CLs OSCE Flashcards
CL AC Hx and symptoms
. 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
CL fit Hx and symptoms
. 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
(Asymptomatic) infiltrative keratitis
. 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
Superior epithelial arcuate lesion (SEAL)
. 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)
Contact lens associated papillary conjunctivitis (CLPC)
. 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
Contact lens red eye (CLARE)
. 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%
Abrasion
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
Desiccation
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
Neovascularisation
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
Dellen
Causes: caused by localised dryness and desiccation
Signs: possible scarring, vascularisation, 3 and 9 o’clock staining
Management: eliminate cause
Oedema
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
Keratitis
Inflammation of cornea
- Infections (bacterial, viral, protozoal, fungal)
- Non-infectious (inflammatory, exposure, latrogenic-caused by medical treatment)
Microbial keratitis
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
- bacterial keratitis: 60-90% of all microbial keratitis
. 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
- Acanthamoeba keratitis
. 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
- fungal keratitis
. 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
- Keratitis caused by virus most common (HSV, VZV)
- 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
- Herpes zoster keratitis (HSK)
. Ophthalmic shingles (corneal involvement in 65%)
. Refer immediate GP (skin lesions) or one week (deep, uveitis,
IOP raised)
- marginal keratitis
. 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
- contact lens peripheral ulcer (CLPU)
. 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
Differential of infective vs non-infective (P.E.D.A.L.S)
. 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
CL TYPES
- RGP (Toric GP/Multifocal GP/spherical GP)
- soft (multifocal/Toric soft/spherical soft)
- Hybrids (scleral/scleral multifocals, ortho-k)
RGP vs SCL
. Rgp
-Better vision
-Corneal irregularity
-Dry eyes
-Compliance
-Scl failure
. Scl
-Comfort
-Infrequent wear
-Environment
-Rgp failure including fitting problems
Properties of CL materials
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
RGP lens materials
- PMMA
Advantages: Great stability, No deposits, low weight
Disadvantages: Zero DK, causes hypoxia, oedema, and central corneal clouding - silicone acrylates
Silicone added to increase Dk
e.g. Boston IV, Dk 26
. more protein deposits
. generally lower Dk values
. poor wettability - 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
SCL materials
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
- 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
Which SCL material to choose?
. more oxygen = SiHy
. if EW or CW = SiHy
. deposits (lipids attracted to SiHy; proteins attracted Hy)
RGP
-Good visual acuity and contrast sensitivity, good for people with high corneal astigmatism
RGP materials
. 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
RGP designs
Spherical: Bi curve C2, Tri curve C3, multicurve – change any curve
Aspherical
RGP lens fitting
. 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
BOZR and Fluorescein pattern
. Rule of thumb: smallest change to make clinically significant impact: 0.1 mm
. If you see air bubble in centre: 0.3 mm flatter
BOZD
. should be 1.50mm larger than pupil size
. if pupils larger than BOZD, px will experience visual disturbances
. large BOZD= less flare/haloes
Smallest change you can make
BOZR=0.05
BOZD=0.5mm
BVP=0.5mm
BOZR and BOZD
. 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
BOZR and TD
. +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
TOO STEEP OR TOO FLAT
. Too steep: little/no movement = not enough tear exchange behind the lens: increase BOZR
. Too flat: lens moves too much= reduce BOZR (steeper)
RGP Observation
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
Aligned
. central very slight clearance (i.e. Pooling)
. Mid periphery aligned
Edge width is acceptable
Steep
. central clearance (i.e. pooling)
. mid periphery touch
. edge width acceptable or too thin
Flat
. central flat (i.e. touch)
. mid periphery clearance (i.e. pooling)
. Edge width too big
Toric WTR
V cornea steeper than H
. 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
Toric ATR
. 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
Steep
central pooling, minimal movement on blink, good centration, thin edge width
Flat
central touch, clearance in periphery, thick edge, excessive movement of lens
FP and back vertex power
. 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
Aspheric RGP
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
MC over AS
-more control over individual areas (BOZD)
AS Preferred over MC
-often successful first fit
-uniform FP
RGP care system
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
Toric RGP
. 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
What happens if spherical RGP is fitted on toric cornea?
. Fluctuations in vision (may be excessive movement, lens may not centre well)
. may cause corneal distortion
RGP toric lens options:
- 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 - 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 - Bitoric: for both corneal + lenticular astigmatism
-no stabilisation required
Soft contact lens fitting
Modalities
. Daily (DW)
. 7 Days and 6 nights (EW)
. 30 days and 29 nights (CW)
. overnight wear (OW)
SCL types
. 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
SCL materials
- Hydrogel (Hy)
. comfortable
. contains water: transports oxygen - 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
SCL care regimes
- Multipurpose solution
-clean, rub, rinse, store - Hydrogen peroxide
-metallic disc in case or tablet to neutralise the disinfectant before wear
-no adverse reaction to preservatives
SCL fitting
- BOZR: depends on availability – 0.60mm – 1.0mm flatter than flattest K
-HVID small – order flatter BOZR
-HVID big – order steeper BOZR - TD: 2.00mm greater than the HVID
-lens covers the cornea in all directions of gaze - Toric lens fitted if (<0.75 DC)
-if >0.75DC use the MSE (sphere + ½ cyl) - lens brand – wettability, modulus, and oxygen transmissibility
Lens evaluation
- VLM
Correct: 0.25-0.50mm
Tight: <0.20mm
Loose: > 1.0mm - Lag
Ideally: up to 1.0mm
Tight: <0.2mm
Loose: >1.0mm - 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% - VA
Tight: improves after blink
Loose: worsens after blink
What are some causes of reduced cl comfort
. incomplete blink
. Dryness- due to AC or fan
. reduced TBUT
. MGD
. Reduced tear prism height – reduced tear volume
Water content
. 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
Modulus
. 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
Dk/t (oxygen transmissibility) vs modulus
. higher modulus = higher DK/t
Water vs modulus
Higher water content = lower modulus
SCL deposits
- proteins
. attracted to hydrogel materials
. papillary conjunctivitis
. patient may have increased lens awareness
. Management: review care routine, change material, change to DW - lipids
. associated with SiHy
. MGD?
. smeary vision, colour fringes
. Management: review care routine, change to DW, treat MGD,
Change material - 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 - Jelly Bumps
. moderate discomfort
. focal, gelatinous lumps
. mucous, lipid protein and Ca build up
. management: care routine, increase lens replacement frequency - Mucin balls
. focal accumulation of mucous
. most common with high modulus: EW of SiHy
. vision affected
. Management: monitor, review lens material+ modality
Toric SCL
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
Presbyopic CL fitting
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
- 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 - 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
Orthokeratology
. 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
Benefits ORTHO K LENSES
. 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
Side effects ORTHO K LENSES
. 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
Keratoconus
. 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
Contact lens options for KC
- 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 - corneal GP’s
Example Rose K2, NO.7 C3/C4 design
Fitted with ‘3 point touch’
Advantages: vision, cheap
Disadvantages: poor comfort, adaptation - scleral
-lens lands on sclera
-no topographer needed
Advantages: vision, comfort, no need to fit the irregular corneal shape - Hybrids
RGP centre surrounded by SCL
Advantages: improved comfort, no dust under the lens, good vision
Disadvantages: handling can be tricky especially after removal
Myopia control contact lenses
. 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
Scleral contact lenses
. 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
Three types scleral lense
. Full scleral (18-24mm)
. Mini Scleral (15-18mm)
. corneo/semi scleral (13-15mm)
Benefits of scleral lenses
comfortable
. good vision
. don’t need to have major surgery
. easy to fit
. predictable results
Fitting mini sclerals
. 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
Lens insertion scleral
. 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
Fitting assessment for Mini scleral lenses
- 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 - 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 - 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
Disadvantages of scleral lenses
. Deposits
. Fogging
Care products SCLERAL
. Soft lens solutions
. Non preserved saline
