Rigid Gas Permeable Lenses (RGP) PDF

Rigid Gas Permeable Lenses (RGP) Flexure On-eye bending Descriptions VS Sizes - Corneal only (9.3mm / 10.8mm …) War...

Rigid Gas Permeable Lenses (RGP) Flexure On-eye bending Descriptions VS Sizes - Corneal only (9.3mm / 10.8mm …) Warpage Permanent distortion By*Highexcessive digital pressure Dk & abrasive cleaner Boston OX Types: Sphere & OrthoK ↓ g e.. Material - Silicone + Fluorine + PMMA (Fluorosilicone acrylate) OR silicone acrylate Hx: PMMA Hardness OK, Stable Initial discomfort Easy care, Resistant to scratch & deposit Potential warpage -> Hypoxia -> 30% syndrome improves O2 permeability Lower rate of CL-related keratitis Good optical Prolong blur (X gas permeable) Improves wettability More comfortable Larger diameter -> Less movement Better optical quality than SCL Avoid irregular cornea distortion (solving by tear lens) Staining - 3&9 o’clock More fragile than PMMA *Silicone: Increase fragility -> flexure More prone to lipid deposit -> Need plasma coating Specific cleaning agents may be required (* Can have MPS / H2O2) For PMMA -> RGP Initial discomfort (*1st time / from PMMA) NEED to EXPLAIN the problem of reduced sensation from PMMA Indications of wearing RGP if wearing PMMA: non-tolerant / Unsatisfactory wearing times / Unacceptable “spectacle blur” / Edge flare Solution sensitivity 1- SCL) > Higher corneal astig Distorted / Irregular cornea/ Corneal scar SCL: vascularisation / Insufficient quality OR quantity of tear film Contraindications of RGP Eyelid not covering S & I limbus Large corneal diameter (large lens -> gravity) Inadequate blinkers Heavy depositors Low lens centration despite modifications Parameters TD (Total diameter): 9.0 - 9.8 for RGP (HVID - 2) BOZD = TD - 1 to 1.5 mm (1.2 by most cases) *** If BOZD + 0.5mm -> NEED BOZR + 0.05 -> NEED BVP - 0.25 BOZR - affect lens fitting PC (peripheral curves) - affect edge fitting * Flatter than BOZR Minus Carrier Lenticular Plus Carrier Lenticular 1 For +ve lens 3 ↳ For -ve lens Central thickness *Aspheric lens design Fit more closely Sophisticated lathes Even pressure Difficult reproductivity & verification Smaller edge lift = less sensation May need to fit flatter than spherical to obtain movement Better astig cover Decentration when corneal apex decenter Absence of transition zones assist tear flow Presbyopia correction possible Toric lens: Spherical BOZR w/ Toric PC -> for stabilize lens -> Edge lift : Lens design VS BOZR VS Edge clearance : Lens design VS Cornea (topography) Radial (normal to lens edge) VS Axial (parallel to primary axis of lens) Edge lift -> Steeper BOZR = Greater edge lift RECELTTREL L BOZR Cornea -> Normal AEC value? Disagreement between 0.05 - 0.08mm 1 J 0.065 REC  Edge lift / Edge clearance - Lens designed flatter then the peripheral cornea Functions Tears exchange Capillary attraction & lens centration forces functioning Avoid pressure -> corneal consult Avoid lens adhesion -> Assist lens removeal by lids If inadequate / insufficient: If excess: Tears exchanges inadequate Frothing (Bubbles @ edge) / dimpling Poor lens movement Excess lens movement Pressure -> accurate staining Lens displace from cornea Lens adhesion & Difficult lens removal (-> 3 & 9 o’clock staining) Poor centration 3 & 9 o’clock staining (from tear film disruption) FOZD FOZR VS FPCR Sag *** Larger sag (low BOZR / Larger lens) = Steeper Lens removal methods Lid manipulation Blinking Suction holder - high level contamination | Danger if dislocate | forceful remove Fitting philosophies of the RGP lenses & Assessment of fitting Assessment of fitting Fitting goal: Alignment / Slightly flatter than alignment (-> Central touch = bearing) For Spherical RGP + toric: make sure steepest Good pupil coverage Even fluorescence Good comfort meridian not compromise corneal health Good vision Mid-peripheral should be darker Good corneal and lens alignment along flatest meridian Good edge clearance -> tear exchange Optimal EC Poor: Flat fit Central touch & Excessive fluorescein Spread to mid-periphery Lid sensation & Unstable vision Superior decentration (I pooling) Steep fit Excessive central pooling Trapped bubbles in centre “Dimple veiling” Hard touch + Narrow meniscus fluorescein Edge clearance too narrow Fitting procedures Starting point: K Value: Flattest K (e.g. 7.98 -> 8.00, impossible then 7.90) X MEAN K ***Consider peripheral cornea as well (cornea >9mm) BVP: as close to ocular Rx as possible (K reading only for central 3mm), +Cyl distribute & e-value Fitting process (Wearing) Clean & Insert * Avoid too much unwanted solution Possible problems: Acute redness (*Last overnight) Check if bubbles trapped w/ diffuse light Tearing Discomfort (outside from normal sensation) Advise patient looking down while blinking normally -> minimise lid sensation Foreign body Sensitivity to solution ! For tearing & moderate-to-severe irritation / discomfort -> Remove, clean, rinse, Reinsert Lens damage Allow 10 minutes settling & tearing (If more tearing then longer) Can check dimpling / wetting problem - Fitting assessment (WHITE LIGHT) Centration Blink normally & Look straight -> Record lens centration W/O effect of upper lid Look if pupil is within BOZD (crossing pupillary margin = flare) Lid Lid-lens relationship: lid attachment (attachment to upper) / extra-palpebral (both eyelid) / inter-palpebral (no eyelid) interaction -> These two most unlikely to produce corneal edema -> Usually for PMMA as small lens !: Lens sensation may be severe as upper cornea steep  Ask the patient to blink naturally -> lens movement (normally: 1.5-2.0mm), speed (medium to fast & smooth) Ask the patient to look left & right *Movement should within limbus for any gaze Movement Push lens gently w/ lower eyelid (Should drop smoothly & vertically to original position) on Blink Flat: move very quickly & Apical rotation (Curved path) Steep: Jerky movement & remain @ corneal apex (=cannot drop down) Fitting assessment (BLUE LIGHT) *Add fluorescein to SUPERIOR conjunctiva Draw and Describe fluorescein pattern !: Fluorescein may Central dilute from reflex tears -> Until subsided Mid-periphery Edge clearance On top of RGP lens -> notice blinking *If decentre -> move back to centre with aids of lid Fluorescein pattern lid attaching? * Edge clearance -> Width Toric cornea w/ Spherical RGP Mid-peripheral “Dumbbell” shape Spherical Steep: Unacceptable touch - - Steep meridian Flat meridian: “close-to” attachment cornea Flat: Too much fluorescein from central & Flat meridian > Steep meridian: w/o too much pooling Central If pooling: Too steep & NEED FLATTER lens If bearing: Too flat & NEED STEEPER lens - W Spherical cornea / toric corneal w/ toric RGP -> Tear layer profile (tear film layer thickness): touching = 0-20 um | slight = about 20 um | pooling > 30 um On-eye movement: Also examine w/ fluorescein in eye -> can also assess patterns from computer simulation (e.g. Kohima & Caroline 2009) If RGP pulled up by upper eyelid -> Pull upper eyelid gently & support lens in the centre of cornea !!!: Not mixing up Acceptable STEEP VS Acceptable FLAT **** NEED to assess as Whole Ordering: Look for Reversal point e.g. pooling bearing, if middle -> can order 0.05mm scale BOZD/LD +- 0.5 BOZR +- 0.05 BVP -+0.25 Look for K, lens fitting, ocular Rx, BVP make sense or not Entering information Type Material Supplier Color Parameters (BOZR, LD, BVP) -> Aim optical alignment @ central -> If dynamic fit not good (decentration, excessive movement…) Adjusting parameters * Lens diameter -> Remember also change BC & BVP if necessary RGP Consultations General eye examination (Hx **previous CL Hx, OH, DFE) Preliminary fitting -> (Hx) requirements, motivation, suitability, wearing hours Contradication (e.g. dropping! / to all CL wear) Expectations (Vision quality VS Comfort VS Health) Motivation (***Suggested by others) -> preliminary data (Rx, K-reading, pupil size *Day&Night, HVID, palpebral aperature, EOH) -> information discussion (lens type, price, routine…) e.g. SCL VS RGP -> Fitting assessment *** Normal VS abnormal discomfort -> Over-refraction -> Lens order Delivery Hx, VA, EOH assessment Assessment of the delivered lenses Instruction education Insert & Removal (Washing hands, fingernails, lens defect check, discomfort reinsert) Lens care and maintenance (Preparation, X Tap water, disinfect, Solutions) Wearing schedule (*O2 level & Presence of lens) New: 1st day - 3 hrs +1 hr / day Max before 1st A/C = 8hrs After: +1 / day Adaptation period -> time needed? Normal VS Abnormal symptoms? Aftercare schedule Aftercare Timeframe Guideline: AC1 - 2wks New wearer? VS Refitting? AC2 - 1mths after AC1 AC3 - 3mths “AC2” -> Actual schedule: Normal replacement? VS with Rx modifications? AC4 - 6mths “AC3” Further - 6-12mths “AC4” Corneal physiology Needed for check OH Evaluate performance and fit (review fitting, effect on eye, integrity of lens) *Normally 4 hours or more but not necessary Discuss any experiencing problems -> Remedial RGP calculation Formula (Corneal curvature Power): Actual cornea n: 1.376 Corneal power (in D) Actual tear n: 1.336 = 337.5 Radius of curvature (in mm) Astigmatism: Mostly by corneal cyl (regular: front surface) Javal’s rule: Rx astig = 1.25*corneal cyl + (+0.50x180) Ocular astig similar to corneal cyl parallel bitoric lens Significantly deviate oblique bitoric Spherical VS Toric lens for RGP correction Spherical limit for high cyl Compromised physical fit Residual astig compromise vision if corneal cyl and ocular astig significantly different Toric indication Corneal cyl (2-2.5 DC) *Must have 2D in RGP lens difference Contraindication for soft CL (unstable rotation, small palpebral fissure, irregular cornea) Parameters no Soft CL available Significant residual astig expected Poor contraction of spherical lens on toric cornea Excess clearance + heavy bearing -> Staining Front curve usually by lab to determine Unsaturated tear meniscus @ steepest meridian Toricity determination (BC) Fully match with corneal cyl -> “Saddle fit” - too steep for steep meridian -> Should be remaining 1/3 to 1/4 of corneal cyl // 0.75D to 1D flatter if toricity not high e.g. power 1 & reading - > Tearles - > power Determine toricity of BC s reading BC - > MGP Noth ↓ - -- Tearles power power SPE DetermineRGPMylindricalpowerneed spherical ( Given Toric BC > - Toricity 2 to d leus (compared If corneal cyl slightly smaller than ocular cyl Spherical lens > Power - -> thinner lens / more flexible material (induce flexure) Easy calculation OK for significant residual physiological astig Cover majority patient Get rid of optical error induced by lens rotation Compromised vision if high residual physiological astigmatism Degraded vision due to off-axis (in higher residual physiological astigmatism) Factors affecting lens on eye Forces acting on RGP lens Eyelid forces - Blinking Blinking: Lid closing - push down VS Lid opening - lift up Only helpful to stabilise lens in extrapalpebral fit (intrapalpebral no effect) Edge surface tension forces - Edge tears meniscus (surface tension) - Edge clearance Wider = better surface tension ! - Excessive also will break Narrow Normal Excessive · ·( Narrow tear meniscus Desaturated tears meniscus - if black Break Lens immobile Capillary forces - water movement due to forces of adhesion, cohesion and surface tension Back surface match closer to surface of cornea = better (more average = better) Flat: less attraction + Greater movement Steep: Less attraction but ALSO suction effect @ peripheral -> lens binding Also need thin layer for tears exchange Centre of gravity Affected by BVP, BOZR, thickness, OVERALL SIZE (*** +: shift posterior, capillary action VS -: increased weight -> drop, + > - unless thick / flat) -ve, thin, steep lens better centration : towards posterior Otherwise: towards the front as no support from cornea (+ve, thick, flat, large lens for flat cornea) Friction - Viscosity & Contact area Better Stability: Large lens w/ good alignment, decrease in post-lens tear film layer thickness, increase in viscosity Otherwise increases movement OLD: 9.2 -> NOW common: 9.6 = + Friction Eyelid forces Edge surface tension force · m Viscosity forces Tear fluid pressure Edge surface tension force # Gravity Other factors: Specific gravity - weight Lenticulation - thickness Refractive index - thickness + weight Edge shape - lid reaction *Anterior round -> +ve / low -ve: edge profile - minus carrier Hardness - lens flexure (Soft = more) -> Most cases: on / steeper than flat K -> Capillary force, Edge surface tension force -> flex towards steep -> Flatter than flat K -> flex to flat meridian Extended wear and disposable lenses Terminologies DW - Daily wear: NO overnight EW - Extended wear: MAX 7 days wear w/o removal !!!: Avoid CW unless strong indication (normally 1 week EW is enough) FW - Flexible wear: DW + EW (occasional) !!!: Wearing SCL to sleep =/= FW lenses (48.7% ppl doing so) CW - Continuous wear: MAX 30 nights w/o removal (*Achievable by replacing EW lenses immediate by another one) OW - Occasional wear: special occasions Extended wear When eyes are closed Advantages Convenient Reduced handling problems in child & elderly Others: glucose IOP Monitor & > - Therapeutic purposes (e.g. protection -> bulbous keratopathy, keratitis sicca / bandage / drug delivery) *ACUVUE -> antihistamine-releasing Constant clear vision (*-> Aphakic / Highly ametropic where hard to gain good vision for spectacles) !: IOL also favor Disadvantages Adverse effect from reduced O2 supply Need consideration & education O2 supply in closed eye: -> Increased risk from DW Aftercare STRONGLY needed + close monitor Conjunctiva + Aq ->Epithelium Mechanisms in eye & factors of risks of infection Aq -> Stroma & Endo & No blinking -> X tear pump & tear debris staying Reduce in O2 supply (mainly from atmosphere) *!: Corneal hypoxia CO2 accumulate -> acidic tears Metabolic activity increases -> temp + Relative Risk of Microbial Keratitis X evaporation -> relatively low osmolarity RGP DW: 1X Epithelium thinning due to decreased rate of mitosis -> easier break down + more prone to infection SCL DW: 2-3X Constant trauma from the movement of the lens on eye RGP EW: 3-4X Accumulation of deposits due to long period between cleaning SCL EW: 8-20X Indications of EW Bandage (Relief S&S, Protection & Support, Promote healing, Maintain hydration, Retain medication) Paediatric (-> High Rx/Aphakic, for constant clear vision & development of normal vision, avoid amblyopia) *Silsoft: only silicone elastomer lens Occupational needed (e.g. on-call -> need immediate) Lack of facilities for lens disinfection (Short term only) MUST higher Dk/t as possible (*SiHy), and frequent replacement of lenses (3mths AT MOST) Contraindications of EW DW unsuccessful Poor / Compromised OHx / GHx Poor compliance Extended wear RGP RGP as less adverse effects than SCL (smaller corneal coverage + tear pump), but only applied EW in Ortho-K Reasons for not using: Discomfort (*Initial) Smaller corneal coverage Abrasions due to foreign bodies, mishandling, dislodgement 3 & 9 o’clock staining Corneal hyperaemia Corneal distortion Lens adherence Cannot absorb medication  Requirements for EW in RGP high Dk (>100) -> Dk required for CL wear sleeping similar effect as sleeping w/o CL (3% edema): 125 (Papas, 1998) VS DW: 24 recommended X Steep fit (on flat K) Only change to Steep fit if binding occurs Dk/t < 34.0 : 8% overnight edema Large TD Smaller TD (Recover to norm during daytime wear) More axial edge lift (around 0.15-0.20mm VS DW of 0.08) Aspheric & Muticurve Schedule for CL patients Aftercare 1st AC: end of DW schedule, EW: 2nd AC: MUST see next morning the first time they wear to sleep * Getting lens 3rd AC: still wearing 1st period (3-1wk) Daily Wear 4th AC: 2 was * 1st Al * 2nd Al * 3rd Al check DW Regular: 1-3 mths > - OK forEhe Wearing Extended Wear 1st CL wear: 6 hrs for 1st day -> daily after -> 7 days: 1st AC Already wearing: Max 10-12 hrs -> 7 days 1st AC -> Check if any problems with DW > 10 hrs * 4th AL -> NO: commence CL Limbus Limbus stem cells : Renewal of corneal epi, -> Damaged: affect epi regeneration -> subsequent coujunctival epi invasion & NV of corneal surface CL affect corneal epi maintenance & turnover -> also affect limbus High Dk SiHy better for maintaining limbus healthy + Show more evidence of adaptive recovery for long-term wear High Dk -> Signals for higher demand for new cells @ limbus -> More cells move toward surface -> Higher shedding rate *Look for entire lens Dk (may vary from central to peripheral *toric lens especially) Average Dk/t for frequent replacement of SCL ~ compromised vision *Avoid perfect vision task For mixed visual demand 2. Select design Need explain pros & cons 3. Trial fitting Need adaptation Loose trial lenses Bino vision checking for stimulating real circumstances 4. Visual assessment Long term visual =/= Trial visual (Recommend 15 days multifocal wearing before assessment) Principles for bifocal Simultaneous (Mainly SCL): seeing distant & near at the same time -> suppress out-of focus image Incident light is divided between distance and near focal -> Blurred image -> suppression Unavoidable compromised vision (Glare, CS) (*More obvious when target low contrast / low lighting) Well centered + Min movement needed Types Aspheric (most) - Concentric but multifocal, gradual change of curvature Center Near (Accommodation, -ve SA) *Demand more for Near VS Center Distant (Pupil gaze *only in RGP,+ve SA) *Demand for distant Back aspheric (better distant) VS Front aspheric (better near) Concentric rings (X common) - small central annular zone (2/3 to 3/4 pupil size) + rings (Bi-/Multi-zone concentric) Diffractive (rare) - Diffractive plate @ back surface -> Spliting into 2 focal points *Pupil dependent Alternating (ONLY RGP - more mobile): switch gaze to switch distance Vision close to spec if successful Types Rotational - Concentric / Aspheric Smaller zone Aspheric front (back any type OK) Stability controlled by prism / Truncation Difficult manufacture Non-rotational - Segmented (Like bifocal lenses) Difficult good fit Larger zone Fit to allow translation between near & distant Stabilty controlled by Prism ballast Low Lower lid / Large palpebral fissure not good candidate Modified monovision - if unsatisfactory (mono + Bi/Multifocal) ***Sensory dominant eye testing Demand near -> CN / high add @ dominant Demand distance -> CD / under-plus OR Mono @ dominant Other: EDOF (Extended Depth of Focus) Elongation of DoF (as a randge) instead of 2 foci points for MF lens -> intermediate better By combining several HOAs @ front surface *Varying power profile Other: Pinhole -> Corneal Inlay - create pinhole effect as implant -> Pinsole SCL @ non-dominant  CL astigmatism Astig consist of: Corneal (~90%) + Lenticular + Other internal Ocular [Javal’ s rule]= 1.25*difference in two meridian - 0.5x090 (lenticular) Classification of ocular astig Regular (Norm) Can be corrected by spectacle Regularity Irregular e.g. keratoconus Cannot be corrected by spectacles Axis Power WTR (high in young ( 0-30 | 150-180 60-120 Meridian ATR high in elderly 60-120 0-30 | 150-180 Oblique 31-59 | 121-149 31-59 | 121-149 Negligible 2.5D Optics of soft CLs All corneal toricity transferred to CL surface Very thin tear layer under the lens -> no power Normally not able to mask astig (except custom-made) Consideration of prescribing toric soft CLs Astig power Visual needs Type of astig Availability of parameters in the stock range / custom-made? *Cyl power Which eye affected? Stability of lens rotation Habitual correction Oxygen transmission Lifestyle / environment Motivation OH / physiologic variations (e.g. tight lids) Availability of products Cost Smaller range of Arial lenses ① power & You vision demand High Easy to determine final lens power Spherical Flow: Multifocal Lens thickness significantly different 8 Reason for CL wearing Starting Final lens fit closer to trial lens Spherical CL + Astig spectacles Cylindrical 1 Complicated calculation Fitting astig patient w/ spherical * At least wait for stabilize /checkpoint for 15 minutes : 5 mins) ( Equivalent sphere Trial lens fitting Tolerance Select Closestfaceparameters *BVPMajority e flit beam method/Clock in 2 meridian method ( * Estimation)& rotate :10 nasal. Rejet for > 20% Not stable Measure rotation & adjust axis when order & some may have orientation marking help to determine angular position (270/0 + 180/90 + 270) Soft toric CL Other fitting assessment CAAS * 100 interval >= -0.75 DC (Same as spherical) When products available + Achieving good correction & fit Fitting: Need to be stabilised = minimise rotation Nasal “kick” or 15 deg rotation when blinking (*Lid movement) *** High cyl stricter than low cyl  Different designs for toric lens stablization ⑳ 0.5 - 1.15 Dism -> Symptoms · Double ① One direction (better insert @ 90 deg) VS Two direction: orientation Front VS Back toric: Back more common as more closely approximate corneal toricity, but no evidence -> Custom-made protocol LD = 2.5-3 mm + HVID BOZR in spherical lens (=mean K + 0.6-0.7mm) Calculate ocular Rx from subjective & BVD -> determine closest Adapt general fitting assessment re-fitting if unexpected results Most commonly rotate 5-10 deg nasally *15minute to record Rotate > 20 deg / not stable should try different CAAS (e.g. 180 -> 20 then cyl 180 -> 160) Oblique lens less stable Empirical fitting: just by calculations Complications of CL Factors that possible victim / cause Key risk factor Tears Environmental Overnight wear Physical (include lens fit) Chemical Extended wear Lens power Microbiological Lens dehydration Immunological (e.g. allergic) Surface deposits / Poor wettability Non-compliance *** Hx (including wearing schedules) & Symptoms Altered blinking LOFTSEA Hypoxia Pre-existing systemic / ocular disease Diseases 1. CL-induced papillary conjunctivitis GPC Signs & Symptoms Mainly Upper palpebral conjunctiva inflammation Roughened, Cobblestone appearance * Enlarged papillae -> Fluorescein One main reason for dropout Hyperaemia Mainly from SCL (RGP less) Itchiness, Discomfort Mainly OU Blurred vision Incidence & Onset varies (0.4 & 48%, 2mth to 14yrs) Intolerance to lenses Mucus strands Grading: 5 areas 2. Neovascularization *** May take long time to disappear At limbus -> to cornea Asymptomatic until reaching pupil (ghost vessels) From hypoxia -> strongly softening -> epithelial irritation May not aware (stimulus) More common in extended SCL / conventional hydrogel SCL * 329 o'clock (*high myope w/ low Dk/t) / RGP (epithelial desiccation) Grading Scale: Superior Other areas 1. Trace 0.5-1.0mm 1. Trace =1.0mm - halfway pupil limbus 4. Severe >=2.5mm 4. Severe > halfway pupil limbus Possible actions Grade 1-2 Grade 3 Toxic / allergic -> new care regimen (cleaning…) Super / Hyper DK RGP (If not possible, then SiHy DW) Long WT -> change WS (DW -> EW / Hydrogel -> SiHy) Need more frequent AC Hypoxia -> increase Dk/t Grade 4 Mechanical effect -> modify lens fit / design Cease CL wear & refer for medical treatment if necessary 3. Corneal oedema (More H2O content than physiological 78%) Diffuse corneal edema Usually in SCL wearers Difficult to detect as diffuse If severe: Changes can be seen in cornea (not only in epithelium) Asymptomatic, but can cause blur / rainbow halos around light sources Grading: Grade 1 ( 1-3 striae (+1 as +1%) Loss of corneal transparency (15% mild -> 19% severe) Vision affected (20%+) Stromal oedema Striae Safe: no action needed Usually @ posterior stroma Possible actions if >5: Vertically oriented Reduce WT Usually not affect vision Switch from DW -> EW / SCL -> RGP *EW might have this @ morning, afternoon not likely Switch to high DK lenses Folds Cease wearing if severe Turning endothelial mosaic Unaffected vision Epithelial oedema *More severe S&S if severe & persistent: Only this change will result in halos Stromal oedema (e.g. CCC) Very vulnerable to damage Corneal Warpage syndrome Hypotonic tears (CO2 accumulate) more likely to be the reason than hypoxia Prenament refractive changes *PMMA many yrs In RGP: Can be Central cornea, not just epithelial Other causes Dependent to DK, WT, CT Excessive tearing Area @ frequently covered by CL Exposure to hypotonic water (swim…) Hazy vision after lens removal ** “Spectacle blur” Long WT Increased light scatter LASIK / cornea cross-linking (*temp) Usually disappear within 30-60 mins Actions depends on cause (E.g. RGP -> refit w/ looser, smaller OR new design OR higher DK lenses) 4. Epithelial microcysts 10-50um Fluid + cellular debris - Small, irregular shape inclusions @ paracentral - mid-peri May from dystrophy (EBMD) / inflammation / infection / chronic hypoxia (*EW) Common especially in extended SCL (*Non-wearer can also) Usually asymptomatic [Unless numerous (>200) -> affect vision] Critical levels: 30-50pcs Asso w/ other ocular changes Mx: Higher Dk lens 5. Endothelial bedewing Appearance New: Whitish & round & @ posterior endothelial surface -> may enter endo Over time: Orange/brown & irregular *inferior central cornea / below pupillary region S&S Actions Prognosis: Slight stinging Reduce WT / Cease Recover within 1 wk Intolerance to CLW Uveitis -> refer for medical treatment Particles may take mths Redness Intolerance also mths Reduced vision 6. Endothelial bleb VS cornea guttata: pernament Small, circumscribed, Irregular shaped black zone Endo oedema -> bulge back (to aq) -> X reflect light Asymptomatic Appear & disappear quick low Dk/t -> form within 10 mins of wearing May be transient Peak @ 20-30 min Suspect O2 supply / acidic change problem Still have some blebs when CL wearing + CO2 while O2 maintain Disappear within hours after lens off Lactic acid Difference noticed between CL no wear Low Dk: soft > RGP, other Dk similar Mx: High Dk/t lens 7. Endothelial polymegethism Varying endo cells size (*Polymorphism & increase polygonality) Actions: Small to Large cell ratio: 1:20 VS Normal 1:5 Monitor EW / long-term PMMA Recover slow process Specular refraction / Specular microscope (-> cell count / mm2) Extreme caution if comtemplating EW lens / cataract surgery Risk factors: Increasing age CL wear with low Dk/t Corneal surgical procedures (*Incision) Grading: 0 - 4 (CoV: 0.14/26/36/47/56) *Normal: 0.27-28 8. Overwear syndrome Decrease in O2 supple -> edema -> epi cell death -> desquamation (peeling) @ central cornea Both RGP & SCL possible Risk: increasing wearing time too fast / Sleep with lenses on Signs Symptoms Hyperemia Severe ocular pain Lid edema Excessive lacrimation Central cornea clouding Foreign body sensation Central cornea punctuate staining Lens intolerance Corneal distortion Photophobia Blurred vision Actions Cease wear until abrasion treated Pain & Discomfort -> pain killers (e.g. aspirin) Antibiotic eye drops (prophylactic) Education Refit (higher Dk/t OR RGP) Deal Croneal warpage Usually within 24 hrs recover, more severe longer time needed 9. Corneal warpage syndrome Poorly fitted RGP + Long term wear (*Ortho-K?) Astigmatism, corneal curvature (flatten/steepen) Usually asso w/ PMMA lens Cause: Mechanical: mould effect (*Stroma involved) Physiologic: low oxygen transmission to cornea  Signs Symptoms: Usually asympomatic Irregular keratometry & topography Deep stromal striae & opacification Management Cease CL wear Refit (?) - if poorly fit 10. Corneal staining 3 & 9 o’clock staining (*Not always 3 & 9 o’clock region) Drying up peri cornea w/ unstable tear film Fluctuate w/ time & environmental conditions Usually bilateral Specific to RGP lenses (factors that contribute): Reduced edge clearance to minimise lens movement If Larger LD -> + thickness (- lens) Reduced surface wettability -> tear instability Main causes: Mechanical problems (conjunctival irregularities / Lid gap: lid cornea -> inadequate resurfacing) Lens fitting (edge thickness / DW: too large OR excessive EC / EW: Inadequate mid-peri OR peri clearance) Inadequate blinking Abnormal tear composition (Heavy lipid contamination / mucin deficiency / inadequate aq) Signs Symptoms Early Later Itchy feeling (increase w/ WT) * May persist after lens removal 3&9 Dellen + Lens awareness Mild diffuse punctate staining Corneal scarring Dry Eye feeling Mild conjunctival hyperemia NV Corneal infection Dimple Veiling Corneal surface indentation by small air bubbles (trapped behind lens) Possible causes: Poor lens fitting Inadequate lens movement Improper lens insertion Action: Usually disappear within minutes after lens removal If reinsertion still have -> need modify fitting / change lens design Furrow staining Groovelive furrow perpendicular to limbus Superior limbal / circumlimbal Cause: No specific, mainly in EW with inadequate lens movement Actions: Switch to a more free-moving lens to improve fitting Switch to daily wear / RGP to prevent further complication Indentation ring Lens binding -> indentation RGP. Ortho-K @ cornea SCL/RGP -> conjunctiva Usually tight lens (Conjunctival from RGP can be flat), Ortho-K from other causes Foreign body scratches Arcuate stain SEALS (Superior epithelial arcuate lesions) 11. Conjucntival staining Conjunctival indentation ring Conjunctival staining Conjunctival epithelial flaps (CEF) Epi splitting from its underlying tissue (Epi + goblet cells dislocation) Might sheath neibouring conjunctiva SiHy*** 3% DW VS 37% CW Flaps marks the vertical movements of SiHy lens 0.5mm away from S&/I quadrants 0.1-0.5mm for DW, 9mm for CW Usually asymptomatic, recover takes 24 hrs - several wks Factors: Age & Gender not factor Modality Edge design (non-rounded?) Asian? -> higher lid tension Actions: Switch lens material / design Change lens-wearing modality 12. CL-associated red eye Chronic Red Eye Mainly in SCL (*esp EW), possible to be in RGP DW evening worst VS EW waking worst (*Limbal redness) Possible causes: Foreign body Lens (contam, lens defect, tight) Corneal hypoxia Allergic/toxic responses Action Cease wear & treat (H2O2? Deposit?) Review modality (WT? WS?) Refer if show no improvement Prognosis usually good, self-limiting after wear cessation CLARE (CL-induce ACUTE RE) “Tight lens syndrome” / “Nonulcerative keratitis” / “Acuteocclusive syndrome” More in EW SCL -> need monitor Sudden onset, unpredictable Signs for adverse response to solutions Unilateral mostly Conjunctival & Limbal injection Redness (*circumcorneal / regional) Diffuse SPK Possible causes: Chemosis (conjunctival) Lens too tight CLPC Eye closure with lens Follicles Mechanical trauma Symptoms Hypersensitivity Pain (Burning/Stinging) Lens deposits Foreign body sensation Hypoxia Itching Hygiene Lacrimation Inadequate disinfection Bacterial / Viral / Fungal - WT / tolerance Photophobia (if severe) Actions: Actions: Cease wearing Saline rinsing check cleaning regimen Ew -> DW Refit new CL / turn to RGP Cease if moderate - severe Preservative-free lens care system Refer if needed Hypoxia -> RGP / SiHy Refer if no improvement 13. CLPC (Contact lens associated capillary conjunctivitis) More seen in upper lid (Upper allergic VS Lower Bacterial) Vascular reaction (fibrovascular mounds w/ central vascular tuft) SiHy wearers: If localised: mechanical etiology (Edge design, lens modulus, surface characteristic) Asymptomatic Isolated to 1-2 areas in palpebral conjunctiva Actions: Cease wear until subsided Refit w/ different SiHy material (If recur -> Avoid SiHy, refit w/ DD or frequent replacement Hydrogel) 14. SLK (Superior lambic keratoconjunctivitis) Redness / Injection + Inflammation @ superior limbic region Bilateral* SCL Signs: Lens intolerance Increased mucous discharge Reduced vision (only if encroach pupil area) Symptoms: Foreign body sensation Burning / Itching Photophobia Intolerance 15. Corneal infiltrates Infiltration / Migration of cellular elements into cornea Hazy, greyish-white, circular / wooly Can be in different layers (? + ? + ?) * Shape | Size | Corneal staining | No. | Location Overlying epi intact CL-induced? (1% non CL wearer) Sterile VS Infected (more serious) Discrete collection of inflammatory cells CL-related: Corneal periphery (within limbus 3mm), clear zone between limbus & infiltrate More common in EW (than DW) Limbal vessels -> leukocytes enter… Possible aetiologies: Tight lens (debris trapped) Hypoxia (*EW) Mechanical trauma Lens deposits Drying Actions: Prognosis: Cease wear immediately Non-infective = excellent Monitor (*close) S&S Resolve quickly Refer for medical care (if moderate+) Infiltrate need few wks (severe up to 3 mths) -After signs subsided- Infective = depends (speed & efficacy of the treatment) DW**** Good if actions taken Flatten lens if too tight Vision can be threatened if delayed treatment WT -> higher Dk/t OR - WT Disposable / RGP / H2O2…  -> Sterile VS infiltrative infiltrative keratitis Immune infiltrate (rare) 16. Corneal infections Micro-organism: excavation of epi + Bowman’s layer stroma -> inflammation & necrosis CL is a major predisposing factor -> Lead to compromised natural ocular defence (e.g. break in epi) -> allow invasion… Non-compliance ALSO contribute Other causes: Green et al. (2008) Constant epithelial trauma (lens movement, reduced tear exchange, occlusion of lysozyme) Common risk factors for keratitis Chronic hypoxia & trauma 22% CL wear Compromised resistance 18% Corneal surface disease Risk + w/ no. of nights of EW (thinning epi) 16% Ocular trauma Symptoms: 11% Prior ocular surgery Red eye Commonly recovered organisms: Pain 17% Pseudomonas aeruginosa Sensitivity to light 9% coagulate-negative stphylococci Watery eyes 8% Staphylococcus aureus Blurry vision 3% Fungi Feeling something is “in” the eyes Most frequent contaminated: Types of micro-organisms: Lens accessories (42%) Bacteria (Pseudomonas aeruginosa, Acanthamoeba…) Px themselves / contam / ocular environment Most common Hand -> (CL) -> eye Fungi (Fusarium *asso w/ CL solution) Severe but uncommon Can penetrate SCL Some type from bathroom & CL case… Route: Case -> lens -> Eye Virus Rare & Not common Most likely: hand -> eye after touching open cold sore just prior to lens insertion Parasite - Acanthamoeba 95% Acanthamoeba asso w/ CL wear (1.56X for DD SCL, 5.4X for overnight wear) From ***home-made saline, water (lake, ocean, hot tub…) Non-specific symptoms as bacterial & viral *** Out-of-proportional pain Action: Dry hands after washing Prevention Avoid swimming w/ lens on OR remove ASAP after swim Cease CL wear until subsided conditions Refer for intensive antibiotic / antiviral / antifungal therapy 17. Contact lens peripheral ulcer (CLPU) Inflammatory reaction- unilateral More common in EW (EW SCL, CW SiHy) *** Bowman’s layer remains intact Round scar @ peri cornea Recurring -> high level of S. aureus / S. epidermidis @ lid & lashes Elimination of hypoxia X eliminate risk of CLPU Asymptomatic / Mild symptoms, relieved after lens removal, milder than MK Mild irritation Redness (*usually Localized / Restricted) Tearing Itching Cause: Gram +ve bacteria colonisation @ CL surface -> toxin -> whitish/gray focal anterior stromal infiltrate @ mid-peri to peri Action After subsided: Cease CL wear Resume w/ caution + new lenses (X old) Close monitor Warn for CW Refer for antibiotics Rest one night before replacement (no lens on) Recurrent -> switch to DW Prognosis: Prevention: Self-limiting: yea rapidly after lens removal Avoid overnight CL wear Greyish scar fades usually >6 mths 18. Contact lens-induced dry eye *Possible that Px already marginal dry eye (no S&S) BEFORE CL wearing -> CL aggravates DE condition Worsen for deposit (end of day), dry, smoky environments Main reason for unsuccessful CL wear Actions: Mild: Deposit -> Cleaning (e.g. Daily cleaner instead of MPS, + enzymatic cleaner if needed) Dry eye -> Encourage Blinking correctly / Train w/ Blinking exercise Dry Eye -> Unpreserved AT !: More difficult if asso w/ hypersensitivity (e.g. hormonal change / preservatives) Severe: Cease CL wear OR Try RGP / SiHy if for Hydrogel Need more comprehensive Dry Eye evaluations -> Classification & Management Refer if continue to have no improvement (systemic problems… etc) Keratoconus Idiopathic Asymmetrical thinnng of corneal stroma Progessive Irregular astigmatism Bilateral (Can have different severity) Apical protrusion Non-inflammatory ectasia Variable degrees of scarring Generally anterior (very rare posterior) Clinical findings that may be useful: Poor vision w/ spectacles Slit lamp: Monocular diplopia Vertical striae (early) Hx Family Hx Munson’s sign Excessive eye rubbing / itching Fleischer’s ring (round pigmented) - Headaches & general as the optic (eye strain) Rizzuti sign Distorted Apical thinning Vision - Rapid VA decrease Subepithelium scarring Scissors motion Rupture of Descemet’s membrane Ret Distortion Protrusion of cornea (Central / inferior) - DO / BIO - Circular shadow + Steepness Keratometry Distorted mires Need extension of range of keratometer CL options for keratoconus Px: SCL Reason: Lens design: Comfort *** RGP easily drop out Spheric optic zone + Aspheric periphery Not easy to drop out Front curve: reinforced optic zone Relatively easier fitting Pressure balancing hole for balanc pressure Scenario: between front & back Fail in wearing RGP improve optic stability Occupational concern Improve O2 transmissibility Some irregular astigmatism still exist (!) Eliminate bubbles & improve tears exchange RGP Forming tear lens -> neutralise corneal irregularity -> mimic cone-like shape of keratoconus cornea Multicurve design with small optic zone Fitting philosophies: Apical clearance VS Apical bearing VS Three point touch (Apex + mid-peri X2 ) Steeper lens Flatter lens Minimize apical scarring risk No bearing @ apical Bearing Facilitates tears exchange Reduce risk of scarring Better quality of vision Preferred Lens seal-off Heavy bearing Limited tears exchange Conreal scarring -> intolerance *** Refer to fitting guide for each design Lens binding Swirl staining Usually start with steeper BOZR Excessive edge lift Endpoint: acceptable dynamic & static fit Ideal: Central feather touch Peripheral edge lift: 0.5-0.7mm Possible problems: Lens sensation (intolerance / drop out…) Relying on corneal profile (increasing failing rate)  Other RGPs: Corneal RGP VS Quadrant specific CL When Px has keratoconus @ one specific quadrant: Corneal RGP: lifting, discomfort & easy to drop out Quadrant specific: increase sag height specific to lifted area -> better centration & stable visual performance Intra-limbal lens If other eye is suitable to be managed by SCL: Intra-limbal lens instead of RGP to reduce comfort difference between the two eyes *** Tip: keratoconic eye edge lift modification increments of 0.04mm to 0.08mm (normal: 0.01 to 0.03) Piggy-back (high plus SCL + RGP on top) High plus SCL for creating central steepened anterior corneal surface that smoothen out the irregularities of the cornea RGP = Hybrid lens Corneo-scleral -> Centration problems Evenly distribute pressure along corneal & scleral surface Improve lens centration Consistent vision (RGP) Good Comfort w/ peri soft lens Prevent dropping out of lens Scleral Design: PC4 PC PCI BC 3 Zones 5 Curves E. g 18 lens -. 2 mm Corneal: BC + PC1 8. 2 BC , 2 0PCI. Limbal: PC2 1. OPC2 Scleral: PC3 + PC4 1 5923.. 0. 5PC4 Special designs Standard Design Keratoconic Design - central curve relatively steeper than peripheral corneal curve Reverse geometry Design - central curve relatively flatter than peripheral corneal curve Fitting: Corneal zone - VRM (Value reduction method) Steeper than steep K (w/ higher sag than cornea) -> flatten /& lower sag until almost touch cornea -> adjust the central vaulting (aim: 100 - 400 um) Limbal zone Complete limbal clearance (If inadequate vault: + chord diameters / steepen curves) Scleral zone Rest evenly @ conjunctiva (should not blanch) Sectorial blanching: need toric PC / reduce diameter Scenarios for use: Extreme Rx Non-compromised OR less severe Px Other designs: Zone specific scleral lens  Reset entirely on cornea Tear lens vaults whole cornea Independent on corneal profile Severity of corneal irregularity does not affect lens fitting Able to achieve good fitting when other designs cannot Cosmetic CL, Prosthetic CL & Prosthetic Eyes Terms Cosmetic CL - tinted / painted CL used to Enhance or Alter appearance of a normal eye Prosthetic CL - tinted / painted CL used to Improve the appearance & Help to correct vision of a disfigured eye Tinted CL - refer both cosmetic and prosthetic CL Prosthetic eye - Artificial eyes CL tinting: Visibility tints Types: SCL: light blue / green RGP: Green, Blue… Identify which lens is for which eye Avoid mistaken if >1 pairs of lens in a family (e.g. ortho-K) Improve the visibility of the lens to Px -> aid handling Does not affect the eye colour Enhancement tints *Dramatically change a person’s iris color Types: Transparent color tints Wide variety of tints available Light iris color Sports enhancement Color deficiency (e.g. Red) -> should it be used in occupations? Dot matrix tints / Blending tints Solid (opaque) but translucent (see-through) tint (Can be more gradually opaque) Limited power range Iris detail (e.g. limbal rings, coronas) available Standard pupil opening restricts vision when dim light May appear artificial Opaque tints Change color of eye completely Stamped onto lens Painted tints Most expensive Approved dyes Customised (can match photograph of the fellow eye) Pupil transparent / opaque Cosmetic CL Indication of cosmetic CL wear Lens Care Regimen Motivation (changing colours) DD if possible Enhance natura color of eye MUST follow manufacturer’s instruction “Big Eye” effect Theatrical (drama…) settings Concerns: Hypoxia Detached color pigment -> safety issues (unknown response to the pigment) Sandwiched/ embedded design? -> 13 of 15 still has detach (Failing rub-off test) 6-15X more bacterial adhesion than lenses passing Not all are unsafe, but need more understanding (!: scarce information of the CCL) -> Need advise appropriately on selection & care Non-compliance, improper use -> risk of MK E.g. Alcohol party Wearing lens to sleep Sleep w/ lens on Overwearng lens Alcohol -> dehydration Improper care Suggest adding AT before lens removal Prosthetic CL Indications for prosthetic wear: Improve appearance of disfigured cornea / sclera / iris / crystalline lens Mask at part of disfigured eye due to ocular trauma / ocular disease / systemic health problems / congenital defects Patching eye (therapy) Reduce glare / photophobia (e.g. Aniridia / Iris defect) ‘Treat’ intractable binocular diplopia Scleral ONLY, XXX corneal design (unstable) Rare used as limited supplier Types of designs: Standard Stock lenses Custom hand painted lenses Well for dark coloured eyes Best for light eye (more exact color match) Less expensive Unlimited number / options Easier to fit in shorter time More expensive Limited options Greater chair time Offset prosthetic lens Mask deviated eye Need to measure HVID, Pupil diameter, lateral decentration & rotation needed