q

explain the principles of grading scales?

A

. grade 0- normal - no action
. grade 1- trace- action rarely required
. grade 2- mild- action possibly required
. grade 3- moderate- action usually required
. grade 4- severe- action required

65
Q

why must you do when using a grading scale?

A

. choose a scale and stick with it

. always write which scale you used

66
Q

how common is corneal staining?

A

. clinically insignificant in 60% of CL wearers
. often asymptomatic ( severity signs not related to symptoms )
. in 35% of non-CL wearers due to incomplete blink or closure

OV2006 contact lenses (11 decks)

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