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Canadian Certified Optometric Assistant > Module 8: Contact Lenses > Flashcards

Module 8: Contact Lenses Flashcards

1
Q

Surrounding eye structures

A

Adnexa

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2
Q

-transparent tissue
-forms anterior refracting surface
- no blood vessels
- light not absorbed or diffused
-with the crystalline lens creates optical power
- has 5 layers (thinner in the center)

A

Cornea

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3
Q

-outermost layer
-5 cell layers thick (10% of thickness)
- 2 surface layers = squamous cells
- middle layers = wing cells
- last layer =basal cells
- water/aqueous do not pass easily
- cells are lipid material
-small attachments= desmosomes> repel water
- adjacent cells interwoven
-heals quickly/ does not scar
- total rejuvination in 7 days

A

Epithelium Layer

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4
Q
  • first two layers of epithelium
    -large & thin cells
  • project microvilli
  • continuosly dying/ sloughed into tear film
    -not as metabolically active as deeper layers
A

Squamous Cells

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5
Q
  • middle 2 layers of epithelium
    -migrate up from deeper layers
  • metabolically active
A

Wing Cells

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6
Q

-deepest layer of epithelium
- made of columnar-shaped cells
-most active cells
-secrete thin membrane lies between bowmans layer
-holds tightly attached to Bowman’s layer

A

Basal Cells

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7
Q
  • modification of stroma
  • made of collagen fibres
  • mucopolysaccharide ground substances
  • does not heal when injured
  • injuries affect visual aquity
A

Bowman’s Membrane

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8
Q
  • 90% of corneal thickness
    -200-250 cell layers (lamellae)
  • lamellae lay parallel to corneal surface
  • has fibroblasts> produce collagen
  • damaged= longterm swelling/infection> invading blood vessels
    -blood vessels supply oxygen but obscure vision
A

Stroma

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9
Q
  • 200-250 cell layers
  • lay parallel to corneal surface
  • made of collagen fibrils
  • surrounded by viscous substance
A

Lamellae Cells

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10
Q
  • produces collagen
  • located inside the Stroma
A

Fibroblast Cells

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11
Q
  • caused by injury/infection in Stroma
  • blood vessels invade but supply nutrients/oxygen
  • can obscure vision
A

Neovascularization

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12
Q
  • Attached to Stroma & Endothelium
  • very resistant to damage
  • thickens with age
  • elastic
A

Descement’s Membrane

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13
Q
  • bottom layer
  • 1 single layer w/ large cells
  • bathed in aqeuous humour
    -maintaines normal water content in stroma
  • very metabolically active
  • light damage = sourronding cells spread out and cover area
  • severe damage = corneal swelling & loss of corneal transparency
A

Endothelium Layer

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14
Q
  • carries dissolved oxygen to epithelium
    -oxygen diffuses through Stroma to endothelium
  • BUT aqueous humour primary supplier of oxygen
  • CL sits on top of/ not touching cornea
  • spreads with each blink
  • 3 layers thick
A

Tear Film

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15
Q
  • important in protecting the eye
  • keeps out foreign bodies
  • keeps eyes moist
  • spreads tear film over cornea/conjuctiva
  • outside = skin
    -inside = conjunctiva
  • fibrous tarsal plates
  • muscles & sebaceous glands
A

Eyelids

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16
Q

-inside layer of the eyelids
-thin/transparent tissue
- rich in blood vessels

A

Conjunctiva/ Eyelids

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17
Q

-almond-shaped opening between eyelids

A

Palpebral Fissure

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18
Q
  • eyelids joined nasally
A

Medial Canthus

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19
Q
  • eyelids joined temporally
A

Lateral Canthus

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20
Q
  • Near inner canthus
    -small hole
  • raised portion on lower lid
    -beginning of drainage system
A

Lacrimal Punctum

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21
Q
  • divided into anterior and posterior by grey line
  • eyelashes (cilia) anterior to grey line
    -meibomian gland ducts @ posterior grey line (mucocutaneous junction)
A

Lid Margin

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22
Q
  • located posterior grey line
  • mucocutaneous juncture
  • tarsus = 30 modified sebaceous glands> secrete sebum oil
A

Meibomian Glands

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23
Q
  • modified sebaceous glands
  • assocaited with lash follicles
  • works with meibomian glands
  • prevents overflow of tears
A

Glands of Zeis

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24
Q
  • pre-corneal fluid
    -thin/liquid layer
  • essential in maintaining cornea optical quality
  • health of cornea & conjuntiva
  • bad flow= dry/rough/opaque
  • 3 layers
A

Tear Film

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25
Q
  • oily layer
  • outtermost layer (first layer)
  • made by meibomian glands
  • stops evaporation of aqeuous humour
  • increases surface tension/vertical stability
    -lubricates the eyelids
A

Lipid Layer

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26
Q
  • made by main lacrimal gland & accessory lacrimal glands
    -thickest layer
    -keeps eyes wet
    -supplies atmospheric oxygen to corneal epithelium
    -antibacterial substances (lactoferrin/lysozyme)
    -provides smooth optical surface by abolishing little irregularities on cornea
  • washes away debris from cornea/conjunctiva
  • deficiency = keratoconjuctivitis sicca (KCS)
A

Aqueous Layer

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27
Q
  • glycoproteins
  • innermost layer
  • produced by goblet cells (conjunctiva)
  • wetting layer
    -smooth surface for light reflection
    -convert corneal epithelium from hydrophobic> hydrophilic surface
    -makes tears stick to eyes
  • without it aqueous solution cannot convert> will not be moistened by aqueous tears
A

Mucin Layer

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28
Q
  • hosts enviroment for CL
    -optically smooth/clean anterior cornea
    -rinsing system/remove debris
    -create reservoir/passageway for gasses (oxygen/carbon dioxide)
    -wetting
    -maintain soft lens hydration
  • create surface tension & capillarity to hold CL in place
A

Pre-Corneal fluid & CL

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29
Q

1) starting in the lacrimal glands= tears
2) tears @ superior cul-de-sac
3) upper & lower puncta
4) into tube-like canliculi
5) emptied into lacrimal sac
6) flow through nasolacrimal ducts
7) ending in the nose

A

Tear Flow

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30
Q

-10-15 times per minute
- provides first 3 layers of eyes with nutrition
- keeps cornea wet
- centering CL
- wiping action = spreads mucin layer> epithelial cells > tear film forms
- without wiping action = epithelium breakdown> transparency of cornea lost
- moves tears & debris > lid margin>puncta> nasal passage
- lower lid = horozontal/transverse/ nasal movement

A

Blinking

31
Q
  • tear pool collects at lower lid margin
    -1/2 pre-corneal fluid volume collects here
  • each blink moves fluid around
A

Marginal Meniscus

32
Q

-oxygen tranmissibility

A

Diffusivity/Solubility

33
Q
  • most common
  • hydrophilic gels (hydrogels)
    -plastic/silicon
    -silicon increased oxygen
A

Soft CL

34
Q
  • generally soft lenses
  • can be worn during sleep
  • increased risk of threatening complications
  • oxygen deprivation
  • high risk of bacterial infections
  • decreased cornea sensitivity= injury risk
A

Continuous Wear (extended wear/EW)

35
Q
  • previously used
  • PMMA material didnt allow flow of oxygen
  • risk of corneal edema
A

Hard (rigid) lenses

36
Q
  • allows oxygen passage 2 ways
    1) permeability through CL
    2) tear exchange
  • maintianes shape= good for torics
  • good for dry eyes/allergies/ infections/ high Rx
  • sharp vision
  • less lens deposits
  • less comfortable
  • long adaptation
  • flare at night
A

Gas Permeable Hard Lenses (GP/RGP)

37
Q

-hybrid lens
- soft/hard within the lens material
- keratoconus= hard center/soft skirt
- hard GP base w/ soft lens coating
-soft lens underneath GP (piggyback)

A

Combination Lenses

38
Q
  • specifically designed GP lenses
  • worn while sleeping
  • re-shapes cornea
  • mild/moderate Rx
  • no correction needed during daytime
A

Accelerated Orthokeratology (AOK)

39
Q
  • CL for high powers
  • post-cataract surgeries without IOL inserted (10+ D)
  • silisoft = babies without IOL
A

Aphakic CL

40
Q
  • to cover & protect the cornea
  • large lenses/ blankets
  • retains moisture
  • pain relief
A

Bandage CL

41
Q
  • for presbyopics
    1) Annular (concentric)
    2) Prism Ballast (translating)
    3) Aspheric
    4) Diffractive
    5) Mono vision
A

Multifocal CL

42
Q
  • uses opposing rings
  • center ring = distance
  • outside rings = near
A

Annular (concentric) CL

43
Q
  • translating
  • resembles bifocal
  • top 1/2 = distance
  • bottom 1/2 = near
A

Prism Ballast CL

44
Q
  • Rx grandually changes from top to bottom
  • top = near
  • bottom = distance
    -PAL like
A

Aspheric CL

45
Q
  • circular grooves
  • back surface of lens
A

Diffractive CL

46
Q
  • OD = distance
  • OS= near
A

Monovision CL

47
Q
  • supported by sclera
  • vaulted over cornea
  • tear-filled pocket (artificial tears)
  • bludge outwards
  • for sensitive corneas
  • irregular corneal shape
A

Scleral CL

48
Q

-increase CL visibility (handeling = light blue)
- reduces photophobia
- enhance or change eye colour
- identify OD from OS
- helps px with colour vision defects

A

Tinted CL

49
Q
  • soft or GP
    -corrects astigmatism (corneal/lenticular)
  • laser marks on soft lens (assesing rotation)
  • can be weighted to keep place
A

Toric CL

50
Q
  • daily use
  • preperation for disinfecting solutions
  • removes oil/mucous/protiens/debris/makeup
  • Has high Ph
    -chelating agents (EDTA) remove metal ions
  • rub lens side-to-side
  • rub lens in pie/triangular pattern
  • 1-2 drops @ end of day
  • ## rinsed in saline
A

Surfactant Cleaning Solution

51
Q
  • risning agent
  • pH varies from brand to brand (may cause stinging)
  • most use buffered products (borate/phosphate)= no stinging
  • some brands may have preservatives
  • no preservatives = not sterile after opening
  • yellow = expired
A

Saline Solutions

52
Q

-soaking solution
- lens storage
- destroys/limits bacteria growth
- prevents scratching from touching case
- hydrates lens
- prevents dried on tear protiens/mucus

A

Disinfecting Solutions

53
Q
  • simple care for soft/GP lenses
  • first cleaned with surfactant
  • use fresh solution
  • inside case overnight
  • minimal risk of allergy
  • doesnt kill fungi/ acanthamoeba
A

Chemical disinfection

54
Q

-quick disinfection time
- 2 step system
- not for longterm storage
- converts to saline (where bacteria can grow)
- most organisms killed in 20 mins
- but best soaked 6-8 hours
- must be neutralized before eye contact
- not nuetralizing = damage/pain for days

A

Hydrogen Peroxide disinfection

55
Q
  • rarely used today (outdated)
  • case/lenses/saline heated high temp
  • higher heat = less time required
  • still most effective
A

Heat disinfection

56
Q
  • light kills bacteria
  • lens inside chamber with special solution
  • takes 15 mins
  • soft lenses only
  • rarely used today
A

UV disinfection

57
Q
  • used with Gas Permeable lenses
  • placed on lens before contact with eyes
  • transforms hydrophobic > hydrophillic
  • mucoid layer take over after intitial process
  • helps clean the lens
  • mechanical buffer between lens/cornea/lids
  • soft lenses can do this with saline
A

Wetting Soultions

58
Q
  • comfort drops
  • used to rewet the eye after insertion
  • not all soultions are compatible with lens types
A

Lubricating Solutions

59
Q
  • used weekly
    -removes protien deposits
  • reduced risk of Giant Papillary Conjunctivitis
  • 1 liquid type, but most are tablets
  • usually used for GP lenses
A

Enzymatic Cleaners

60
Q
  • no substances leach from material used
  • clean with cleaning solution (rubbing(
  • rinse with saline or disinfectant
  • air dry upside down
  • can you toothbrush for deeper clean
  • can boil the case once a week
  • replace every time with new bottle solution
A

Lens Cases

61
Q
  • gritty/scratchy/sandy
  • cornea can be compromised longterm
  • blinking problems
  • dirty lenses
  • environment
  • hormonal changes
  • medications
    -tear chemistry
A

Dryness complication

62
Q
  • calcium deposits (crystals)
  • fungus (hairy/grey/brown/pink/orange)
    -Jelly bumps (white) = px tear chemistry
  • protein deposits (white film)
  • rust spots (brown/orange) metal flakes
A

Deposits/discolorations

63
Q
  • corneal epithelium rubbed off
  • caused by ill-fitting lens
  • overwearing
  • injury by foreign body
  • pain and photophobia
A

Abraisions

64
Q

-Swelling of cornea
- greater than normal fluid absorption
-overwearing poor fit
- dirty lens
- foggy vision
- damage deeper layers

A

Edema

65
Q
  • redness
  • discomfort
    -discharge
    -Acanthamoeba
  • Pseufomonas
A

Eye infections

66
Q
  • exposed to tap water
  • swimming pools
  • hot tubs
    -distilled water
A

Acanthamoeba

67
Q
  • wetting lenes inside mouth
A

Pseudomonas

68
Q
  • not cleaning CL adequately w/ surfactant
  • protein builds up
  • px develops allergy to proteins
  • eyelid = orange/bumpy
  • muscous/itching/blurry vision
  • topical steroids
  • discontinue entirely/ period of time
A

Giant Papillary Conjunctivitis

69
Q
  • lack of oxygen on cornea
  • new blood vessels grow from limbus
  • caused by tight-fit
  • overwearring
  • dirty lenses
    -interfere with vision
A

Neovascularization

70
Q
  • mild discomfort
  • vision may be different from glasses
  • one eye might have better vision
A

Expected Soft Lens ajdustmen

71
Q

-pain
- extreme photophobia
- redness
- halos around lights
- change in vision
- cloudy vision
- flare
- vision blurred after 1 hour removal

A

Abnormal Soft Lens /GP reactions

72
Q
  • tearing
  • awareness sensation
  • sensitive to light/wind/smoke/dust
  • slightly blurred vision (excess tears)
  • slight redness
  • mild itching
  • mild fatigue
A

Expected GP adjustments

73
Q

-manipulate lens with fingers through eyelid
- push lens on centre with fingers on lid margin
- move lens centrally> roated eye> fingers hold
-look in opposite direction> hold lens> pressure at canthus> rotate until slides under lens

A

Re-Center GP lens

Canadian Certified Optometric Assistant (9 decks)

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