Course # Intra Corneal Ring Segments Contact Lens Management of Irregular Astigmatism

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1 Course # 772 Intra Corneal Ring Segments Contact Lens Management of Irregular Astigmatism

2 Intra Corneal Ring Segments Contact Lens Management of Irregular Astigmatism Financial Disclosure I do not own stock in any contact lens or lens care company I have not received funding from any company mentioned in this presentation Michael A. Ward, MMSc, FCLSA Emory University Astigmatism In optics, astigmatism (from Greek: α a "without" + stigmatos, spot,) is when an optical system has different foci for rays that propagate in two perpendicular planes. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances Astigmatism Keratometry astigmatism Regular Astigmatism Principal Axis 90 apart Corneal astigmatism is indicated by the difference in keratometric readings Example: K: 43.00/45.00 X 90, indicates 2 diopters of corneal astigmatism located at 90 (WTR) ATR astigmatism Steep at 180 WTR astigmatism Steep at 90 1

3 Steep at 90 With The Rule (common) Astigmatism Irregular Astigmatism Principle meridians are not 90 apart Cornea Irregular Astigmatism Causes and Indications Ectasias Keratoconus Pellucid marginal degeneration Post surgical RK/AK/Hex K Lasik/Lasek/PRK Penetrating keratoplasty ICRS Scars Salzmann s Post trauma Eyelid lesions Keratoconus Topography Photo / Axial / True True, absolute, tangential and instantaneous are all names for views represented by using the actual data points Videokeratoscopy True View Meridional or axial views use a spherically biased algorithm that effectively averages all points as if the cornea were a sphere Normalized refers to scale Videokeratoscopy Axial View 2

4 Keratoconus Suspect Keratoconus relative sparing of visual axis Keratoconus management options Post Refractive Surgery Topographic Categories Do nothing Spectacles: limited to correcting spheres and regular astigmatism Contact lenses: can correct regular and irregular astigmatism Surgery: ablative, implant, penetrating keratoplasty Combinations Incisional RK, Hex K, AK Ablative PRK, Lasik, Lasek ICRS Incisional Keratotomies RK, Hex K, AK Increasing number of patients are returning for further correction due to progressive hyperopic shift Use RGPs for best VA Si H for secondary option Avoid thick SCL due to propensity for vascularization along incisions Incisional Keratotomies RK, Hex K, AK Large diameter RGP lenses required May use reverse curve (steeper secondary curve than base curve) Central pooling Pressure is on elbow; watch for staining 3

5 Incisional Keratotomies RK, Hex K, AK If patient had surgery years prior and has been happy until recent years, look for other causes of visual impairment If due to hyperopic shift (spherical), a simple Si H SCL will probably work by returning pt to previous post RK correction Check for early cataract changes; even mild lenticular changes (PSC) can significantly impact visual quality in these patients due to potentially significant glare Hex K Difficult RGP lens stability Use SCL if possible Tandem SCL/RGP system is often helpful here Balance any anisometropia >4D; augment with spectacles if necessary Ablative Keratoplasties PRK, LASIK, LASEK Simple over/under corrections and mild residual astigmatisms can be adequately corrected with soft lens spheres and torics If correctable with refraction, then SCL should work Irregular astigmatisms require rigid lens correction RGP Fitting Post LASIK just the facts Choose initial BC 2 diopters steeper than mean post op Ks Start with 10.5 diameter; larger to increase centration Use over refraction for power determination Choose aspheric design with 0.17 edge lift (Star A ) Use fluorescein patterns as guide to finalize fit Use mid to high Dk material (e.g. Boston XO, XO 2,Optimum X) Contact Lens Management after PRK / LASIK Summary GP Fluorescein patterns show apical clearance, midperipheral alignment and PC clearance Fit when refraction stable, 4 12 wk. SCL okay, but won t correct irregular astigmatism; GPs preferred 4

6 CL Correction over ICRS Intacs / PPLK Left Eye Pre and Post ICRS Topography: Lasik like periphery with KC like center RGP needed to improve VA; SCL will not correct Fit large lenses with vault, or minimal pressure Piggyback often required Carefully monitor thickness of corneal tissue over ICRS Before After Historical Piggyback Lens Use CASE REPORT ICRS Piggyback lens fitting is not new It has been used with varied success for decades Often used as a last resort effort to delay corneal surgery Hypoxia was the most common complication limiting its use Silicone hydrogels have solved the hypoxia problem and greatly increased PB lens usage Purpose To provide the corneal protective properties of a soft lens and the refractive benefits of a rigid lens A soft lens material is used to Protect from environmental debris and to minimize FBS from GP lens Provide shape support to anterior ocular surface Indications for Tandem SCL/GP Lens Fitting First time GP lens wear as a temporary crutch Previous GP or Hybrid lens failure Irregular surface Apical nodule KC like post surgical ectasia Epithelial basement membrane dystrophy 5

7 Two Basic Methods of Piggyback Lens Fitting 1) Design GP lens to fit cornea, then dispense with SCL under GP 2) Place SCL on cornea, then fit GP to align with anterior SCL surface Fit standard or custom KC designs as usual Choose SCL base lens to use at dispense Silicone hydrogel usually steeper BC if options Method 1 Fit GP to Cornea Fit SCL on cornea use Si H materials when possible Measure keratometry over SCL Fit GP to SCL anterior surface select initial BC on flat K use fluorescein to check fit Method 2 Fit GP to SCL Soft (Base) Lens Options Silicone Hydrogel Materials approved for therapeutic use PureVision (Dk/t=110) Good O2, handling & reasonable draping Acuvue Oasys (Dk/t=147) Better O2; good handling & draping, 100%UVA & 96% UVB block Focus Night&Day (Dk/t=175) Highest O2; stiff, does not drape well; no tint, Modulus Vs Water Content Rigid Lens Options Menicon Z (Dk=189) Very High Dk 30d CW approval Boston XO (Dk=100), Boston XO 2 (Dk=141) Optimum Extreme (Dk=125 CLSpectrum August

8 Focus Night&Day base lens Rose K top lens Tandem system Contact Lens Care Recommendations For SCL/GP combined Tandem system: Remove GP, clean with GP daily cleaner, rinse and store in Complete MPS Do not use Boston Cleaner on Menicon or other surface treated materials Remove SCL, clean, rinse and store in Complete MPS In the morning, rinse & wet both lenses with Complete MPS prior to placing on eye Do Not Allow GP Solutions to Come in Contact with SCL materials Ward, MA; January 2006 CLSpectrum Case Report Novel Use of a Piggyback Lens System Scleral lenses are large lenses that vault the cornea, are fluid filled and land on the sclera Scleral Lenses Case Report Contact Lens Management of Granular Corneal Dystrophy 7

9 Alphacor Artificial Corneas Comparison with dpk Case Report 8