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
- oily layer - outtermost layer (first layer) - made by meibomian glands - stops evaporation of aqeuous humour - increases surface tension/vertical stability -lubricates the eyelids
Lipid Layer
26
- 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)
Aqueous Layer
27
- 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
Mucin Layer
28
- 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
Pre-Corneal fluid & CL
29
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
Tear Flow
30
-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
Blinking
31
- tear pool collects at lower lid margin -1/2 pre-corneal fluid volume collects here - each blink moves fluid around
Marginal Meniscus
32
-oxygen tranmissibility
Diffusivity/Solubility
33
- most common - hydrophilic gels (hydrogels) -plastic/silicon -silicon increased oxygen
Soft CL
34
- 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
Continuous Wear (extended wear/EW)
35
- previously used - PMMA material didnt allow flow of oxygen - risk of corneal edema
Hard (rigid) lenses
36
- 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
Gas Permeable Hard Lenses (GP/RGP)
37
-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)
Combination Lenses
38
- specifically designed GP lenses - worn while sleeping - re-shapes cornea - mild/moderate Rx - no correction needed during daytime
Accelerated Orthokeratology (AOK)
39
- CL for high powers - post-cataract surgeries without IOL inserted (10+ D) - silisoft = babies without IOL
Aphakic CL
40
- to cover & protect the cornea - large lenses/ blankets - retains moisture - pain relief
Bandage CL
41
- for presbyopics 1) Annular (concentric) 2) Prism Ballast (translating) 3) Aspheric 4) Diffractive 5) Mono vision
Multifocal CL
42
- uses opposing rings - center ring = distance - outside rings = near
Annular (concentric) CL
43
- translating - resembles bifocal - top 1/2 = distance - bottom 1/2 = near
Prism Ballast CL
44
- Rx grandually changes from top to bottom - top = near - bottom = distance -PAL like
Aspheric CL
45
- circular grooves - back surface of lens
Diffractive CL
46
- OD = distance - OS= near
Monovision CL
47
- supported by sclera - vaulted over cornea - tear-filled pocket (artificial tears) - bludge outwards - for sensitive corneas - irregular corneal shape
Scleral CL
48
-increase CL visibility (handeling = light blue) - reduces photophobia - enhance or change eye colour - identify OD from OS - helps px with colour vision defects
Tinted CL
49
- soft or GP -corrects astigmatism (corneal/lenticular) - laser marks on soft lens (assesing rotation) - can be weighted to keep place
Toric CL
50
- 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 -
Surfactant Cleaning Solution
51
- 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
Saline Solutions
52
-soaking solution - lens storage - destroys/limits bacteria growth - prevents scratching from touching case - hydrates lens - prevents dried on tear protiens/mucus
Disinfecting Solutions
53
- simple care for soft/GP lenses - first cleaned with surfactant - use fresh solution - inside case overnight - minimal risk of allergy - doesnt kill fungi/ acanthamoeba
Chemical disinfection
54
-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
Hydrogen Peroxide disinfection
55
- rarely used today (outdated) - case/lenses/saline heated high temp - higher heat = less time required - still most effective
Heat disinfection
56
- light kills bacteria - lens inside chamber with special solution - takes 15 mins - soft lenses only - rarely used today
UV disinfection
57
- 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
Wetting Soultions
58
- comfort drops - used to rewet the eye after insertion - not all soultions are compatible with lens types
Lubricating Solutions
59
- used weekly -removes protien deposits - reduced risk of Giant Papillary Conjunctivitis - 1 liquid type, but most are tablets - usually used for GP lenses
Enzymatic Cleaners
60
- 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
Lens Cases
61
- gritty/scratchy/sandy - cornea can be compromised longterm - blinking problems - dirty lenses - environment - hormonal changes - medications -tear chemistry
Dryness complication
62
- 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
Deposits/discolorations
63
- corneal epithelium rubbed off - caused by ill-fitting lens - overwearing - injury by foreign body - pain and photophobia
Abraisions
64
-Swelling of cornea - greater than normal fluid absorption -overwearing poor fit - dirty lens - foggy vision - damage deeper layers
Edema
65
- redness - discomfort -discharge -Acanthamoeba - Pseufomonas
Eye infections
66
- exposed to tap water - swimming pools - hot tubs -distilled water
Acanthamoeba
67
- wetting lenes inside mouth
Pseudomonas
68
- 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
Giant Papillary Conjunctivitis
69
- lack of oxygen on cornea - new blood vessels grow from limbus - caused by tight-fit - overwearring - dirty lenses -interfere with vision
Neovascularization
70
- mild discomfort - vision may be different from glasses - one eye might have better vision
Expected Soft Lens ajdustmen
71
-pain - extreme photophobia - redness - halos around lights - change in vision - cloudy vision - flare - vision blurred after 1 hour removal
Abnormal Soft Lens /GP reactions
72
- tearing - awareness sensation - sensitive to light/wind/smoke/dust - slightly blurred vision (excess tears) - slight redness - mild itching - mild fatigue
Expected GP adjustments
73
-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
Re-Center GP lens