3The Ideal Ortho-K Patient Suitable candidates for Ortho-KAge of Patient – older than 6 yearsSpherical refractive power +5D to DCylindrical refractive power:-1.50D or less W-T-Rule astigmatism-0.75D or less A-T-Rule astigmatismChildren with progressive myopiaPatients free of corneal pathologyPatients that are committed to initial and ongoing cost of treatment
4Screen for a healthy cornea Don’t fit when:Cornea is distortedEye Rubbing (treat allergies & habit)Soft or RGP imprints (allow rehabilitation)Corneal abnormalitiesIrregular corneal astigmatismKeratoconusPellucid Marginal DegenerationLid or corneal pathology is present
6Topographer Accuracy depends on: Software algorithms used to reconstruct corneal shape (update software)Stability of the patient’s tear film during capture (use wetting drops)Head position & movement during captureLid aperture (open eyes)Number of reading done to get statistically significant accuracyTake multiple readingsOmit high & low values
10Empirical Fitting Systems Corneal information is given to labLab designs lensLens worksOr it doesn’t!
11Systemised Fitting Systems General fitting process:Initial lens is chosen from chartFit with diagnostic trial lenses and evaluate NaFL pattern – Look for Bull’s eye patternInitial lens should not be too flat and should move 1 – 2mm on blinkEvaluate after 30 min using the topographerDoes the Px show a central flattening effect ?
12Systemised Fitting Systems General fitting processIf diagnostic lens looks acceptable, allow Px to wear overnight and evaluate the next morningIf the lens is too tight or too loose a different lens can be chosen from trial set and refitted
13Systemised Fitting Systems Lens adaptation and follow-upCentration is critical.Movement: 1 – 2 mm with blinking.Flourescein pattern: Bulls eye pattern.
15The Orthokeratology Company GOV – Global Ortho-K VisionVipok II – Non Conformed <-5.00DXMJ– Conformed <-5.00DXM – Conformed >5.00 <10.00DH – HyperopiaHP – Hyperopia PresbyopiaMP – Miopic PresbyopiaPost Lasik & KeratoconusWebsite (Plan Date Jan 2008)OrderingBlogPx & Prac Education
16The GOV System Advanced inventory system Multi-curve aspheric conformed Reverse Geometry LensesSimple method for myopia & hyperopia correctionYou are in control of the lens fit – not laboratoriesCorrect from +5.00D to DGOALA simple method to start Orthokeratology allowing for growth into fitting higher powers with the confidence that there is a support group.
17Benifits Simple effective system You choose the appropriate lens and make changesImmediate dispensing – (full trial set)Efficient and effective method to increase turnoverDevelop a specialty Ortho-k practiceConfidently fit with GOV support
18GOVTM lens details Base curve Hydraulic massage to central corneaConformed fitting curve (1st reverse zone)Space for tear circulation & tissue moldingAlignment curve (2nd reverse)Peripheral compression & centrationPeripheral curveTear reservoir for cornea wetting
19Predetermined OAD (lens size) OADs of trial lenses are predeterminedFlatter Ks accompany larger corneasSteeper Ks accompany smaller corneasKM rangeOAD% of HVIDBest-fit HVID40.00 ~ 42.2511.2 mm96%11.3~11.9 mm42.50 ~ 43.7510.8 mm94%11.2~11.6 mm44.00 ~ 47.5010.4 mm93%10.8~11.4 mm
20Fitting GOVTM Lenses External ocular exam Measure refraction, keratometry & HVIDSelect K-code by Mean KSelect Power-code by S.E.Order lenses Empirically and/or with trial fitK-code / Power-code / Color / Material / OADLens sizePredeterminedMatch Corneal size by Best-fit HVID
21Orthokeratology The GOV System K-code: Mean K = (Steep K + Flat K) / 2 Carry value up to 2 decimal places (0.01)Km in DioptersPower Calculation:SE = Spherical Spec power – [K astigmatism / 2]Spherical power must not be vertexedK astigmatism = steep K – flat K (in Dioptres)
22OAD 11.2 mm Best fit cornea 11.3~11.9 mm (OAD=95-97% of HVID) Mean K/ S.EOAD 11.2 mm Best fit cornea 11.3~11.9 mm (OAD=95-97% of HVID)A 39.87~40.11 (40.00)40.00/-1.540.00/-2.040.00/-2.540.00/-3.040.00/-3.540.00/-4.040.00/-4.540.00/-5.0B 40.12~40.36 (40.25)40.25/-1.540.25/-2.040.25/-2.540.25/-3.040.25/-3.540.25/-4.040.25/-4.540.25/-5.0C 40.37~40.66 (40.50)40.50/-1.540.50/-2.040.50/-2.540.50/-3.040.50/-3.540.50/-4.040.50/-4.540.50/-5.0D 40.67~40.86 (40.75)40.75/-1.540.75/-2.040.75/-2.540.75/-3.040.75/-3.540.75/-4.040.75/-4.540.75/-5.0E 40.87~41.11 (41.00)41.00/-1.541.00/-2.041.00/-2.541.00/-3.041.00/-3.541.00/-4.041.00/-4.541.00/-5.0F 41.12~41.36 (41.25)41.25/-1.541.25/-2.041.25/-2.541.25/-3.041.25/-3.541.25/-4.041.25/-4.541.25/-5.0G 41.37~41.66 (41.50)41.50/-1.541.50/-2.041.50/-2.541.50/-3.041.50/-3.541.50/-4.041.50/-4.541.50/-5.0H 41.67~41.86 (41.75)41.75/-1.541.75/-2.041.75/-2.541.75/-3.041.75/-3.541.75/-4.041.75/-4.541.75/-5.0I 41.87~42.11 (42.00)42.00/-1.542.00/-2.042.00/-2.542.00/-3.042.00/-3.542.00/-4.042.00/-4.542.00/-5.0J 42.12~42.36 (42.25)42.25/-1.542.25/-2.042.25/-2.542.25/-3.042.25/-3.542.25/-4.042.25/-4.542.25/-5.0OAD 10.8 mm Best fit cornea: 11.2~11.6 mm (OAD=93-95% of HVID)K 42.37~42.66 (42.50)42.50/-1.542.50/-2.042.50/-2.542.50/-3.042.50/-3.542.50/-4.042.50/-4.542.50/-5.0L 42.67~42.86 (42.75)42.75/-1.542.75/-2.042.75/-2.542.75/-3.042.75/-3.542.75/-4.042.75/-4.542.75/-5.0M 42.87~43.11 (43.00)43.00/-1.543.00/-2.043.00/-2.543.00/-3.043.00/-3.543.00/-4.043.00/-4.543.00/-5.0N 43.12~43.36 (43.25)43.25/-1.543.25/-2.043.25/-2.543.25/-3.043.25/-3.543.25/-4.043.25/-4.543.25/-5.0O 43.37~43.66 (43.50)43.50/-1.543.50/-2.043.50/-2.543.50/-3.043.50/-3.543.50/-4.043.50/-4.543.50/-5.0P 43.67~43.86 (43.75)43.75/-1.543.75/-2.043.75/-2.543.75/-3.043.75/-3.543.75/-4.043.75/-4.543.75/-5.0OAD 10.4 mm Best fit cornea: 10.8~11.4 mm (OAD=92-94% of HVID)Q 43.87~44.11 (44.00)44.00/-1.544.00/-2.044.00/-2.544.00/-3.044.00/-3.544.00/-4.044.00/-4.544.00/-5.0R 44.12~44.36 (44.25)44.25/-1.544.25/-2.044.25/-2.544.25/-3.044.25/-3.544.25/-4.044.25/-4.544.25/-5.0S 44.37~44.66 (44.50)44.50/-1.544.50/-2.044.50/-2.544.50/-3.044.50/-3.544.50/-4.044.50/-4.544.50/-5.0T 44.67~44.86 (44.75)44.75/-1.544.75/-2.044.75/-2.544.75/-3.044.75/-3.544.75/-4.044.75/-4.544.75/-5.0U 44.87~45.11 (45.00)45.00/-1.545.00/-2.045.00/-2.545.00/-3.045.00/-3.545.00/-4.045.00/-4.545.00/-5.0V 45.12~45.36 (45.25)45.25/-1.545.25/-2.045.25/-2.545.25/-3.045.25/-3.545.25/-4.045.25/-4.545.25/-5.0W 45.37~45.66 (45.50)45.50/-1.545.50/-2.045.50/-2.545.50/-3.045.50/-3.545.50/-4.045.50/-4.545.50/-5.0X 45.67~45.86 (45.75)45.75/-1.545.75/-2.045.75/-2.545.75/-3.045.75/-3.545.75/-4.045.75/-4.545.75/-5.0Y 45.87~46.11 (46.00)46.00/-1.546.00/-2.046.00/-2.546.00/-3.046.00/-3.546.00/-4.046.00/-4.546.00/-5.0Z 46.12~46.36 (46.25)46.25/-1.546.25/-2.046.25/-2.546.25/-3.046.25/-3.546.25/-4.046.25/-4.546.25/-5.0ZA 46.37~46.66 (46.50)46.50/-1.546.50/-2.046.50/-2.546.50/-3.046.50/-3.546.50/-4.046.50/-4.546.50/-5.0ZB 46.67~46.86 (46.75)46.75/-1.546.75/-2.046.75/-2.546.75/-3.046.75/-3.546.75/-4.046.75/-4.546.75/-5.0ZC 46.87~47.11 (47.00)47.00/-1.547.00/-2.047.00/-2.547.00/-3.047.00/-3.547.00/-4.047.00/-4.547.00/-5.0ZD 47.12~47.36 (47.25)47.25/-1.547.25/-2.047.25/-2.547.25/-3.047.25/-3.547.25/-4.047.25/-4.547.25/-5.0ZE 47.37~47.66 (47.50)47.50/-1.547.50/-2.047.50/-2.547.50/-3.047.50/-3.547.50/-4.047.50/-4.547.50/-5.0Trial set
24Empirically with trial fit Prescribe a looser lens empiricallySubtract 0.50D from K code (flatter K code)Add D to power-code (less minus)Order lens by: XMJ / (43.25) / / 10.8 mmPrescribe a tighter lens empiricallyAdd 0.50 D to K code (steeper K code)Add D to power code (more minus)Order lens by: XMJ / (44.25) / / 10.4 mm
25Prescribe by over refract trial lens Select first trial lens by mean KXMJ/(43.75)/-3.00, if fit is loosetry XMJ/(44.25)/ to tighten ACOver refraction of XMJ/(44.25)/-3.00 = –1.50 DPower-code = (-1.50) = -4.50Order M4 lens by:XMJ/(44.25)/-4.50/10.4 mm(Predetermined OAD)
40Central IslandSmall areas of distortion along or near the visual axis
41Central Island Cause: Alignment curve too tight Excessive uncorrected astigmatism resulting in unequal forces on the corneaSolution:Decrease sagittal depth of lens by flattening alignment curvemove up the columnDecentered lens must be centeredFlatten the BC if caused by uncorrected astigmatismmove one column right.
59Estimate lens sizeObtain white to white corneal Diameter by TopographyVerify Visible Iris Diameter (VID), horizontal & vertically manuallyCompare VID to Best-fit VID of the K-codeIf VID too large (larger cornea, smaller lens)Loose fit, Decentration, Poor effectIf VID too small (smaller cornea, larger lens)Tight fit, Lens Bridging, Central island
60Standard lens sizes Default OAD based on KM KM ranges 40.00 ~ mm42.50 ~ mm44.00 ~ mm
61Big Corneas KM =< (flatter) 42.25D KM between 42.50 – 43.75D Rule of thumb:KM =< (flatter) 42.25D95% to 97% coverage of VIDKM between – 43.75D93% to 95% coverage of VIDKM => (steeper) 44.00D92% to 94% coverage of VID93% - 95% coverage of VID would suit most corneas most of the time.
62Big Corneas Use existing trial lenses to evaluate alignment curves Determine lens Diameter (OAD)93% of VID if KM =>44.0094% of VID if KM96% of VID if KM =<42.25It is NOT necessary to alter K-kode (alignment) when adjusting for OADIn high minus lenses (±40% of cases) a flatter alignment lens will be need later on
63Big Corneas Example: V (45.25D) Lens best fit. VID: 12mm 93% VID coverage = 11.2mm94% VID coverage = 11.4mm96% VID coverage = 11.6mmV lens (KM steeper than 44.00D) = 11.2mm
64Big Corneas Example how to order: V Lens best fit. VID: 12mm V lens (KM steeper than 44.00D) = 11.2mmEg. 2V04, 11.20mm or XMJ/45.25/-3.00/11.2mm
65Lens Size 86% too small 89% too small 95% Optimal 98% slightly large 這張圖片，比較鬆緊不同的配鏡狀態，提供給各位醫師做鏡片選擇時的參考。95% Optimal98% slightly large105% very large