Excimer laser refractive surgery : corneal wound ... - Helda - Helsinki.fi

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Based on these results, we demonstrated that the long-term outcomes after PRK and LASIK were safe and efficient, with similar stability for both procedures. The PRK outcomes were similar when treated by broad-beam or scanning slit laser. LASIK was better than PRK to correct moderate-to-high astigmatism, yet both procedures showed a tendency of undercorrection. Irregular astigmatism was proven to be able to depend exclusively from the corneal epithelium. If this kind of astigmatism is present in the cornea and a customized PRK/LASIK correction is done based on wavefront measurements an irregular astigmatism may be produced rather than treated. Corneal sensory nerve recovery should have an important role in the modulation of the corneal wound healing and post-operative anterior stromal scarring. PRK enhancement may be an option in eyes with previous LASIK after a sufficient time interval that in at least 2 years. 12
1 INTRODUCTION Refractive errors have a major impact on public health questions, such as visual requirements at work. It has been calculated that 2.5-4.3 billion dollars are spent each year in the USA only for the inspection and correction of myopia (Sandoval et al. 2005). Spectacles are the most used and safest choice for correcting refractive errors, followed by contact lenses and refractive surgery. The number of corneal refractive surgeries grows every year (Sandoval et al. 2005) despite the fact that risks, such as breaking of the spectacles and infections associated with contact lenses, appear minimal in relation to the risks of refractive surgery even though the complication rates are considered low. Corneal refractive surgery aims at controlled alteration of the shape of the cornea. Such surgery performed on a completely healthy eye places high demands on the control of wound healing. Corneal refractive procedures are divided into those that change the corneal curvature with relaxing incisions and those that add or remove tissue from the cornea to change its curvature (Barraquer JI 1964). The corneal refractive results are based in the law of thickness introduced by Barraquer in 1964 (Barraquer JI 1964) “changing the thickness of the cornea follows the idea that the cornea is a stable lens, removing tissue in the center or adding tissue on the periphery therefore flattens the cornea.” The argon fluoride (193 nm) excimer laser permits the excision of corneal tissue with minimal damage to the adjacent tissues. It uses high energy ultraviolet radiation to break the covalent bonds between molecules in the corneal stroma without generating high levels of heat (Krauss et al. 1986). This procedure has been termed photoablative process and is the principal reason making laser refractive surgery a relative predictable and safer procedure. The therapeutic treatment of corneal opacities and irregularities by excimer laser is called phototherapeutic keratectomy (PTK) (Fagerholm 2003). In refractive corrections, photorefractive keratectomy (PRK) modifies the anterior corneal surface ablating the anterior corneal stroma and generating a new radius of curvature to decrease refractive error. The most popular refractive surgery is Laser in-situ keratomileusis (LASIK) (Sandoval et al. 2005). This uses PRK technology but performs the procedure at the stromal level after the creation of a lamellar flap formed with a mechanical microkeratome (Updegraff and Kritzinger 2000). The present study was undertaken to assess the long-term postoperative outcomes of the two most common laser refractive surgeries (PRK and LASIK) to treat myopia. The effect of excimer laser surgery in the treatment of regular astigmatism by these two different techniques was analysed. The presence of irregular astigmatism secondary to epithelial irregularities was also evaluated. In addition, it was also of interest to study the correlation of corneal nerve density and postoperative corneal wound healing after excimer laser refractive surgery. 13
Page 1 and 2: Department of Ophthalmology Univers
Page 3 and 4: “When you want something, all the
Page 5 and 6: 3 AIMS OF THE STUDY 35 4 PATIENTS A
Page 7 and 8: STUDY V. PRK enhancement 58 7 SUMMA
Page 9 and 10: ABBREVIATIONS ArF Argon Fluoride AS
Page 11: ABSTRACT Although the first procedu
Page 15 and 16: from anterior to posterior by the e
Page 17 and 18: et al. 1991, Gallar et al. 1993, Ta
Page 19 and 20: 2.3.2 Interaction of excimer laser
Page 21 and 22: at that time an extracorporeal trea
Page 23 and 24: Twelve to 24 hours after the onset
Page 25 and 26: 2.5 PREOPERATIVE ASSESSMENT OF REFR
Page 27 and 28: 2009, Stephenson et al. 1998) have
Page 29 and 30: 2.6.2 LASIK outcomes Although LASIK
Page 31 and 32: 2.7 PRK AND LASIK COMPLICATIONS Exc
Page 33 and 34: Dry eye Dry eye is one of the most
Page 35 and 36: 3 AIMS OF THE STUDY The general pur
Page 37 and 38: 4.2 PROTOCOLS The patients included
Page 39 and 40: 4.3.7 Study subjects 4.3.7.1 Study
Page 41 and 42: with the post hoc Dunn multiple com
Page 43 and 44: LASIK UCVA ≤0.0 was achieved post
Page 45 and 46: Table 6 Safety postoperative values
Page 47 and 48: 5.2 STUDIES III AND IV. Regular and
Page 49 and 50: Stability PRK Mean MRSE at six mont
Page 51 and 52: 4 3 2 1 0 1 2 3 4 Normalized Error
Page 53 and 54: Safety Nine eyes out of eleven gain
Page 55 and 56: ±1.00 D of the intended correction
Page 57 and 58: a tendency to overcorrection in MRS
Page 59 and 60: 7 SUMMARY AND CONCLUSIONS The prese
Page 61 and 62: I am grateful to Ms. Elina Haapanie
Page 63 and 64:
Azar DT and Farah SG (1998): Laser
Page 65 and 66:
Donnenfeld ED, Ehrenhaus M, Solomon
Page 67 and 68:
Hay ED (1979): Development of the v
Page 69 and 70:
Kornmehl EW, Steinert RF and Puliaf
Page 71 and 72:
McDonald MB, Kaufman HE, Frantz JM,
Page 73 and 74:
Pallikaris IG, Kymionis GD, Panagop
Page 75 and 76:
Sakimoto T, Rosenblatt MI and Azar
Page 77 and 78:
Toda I, Asano-Kato N, Komai-Hori Y
Page 79:
ORIGINAL PUBLICATIONS 79
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