Laser eye surgery indications

Transcription

1 Laser eye surgery indications Petros Smahliou, MD, FRCS, EBO Athens, March 2018

2 Laser eye surgery: Common Significant ametropia indications Anisometropia Anisoeikonia Intolerance of spectacle use (eg. High amount of astigmatism) Intolerance of contact lens use Life style

3 Age limits Over 18/20 years(?) old and stable refraction Under 60 years old (?) Under investigation treatments in chlildren for amblyopia Touch ups in elders after cataract operations

4 INCLUSION CRITERIA Age 18 /20 years or older Stable refraction of at least one year s duration Myopia up, diopters, Astigmatism up 6.00 diopters, Hyperopia up diopters

5 EXCLUSION CRITERIA absolute eye-related - Keratoconus - Herpetic keratitis, - Some corneal dystrophies or degenerations (Avellino or Granular, Lattice,Reiss-Bucklers) - Cataract, Glaucoma or other pathology, including scarring, lagophthalmos, dry eye, blepharitis, uveitis and macula problems - Unstable refraction

6 EXCLUSION CRITERIA relative eye-related Single eye or lazy eye (?) Very high, or low Ks Irregular astigmatism Controled glaucoma or glaucoma suspect Controled DM Previous AKs or RKs Drugs (isotretinoin, amiodarone, oestrogens) Mild dry eye Age less than 20 in male myopes

7 EXCLUSION CRITERIA general Atopy (severe & spread) Diabetes mellitus (uncontrolled) History of keloids Pregnancy or lactation Autoimmune disease (?) Immunosuppression or immunocompromised status Drugs (isotretinoin, amiodarone, oestrogens)

8 METHOD Technique according to refractive error Refraction Technique Myopia Hyperopia Astigmatism PRK dpt Contradiction? dpt LASIK dpt dpt dpt Femto LASIK dpt dpt dpt

9 PRK indications Low refractive errors (up to -4,00 dpt & - 2,00 dpt astgm) Contact sports (eg. boxing) Predisposition to trauma (martial arts, military) Anterior basement membrane dystrophy History of recurrent erosions Deep orbits (difficulty to obtain good suction) Patient preference

10 PRK indications Scleral buckles placed anteriorly Pterygia or naevae Thin and suspicious corneas Patients with moderate dry eye Best option for an inexperience refractive surgeon (simpler than Lasik)

11 Lasik indications High myopia(>6d) High astigmatism(>2d) Hyperopia Opt for fast recovery and no pain

12 So Which method to choose???

13 From Lasik to Femtosecond Lasik Advancement in laser technology Excellent precision Safer (and faster?) flap creation Thinner and different shape flaps Today is the safest method of refractive surgery

14 Femtosecond Lasik VS Lasik Flap incision more accurate Reduced flap-related complications (free caps, irregular cuts) Safer than conventional Lasik procedure Faster and better healing Less aberrations, better quality of vision

15 Why choose Femto Lasik? Increased presicion with improved flap safety Better thickness predictability Capability of thinner flaps to accommodate thin corneas Greater surgeon choice and control over flap & thickness diameter Better vision

16 Why choose Femto Lasik? Stronger flap adherence Ability to abort and reapply the suction during flap creation Decreased incidence of epithelial ingrowth Lesser incidence of dry eyes or hemorrhage of the limbal vessels

17 Why choose Femto Lasik? Highest precision Homogenous flaps Uniform thickness & shape Better flap stability Accuracy when folded back Highest safety Eliminated complications Infections almost impossible Best possible outcomes Better results predictability than Lasik

18 Femtosecond Lasik additional indications & applications Cataract surgery Astigmatic keratotomies Intrastromal tunnels for rings Keratoplasties SMILE Treating presbyopia (radial lensotomy) Intrastromal ablations (intracor)

19 From PRK to Trans PRK Trans PRK (Transepithelial Photorefractive Keratectomy) No touch PRK The epithelium is removed by laser (no mechanically) Smoother tissue removal Smoother handling

20 Trans PRK

21 Trans PRK vs PRK Faster procedure Safer Less pain Faster recovery Less complications

22 When do Trans PRK? If the patient is not a good Lasik candidate (eg. Small eyes) Thin cornea (PRK X-tra) In anxious patients (afraid of Lasik procedure due to flap formation) In patients who have already undergone refractive surgery In CLX cases

23 When do Trans PRK? Trans PRK is a method with: Less chance of complications Long-term results comparable or better than Lasik Accuracy and ease on management

24 LASIK indications Initial corneal thickness in LASIK > 500 μm Initial corneal thickness in PRK > 470 μm Thickness norm < 50% (60%) Residual stroma thickness in LASIK Residual stroma thickness in PRK Depth removal Keratometry limits (for mechanical keratome) Keratometry limits (spherical aberration) > 300 μm > 400 μm < 135 μm dpt < dpt, > dpt Topography criteria Relatively and absolutely

25 Extreme refractive errors Myopia over -10,00 D (or less in thin corneas) and age 21 to 50 we prefer phakic IOLs Myopia over -10,00 D (or less in thin corneas) and age over 50 we prefer RLE Hypermetropia over +6 we prefer phakic IOLs if the AC depth is adequate, or RLE even in younger patients (multifocal IOL ) Combine with surface ablation

26 Pentacam HR inclusion criteria - Anterior float criteria: normal values: <+12μm (or10μm) suspicious: from12μm to15μm ΚCN : >15μm - Posterior float criteria: normal values: <+17μm suspicious: from18μm to20μm ΚCN : >20μm

27 Pentacam HR inclusion criteria2 Hight difference criterio: >5μm difference between anterior and posterior float Tongue like extensions - Pachymetry criteria - <470μ for PRK, <500μ for LASIK - TL inferior and more than 4mm of the GC - >30m difference between superior and inferior points - Topometric map: inferior qvalue>-0,55

28 Pentacam HR inclusion criteria3 - Keratometry criteria: - Kmax>48,5D - SRAX angle>22* - Kdif>3,00D with steepest the vertical merid - I-S Rabinowitz ratio >+2D - Rowsey s rule of 2% (Ks>45D, Kmax>2D between the two eyes) - Very high vertical coma

29 The most common display is a 4-map

30 4 map Anterior (Axial) sagittal Anterior elevation map Corneal thickness map Posterior elevation map

31 Corneal morphology Incidence of the morphology of topographic contour Central round shape 22.6% Central oval shape 20.8% Symmetrical bow tie 17.4% Asymmetric bow tie 49.6% Anomalous shape 7.1%

32 1-Anterior sagittal (axial)map Normal pattern 1- Symmetric bow tie pattern 2-Segments S and I are equal, 3- Their axes are aligned..

33 1-Anterior sagittal (axial)map Normal Parameters. At 5mm circle inferior power higher than superior less than 1.5D on the steep axis The superior point may rarely have a higher value than the inferior one; less than 2.50 D.

34 1-Anterior sagittal (axial)map Abnormal shapes

35 Important risky point in Anterior sagittal (axial)map 1-K>48D 2-Angulation 3-Astigmatism >6D in either surface 4-Against the rule astigmatism 5-Inferior superior asymmetry 6-Difference between the inferior and superior more than 1.50 D

36 1-Anterior sagittal (axial)map Angulations more than 30

37 1-Anterior sagittal (axial)map Asymmetric bow tie More lower steepness More than 1.5 D

38 1-Anterior sagittal (axial)map Asymmetric bow tie upper steepness difference more than 2.5D

39 1-Anterior sagittal (axial)map Asymetric + angle

40 1-Anterior sagittal (axial)map Smile predisposed to ectasia

41 1-Anterior sagittal (axial)map junctional predisposed to ectasia

42 1-Anterior sagittal (axial)map Vortex predisposed to ectasia

43 2-3-ANTERIOR AND POSTERIOR Shape. The normal shape is the hourglass Abnormal shapes Irregular, -Tongue-like extensions -Isolated islands ELEVATION MAP

44 2-3-ANTERIOR AND POSTERIOR Parameters.. The highest plus value within the central 5- mm zone; Normal values are <12 μm anterior <15 μm posterior Abnormal difference between front and back elevation more than 5u ELEVATION MAP

45 Normal shape is the hourglass Abnormal shapes include irregular, tongue-like extensions and isolated islands Abnormal isolated islands Abnormal shapes include irregular, tongue-like extensions

46 The cone can be localized using the The location may be -central, -eccentric, -peripheral elevation maps.

47 4-PACHYMETRY MAP Pattern The normal pattern is concentric The abnormal patterns include 1-Horizontaldisplacement, 2-dome-like, 3-globus, 4-and bell shapes

48 4-PACHYMETRY MAP Abnormal -Dome shape. -Displaced thinnest location

49 4-PACHYMETRY MAP Abnormal Horizontal displacement of corneal shape

50 4-PACHYMETRY MAP The bell shape seen in pellucid marginal degeneration

51 4-PACHYMETRY MAP Abnormal parameter 1- Abnormal less than 470 μm thickness at the TL with normal tomography, 2- Abnormal less than 500 μm thickness at the TL with abnormal tomography 0 μm.

52 4-PACHYMETRY MAP Abnormal parameter 3-Thickness Difference between bachy apex and thin. Loc.> 10u Early KC 4-Bachy apex Lower Location Y more than -500

53 4-PACHYMETRY MAP Abnormal parameter 5-Pachy. Thickness between superior(s) and inferior (I) points is 30 μm. At 5mm circle 6-Abnormal thickness at the TL between the patient s two eyes; more than 30 μm.

54 Thickness Profiles corneal thickness spatial profile (CTSP) The average progression of thickness starting from the TL to corneal periphery percentage thickness increase (PTI). The percentage of progression of the thickness The normal profile is a curved line plotted in red, following the black dotted curves, High average, Fast transition of thickness between the Low flat average corneal edema. A normal profile follows the normative curves with an average < 1.2 (red

55 Thickness Profiles Abnormal profiles include: a. Quick Slope The red curve leaves its course before the 6-mm zone. It is encountered in forme fruste keratoconus (FFKC) and ectatic disorders.. The average is usually high (> 1.1)

56 Thickness Profiles b. S-shape The red curve has a shape of an S. It is encountered in FFKC and ectatic disorders. The average is usually high (> 1.1).

57 Thickness Profiles c. Flat shape The red curve takes a straight course. It is encountered in diseased thickened (oedematous) corneas such as Fuch s dystrophy and cornea Guttata. The average is low < 0.8 (red ellipse)

58 Thickness Profiles d. Inverted The red curve follows an upward course. It is encountered in some cases of PMD. The average is very low (< 0.8) and may take a minus value

59 Pupil Center Corneal thickness Location Important in decentration technique when treating hyperopia, astigmatism or corneal irregularities. They are also important to evaluate angle kappa. Normal x-coordinate 200 μm (or 5 ).

60 Pupil diameter Diameter of pupil in (photopicp mesopic scotopic). Adjusting optical zone(oz)diameter, mm larger than the scotopic pupil size.

61 5-K readings Normal maximum not more than 49D Normal minimum not less than 34D The normal difference between K max and the steep less than 1.00 D.

62 5-K readings Flat myopia The rule D correction reduces the flat K by 0.75 D. The final flat sim K should not go below D, or positive spherical aberration will be induced

63 5-K readings Steep Hyperopia The rule each 1.00 D correction increase the K max 1.20 D The final K max should not exceed D; otherwise, negative spherical aberrations are induced..

64 Measure the spherical aberration Measurement undertaken At 6mm diameter at 4 meridian Q value Sum. Vertical is most important (Normal vertical Aspheric cornea with least spherical apparition )

65 Q value (spherical aberration) -2 advanced keratoconus or after hyperopia correction+5-1 moderate keratoconus or after hyperopia correction Vertical normal Aspheric cornea with least spherical apparition 0 spherical cornea with spherical apparition +1 after correction of -5 myopia +2 after correction of -12 myopia

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67 CONCLUSIONS Refractive surgery is safe and effective Strict anatomic and refractive rules apply Age considerations are important Impressive technological advancements Adhere to the guidelines Meticulous examination and measurements Better safe than sorry

68 Thank you

69

70 6-Topographic astigmatism.. Disparity between these Topographic and manifest astigmatism 1-misalignment during capture, 2-irregular astigmatism, 3-tear film disturbance, 4-corneal haze 5-lenticular astigmatism (including subtle cataract).

71 Disparity between Topographic astigmatism and manifest astigmatism. If lenticular astigmatism is present without cataract and there is disparity, avoid overcorrection or converting the orientation of the topographic astigmatism -/-3x180 corrected as -0.5/-2x180

72 Disparity between Topographic astigmatism and manifest astigmatism. For example, if the manifest astigmatism is X 180º and the topographic astigmatism is X 180º, correcting the full manifest astigmatism will induce X 90º, which the patient may not tolerate despite zero manifest refraction. In such a case, one of the recommendations is to correct X 180º and adjust the sphere to achieve the same spherical equivalent (eg, X 180º corrected to X 180º.

73 7-Pupil coordinates. The horizontal (x) coordinate of the pupil center reflects angle kappa. The normal value of the latter is less than 100 μm (<5 ). Angle kappa is important for the decentration technique used in hyperopic and highly astigmatic photorefractive correction. A large angle kappa can also explain the skew seen in some curvature and elevation patterns.

74 General guidelines Thickness Rules K-reading Rules Astigmatism Rules Pupil Center and Angle Kappa Rules

75 Thickness Rules Munnerlyn formula calculates the ablation depth (AD) for myopia and myopic astigmatism: AD (μm) = 1/3 (OZ diameter [mm])2 (intended correction [D])..

76 Scotopic The range of low light levels below cone threshold where visual responses has only rod signals Mesopic The range of intermediate light levels between cone threshold and rod saturation Photopic The range of high light levels above rod saturation where vision is mediated by signals from cone photoreceptors. Pupil diameter

77 Thickness Rules When Scotopic pupil >5.5mm Do Ablation OZ = 6.5 mm When Scotopic pupil <5mm Do Aplation OZ = 5.5 mm So 1D Ablate 14um. 1D Ablate 10um In small thickness save tissue

78 RSB Rule 1 Thickness Rules The RSB should be at least 300um

79 RSB Rule 2 Thickness Rules The AD should be at most 20% of the original corneal thickness at the TL..

80 RSB Rule 3 Thickness Rules In LASIK, the AD differs according to OZ diameter and laser profile. For easy calculations, 15 μm will be used... Aplation OZ = 5.5 mm 1D = 10um Ablation OZ = 6.5 mm 1D = 14um

81 Thickness Rules RSB Rule 4 For safety, Least ablation depth Most residual stromal bed.

82 RSB Rule 5 Thickness Rules AD In PRK, not to exceed 70-80μ to avoid haze, Corrected about 6 D(X15) Final residual stoma not less than 400um.

83 RSB Rule 6 Thickness Rules In LASIK and PRK, use the absolute sum of the spherical and cylindrical components 4 D sph/ 3 D = 7x15.

84 RSB Rule 7 Thickness Rules In hyperopic treatment the central ablation is zero, whereas the maximum AD is peripheral where the cornea is thick. Try correct up to +4 D by LASIK in order to minimize biomechanical response In general, the preoperative TL should be > 470 μm.

85 RSB Rule 8 Thickness Rules For calculations in mixed astigmatism, The equation should be converted into plus cylinder formula before calculating the RSB. +2 D sph/ 4 D cyl converted to 2 D sph/+4 D cyl RSB rules are applied on the 2 D sph

86 RSB Rule 9 Thickness Rules In WFGT profiles, the AD differs according to the type and severity of HOA(s). Therefore, AD and RSB should be calculated on site.

87 General guidelines Thickness Rules K-reading Rules Astigmatism Rules Pupil Center and Angle Kappa Rule

88 K-reading Rules First The recommended amount of correction should be calculated according to RSB rules Second then according to K-reading rules.

89 K-reading Rules Flat K Rule Correcting each 1 D reduces the flat K by 0.75 D. Final flat K according to the amount of myopic ablation should be > 34 D.

90 K-reading Rules K-max Rule Correcting each +1 D increases K-max by 1.2 D. K-max according to the amount of hyperopic ablation should be < 49 D.

91 Flat K Rule K-reading Rules K-max Rule Correcting each 1 D reduces the flat K by 0.75 D. Correcting each +1 D increases K-max by 1.2 D. The final flat K > 34 D. The final steep K < 49 D.

92 General guidelines Thickness Rules K-reading Rules Astigmatism Rules Pupil Center and Angle Kappa Rule

93 Astigmatism Rules Myopic Astigmatism Rules The astigmatic correction flattens the steep K and brings it to flat K Thereafter, the spherical correction flattens all.

94 Astigmatism Rules Hyperopic Astigmatism Rules the astigmatic correction steepens the flat K and brings it to steepk. Thereafter, the spherical correction steepens all.

95 Astigmatism Rules Mixed Astigmatism Rules The astigmatic correction steepens the flat K and brings it to steep K Thereafter, the spherical correction flattens all.

96 General guidelines Thickness Rules K-reading Rules Astigmatism Rules Pupil Center and Angle Kappa Rule

97 Pupil Center and Angle Kappa Rule Angle Kappa is the angle between the visual axis and the axis that passes through the pupil center.. Angle Kappa Angle kappa is considered significant when it is > 5 (x > 200 μm).

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99 Large angle Kapa When angle kappa is > 100 μm (x > 200 μm), the capture should be repeated to exclude misalignment. 1-false positives or false negatives such as the skewed hourglass pattern in elevation maps. 2- When treating hyperopia or 2 D of astigmatism, optimal resul ts can be achieved when the center of ablation coincides with the optical axis of the eye. This can be achieved by decentering the ablation profile for the amount of angle kappa; this is called offset pupil or decentration. 3-Finally, decentered pupil (corectopia) is a case of concern, especially when PIOL implantation is indicated.

100 Thank you

101 -Keratometry readings (k1, k2)- -Radii of curvature (Rh, Rv), -Mean keratometry mm zone (Km),

102 Pachymetry data of the 1-Pupil center, 2- apex, 3- thinnest point, and their locations are followed by maximum curvature amount and location..

103 Isolated island in front or back with normal elevation

104 Topometric Map The most important is vertical inferior Normal < -0.5 Border line -0.5 and Abnormal> The most important sector is the 6 mm or 20 sector