Intraocular Refractive Surgery Options

1. Intraocular Refractive Surgery Options Mark Lesher, MD Eye Associates of New Mexico NMAOT Fall Meeting September 22, 2012

2. Basic Ocular Anatomy Overview

3. The Eye’s Optical System • Light rays enter eye through pupil • Cornea is primary refractor of light rays • Crystalline lens is the second part of the eye’s focusing system • Both the cornea and the lens work to keep light rays focused on the retina

4. The Cornea • Clear “watch crystal” of the eye • Avascular • Powerful refracting system • Provides 2/3, or about 40 diopters of the eye’s focusing power

5. The Cornea • Consists of 5 layers • Epithelium • Bowman’s membrane • Stroma • Descemet’s membrane • Endothelium http://e-learning.perubatan.org/index.php?topic=802.0

6. Crystalline Lens • Crystalline lens is a clear, biconvex structure • No blood supply • No nerve supply • Provides 1/3, or about 20 diopters of the eye’s focusing power • Located behind iris • Adult lens is approximately 10mm in diameter

7. Crystalline Lens • Lens is composed primarily of protein fibers • Fibers arranged in a specific pattern • Allow transmission, refraction of light with minimal scatter • Reduce spherical aberration • Lens continues to add fibers throughout life http://www.chinaphar.com/1671-4083/25/figs/1250f1.jpg

8. Refractive Surgery • What is refractive surgery? • Surgery to change the refractive error of the eye • Can treat myopia, hyperopia, astigmatism, presbyopia • Refractive surgery can be corneal or intraocular

9. Refractive Errors

10. Myopia • Long axial length and/or steep K readings • Light rays focus in front of the retina • Causes distance objects to be blurred • Glasses or contact lenses refocus light rays onto retina http://commons.wikimedia.org/wiki/File:Myopia-2-2.svg

11. Hyperopia • Short axial length and/or flat K readings • Light rays would be focused behind retina • Near objects and often distance objects blurred • Glasses or contact lenses refocus light rays onto retina http://health.learninginfo.org/farsightedness.htm

12. Astigmatism • One of the corneal meridians is steeper than the other, so light rays are refracted to 2 points instead of 1 • The astigmatic cornea can be considered shaped like a football instead of a basketball • Spherocylindrical lenses, toric contact lenses refocus light rays onto retina

13. Presbyopia • The natural lens contracts and expands to allow focusing of images • Accommodation • As the lens becomes thicker through life, this flexibility lessens • Presbyopia begins after age 40 • Reduction of the focusing power of the lens results in increased need for near correction

14. So…. What are the options for getting people out of glasses and contact lenses?

15. Corneal Refractive Surgery LASIK, PRK

16. LASIK • Laser-Assisted In Situ Keratomileusis • Uses excimer laser to reshape cornea • Approved to correct • Nearsightedness—up to -14.00 diopters sphere • Farsightedness– up to +5.00 diopters sphere • Astigmatism—up to 5.00 diopters

17. LASIK: Procedure • The globe is held in place with gentle suction while a femtosecond laser is used to cut a very precise “flap” in the anterior cornea • Flap diameter and width can be precisely controlled by programming parameters into laser • Once flap is cut, it is lifted back and excimer laser is applied to stromal bed • Laser quickly reshapes cornea, by flattening the central cornea (myopic treatment) or steepening the central cornea (hyperopic treatment) • Once laser is complete, the flap is put back in place http://www.thelasikzone.com/LASIK-Risks/

18. LASIK • LASIK is fast, safe and popular! • Wide range of available treatment parameters • Quick visual recovery • Minimal or no pain

19. LASIK: Not for Everyone! • Certain patients are not candidates for LASIK • Thin corneas • High refractive errors • Severe dry eye • Certain systemic conditions that predispose to dry eye

20. PRK • Some patients who are not LASIK candidates may still be candidates for a different type of corneal refractive surgery—PRK • PRK (photorefractive keratectomy) involves applying the excimer laser to reshape the cornea, without cutting a corneal flap • The epithelial layer of the cornea is removed • Excimer laser is applied directly beneath • A bandage contact lens is placed for 3-4 days, while the cornea re-epithelializes

21. PRK • PRK may be a better option for some patients because • No flap means treatment is more anterior on the cornea • Less risk for corneal ectasia (progressive corneal steepening) • Corneal nerves are not cut • Lower risk of postop dry eye syndrome • May be better option for patients with anterior basement membrane disease

22. PRK • PRK recovery is not so quick and painless! • Epithelium takes several days to grow back • Discomfort is fairly common in the first 4-7 days • Vision takes several weeks to stabilize • But for some patients, PRK is a safer option than LASIK

23. Preoperative Testing for Corneal Refractive Surgery • Pentacam • Aberrometry (Wavescan) • Refraction • Corneal topography • Corneal Pachymetry

24. Intraocular Refractive Procedures The ICL

25. The VisianICL™ • ICL stands for “Implantable Contact Lens” • This lens is implanted behind the iris, in front of the natural lens • The natural lens is not removed, so the patient does not lose accommodation

26. ICL is Very Thin < 100 um < 50 microns 500-600 um

27. ICL Procedure • Procedure is performed in the operating room • Patient is given IV sedation • A small (3mm) incision is made at the limbus • Viscoelastic is inserted in the eye

28. ICL Procedure • The ICL is folded and implanted through the 3mm incision, and gently unfolds inside the eye • The viscoelastic is removed • Prior to surgery, a peripheral iridectomy is made using a laser • This reduces the risk of elevated intraocular pressure once the ICL is in place • http://www.youtube.com/watch?v=RO0AHHDYx80

29. Who is a Candidate for ICLs? • Age 21-45 • Myopia -3.00 to -15.00 • <2.5 diopters of astigmatism • Anterior chamber depth 3.0mm or greater • Stable refractive error

30. Who is a Candidate for ICLs? • Patients who are not candidates for any type of corneal refractive surgery may be excellent ICL candidates • Cornea is too thin • Refractive error is too high • Corneal surgery could induce unwanted optical aberrations • Patient doesn’t want the potential risk of having a LASIK flap and doesn’t want the prolonged healing time of PRK

31. Preoperative Testing for ICLs • Accurate refraction • Very important! • Optical Coherence Biometry (IOL Master) • Axial length • Anterior chamber depth • Horizontal white to white • Corneal topography • Corneal pachymetry

32. Other Intraocular Refractive Procedures Refractive Lens Exchange

33. Refractive Lens Exchange • During cataract surgery, the natural lens of the eye is removed and replaced with an artificial lens implant (IOL) • The IOL that is placed in the eye compensates for the patient’s natural refractive error • A lower power IOL is used in myopes, a higher power IOL is used in hyperopes • Even if a patient does not have a cataract, the same procedure can be performed to correct refractive errors • This is called a Refractive Lens Exchange

34. Refractive Lens Exchange Procedure • Small incision made in temporal limbus • Anterior portion of lens capsule is removed • Lens is gently loosened with balanced salt solution • Phacoemulsification • Ultrasound used to break up lens contents and suction them out

35. Refractive Lens Exchange Procedure • After natural lens is removed, the IOL is placed in capsular bag • Intraocular lens is foldable, so it goes through a small incision • Lens gently unfolds inside the eye

36. Who is a Candidate for Refractive Lens Exchange? • Older patients who have already lost accommodation • Myopes or hyperopes • Hyperopes are great candidates • Patients with astigmatism • Patients with early cataract changes • Patients wishing to reduce their need for distance and near correction • Multifocal IOLs, monovision, blended vision

37. IOL Options • Recent technology has led to improvements in IOL design and function • Aspheric technology • Multifocal • Astigmatism-correcting

38. Standard IOLs • Most IOLs on the market today are aspheric • Aspheric IOLs are intended to mimic the natural shape of the young adult lens • Reduce spherical aberration • This enhances image quality, particularly in low light situations

39. Standard IOLs • Standard IOLs are single-focus and eliminate accommodation • Patients who are focused at distance need reading glasses • Because of the focus limitations of standard IOLs, some patients opt for monovision or blended vision in order to achieve greater spectacle independence

40. Monovision • Dominant eye focused for distance, non-dominant eye for reading • Achieves level of glasses independence, but some compromise • Loss of depth perception • Defocus of near eye can cause glare at night • Prolonged reading may be difficult • Some patients may not tolerate monovision • It is best to do monovision on patients who have already adapted to it with contact lenses

41. Blended Vision • Dominant eye focused for distance, non-dominant eye for intermediate • Alternatively, dominant eye may be at intermediate and non-dominant at near • Achieves similar result to monovision, without compromising depth perception • Patients will still need glasses for some activities, but it does reduce their dependence on them

42. Multifocal IOLs • Multifocal IOLs are designed to give patients both distance AND near vision in each eye • Does not reduce depth perception • High level of spectacle independence

43. Multifocal IOLs • There are several multifocal IOLs available on the market • Alcon AcrysofReSTOR • Tecnis® Multifocal • AMO ReZoom

44. Multifocal IOLs • The Alcon AcrysofReSTOR is the most common multifocal IOL used at EANM • The ReSTOR provides reliable distance and near vision • Typically 20/30 or better at both distance and near without correction

45. Multifocal IOLs • The ReSTOR IOL uses diffractive technology to achieve multifocality • A diffractive optic splits the amount of light energy entering the eye, so 50% is distance and 50% near

46. Multifocal IOLs • The diffractive optic provides 2 focal points, but can have some side effects • Glare/halos at night • Decreased contrast sensitivity http://www.armchairgeneral.com/forums/showthread.php?t=80924&page=30

47. Toric IOLs • IOLs are now available to correct astigmatism • The most commonly used toric IOL corrects between 1.0-4.0 diopters of astigmatism • The Alcon Acrysof®Toric IOL is the same size and shape as the standard IOL, but has astigmatism correction built into the optic • Toric IOLs are monofocal • Patients corrected for distance will need readers

49. Toric IOLs • Patients who are being evaluated for toric IOLs need special preoperative testing • This topography shows 2.00 diopters at 87° OD and 2.75 diopters at 104° OS

50. Toric IOLs • The patient’s corneal readings are then programmed into the Alcon Toric Calculator • The calculator shows • The appropriate toric power to correct the astigmatism • The axis of placement • The anticipated residual astigmatism