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REFRACTIVE SURGERIES CLASSIFICATION REFRACTIVE SURGERIES CORNEA BASED -RK -PRK -LASIK -EPILASIK -LASEK -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 LASIK(Laser Assisted In Situ Keratomileusis) Procedure using laser to ablate the tissue from the corneal stroma to change the refractive power of the cornea Types of lasers used Excimer-Excited dimer of two atoms -an inert gas(Argon) -Halide(Fluoride) which releases ultraviolet energy at193nm for corneal ablation Patient selection Patients need to be fully informed about potential risks,benefits and realistic expectations Age > 18 years Refractive status stable > 1 year. Current FDA approval Myopia-upto -12D Hyperopia –upto +6D Astigmatism-upto 7D CCT such that minimum safe bed thickness left(250-270µ). Post op Corneal thickness should not be <410µ. Cornea not too flat or steep.<36D or >49D(Poor Optics). CONTRAINDICATIONS Systemic factors Poorly controlled IDDM Pregnancy/lactation Autoimmune / connective tissue disorders(RA,SLE,PAN etc) Clinically significant Atopy,Immunosuppressed patients Keloid tendency(esp PPK) Slow wound healing-Marfans,Ehler-Danlos Systemic Infection-(HIV,TB) Drugs-Azathioprene,Steroids(Slow wound healing) CONTRAINDICATIONS Ocular Factors Glaucoma,RP(Suction Pressure-ON damage,Blebs) Previous h/o RD or f/h of RD. One eyed individual Pre-existing dry eye,Keratoconus.pellucid marginal degeneration,Superficial corneal dystrophy,RCE,Uveitis,early Lenticular changes h/o Herpetic Keratitis(one year prior to surgery) PREOPERATIVE EVALUATION PRIOR TO LASIK Record UCVA and BCVA Dry and wet manifest Pupillometry-Infrared Pupillometer -Aberrometer Large pupil-Increased HOA perceived so increased glare -Can change Optic Zone Slit Lamp Examination Rule out blepharitis, miebomianitis, pingecula, Pterygium,corneal neovascularization Other contraindications for LASIK. IOP by applanation Dilated Fundus Examination to role out holes ,tears. Tear film asessment-Schirmers,TBUT and Lissamine staining Blink Rate-(Normal---3-7/min) Corneal Topography Schiempfug /Scanning slit/placido disc Stop RGP lenses 2 weeks prior and soft lenses I wk prior To rule out early Keratoconus and other ectasias For mean K values Pachymetry -For CCT (Ultrasound/Optical) Contrast Sensitivity testing for pre-operative baseline. BASIC STEPS AND MACHINE SPECIFICATIONS Topical anasthesia-Proparacaine 0.5%, Lignocaine 4%. Surgical Painting and draping(Lint Free). Lid speculum with aspiration. Corneal marking-Orientation of free cap Creation of flap 1st Step-Creation of suction by suction pump to raise the IOP to 65 mm Hg which is necessary for the microkeratome to create a pass and resect the corneal flap. This is crosschecked with Barraquers tonometer. 2nd step-Resection of corneal flap Microkeratome Femtosecond Laser (Intralase) Microkeratome Uses Disposable blades Blade Plate can be set at 90µ,120µ,140µ,160µ and180µ. Nasal or superior hinge flaps can be created. Eg.Hansatome,XP Microkeratome, ACS, Carriazo Barraquer, Moria,Amadeus Femtosecond Laser for Flap Creates photodisruption using femtosecond solid state laser with wavelength of 1053nm. Needs lower vacum. Very short pulse with spot size of 3µ-High precision cutting device. Any hinge can be made Can make flaps as thin as 100µ(Sub Bowmanns Keratomileusis) Flap has vertical edges –so reduced epithelial ingrowth. Microkeratome flap thicker in periphery and thinner in the centre.Not so with Intralase(Planar). 3rd Step-Delivery of Laser After flap is lifted, laser is applied to the stroma according to the ablation profile calculated by the machine. Laser beam is delivered by the following ways depending on the machineBeam Delivery Broad Beam Scanning Slit Beam Flying Spot Most machines employ a flying spot to deliver laser with the help of incorporated eye tracker. 4th step-Reposition Of the Flap After irrigating interface ,flap reposited Adhesion test-Striae test COMPLICATIONS OF LASIK Under/over correction and regression (over time). Post –op Keratectasia Presents 1-12 months Progressive regression Treatment-RGP,Corneal transplant. Prevention-Leave residual stromal bed>280 -Do surface ablation -Don’t violate corneal topography diagnosis of forme-fruste keratoconus COMPLICATIONS OF LASIK Night vision disturbances-Haloes/Glare Decenteration and central islands. 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 COMPLICATIONS OF LASIK Post op Glaucoma(Pseudo DLK)-Steroid induced. Vitreoretinal Complications Increased risk of RD due to alteration of anterior vitreous by suction ring-Risk 0.08%. PVD(0.1% Risk) Macular Hemorrage(0.1% Risk) COMPLICATIONS OF LASIK Flap Complications Button Hole-If K>50D,due to central corneal buckling. Irregular thin flap- Inadequate suction/old blade Short Flap-Hinge encroaches on visual axis-Due to jamming of microkeratome with hair/FB SHORT FLAP Free Cap-Due to flat pre –op K(<38D). .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 MACROSTRIAE Microstriae-Flap in position but fine wrinkles seen superficially -Due to large myopic ablation -Rx- Observe.They resolve spontaneously MICROSTRIAE Bleeding during flap cutting due to corneal neovascularization in contact lens users Interface Inflammation(Sands Of sahara/DLK)-Non-Infective inflammation at the interface seen in 1st week after LASIK. Diffuse,confluent,white granular material at the interface 1-7 days after LASIK. Slight CCC No AC reaction Reduced Visual acuity Grade 1- Focal involvement Normal V/A. Rx Intensive topical steroids. II – Diffuse involvement –Normal V/A. Rx-Add systemic steroids. III – Diffuse confluent granular depositsReduced V/A.No AC reaction. Rx-Same as above+Antibiotics IV - Diffuse confluent granular deposits +intense central striae. Marked Reduced V/A Rx-Interface irrigation + above Epithelial ingrowth-Presents 1-3 months after LASIK. Causes-Epithelial cells trapped under flap Risk factors-Peripheral epithelial defects -Poor flap adhesion -Buttonholed flaps -Repeat LASIK 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—Lift flap and remove the sheets of epithelium.Can use MMC. EPILASIK / LASEK Anterior stroma of cornea (ant. 1/3 rd) has stronger interlamellar connections than post. 2/3rd. So surface ablation preserves the structural integrity better than LASIK especially in the correction of moderate to high myopia. LASEK-Camellins Technique 20% absolute alcohol used for 20-35s. To raise epithelial flap. Flap reposited after ablation EPILASIK- Epithelial keratome used to lift epithelial flap of about 60-80µ thick. Epithelial keratomes use - PMMA blades -Metal Epithelial Separator CORNEAL INLAYS Increase the depth of focus by using pinhole optics. Inlays have 1.6mm centre with 3.6mm surround. Near vision improves by 1.5D with no loss of distant vision. Used in the non –dominant eye. These are hydrogel based.Placed in a tunnel 200400 µ deep in centre of cornea. AcuSof Corneal inlay Phakic IOLs An intra-ocular lens is placed inside the eye in front of the patient’s natural lens. These are available in three types 1. 2. 3. Anterior chamber angle fixated IOL – Nuvita (Bausch & Lomb), Kelman duet, I care (corneal), Vivarte (Ciba vision) Iris supported phakic IOL – Verisyse/ Artisan (AMO/Ophtec) Plate lens that fits between the iris & the crystalline lens – Starr implantable contact lens (ICL), PRL (Ciba). Indications Age above 18 years Stable refraction for one year Patients not suitable for LASIK/LASEK due to high powers or thin corneas AC depth 3.0 mm Endothelial count >2000cells/cumm No other ocular pathology Contraindications Myopia other than axial myopia Corneal dystrophy/ Endothelial cell count <2000cells/cumm Anterior chamber depth less than 3.0mm History of uveitis Presence of anterior/posterior synechiae Glaucoma or IOP higher than 20 mmHg Evidence of nuclear sclerosis or developing cataract Personal or family history of retinal detachment Diabetes mellitus Verisyse Phakic IOL Pre-op assesment for phakic IOL Refraction – Objective & subjective acceptance at 12mm vertex distance Anterior chamber depth – from epiuthelium to endothelium Anterior & posterior segment examinations K-reading & Topography – Orbscan-II Intra-ocular pressure White to white measurement Specular microscopy Veriflex (artiflex) Foldable iris claw lens. It is a modification of Verisyse (Artisan) phakic IOl. Posterior chamber lenses These phakic IOLs are placed in the posterior chamber between the iris & the crystalline lens. These are Starr ICL 2. Cibavision PRL 3. IPCL 1. STAAR ICL The STAAR Collamer ICL and the TORIC ICL are posterior chamber phakic intraocular lenses. Made of Collamer, STAAR’s proprietary collagen copolymer (collagen/HEMA), the lens rests behind the iris in the ciliary sulcus. Complications ICL decentration Pupillary block Pigment dispersion Subcapsular cataract Advantages of phakic IOLs over laser corrective procedures A higher range of refractive errors can be corrected Reversible: Phakic IOL implantation is a potentially reversible procedure Safe: No structural changes are induced. Hence it is safe in any eye with high error & also thin corneas. Better quality of vision: Quality of vision (contrast sensitivity) is better than the laser refractive procedures in eyes with higher refractive errors and no induced higher order aberrations. There is also a considerable improvement in BVCA with these lenses because of the magnification effect. Highly skilled procedure: Prevents misuse of the procedure. Bioptics Bioptics is a combination of phakic IOL and LASIK. Bioptics is done for the correction of the residual spherocylindrical power when a spherical implant is used.