refractive surgeries

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  • Due to iris trauma during surgery
  • refractive surgeries

    1. 1. REFRACTIVE SURGERIES Dr. NEHA PATHAK 2 nd year PG Resident Deptt. of Ophthalmology Govt. Medical College, Kota
    2. 2. Eye’s refractive power determined by 3 variables - 1. Power of the cornea 2. Power of the lens 3. Length of the eye EMMETROPIA - Optically normal eye - Image of the object being viewed is focused on retina - Resulting in clear & sharp vision
    3. 3. AMMETROPIA – A condition of refractive error - Causes blurred vision as image is not focused on retina 1. Myopia - Near-sightedness Image is focused in front of retina 2. Hyperopia - Far-sightedness - Image is focused behind retina
    4. 4. 3. Astigmatism – Refraction varies in different meridia - Rays of light entering eye can’t converge to a point focus but form focal lines 4. Presbyopia – Eye sight of old age - Physiological insufficiency of accomodation leading to progressive fall in near vision - Mechanism : 1. Senile lens hardening
    5. 5. PUPIL SIZE & CENTRATION OF REFRACTIVE PROCEDURES    Rays of light from a point source are refracted by the area of cornea overlying the entrance pupil . This area is c/a the corneal optical zone . Entrance pupil - Virtual image of anatomical pupil formed by magnifying effect of the cornea – larger & closer to cornea. Optical zone in a keratorefractive procedure : “The area of central cornea that bears the refractive change caused by the surgery”.
    6. 6. FACTORS DETERMINING CENTRATION OF KERATOREFRACTIVE PROCEDURES Foveal photoreceptors orient themselves towards centre of the pupil (StilesCrawford effect), even if entrance pupil becomes eccentric.  Pupillary dilatation under mesopic & scotopic conditions, beyond the edge of the optical zone causes edge glare & haloes => Favour the centration of KR procedures on the 
    7. 7. CLASSIFICATION OF REFRACTIVE PROCEDURES REFRACTIVE SURGERIES CORNEA BASED        R.K. PRK LASIK EPILASIK LASEK Conductive Keratoplasty Corneal Inlays and rings LENTICULAR BASED    Clear Lens extraction for myopia Phakic IOL Prelex Clear Lens Extraction with use of Multifocal IOL’s COMBINED(BIOPTICS) • Combination of the two
    8. 8. KERATOREFRACTIVE SURGICAL PROCEDURES LOCATION ADDITION SUBTRACTIO N RELAXATION COMPRES SION SUPERFICIAL 1.EPIKERATO PHAKIA 2.SYNTHETIC EPIKERATOP HAKIA 1.PRK 2 LASEK 3.Epi-LASIK ---------- INTRASTOMAL 1.KERATOPHA KIA 2.INTRACORN EAL LENSES 3.PINHOLE APERTURES 1.LASIK 2.WAVEFRONT GUIDED LASIK 3.IntraLASIK (IntraLase) LAMELLAR KERATOPLAST Y PERIPHERAL INTRACORNE AL STROMAL RING WEDGE RESECTION 1.RADIAL KERATOTOMY 2.ARCUATE KERATOTOMY CORNEAL MOLDING 1.THERMOK ERATOPLAS TY. 2.COMPRES SION SUTURES
    9. 9. PREOPERATIVE EVALUATION Involves 1)Screening,  2)History taking,  3)Preoperative examination &  4)counselling 
    10. 10.  Systemic Contraindications Diabetes mellitus ( if corneal sensation is not intact )  Pregnancy/lactation  Autoimmune / connective tissue disorders(RA,SLE,PAN etc)/ Immunodeficiency  Abnormal wound healing-Marfans,EhlerDanlos -Keloids  Systemic Infection-(HIV,TB)  Drugs-Azathioprene,Steroids(Slow wound healing) -Antihypertensives,
    11. 11. OPHTHALMIC CONTRAINDICATIONS     Disorders that may be exacerbated by PRK - HZO (if active during last 6 months) - Glaucoma Dry eye – Keratoconjunctivitis sicca, Exposure keratitis, Lid disorders Abnormal corneal shape - Shape changes induced by contact lens - High irregular astigmatism - Corneal ectasias : Keratoconus, Keratoglobus, Pellucid marginal degeneration Uveitis, Lenticular changes, Progressive retinal ds., myopic degeneration, Diabetic retinopathy, RP, RD
    12. 12. OPHTHALMIC EXAMINATION      VISUAL ACUITY – Distance & Near : with & without correction REFRACTION – Current spectacle correction - Manifest refraction - Cycloplegic refraction (1% cyclopentolate ) EXTERNAL EXAMINATION – Ocular dominance - Ocular motility - Gross external examination SLIT-LAMP EXAMINATION – Fluorescein & vital stain JONES’ BASAL TEAR SECRETION RATE
    13. 13. TOPOGRAPHIC ANALYSIS 1) Keratometry (measures Videokeratography central 3 mm corneal curvature) early KC) 2) Computerized (only way to uncover
    14. 14. PACHYMETRY - measuring thickness of cornea ULTRASONIC PACHYMETRY Recommendations for minimum bed thickness (250µ) based upon ultrasonic devices 1)
    15. 15. 2) ORBSCAN DEVICE - Optical device - Advantage – can provide thickness measurements throughout the cornea
    16. 16. EPIKERATOPHAKIA     EPIKERATOPLASTY/ ONLAY LAMELLAR KERATOPLASTY Removal of epithelium from central cornea  peripheral annular keratotomy  lyophilized donor lenticule is reconstituted & sewn into the annular keratotomy site Adv. - simplicity & reversibility Disadv – irregular astigmatism, delayed visual recovery, prolonged epithelial defects. Abandoned procedure now.
    17. 17. Radial Keratotomy (RK)    Series of 4-8 deep, radial corneal stromal incisions Weaken the paracentral & peripheral cornea & flatten the central cornea I/C- keratoconus astigmatism
    18. 18. LONG-TERM COMPLICATION S - Bullous keratopathy secondary to endothelial cell loss - Low stability of refraction 
    19. 19. Astigmatic Keratotomy (AK) For astigmatism only  1-2 tranverse relaxing mid-peripheral corneal incisions  Arcuate or straight fashion  Perpendicular to the steep meridian  Localized ectasia of peripheral cornea & central flattening of the incised meridian 
    20. 20. May be combined with LASIK, PRK, LASEK, Cataract extraction.
    21. 21. Cataract surgery - Limbal Relaxing Incisions have gained popularity- more comfortable for patient than arcuate or transverse mid-peripheral incisions
    22. 22. PHOTOREFRACTIVE KERATECTOMY First widely used procedure with the excimer laser (1987)
    23. 23. PHOTOREFRACTIVE KERATECTOMY Outer layer of cornea is removed then laser is applied  vision improves as surface heals after 4 to 7 days  discomfort present during healing  can cause corneal scarring 
    24. 24. PRK for Myopia
    25. 25.      No microkeratome involved No flap created Ultimate visual results similar to LASIK Longer recovery period (> 2 weeks) Complications similar to LASIK; Haze
    26. 26. LASIK (Laser-assisted in situ keratomileusis)    Most commonly performed refractive surgery Combines lamellar corneal surgery with accuracy of the excimer laser Excimer laser ablation of corneal stroma beneath a hinged corneal flap that is created with a mechanical femtosecond laser microkeratome
    27. 27. HISTORICAL REVIEW        Barraquer first described lamellar refractive surgery in 1949 Dr. Ruiz introduced microtome propelled by gears & keratomiluesis in situ in early 1980s Dr. Leo Bores performed 1 st keratomiluesis in situ in 1987 in the US Burrato reported use of excimer laser in situ after a cap of corneal tissue was removed Pallikaris – idea of combining precision of excimer laser with lamellar corneal surgery LASIK was introduced & developed at the Univ. of Crete, Greece Wavefront-guided LASIK became available in the US in 2003
    28. 28. Types of lasers used Excimer : for corneal stromal ablation Non-Excimer solid state lasers : for flap creation
    29. 29. EXCIMER LASERS  Excited   dimer of two atoms -an inert gas(Argon) -a Halide(Fluoride)  releases ultraviolet energy at193nm Reshapes corneal surface by removing anterior stromal tissue Process – Non-thermal Ablative Photodecomposition
    30. 30. Laser delivery patterns : 1) Broad-beam lasers - deliver a large diameter beam of laser – starts small & expands as the laser is delivered ADV. Less operative time DISADV. Creation of central islands ( difficulty to maintain uniform consistency over a larger diameter beam)
    31. 31. 2) Scanning excimer lasers: - Scanning-slit laser - Flying spot laser Provide smoother ablation than the old broad-beam lasers
    32. 32.  Advantage of Non-Excimer solid state lasers No toxic excimer gases  Wavelength closer to absorption peak of corneal collagen—less thermal and collateral damage  Better pulse to pulse stability  Not absorbed by air,water,tear fluid-so less sensitive to humidity or room temperature  No purging with inert gases required.
    33. 33. Patient selection     Patients need to be fully informed about potential risks,benefits and realistic expectations Age should be above 18 years Refractive status should have been stable for at least 1 year. Current FDA approval   Myopia-upto -15D Hyperopia –upto +6D Astigmatism-upto 6D
    34. 34.     CCT such that minimum safe bed thickness left(250-270µ).Post op Corneal thickness should not be <410µ. Extreme keratometric values ( flatter than 41.00 or steeper than 47.00) avoided Videokeratoghic clues to a KC suspect: K value > 47.2 D, Inferior steepening of > 1.4 D, difference of > 1.9 between K values of both eyes Contact lens free period before examination : 3-4 wks for rigid contact lens wearers 2 wks for soft contact lens wearers
    35. 35. BASIC MECHANISM     Normal cornea – prolate shape ( greater curvature centrally ) Myopic correction – create an oblate shape by central corneal laser ablation Hyperopia - Excimer laser ablation at midperiphery  steepening of central cornea Mixed astigmatism – 1)Bitoric LASIK technique – flattening the steep meridian with paracentral ablation over the flat meridian 2)Cross-cylinder technique – dividing cylinder power into 2 symmetrical parts – half of the correction is treated on the positive meridian & half on the negative
    36. 36. MUNNERLYN EQUATION    Roughly defines the depth of ablation required to achieve a specific amount of correction For 1 D correction  depth of ablation required (in microns) one-third of the square of diameter (in mm) So each spherical equivalent diopter of myopic correction performed at a 6mm optical zone will ablate 12 microns of tissue
    37. 37. OPERATIVE PROCEDURE        5mg Diazepam 5-10 min before procedure Verification of entered computer data before starting procedure Topical anasthesia-Proparacaine 0.5%, Lignocaine 4%. Surgical Painting and draping Lid speculum with aspiration Proper centration over pupil & maintenance by the aid of Tracking systems & iris registration C/L eye taped shut to prevent cross-fixation
    38. 38. 1 st step - Creation of flap    Corneal marking with ink Adequate placement of suction ring using bimanual technique Suction engagement by foot control
    39. 39. Adequate IOP (>65mmHg) which is necessary for the microkeratome to create a pass and resect the corneal flap.  verified by BARRAQUER TONOMETER  confirmed by patient – temporary loss of visualization of fixation light 
    40. 40. 2nd step - Resection of corneal flap  Artficial tear drops instilled  MICROKERATOMES 1) Steel Microkeratome -Uses Disposable blades -Blade Plate can be set at 120µ,140µ,160µ and180µ. -Nasal or superiorly hinge flaps can be created. -Eg.Hansatome,ACS,Carriazo Barraquer, Moria. 2) Waterjet Keratome -Less debris & collateral damage than blade
    41. 41. 3) Laser Keratome (IntraLase) - Solid-state laser 1053 nm wavelength 3 µm spot size- high precision Uses brief Femtosecond laser pulses to cause disruption in a lamellar plane - Needs lower vacuum & any hinge can be made - Can make flaps as thin as 100µ(Sub Bowmans Keratomileusis)
    42. 42. - Flap has vertical edges –so reduced epithelial ingrowth. - Steel Microkeratome flap thicker in periphery and thinner in the centre. Not so with Intralase(Planar).
    43. 43. 3 rd Step-Delivery of Laser After flap is lifted,assessment of residual corneal bed thickness usin USG pachymetry  laser is applied to the stroma according to the ablation profile calculated by the machine.  Excimer Laser beam is delivered by the following ways depending on the machineBeam Delivery Broad Beam Scanning Slit Beam Flying Spot
    44. 44.  Most machines employ a flying spot to deliver laser with the help of incorporated eye tracker or iris registration.
    45. 45. 4 th step-Reposition Of the Flap After irrigating interface ,flap reposited  Sweeping movements with a wet cellulose sponge  From the hinge towards the periphery of flap  Adhesion verified – stretching the flap towards gutter  Topical antibiotic, steroid & lubricant instillation  transparent plastic shields
    46. 46. WAVEFRONT-GUIDED (CUSTOMIZED) EXCIMER LASER REFRACTIVE SURGERY  To correct higher-order aberrations in addition to lower- order sphero-cylinder corrections - LOWER ORDER Nearsightedness Farsightedness Astigmatism - HIGHER ORDER Spherical aberration Chromatic aberration Diffraction Curvature of field Coma Trefoils Quadrifoils
    47. 47.  Higher order aberrations occur in visually significant manner in 1015% of population  Cannot be corrected with spherocylinder lens or conventional laser refractive surgery  Correction – Hard contact lenses - Wavefront-guided customized
    48. 48. MEASUREMENT OF WAVEFRONT ABERRATIONS (ABERROMETRY) ABERROMETER OUTGOING ABERROMETERS Analyze outgoing light that emerges From retina & passes through the Optical system of eye Hartmann-Shack Aberrometer (most commonly used) INGOING ABERROMETERS Analyze ingoing light that forms an image on the retina Tscherning Aberrometer Ray Tracing Aberrometer Scanning Slit Refractometer
    49. 49. ANALYSIS & DECOMPOSITION OF WAVEFRONT ABERRATIONS INTO COMPONENTS ANALYSIS OF ABERRATIONS ZERNIKE POLYNOMIALS (most commonly used) FOURIER ANALYSIS
    50. 50. CUSTOMIZATION OF ABLATION PROFILE TYPES OF CUSTOMIZATION TOPOGRAPHY-GUIDED ABLATION (Conventional laser surgery) WAVEFRONT-GUIDED ABLATION (Customized laser surgery)
    51. 51.  Conversion of wavefront measurement data to an ablation profile   Imported to an excimer laser   Precise registration of these patterns on cornea by eye trcking & iris registration technology   Precise wavefront-guided ablation during LASIK is achieved
    52. 52. CUSTOMIZED ABLATION PLATFORMS 1) Nidek Advanced Vision EXcimer Laser system    OPD-Scan optical path difference scanning system (combines measurement of corneal topography & aberrometry) Develops customized ablation profile EC-5000CX II excimer
    53. 53. 2) VISX S4 CustomVue Platform (Santa Clara, CA)  Wavescan wavefront system – Hartmann-Shack wavefront sensor  STAR S4 excimer laser sytem delivers customized laser ablation
    54. 54. 3) Alcon Customized Cornea Platform  LADARWave wavefront sensor ( a HartmannShack eberrometer)  LADARVision system to deliver customized
    55. 55. 4)Bausch and Lomb Zyoptix System  Diagnostic part : - Zywave aberrometer – a Hartmann-Shack sensor - ORBSCAN – 3D information about cornea  Truncated Gaussian beam laser – 2 sizes –  2mm – corrects majority of refractive error in short time  1mm – more specific ablation pattern on
    56. 56. 5) Allegretto Wavefront-Guided Ablation  Allegretto wave analyzer – Tscherning Aberrometer  Allegretto excimer laser system – high repetition rate spot laser (200Hz) with
    57. 57. COMPLICATIONS INTRAOPERATIVE COMPLICATIONS 1) Incomplete flap – premature termination of microkeratome advancement - inadequate globe exposure - loss of suction during pass Never reverse microtome & then go forward  penetration to a deeper level than initial pass
    58. 58. 2) Thin flap - due to poor suction - difficult to reposition & likely to wrinkle 3) Buttonholed flap - If K > 50 D - Ablation should not be performed, flap repositioned 4) Full thickness resection
    59. 59. 5) Free cap – flat/ small cornea, poor suction - Small / decentered : procedure aborted - Adequate size/ well centered : placed on conjunctiva with epithelial side down & procedure completed 6) Epithelial defects – prevented by adequate lubrication
    60. 60. ABLATION COMPLICATIONS 1) Central islands – small central elevations a) abnormal beam profile (broad beam lasers) b) particulate matter blocking subsequent laser pulses c) increased hydration 2) Decentration – current lasres with incorporated eye-tracking & iris registration systems 3) Under/ Over-correction - excessive hydration : undercorrection - desiccation : overcorrection & haze
    61. 61. POSTOPERATIVE COMPLICATIONS meibomian gland 1) Interface debris – mostly material – cleaning of interface with BSS 2) Flap displacement – first 24 hrs - lifted & repositioned 3) Night vision disturbances – haloes / glare 4) Post Lasik Dry eye     Fluctuating vision,SPK Temporary neuropathic cornea Confocal microscopy-90% reduction in corneal nerve fibres-regeneration by 1 year. Rx-Preservative Free lubricants
    62. 62. 5) Punctate epithelial keratopathy – pre-existing dry eye / blepharitis - tt frequent lubrication , punctal plugs 6) Diffuse lamellar keratitis (Sands of Sahara syn) - non-infective interface inflammation - 1 st week after LASIK - fine granular sand-like infiltrate in the interface periphery - if not treated  corneal scarring
    63. 63.  Grade 1Focal involvement - Normal V/A. - Rx Intensive topical steroids.  Grade II – Diffuse involvement – Normal V/A. - Rx-Add systemic steroids.
    64. 64.  Grade III – Diffuse confluent granular deposits - Reduced V/A.No AC reaction. - Rx-Same as above+Antibiotics  Grade IV – Diffuse confluent granular deposits +intense central striae. - Marked Reduced V/A - Rx-Interface irrigation + above
    65. 65.  Causes -Proposed Theory  Bacterial cell wall endotoxin  Cleaning solution toxicity  Talc from gloves  Miebomian secretions
    66. 66. 7) Flap striae & microstriae Flap undulations Macrostriae -Linear lines in clusters,seen on retroillumination Causes-Incorrect position of flap -Movement of flap after LASIK Rx-Lift flap -Rehydrate and float it back -Check for flap adhesion
    67. 67. Microstriae -Flap in position but fine wrinkles seen superficially -Due to large myopic ablation -Rx- Observe.They resolve spontaneously
    68. 68. 8) Epithelial ingrowth  Presents 1-3 months after LASIK.  Causes-Epithelial cells trapped under flap  Risk factors -Peripheral epithelial defect -Poor flap adhesion -Buttonholed flaps -Repeat LASIK
    69. 69.  Classification GRADE 1-Faint white line <2mm from flap edge  GRADE 2-Opaque cells <2mm from flap edge with rolled flap edge  GRADE 3-Grey to white fine opaque line extending >2mm from flap edge.  GRADE 4-If ingrowth >2mm from edge with documented progression Rx flap lifted  epithelium scraped at stroma & under flap  repositioned. Mitomycin-C can be used
    70. 70. 9) Infectious keratitis – vision threatening - M/C organisms – Atypical mycobacteria, Staphylococci - Prevention – prophylactic antibiotics - Pre-treatment of meibomian gl. disease - sterile instruments & techniques - suction lid specula
    71. 71. 10) Keractasia - Ablation beyond 250 µm of posterior corneal stroma - LASIK performed on unrecognized KC suspects - tt – RGP lenses, corneal transplant 11) Post op Glaucoma(Pseudo DLK) -Steroid induced. 12) Vitreoretinal Complications Increased risk of RD due to alteration of anterior vitreous by suction ring-Risk 0.08%.
    72. 72. LASEK & Epi-LASIK Corneal surface ablative refractive procedures  Anterior stroma of cornea (ant. 1/3 rd) has stronger interlamellar connections than post. 2/3 rd . So surface ablation preserves the structural integrity better than LASIK especially in the correction of 
    73. 73. LASEK Creating an epithelial flap with dilute alcohol (18%) applied for 25-35 seconds & repositioning this flap after laser ablation  Plane of cleavage Hemidesmosomal attachments in the most superficial part of lamina lucida of BM 
    74. 74. Epi-LASIK Use of a motorized epithelial separator with oscillating blade, to mechanically separate a 60-80µ corneal epithelial flap from stroma & repositioning this flap after laser ablation  Plane of cleavage Not within but underneath the Basement Membrane 
    75. 75. HISTORY 1 st LASEK 1996 by Dr. Azar  Cimberle & Camellin independently coined the term LASEK  Epi-LASIK a recent development in refractive surgery technology 
    76. 76. ADVANTAGES OVER PRK Greater post-operative comfort  Faster visual recovery  allows bilateral simultaneous surgery  Reduced risk of corneal haze 
    77. 77. ADVANTAGES OVER LASIK Flap related complications are eliminated in LASEK  If microkeratome related complications occur during EpiLASIK, procedure can be easily converted to PRK & completed  Absence of corneal lamellar flap in both procedures, reduces risk of keractasia 
    78. 78. COMPLICATIONS INTRAOPERATIVE LASEK related 1) Alcohol leakage problems: during surgery 2) Incomplete flap epithelial detachment (insufficient alcohol exposure) Epi-LASIK related Flap-related - free flap - incomplete - buttonholing
    79. 79. EARLY POST-OP COMPLICATIONS Delayed epithelial healing (3-5 days)  Pain – resolution of pain accompanies epithelial closure  Infiltrates & Infection - Sterile infiltrates: alcoholpredisposing factor  Dry eye  Corneal haze – with increased ablation depths 
    80. 80. Laser Thermo-Keratoplasty (LTK)      FDA approval Jan 2000 Ho:YAG (Holmium:yttrium-aluminiumgarnet) laser – deliver laser energy to periphery of cornea For Hyperopia (0.75 to 2.5 D) Takes months to stabilize In time, the effect wears off in a substantial number of cases
    81. 81. Laser Thermal Keratoplasty (LTK)
    82. 82. CONDUCTIVE KERATOPLASTY Application of low-energy, high frequency radiofrequency current to heat & shrink peripheral & paracentral stromal collagen  resulting in steepening of central cornea  Used for hyperopia (1 – 2.25D), hyperopic astigmatism and presbyopia  FDA approved 2002  Provides better stability than the previously used procedure Laser 
    83. 83.  CORNEAL RESPONSE TO HEAT 55 – 58 ˚C  collagen shrinkage (disruption of H bonds of tertiary collagen structure) 65 – 78 ˚C  collagen relaxation > 78 ˚C  collagen necrosis
    84. 84.   Hyperopia Lower corrections : 8 spots at 6mm optical zone & 8 spots at 7mm optical zone Greater corrections : 24 spots applied ( 8 additional (+2 to +2.50D ) spots at 8mm optical zone) Even greater corrections : 32 spots Hyperopic astigmatism Peripheral heat spots along a single (flatter) meridian
    85. 85. Conductive Keratoplasty (CK)
    86. 86. SCLERAL EXPANSION BANDS     Designed to treat presbyopia Not FDA approved Theory: Presbyopia is due to slackening of fibers attached to the lens. Figure : Implanted scleral expansion band (full circular band model)
    87. 87. Intrastromal Corneal Ring Segments (Intacs) PMMA arcuate segments placed within peripheral cornea to correct myopia  FDA Approved 1999  < 3.0 D myopia , < 1.0D Astigmatism  Emerging role as an adjunct for keratoconus & corneal ectasia 
    88. 88.  1 st generation ICRS : 360˚ ICRS Current design: 2 PMMA segments,150˚ arc length  Hexagonal cross section  Fixed inner diam. 6.8 mm Fixed outer diam. 8.1 mm
    89. 89. Refractive effect directly related to thickness INTACS THICKNESS (mm) 0.25 RECOMMENDED PRESCRIBING RANGE (D) 0.30 -1.75 to -2.25 0.35 -2.38 to -3.00 -1.00 to -1.63
    90. 90. SURGICAL TECHNIQUE ICRS channel formation at 2/3 rd corneal depth, outside central optical zone  Insertion of segment  Suturing of entry site  Adv  Reversibility  Hyperacuitty 
    91. 91. PHAKIC INTRAOCULAR LENSES  Artificial lenses implanted in the anterior or posterior chamber in the presence of the natural crystalline lens to correct refractive errors  Intraoperative iridectomy or preoperative Nd:YAG laser iridotomies – necessary to avoid post-op pupillary block glaucoma
    92. 92.  3 types Anterior chamber-angle supported PIOL AC iris-fixated Posterior chamber PIOL  Early models – PMMA Newer models – foldable (more safe & efficacious) 
    93. 93. AC angle-supported AC iris-fixated NuVita (Bausch & Lomb) Vivarte (Ciba vision) Kelman Duet I-CARE Acrysof AC Verisyse/ Artisan (AMO/Ophtec) Artiflex/ Veriflex PC sulcus-supported Implantable Contact Lens (ICL) Phakic Refractive Lens (PRL) Sticklens
    94. 94. GENERAL CRITERIA FOR IMPLANTING PHAKIC IOLs       Age above 18 years Stable refraction (< 0.5D change for 6 months) Ammetropia not suitable for Excimer laser surgery (high powers or thin cornea) AC depth >= 3.2mm for iris-claw lens >= 2.5mm for pc PIOLs Minimum endothelial cell density > 3500 cells/mm² at 21 yrs age > 2800 cells/mm² at 31 yrs age > 2200 cells/mm² at 41 yrs age > 2000 cells/mm² at 45 yrs age No other ocular pathology (corneal disorders, glaucoma, uveitis, cataract)
    95. 95. Indications  High Myopia December 2004, FDA approved 1 st PIOL : Verisyse/ Artisan ‘iris-claw’ lens Myopia -5 to -20 D Astigmatism upto 2.5 D December 2005, FDA approved a 2 nd PIOL : Visian ICL(Implantable Contact Lens) Myopia -3 to -20 D Astigmatism upto 2.5 D  High Hyperopia Upto +3.0 D
    96. 96. Ancillary tests IOL power calculation AC PIOL - Power calculation is independent of axial length of eye - Depends on : 1)Central corneal curvaturekeratometry (k) 2) ACD 3) Preoperative spherical equivalent PC PIOL - Corneal thickness & axial length also taken into consideration
    97. 97. AC DIMENSIONS & SIZING OF PIOL Most of the complications arise due to inaccurate sizin of PIOLs  External measurement from limbus-tolimbus( white-to-white dist.)  Gives approx estimation of AC diameter - Measured b/w 3 & 9 o’clock meridians with calipers - ORBSCAN - Videokeratoscopes - High frequency UBM 
    98. 98. Diam of lens = w-w dist + 0.5 to 1.0 mm (For both angle & sulcus-supported PIOLs)
    99. 99. AC angle-supported PIOLs NuVita
    100. 100. Vivarte
    101. 101. AC iris-fixated PIOLs Artisan/ Verisyse Most commonly used phakic IOL
    102. 102. Artiflex/ Veriflex
    103. 103. PC sulcus-supported PIOL Implantable Contact Lens (ICL)
    104. 104. ADVANTAGES Most stable & predictable refractive method  Newer designs – improved safety & efficacy  Reversible  Significant gain of postoperative BCVA in myopia – reduction in image minification  No loss of contrast sensitivity (as seen in LASIK) 
    105. 105. COMPLICATIONS Haloes & glare  Pupillary ovalization ( Angle supported PIOLs)  Endothelial damage  Elevation of IOP  Uveits (iris trauma during surgery)  Cataract (mostly nuclear) 
    106. 106. COMPLICATIONS Anterior chamber inflammation/ pigment dispersion – repeated traumatic attempts at iris enclavation (Iris-fixated PIOLs)  Iris atrophy & IOL dislocation (Irisfixated PIOLs)  Hyphaema (Iris-fixated PIOLs)  Decentration / Dislocation into vitreous cavity (PC PIOLs) 
    107. 107. BIOPTICS Concept of first implanting a phakic IOL to reduce the amount of myopia, then fine tuning the residual correction with LASIK  I/Cs –extremely high myopia - high astigmatism - lens power not available  Combination has expanded the limits of refractive surgery 

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