Laser EYE SURGERY. LASIK and Excimer Lasers Michael Hutchins

Transcription

1 Laser EYE SURGERY LASIK and Excimer Lasers Michael Hutchins

2 The PROBLEM pia - near sightedness sed by either an elongated or steep cornera. focal point is in front of the a instead of on it. cally corrected with concave

3 THE PROBLEM ropia - far sightedness ed by a flat cornea or rt eye. l point is behind the a. ected with concave s (positive optical

4 THE PROBLEM matism arises from different focal points in different es of the eye. sed by non-uniform curvature of the cornea or scarrin ens. ular astigmatism cannot be fixed by glasses, just conta

5 NTERNAL CORRECTIONS IK - Laser Assisted in SItu Keratomileusis tomileusis is the procedure of opening the eye and ing the cornea. IK uses an excimer laser to perform the alterations an r a knife or a femtosecond laser to create the openin IK is an alternative to wearing glasses or contacts as it

6 LASIK IK began in 1950 in Bogotá, Columbia with the lopment of keratomileusis. eakthrough was the 1973 announcement of the excim. holam Peyman filed the first LASIK patent in 1989 a thod for modifying corneal curvature. It includes the edure of revealing the cornea, using an excimer laser

7 LASIK SIK is performed while awake h an occasional mild sedative. hinged flap is cut with either a tal blade or a femtosecond er. Excimer laser remodels the rnea by ablating tissue. e flap is repositioned and left

8 LASIK ing the flap is either done with a microkeratome or a osecond laser.

9 Excimer Lasers mer lasers are UV lasers that utilize le gas halides. y often use a combination of an inert such as argon, krypton or xenon h a highly reactive gas like chlorine or rine. hort lived molecule called an excimer

10 Excimer Lasers ers are formed n the inert gas into an excited, in this state they with the halide rm a molecule.

11 Excimer Lasers n the noble gas rns to its ground it repels the halide h gives rise to the violet light.

12 EXCIMER LASERS al wavelengths for us excimers. bond energy of an H-O of H2O is about 4.76 nd to break a C-H bond hane it is 4.38 ev le light is 2-3 ev while Excimer Wavelength (nm) Energy (e Ar2* Kr2* F Xe2* 172 & & 7.0 ArF KrF XeBr XeCl XeF CaF KrCl Cl

13 Excimer Lasers ultraviolet light is absorbed by tissue and organic matte dded energy breaks the bonds of molecules at the sur e molecules ablate into the air without adding heat to. This is called Ablative Photodecomposition. ent excimer lasers typically pulse for 10 ns at 100 Hz. e used in eye surgery reposition to follow the eye 400 s per second.

14 Excimer Lasers ow absorption depth: 0.1.5µm. gy highly absorbed by rials. orm power density over ively large area. Discharge circuit - expen and require frequent maintenancelaser gas mix is toxic and corrosive. The laser must be refilled fresh gas regularly.

15 LASIK Side Effects me higher order abberations can cur as they cannot be diagnosed h normal eye exams. e is halos and starbursts: vision ne during the day but at night pupil can expand and pass the ge of the LASIK flap, this gives to halos and other abberations. Surgery induced dry eyes Over or under correction Visual acuity fluctuation Halos or starbursts around sources at night Light sensitivity Ghost images Wrinkles in flap Decentered ablation Debris or growth under fl Induced astigmatism Corneal Ectasia Floaters Epitheliun erosion

16 LASIK Alternatives IK is limited by the excimer laser and can cause some age to the eyes nerves so new methods are being loped. ther popular method is PRK it is similar to LASIK with ssitating a flap to be cut (necessary for pilots). pared to LASIK it has a longer recovery period and m mfort.

17 References ipedia entries on: LASIK, Excimer Laser, Excimer, Myo eropia, Astigmatism (eye), Keratomileusis, Photorefrac tectomy -Wikipedia images from: ://eyeclinicpc.com/lasik/lasik.htm and