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CLs OSCE Flashcards

1
Q

CL AC Hx and symptoms

A

. Rfv
. Lee and last ac
. Vision: dv, iv, nv (fluctuating, does blinking affect va) - floads
. Current cls: confirm lens type, rx
. Wearing time: today and usual: /24, /7
. Comfort (lenses drying out, ocular discomfort, redness, pain)
. Hygiene/lens care – solution, regime, wash hands
. General health/allergies
. Medication
. Ocular history (ambl, strab, hes, recent infections)
. Lifestyle: driving, occupation, hobbies

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2
Q

CL fit Hx and symptoms

A

. Rfv
. Lee
. Motivation for cl wear
. Intended wt
. Lapsed/ new cl wearer
. If lapsed ask cl history: type of cls previously worn, any issues, reason for stopping
. Any lens/modality preferences
. Va with specs?
. General health/allergies
. Medication
. Ocular history (ambl, strab, hes, recent infection)
. Lifestyle: driving, occupation, hobbies

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3
Q

(Asymptomatic) infiltrative keratitis

A

. White spots in cornea (infiltrates)
. Causes: response to hypoxia, bacteria, lens deposits, allergic reaction,
Poor hygiene

. Signs: moderately red and slightly watery

. Symptoms: mild foreign body sensation, mild photophobia

. Management:
-Temporary discontinuation
-Most signs and symptoms resolve within 48 hours
-Infiltrates resolve over 2-3 weeks
-Advice against ew
-If reoccur, switch to dd
-Careful monitoring
-Ocular lubricants and cold compress for symptomatic relief

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4
Q

Superior epithelial arcuate lesion (SEAL)

A

. Causes: mechanical pressure due to design or material in the superior cornea, below superior eyelid

. Signs: arcuate staining parallel to superior limbus (from 10 o’clock to 2 o’clock)

. Symptoms: unilateral, asymmetric, mildly symptomatic, foreign body sensation, irritation
. Mostly seen in patient’s wearing high modulus silicone hydrogel contact lenses

. Management:
-Cease cl wear for 1-7 days (depends on severity)
-Lubricants for symptomatic relief
-Review lens fit or material (use thinner, more flexible lens material)

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5
Q

Contact lens associated papillary conjunctivitis (CLPC)

A

. Causes: conjunctival inflammation, immunological response due to hypersensitivity to lens deposits or solution or mechanical response due to lens design or modulus

Symptoms early stages: discomfort towards the end of the day, itching,
Mucous on waking
Symptoms later stages: excessive discomfort, itching,
Lens movement as lens gets stuck to papillae

. Common in atopic patients (ask about gh
Clpc management:
. If grade > 2 (cease lens wear, lens wear can continue if symptoms permit, improve lens hygiene)
. Alter the lens material
. Replacing the lens more frequently
. Treating mgd
. Ocular lubricants for symptomatic relief
. Reducing wearing time
. Suspending or ceasing lens wear

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6
Q

Contact lens red eye (CLARE)

A

. Cause: inflammatory response of cornea and conjunctiva subsequent to period of eye closure with CL wear, due to endotoxins from gram negative bacteria

Signs: unilateral, acute hyperaemia, diffuse infiltrative keratitis, possibly AC
Reaction, VA unaffected

. Symptoms: itching, congestion, pain indicates corneal involvement,
Woken at night with painful red eye

. Risk factors: upper respiratory tract infection, high water content cls, tightly fitted cls due to minimal movement which decrease tear lens exchange
ASK ABOUT RECENT ILLNESS

. Management:
-Cease lens wear
-Self-limiting
-Temporary discontinuation CL wear
-Careful monitoring
-Advice risk of recurrence is 50-70%

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7
Q

Abrasion

A

Causes: insertion and removal, fingernails, due to lens imperfection
Symptoms: FB sensation, discomfort and pain, photophobia
Management: remove cause and cease lens wear for 24hrs

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8
Q

Desiccation

A

Causes: localised disruption of the corneal surface, incomplete blinking
Signs: punctate fluorescein staining often inferior band
Symptoms: dryness symptoms
Management: refit lens and use lubricants

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9
Q

Neovascularisation

A

Causes: due to hypoxia or lactic acid build up due to restricted venous drainage by a steep fitting lens
Management: high DK/t lens, decrease WT, steroids, or surgical intervention

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10
Q

Dellen

A

Causes: caused by localised dryness and desiccation
Signs: possible scarring, vascularisation, 3 and 9 o’clock staining
Management: eliminate cause

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11
Q

Oedema

A

Causes: increase in tissue fluid
Signs: striae (fine wispy white lines), haze (loss of corneal transparency)
Symptoms: degradation of vision
Management: increase DK/t and reduce WT

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12
Q

Keratitis

A

Inflammation of cornea

  1. Infections (bacterial, viral, protozoal, fungal)
  2. Non-infectious (inflammatory, exposure, latrogenic-caused by medical treatment)
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13
Q

Microbial keratitis

A

Causes: bacteria, fungi, viruses, protozoa

Risk factors: trauma, contact lens wear, surgery, ocular surface disease,
immunosuppression

Symptoms: FB sensation, worse on removal of lens, pain mild to severe, redness,
severe photophobia, discharge, blurred vision, awareness of yellow/white spot,
unilateral

Signs: lid oedema, epiphora, discharge, conjunctival hyperaemia, central corneal lesion, stromal infiltration beneath lesion, AC cells and flare

DD: sterile infiltrative keratitis (CLPU)

Management: emergency referral due to sight threatening nature

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14
Q
  1. bacterial keratitis: 60-90% of all microbial keratitis
A

. Caused by gram +ve and gram -ve microorganisms

. Risk factors: EW, poor hygiene, non-contact lens wearers (immunosuppression,
Ocular surface disease, trauma)

. Signs: infiltrate (generally central, large>1mm, full thickness epithelial loss), severe hyperaemia, AC reaction (cells, flare to hypopyon), lid oedema

. Symptoms: unilateral, moderate to severe pain, reduced vision depends on location, photophobia

. Management:
-Refer to A and E
-Immediately cease lens wear
-Corneal scrape or biopsy (take cl case to hospital) to determine which microorganism
-Intensive anti-microbial treatment such as fluroquinolone
-Close monitory

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15
Q
  1. Acanthamoeba keratitis
A

. Acanthamoeba is a free-living amoeba (protozoa) commonly found in living water,
It can cause a parasitic infection mostly seen in CL wearers, 90% occurs in SCL

. Risk factors: swimming or showering in lenses or use of tap water in cleaning regimes

. Symptoms: very painful, decreased vision, FB sensation, photophobia, tearing and
Discharge

. Signs: often diagnosed as HSV, radial perineuritis, anterior stromal infiltrates, AC activity, eventually ring infiltrates

. DD: in early stages dry eyes, HSV keratitis, recurrent corneal erosion, CL associated keratitis, bacterial, fungal, viral, or sterile keratitis

. Management: emergency referral due to sight threatening, biopsy and culture

. Prognosis: worse than any other infective keratitis unless caught early

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16
Q
  1. fungal keratitis
A

. Causes: very rare in the UK, typical in tropical/warm countries, caused by moulds, suspect if following trauma whilst gardening

. Clinical features: similar to bacterial keratitis

. Management: antifungals

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17
Q
  1. Keratitis caused by virus most common (HSV, VZV)
A
  1. Herpes simplex virus (HSV)
    . primary/recurrent/congenital
    . most HSV-1

Symptoms: unilateral, pain, photophobia, reduced VA, redness

Signs: punctate lesion coalescing into dendriform pattern, AC,
Raised IOP, keratic precipitates, geographical ulcer

DD: Herpes zoster keratitis, bacterial keratitis

Management: acute or recurrent HSK with no stromal involvement (urgent referral within 1 week), if stromal involvement in child or CL wear (emergency), topical ganciclovir

  1. Herpes zoster keratitis (HSK)
    . Ophthalmic shingles (corneal involvement in 65%)
    . Refer immediate GP (skin lesions) or one week (deep, uveitis,
    IOP raised)
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18
Q
  1. marginal keratitis
A

. Causes: inflammatory response to bacterial toxins on lids
. Non-infective
. Signs: accumulation/infiltration of white cells, epithelial defect/staining
. Management: refer, topical steroids and antibiotics, lid hygiene

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19
Q
  1. contact lens peripheral ulcer (CLPU)
A

. Causes: corneal response to bacterial toxins, immunological reactions, inflammation,
Sleeping with contact lenses

. Symptoms: eye moderately red or slightly watery, mild fb sensation better on
Lens removal, mild photophobia

. Signs: peripheral anterior stromal infiltrate, single or multiple, small>1.0mm,
Mild hyperaemia, epiphora, ac quiet or mildly inflamed, no lid oedema, usually unilateral

Ask about discharge, itchiness, cl wear, poh including surgery
. Dd: microbial keratitis, marginal keratitis, corneal scar, herpes simplex keratitis

Management: discontinue lens wear – most resolve within 48hrs, infiltrates resolve over 2-3 weeks, no ew, possibility of recurrence, examined daily for a week, no need to refer (only if unsure about mk), if no healing after 3-4 days refer – ocular lubricants, lid hygiene

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20
Q

Differential of infective vs non-infective (P.E.D.A.L.S)

A

. PAIN
-infective: intense worse on removal
-non-infective: little/absent relieved on lens removal

. EPITHELIUM
- infective: deep if ulcer
-non-infective: staining of overlying infiltrate

. DISCHARGE
-infective: muco-purulent discharge
-non-invective: none

. ANTERIOR CHAMBER
-infective: flare and cells from active infection
-non-infective: no signs

. LOCATION
-infective: single located centrally
-non-infective: multiple or single in the periphery

. SIZE
-infective: larger >1mm
-non-infective: small <1mm

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21
Q

CL TYPES

A
  1. RGP (Toric GP/Multifocal GP/spherical GP)
  2. soft (multifocal/Toric soft/spherical soft)
  3. Hybrids (scleral/scleral multifocals, ortho-k)
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22
Q

RGP vs SCL

A

. Rgp
-Better vision
-Corneal irregularity
-Dry eyes
-Compliance
-Scl failure

. Scl
-Comfort
-Infrequent wear
-Environment
-Rgp failure including fitting problems

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23
Q

Properties of CL materials

A

oxygen transmissibility (DK/t): amount of oxygen passing through a contact lens of specified thickness over a set amount of time and pressure difference
. Low DK/t can result in corneal changes: oedema, microcysts, blebs

Wettability: the ability of a drop of liquid to adhere to a solid surface
. greater wettability= improved vision and comfort and deposit resistance

Modulus: how well does the material resist deformation by pulling or stretching
. higher modulus= stiffer and better resistance to deformation, but px may complain of FB sensation due to stiffer lens material

Refractive index:
. increased refractive index = thinner lenses

Specific gravity: could be used to control RGP centration on cornea

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24
Q

RGP lens materials

A
  1. PMMA
    Advantages: Great stability, No deposits, low weight
    Disadvantages: Zero DK, causes hypoxia, oedema, and central corneal clouding
  2. silicone acrylates
    Silicone added to increase Dk
    e.g. Boston IV, Dk 26
    . more protein deposits
    . generally lower Dk values
    . poor wettability
  3. Fluorosilicone acrylates
    . Fluorine increase Dk
    . Higher SA content improves DK, but often reduces wettability
    e.g. Boston ES, DK 31 and Boston XO, Dk 100
    . improved wettability
    . more prone to lipid deposits, little protein deposits

FSA versus SA
Advantages
-increased oxygen permeability
-less hydrophobic
-less protein deposits

Disadvantages
-less stable
-more lipid
-higher modular weight

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25
Q

SCL materials

A

Low water content hydrogel material signs: limbal hyperaemia, neovascularisation. Epithelial microcysts, stromal striae

Higher water content of SCLs is important for oxygen to pass through the material to the cornea
. Advantages: high water content is great for health of the eye
. Disadvantage: dehydration causes significant corneal staining especially in thin lenses
. lens feels dry towards the end of the day due to dehydration
. it attracts more lens deposits

  1. silicone hydrogel (SiHy)
    Blend hydrogel characteristics (wetting, comfort, movement) with silicone characteristic (high oxygen permeability= less hypoxia)

Advantages of SiHy
. high oxygen permeability= less hypoxia
-less hyperaemia, less limbal injection, less vascularization, less corneal oedema, better comfort
Disadvantages of SiHy
. maximum oxygen permeability, but not always maximum comfort, increased modulus, possible FB sensation due to stiffer material
. high modulus: stiff material: discomfort= SEAL mechanical
. low modulus: poorer handling
. more prone to lipid deposition

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26
Q

Which SCL material to choose?

A

. more oxygen = SiHy
. if EW or CW = SiHy
. deposits (lipids attracted to SiHy; proteins attracted Hy)

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27
Q

RGP

A

-Good visual acuity and contrast sensitivity, good for people with high corneal astigmatism

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28
Q

RGP materials

A

. High Dk/t allows more oxygen to the eye = improves health of eye= less corneal/limbal vascularization
. High Dk/t = less stable on cornea, more prone to deposits

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29
Q

RGP designs

A

Spherical: Bi curve C2, Tri curve C3, multicurve – change any curve

Aspherical

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30
Q

RGP lens fitting

A

. Trial lens based on keratometry reading
. TD=1.5 - 2.0mm smaller than HVID
. calculate corneal astigmatism: 0.05mm=0.25D or 0.1mm=0.5D

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31
Q

BOZR and Fluorescein pattern

A

. Rule of thumb: smallest change to make clinically significant impact: 0.1 mm
. If you see air bubble in centre: 0.3 mm flatter

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32
Q

BOZD

A

. should be 1.50mm larger than pupil size
. if pupils larger than BOZD, px will experience visual disturbances
. large BOZD= less flare/haloes

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33
Q

Smallest change you can make

A

BOZR=0.05
BOZD=0.5mm
BVP=0.5mm

34
Q

BOZR and BOZD

A

. 0.5mm change in BOZD= 0.05mm change in BOZR to keep same Fluro pattern
. Example BOZR=8.00mm BOZD=7.50mm, new BOZD=8.0mm BOZR=8.05mm
. 1 step (0.05mm) larger BOZD means the Fluro pattern becomes 1 step (0.05 steeper), to keep same Fluro pattern you need to make the BOZR 1 step (0.05mm) flatter

35
Q

BOZR and TD

A

. +0.50mm to TD – flatten BOZR by 0.05mm
. -0.50mm to TD – steepen BOZR by 0.05mm
. Example: BOZR=7.80mm TD=9.30mm, increase TD by 0.50mm=9.80mm BOZR=7.85mm
. increasing TD by 1 step (+0.5mm), the Fluro pattern becomes 1 step (0.05mm) steeper, to keep same Fluro pattern, make BOZR 1 step (0.05mm) flatter

36
Q

TOO STEEP OR TOO FLAT

A

. Too steep: little/no movement = not enough tear exchange behind the lens: increase BOZR
. Too flat: lens moves too much= reduce BOZR (steeper)

37
Q

RGP Observation

A

Central part of the lens:
. BOZR (related to lens fit) – should be aligned or slightly steep
. BOZD (related to vision) – should be larger than pupil in mesopic condition
. Mid peripheral: should be aligned
. Peripheral: edge width less than 1.0mm
. TD should be less than 2mm smaller than HVID

38
Q

Aligned

A

. central very slight clearance (i.e. Pooling)
. Mid periphery aligned
Edge width is acceptable

39
Q

Steep

A

. central clearance (i.e. pooling)
. mid periphery touch
. edge width acceptable or too thin

40
Q

Flat

A

. central flat (i.e. touch)
. mid periphery clearance (i.e. pooling)
. Edge width too big

41
Q

Toric WTR
V cornea steeper than H

A

. horizontally (central aligned or very slight clearance i.e. pooling)
. Mid periphery aligned (i.e. slight touch- darker area on both sides)
. edge width acceptable

. Vertically (central flat i.e. touch)
. mid periphery clearance (i.e. pooling)
. edge width too much

42
Q

Toric ATR

A

. horizontally (central flat i.e. touch)
. mid periphery clearance (i.e. pooling)
. edge width too much

. Vertically (central aligned)
. mid periphery aligned
. edge width acceptable

43
Q

Steep

A

central pooling, minimal movement on blink, good centration, thin edge width

44
Q

Flat

A

central touch, clearance in periphery, thick edge, excessive movement of lens

45
Q

FP and back vertex power

A

. BOZR +0.1mm change = BVP+ 0.50D change
. BOZR -0.1mm change= BVP -0.50D change
. central pooling causes -ve over refraction
. steeper BOZR = positive tear power= more negative BVP
. flatter BOZR = more negative tear power= more positive BVP

46
Q

Aspheric RGP

A

Advantages:
-achieves true alignment-fit close to corneal topography
-more comfortable – pressure evenly distributed over cornea
-useful in higher astigmatism

Disadvantages:
-flat fitting – to aid movements
-can induce residual astigmatism and aberration

e.g. Quasar lens from No 7

47
Q

MC over AS

A

-more control over individual areas (BOZD)

48
Q

AS Preferred over MC

A

-often successful first fit
-uniform FP

49
Q

RGP care system

A

Boston 2 step (cleaner and conditioner) or GP multi action and flat case
. place cleaning solution onto the lens and rub for 30 seconds using little finger, use saline to remove any loosened debris and wash away the cleaning solution, place a drop of conditioning solution on the lens and store in conditioning solution

50
Q

Toric RGP

A

. If corneal astigmatism is more than -2.50DC, px must be fitted with toric RGP

. Refractive astigmatism= corneal + lenticular
-refractive astigmatism = spectacle Rx
-corneal astigmatism = difference between keratometry reading, 0.05 mm difference = 0.25 CA

51
Q

What happens if spherical RGP is fitted on toric cornea?

A

. Fluctuations in vision (may be excessive movement, lens may not centre well)
. may cause corneal distortion

52
Q

RGP toric lens options:

A
  1. Back surface toric: if CA >2.50D/difference in k is more than 0.50mm
    -This improves fit and visual performance
    -No stabilisation required as lens rotation minimal
  2. Front surface: for any remaining significant lenticular astigmatism (>0.75D)
    -front surface torics may required to improve VA where residual astigmatism is present
    -stabilisation required, as the lens need to orientate correctly, request prism ballast/truncation
  3. Bitoric: for both corneal + lenticular astigmatism
    -no stabilisation required
53
Q

Soft contact lens fitting

Modalities

A

. Daily (DW)
. 7 Days and 6 nights (EW)
. 30 days and 29 nights (CW)
. overnight wear (OW)

54
Q

SCL types

A

. Daily sphere contact lenses e.g. MyDay, Clariti 1 Day
. Daily toric contact lenses e.g. 1 Day moist (Acuvue)
. Monthly sphere contact lenses e.g. Bioinfinity
. Monthly toric contact lenses e.g. Bioinfinity
. 2-week replacement e.g. Acuvue Oasys with Transitions

55
Q

SCL materials

A
  1. Hydrogel (Hy)
    . comfortable
    . contains water: transports oxygen
  2. silicone hydrogel (SiHy)
    . more oxygen than Hy
    . allowed for use for EW/CW
    . greater modulus than Hy (can cause SEALs, CLPC, Mucin balls)
    . higher Dk- good for px with hypoxia/corneal oedema
    . more oxygen to cornea compared to hydrogel materials (less hypoxia, less limbal injection, less vascularization, less corneal oedema)
    . lower water content – slower dehydration
    . higher modulus = reduced comfort = FB sensation
56
Q

SCL care regimes

A
  1. Multipurpose solution
    -clean, rub, rinse, store
  2. Hydrogen peroxide
    -metallic disc in case or tablet to neutralise the disinfectant before wear
    -no adverse reaction to preservatives
57
Q

SCL fitting

A
  1. BOZR: depends on availability – 0.60mm – 1.0mm flatter than flattest K
    -HVID small – order flatter BOZR
    -HVID big – order steeper BOZR
  2. TD: 2.00mm greater than the HVID
    -lens covers the cornea in all directions of gaze
  3. Toric lens fitted if (<0.75 DC)
    -if >0.75DC use the MSE (sphere + ½ cyl)
  4. lens brand – wettability, modulus, and oxygen transmissibility
58
Q

Lens evaluation

A
  1. VLM
    Correct: 0.25-0.50mm
    Tight: <0.20mm
    Loose: > 1.0mm
  2. Lag
    Ideally: up to 1.0mm
    Tight: <0.2mm
    Loose: >1.0mm
  3. push up test
    Correct: 40-60%
    Tight: difficult to move 65-100%
    Loose: easy movement 35-0%
    -you must change the lens if PUT>75% or <25%
  4. VA
    Tight: improves after blink
    Loose: worsens after blink
59
Q

What are some causes of reduced cl comfort

A

. incomplete blink
. Dryness- due to AC or fan
. reduced TBUT
. MGD
. Reduced tear prism height – reduced tear volume

60
Q

Water content

A

. high water content important for oxygen to pass through the material to cornea
. high water content attract more proteins, dehydration
. increased water will increase Dk
. increased water will decrease modulus

61
Q

Modulus

A

. high modulus: stiff material: discomfort, resist deformation
. high modulus in SiHy: causes SEALs and mucin balls
. low modulus: easy to fit, increased comfort, reduced SEAL, poor handling

62
Q

Dk/t (oxygen transmissibility) vs modulus

A

. higher modulus = higher DK/t

63
Q

Water vs modulus

A

Higher water content = lower modulus

64
Q

SCL deposits

A
  1. proteins
    . attracted to hydrogel materials
    . papillary conjunctivitis
    . patient may have increased lens awareness
    . Management: review care routine, change material, change to DW
  2. lipids
    . associated with SiHy
    . MGD?
    . smeary vision, colour fringes
    . Management: review care routine, change to DW, treat MGD,
    Change material
  3. fungal
    . contamination of lens by fungus
    . areas of growth over lens
    . poor hygiene
    . associated with intermittent wearers and long-term lens storage
    . management: replace lens, review hygiene, DW
  4. Jelly Bumps
    . moderate discomfort
    . focal, gelatinous lumps
    . mucous, lipid protein and Ca build up
    . management: care routine, increase lens replacement frequency
  5. Mucin balls
    . focal accumulation of mucous
    . most common with high modulus: EW of SiHy
    . vision affected
    . Management: monitor, review lens material+ modality
65
Q

Toric SCL

A

Toric fits: cyl more than -0.75DS
Toric stabilisation techniques:
1. prism ballast
2. dynamic stabilisation

LARS method:
Left
Add
Right
Subtract

CAAS
Clockwise
Add
Anti-clockwise
Subtract

Example:
-1.00/-1.25 x 10
10 degrees clockwise
-1.00/-1.25 x 20

-2.50/-1.75 x 90
20 degrees anti-clockwise
-2.50/-1/75 x 70

66
Q

Presbyopic CL fitting

A

Identify sensory dominance
. with distance correction ask px to view the cart
. present a (+1.00/+2.00)
. ask the px which lens blur more
. letter more blurred in front of dominant eye

Options
1. over spectacles (distance contact lenses and reading spectacles over)
Advantages: no difference to cost, clear binocular vision at near and distance
Disadvantages: still need specs, poor cosmesis

  1. monovision
    . dominant eye is fully corrected for distance, other has reading prescription added to distance Rx
    . Advantages: no increase in cost, useful for existing wearers
    . Disadvantages: loss of stereopsis and contrast, adaptation required, cannot be used on monocular patients, not suitable for patients with strong near visual task demand
  2. multifocal
    . two images placed simultaneously on retina/doesn’t rely on lens movements
    . three subcategories (aspheric design, multizone, zonal aspheric)
    . Advantages: does not rely on lens movement, stereoacuity
    . disadvantages: adaptation, loss of contrast sensitivity, dependence on pupil size in the aspheric design

Fitting consideration
. Hx and symptoms
. patient expectations
. refractive error
. pupil size

67
Q

Orthokeratology

A

. corrects refractive errors in vision by changing the chape of the cornea with the temporary use of progressively flatter hard contact lenses
. the cornea is a transparent, flexible window at the front of the eye which lets light pass through the retina
. ortho-k reshape the cornea and change how light rays are bent when passing through, therefore correcting refractive error

What are they?
. They are RGP, it’s the firm material of these contact lenses that is able to reshape the flexible cornea
. worn overnight, removed when you wake up

68
Q

Benefits ORTHO K LENSES

A

. successful overnight wear results in good vision that can be maintained throughout the day post lens removal
. completely reversible
. people under the age of 40 with mild to moderate short-sightedness
. people who work in dusty environments
. people with dry eye, allergies, or discomfort
. sports

69
Q

Side effects ORTHO K LENSES

A

. require more time to fit
. aftercare is more frequent to ensure efficacy and safety
. full correction may not be achievable for all
. poor compliance which can cause infections
. corneal staining

70
Q

Keratoconus

A

. corneal thinning causing a cone-like bulge to develop
. causes irregular astigmatism
. onset is usually in teenage years
. if one parent has the disease, then each child has 50% chance of inheriting it

. signs and symptoms: worsening VA, increased irregular astigmatism, corneal thinning
. signs: oval shaped keratometry mires, steepest and flattest meridians not perpendicular, scissoring reflex with retinoscopy

71
Q

Contact lens options for KC

A
  1. soft KC lenses
    Advantages: comfort, simple to fit
    Disadvantages: thick lenses so even in high oxygen material Dk/t isn’t great, may not improve VA in advanced KC
  2. corneal GP’s
    Example Rose K2, NO.7 C3/C4 design
    Fitted with ‘3 point touch’
    Advantages: vision, cheap
    Disadvantages: poor comfort, adaptation
  3. scleral
    -lens lands on sclera
    -no topographer needed
    Advantages: vision, comfort, no need to fit the irregular corneal shape
  4. Hybrids
    RGP centre surrounded by SCL
    Advantages: improved comfort, no dust under the lens, good vision
    Disadvantages: handling can be tricky especially after removal
72
Q

Myopia control contact lenses

A

. correct near-sightedness and slows the progression of myopia in children aged 8-12
. important to manage myopia as lowers the risk of ocular disease such as RD and myopic atrophy
. Example MiSight 1 day which is a daily disposable contact lens
. works by controlling both axial length increase and myopia progression while fully correcting refractive error

73
Q

Scleral contact lenses

A

. They are lens which extend out on to the sclera (diameter can reach 22mm+)
. Mainly used when SCL don’t work

Why are they used?
For irregular astigmatism caused by
- Keratoconus
- Post corneal Trauma
- Post keratoplasty
- Post refractive surgery
- Exposure/protective

74
Q

Three types scleral lense

A

. Full scleral (18-24mm)
. Mini Scleral (15-18mm)
. corneo/semi scleral (13-15mm)

75
Q

Benefits of scleral lenses

A

comfortable
. good vision
. don’t need to have major surgery
. easy to fit
. predictable results

76
Q

Fitting mini sclerals

A

. Designed to vault the cornea entirely
. No contact with the cornea means: you can fit irregular cornea, protect corneal surface, minimise scarring
. fitted by sag/depth rather than by curvature
1. The lens should clear the entire cornea
2. The lens should clear the limbus
3. The lens should land on the sclera

77
Q

Lens insertion scleral

A

. Put preservative-free saline and sodium fluorescein into the lens
. have the patient look down
. practitioner holds upper lid with one hand and inserts lens with the other

78
Q

Fitting assessment for Mini scleral lenses

A
  1. central clearance zone
    -Make sure no underlying air bubbles
    -need clearance over the entire cornea
    -use optic section to compare thickens of lens to thickness of tear lens
  2. limbal clearance
    -look to see if fluorescein bleeds out from the centre to conjunctiva
    (observe in white light)
    -adjust limbal clearance by altering central curve
    -flatten gives greater clearance without changing the sag
  3. Scleral landing
    -sclera is supporting entire weight on lens, landing needs to be
    Smooth and not impinging any vessel

-lens too steep- central bubbles and pooling, scleral impingement, move to flatter lens
-lens too flat- stand off edge, central corneal compression, move to steeper lens

79
Q

Disadvantages of scleral lenses

A

. Deposits
. Fogging

80
Q

Care products SCLERAL

A

. Soft lens solutions
. Non preserved saline

OSCEs (2 decks)

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