Small Incision Lenticule Extraction (SMILE): Surgical Technique and Challenges (Comprehensive Text and Video Guide) Jeewan S Titiyal, Manpreet Kaur
INDEX
Page numbers followed by f refer to figure, fc refer to flow chart, t refer to table.
A
Aberration, higher-order 12, 17, 159
Ablation zone diameter 149
Accurate centration 126
Acne vulgaris, treatment of 11
Allograft 167
Ambrósio relational thickness 15
Anterior segment optical coherence tomography 89, 100, 105f, 107f, 120, 121, 139, 140
ASOCT See Anterior segment optical coherence tomography
Astigmatic keratotomy 5
Astigmatism 16
Autograft 167
Automated lamellar keratoplasty 2
B
Balanced salt solution 49
Barraquer-Krumeich-Swinger 2
nonfreeze technique 3
BCVA See Best corrected visual acuity
Belin-Ambrósio enhanced ectasia display 15
Best corrected visual acuity 10, 12, 115, 164
Black spots 94, 95, 100
prevention 95
Bowman's layer 119
C
Cap cut 54
Cap microstriae 114, 118
management 119
pathophysiology 119
Cap parameters 40, 54f
Cap side-cut 55
Cap-lenticular adhesion
case of 107f
sinskey hook 101f
Carl Zeiss contact lens 88
Centration 73
Chung's swing technique 59
Cleavage planes, dissection of 73
Collagen cross-linking 161, 170
Contact glass interface, treatment pack with 35f
Contact lens 50f, 94f
related factors 95
Contrast sensitivity 13, 78, 83
Corneal
biomechanical strength 78, 85
biomechanics 153, 154
clarity 78, 83
ectasia 130
hysteresis 27, 78, 85, 153
innervation 155
keratocyte density 24
light reflex, coaxially sighted 51
nerve fiber
anatomy of 23
layer changes 24
pachymetry 15, 153
refractive surgery 3
evolution of 2fc
resistance factor 27, 78, 85, 153
sensations 29, 78, 84
stromal equivalent 168, 169f
sub-basal nerve fibers 25f
topography 15, 152
regular 152
vertex centration 129
visualization Scheimpflug technology 22, 27
wound healing 21
cascade 21
postoperative 21
Corrected distance visual acuity 79
Corvis ST See Corneal visualization Scheimpflug technology
Cryopreservation 171
Curvilinear lenticulerrhexis, continuous 58, 103
D
Dense opaque bubble layer 96f
Diabetes mellitus 10
Diffuse lamellar keratitis 115, 131
pathophysiology 131
Docking 52f, 73
related factors 95
Dry eye 114, 118, 154
management 118
pathophysiology 118
prevention 118
syndrome 14
E
Ectasia 115, 130
management 131
pathophysiology 130
risk score system 15
Endokeratophakia 167
Epidermal growth factor 21
Epikeratophakia 169
Epithelial defect 110
during surgery 120
extent of 105f
management 110
Epithelial ingrowth 114, 119
diagnosis of 121
pathophysiology 119
Eyes, number of 79
F
Femtosecond laser
application 49, 53, 69f, 96f
delivery 52f, 67f, 145f, 162
in corneal refractive surgery 4
intrastromal lenticular
implantation 167
tectonic keratoplasty with 167
settings and treatment parameters 53f
technology 6, 148
evolution of 1
Femtosecond laser-assisted in situ keratomileusis 9, 65, 148, 154
Femtosecond lenticule extraction 10, 28, 32, 68, 68f, 99, 103, 146
Fixation ring 62f
FLEx See Femtosecond lenticule extraction
FS-LASIK See Femtosecond laser-assisted in situ keratomileusis
Fundus examination 14
G
Glaucoma 1
H
Herpes infection 11
Hyperopia 16, 161
surgical correction of 161
treatment of 167
Hyperopic lenticule 162, 163f
Hyperopic refractive correction 18
Hyperopic SMILE lenticule 162t
I
Immune-deficient states 10
In situ keratomileusis 3
Infectious keratitis 132
management 133
Inflammatory mediators 28
Infrared illumination 37
Interface debris 132
Interface haze 113, 114
management 117
pathophysiology 113
prevention 117
Intraocular pressure 5, 26, 149, 150
preoperative 15
Intraoperative manipulations, increased 124
Intraoperative signs 103
Intraoperative suction loss 90t, 138
management of 92fc
Intrastromal lenticule 67f, 68f
Irregular topography 114, 123
management 124
K
Keratitis, infective 115
Keratoconus 130
progression, management of 169
Keratoplasty 5
Kyphosis 12
L
Lamellar dissectors 60f
LASER See Light amplification by stimulated emission of radiation
Laser
arm 36
in ophthalmology 1
keratome 35f
parameters for small incision lenticule extraction 42t
settings 99, 124
selection of 41
spots depicting spot distance 43f
Laser-assisted
in situ keratomileusis 4, 16, 22, 92, 113, 115, 141, 142, 149t, 154t, 159f
postoperative 155f
subepithelial keratomileusis 2
Laser-induced optical breakdown 32, 95
LASIK See Laser-assisted in situ keratomileusis
Lenticule
characteristics 99, 100, 162
creation sequence and time 162
cut 54
diameter 39
dissection 99, 102
difficult 139
management of difficult 100fc
pathophysiology of difficult 100fc
dissection and extraction 36, 49, 55
modified techniques for 55
pathophysiology of difficult 98f
edge identification 74f
extraction
anatomical effects of 104f
difficult 89, 97
management, difficult 100
microforceps for 61f
pathophysiology, difficult 98
physiological effects of difficult 104f
sub-cap 141, 145, 166
minimum thickness of 40
parameters 38, 39f, 40
preservation 170
side-cut 54
stripper 62f
thickness 131
Light amplification by stimulated emission of radiation 1
Lims corneoscleral forceps 62, 63f
LIOB See Laser-induced optical breakdown
Low-suction system 90
M
Manifest refraction spherical equivalent 78, 82, 149, 161
MASER See Microwave amplification by stimulated emission of radiation
Mitomycin C 115
MRSE See Manifest refraction spherical equivalent
Myopia 161
and myopic astigmatism 79t82t
high 79, 81, 82, 130
low 79, 81, 82
with astigmatism 79, 81
with corneal opacity 164
Myopic 162t
astigmatism 163
lenticule 162
N
Neodymium-doped yttrium lithium fluoride 4
Nerve fiber layer, preoperative sub-basal 156f
Nerve growth factor 28
O
Ocular
adnexal examination 13
allergic disease 11
ectatic diseases 11
examination 13
comprehensive 12
motility assessment 13
response analyzer 22, 27, 78, 85, 154
surface
disease index 22, 29, 78, 85
disease, mild 16
disorders 17
examination 14
stability 29, 155
surface-related
factors 95
problems 154
Opaque bubble layer 89, 95, 99, 108, 115, 124
management 97
Optical aberrations 78, 83, 115, 125
management 125
Optical zone 38
diameter 149
OSDI See Ocular surface disease index
P
Palpebral fissures, small 17
Paracentral cap tear 106f
Patient supporting system 36
PEARL See Presbyopic allogenic refractive lenticule
Pellucid marginal degeneration 11
Peripheral small abrasions 110
Photorefractive keratectomy 2, 3, 26, 13, 89, 115, 140, 141, 142, 154, 155, 164
Phototherapeutic keratectomy 2
Postkeratoplasty refractive correction 164
Post-LASIK ectasia, management of 170
Post-SMILE
enhancement 145f
and retreatment 137
retreatment, decision-making in 140fc
Potential visual complaints of blurred vision 124f
Presbyopia 163
Presbyopic allogenic refractive lenticule 163
PRK See Photorefractive keratectomy
Pseudo-small incision lenticule extraction 69, 69f
Pulse energy
decreased 44
increased 44
on small incision lenticule extraction 44t
Pupillary examination 14
R
Refraction 13
Refractive applications of SMILE, expanding 161
Refractive error 11, 100, 151
higher 16
magnitude of 72, 138
Refractive lenticule 67f
extraction 77
flap-based 66
flapless 148
wet-lab training for 67f
of SMILE, applications of 166
Refractive outcomes 77, 154, 156
Refractive surgery 1, 16t
Reimplantation techniques 171
Residual stromal bed thickness 41, 115, 139, 140, 149
low 130
Retained lenticule 89, 108, 109
management 109
prevention 108
Retinal tears 11
Rigid gas permeables 11
RSBT See Residual stromal bed thickness
S
Schirmer's test 118
Scoliosis 12
Seibel spatula 68f
Shimmer sign 55, 58
Sinskey hook-assisted lenticule extraction 101f
Slit illumination 37
Slit-lamp examination 14
Small incision lenticule extraction 9, 9t, 12, 16, 16t, 21, 22t, 25f, 26f, 32, 38t, 39f, 46, 47t, 49t, 52f, 56f, 58t, 65, 66, 66t, 70, 71t, 77, 88, 89t, 99, 105, 113, 114t, 137, 142f, 148, 149t, 154t, 156f, 161
biomechanical
changes after 26
properties after 27
cap parameters for 39f
case of 96f
differs from lasik 148
efficacy of 79t
epithelial 61
for re-treatment after refractive surgery 166
forceps 61
functional changes after 29
healing cascade after 23fc
in hyperopia 83
in thick-flap lasik 166
lamellar dissectors 59
lenticule 107f
strippers 62
performing 45t
physiological outcomes of 78t
postoperative 155f
complications in 113
predictability of 81t
pros and cons of 159f
refractive outcomes of 78t
repeat 166
retreatment after 141t
safety of 80t
stability of 82t
starburst in left eye after 124f
stepwise learning curve of 66f
surgical instruments during 60f
surgical technique of 46
treatment parameters for 40t
SMILE See Small incision lenticule extraction
Spherical aberrations 14
Spherical powers 149
Stromal expansion 170
Stromal keratocyte density, anterior 26f
Stromal lenticule, storage of 170
Stromal nerve plexus, anterior 24
Suction loss 88, 138
management 92
pathophysiology 88
prevention 91
Surgical instruments 59
Surgical procedure 149
T
TBUT See Tear film breakup time
Tear
meniscus 52f
side-cut 89, 106f
Tear film
breakup time 12, 22, 78
changes 78
stability 84
Technolas perfect vision 5
Thin-flap lasik 142
Tonometry 15
Topical anesthesia 95
Total lenticule thickness 40
Traumatic dislocation of flaps 17
U
UDVA See Uncorrected distance visual acuity
Ultrathin cornea 170
Uncorrected distance visual acuity 78
Uncorrected visual acuity 10, 12
Universal wire speculum 62, 63f
Uveitis 11
V
Vacuum system 36
Visual
acuity 13, 77, 78, 157
uncorrected distance 79, 165
function analysis 124f
quality 78, 82, 157
recovery 154, 156
time 78, 82
VisuMax femtosecond laser system 32, 33f, 40t
components of 34t
functional components of 34f
technical specifications of 45t
VisuMax femtosecond laser-assisted small incision 161
VisuMax laser 5, 145f
circle pattern of 143, 144f
VisuMax system 164
W
Weighing pros and cons 158
Wet-lab training 67
White-ring sign 58, 103
Y
Y-shaped instrument 62
×
Chapter Notes

Save Clear


Evolution of Femtosecond Laser Technology in Refractive SurgeryChapter 1

Sridevi Nair,
Manpreet Kaur,
Jeewan S Titiyal
 
INTRODUCTION
The history of medicine is replete with instances of path-breaking discoveries and inventions, which have had a significant impact on mankind. Light amplification by stimulated emission of radiation (LASER) is an instance of one such landmark development, which has changed the management of numerous diseases in the field of medicine, especially in ophthalmology. We have briefly outlined the evolution of lasers in ophthalmology, with an emphasis on femtosecond laser technology. The changing paradigm of cornea-based refractive surgeries has been described, from the early mechanical reshaping of the cornea to the present day flapless femtosecond laser-assisted refractive lenticule extraction (Flowchart 1.1).
 
LASERS IN OPHTHALMOLOGY: A BRIEF HISTORY
Today, one tends to associate the term LASER with precision, accuracy and speed. However, its evolution has taken decades of work by numerous scientists around the world. The use of light as a therapeutic agent in ophthalmology dates back to the 1940s, when Meyer-Schwickerath first focused strong sunlight on the retina of patients with choroidal melanomas in order to treat them.1 The concept of stimulated emission was introduced by Einstein in 1917.2 Townes and Schawlow used microwave radiation as the external source for stimulated emission and developed microwave amplification by stimulated emission of radiation (MASER). Gordon provided the concept of using light as the source for stimulated emission, and thus coined the term light amplification by stimulated emission of radiation or LASER.3
Laser radiation has the advantage of being highly coherent, monochromatic and collimated. The first functional laser was developed by Maiman in 1960.4 Zaret produced the first ocular lesion using ruby laser in 1961.5 In 1964, Bridges developed the argon laser with emission in the blue and green wavelengths.6 In 1970, Basov built a laser using xenon dimer gas, and called it excimer laser (an abbreviation for excited dimer).72
zoom view
Flowchart 1.1: Evolution of corneal refractive surgery.
(PTK: Phototherapeutic keratectomy; BKS: Barraquer-Krumeich-Swinger; ALK: Automated lamellar keratoplasty; PRK: Photorefractive keratectomy; FDA: Food and Drug Administration; LASEK: L aser-assisted subepithelial keratomileusis; SMILE: Small incision lenticule extraction; LASIK: Laser-assisted in situ keratomileusis).
3Argon fluoride laser, a type of excimer laser, was developed in 1976, with emission in the ultraviolet range at a wavelength of 193 nm.8
 
CORNEAL REFRACTIVE SURGERY: TRACING THE BEGINNING
The history of corneal refractive surgery dates back to the year 1896, when Lendeer Jans Lans gave the idea of reshaping the cornea for correcting corneal astigmatism using penetrating corneal cuts. He concluded that traverse incisions flattened the cornea in the meridian perpendicular to the incisions.9
Decades later, in the 1930s, Tsutomu Sato conceptualized this principle in the form of the technique of radial keratotomy, a procedure which was later popularized by Fyodorov et al. Sato had observed a flattening effect in the cornea of keratoconus patients after an episode of acute hydrops. He subsequently created both anterior and posterior corneal incisions to cause flattening in order to correct myopia. Radial keratotomy gained immense popularity during the 1970s and 1980s for the surgical correction of myopia.10
In 1964, Jose Ignacio Barraquer, belonging to the third generation of a family of famous ophthalmologists in Spain, introduced the idea of keratomileusis, which literally meant corneal carving. He used a manual microkeratome for lamellar dissection of cornea. The disc, thus obtained, was frozen (with liquid nitrogen or solid carbon dioxide) and cryolathed on its posterior surface based on the refractive correction required. This disc was then sutured onto the corneal stromal bed. However, the technique was not very suitable to correct astigmatism.11 Later on, his pupils developed the Barraquer-Krumeich-Swinger (BKS) nonfreeze technique, which did not require the freezing of the dissected corneal disc, thereby leading to fewer postoperative complications and faster visual recovery.12 Ruiz modified the technique by doing an in situ keratomileusis, wherein he resected a layer of tissue from the stromal bed itself by passing the microkeratome at a different depth after making the initial cap. He is also credited with the development of an automated microkeratome, producing a more regular corneal surface with greater precision. He demonstrated the formation of a corneal flap by stopping the microkeratome head before the end of the pass, followed by stromal bed resection and repositioning of the flap. This helped in avoiding the cap related complications.13,14
The introduction of argon fluoride laser in 1981 heralded a major breakthrough in the field of refractive surgery. It allowed enhanced precision levels and led to the creation of clean, etched-out lesions with minimal collateral damage.
The utility of excimer laser was subsequently expanded to radial keratotomy as well as photorefractive keratectomy (PRK).15184
Pallikaris described the present technique of laser-assisted in situ keratomileusis (LASIK) in 1991. He created a hinged corneal flap using a guarded microkeratome followed by excimer laser-assisted stromal ablation.19
The late 1980s and early 1990s witnessed an increasing use of picosecond and nanosecond lasers for in situ keratomileusis and corneal flap creation. These lasers were the precursors of femtosecond lasers, which were introduced in the subsequent decade.
In 1996, Ito et al. attempted the use of a 1,053 nm picosecond laser (10−12) to create a corneal flap as well as a stromal lenticule in experimental rabbit eyes. The infrared picosecond laser replaced the functions of microkeratome and excimer laser, and this experimental technique formed the basis of refractive lenticule extraction by Sekundo et al. in 2008.20 In 1998, Krueger et al. used the picosecond laser [Neodymium-doped yttrium lithium fluoride (Nd:YLF), 1053 nm; energy: 25 µJ/pulse, 30 picoseconds] in a case with −15 D myopia to create the corneal flap and perform excimer laser- assisted stromal ablation. They also attempted both flap creation and stromal lenticule creation [again, a precursor to femtosecond lenticule extraction (FLEx)] with the picosecond laser.21 Krueger et al. (1996) evaluated the corneal stroma ultrastructure after picosecond laser photodisruption and observed multiple, coalescing intrastromal cavities parallel to the corneal surface, without any thermal necrosis or coagulative change in the region of tissue interaction.22 The incision quality and precision produced by picosecond lasers were comparable to that produced by excimer laser.23
 
FEMTOSECOND LASERS IN CORNEAL REFRACTIVE SURGERY
Femtosecond lasers in ophthalmology were introduced by Kurtz et al. in 1998, who created corneal flaps in primate cadaver eyes with high precision and smooth lamellar dissection planes.24 Dr Tibor Juhasz and his team are credited with designing and building the first surgical ophthalmic femtosecond laser system. He worked in collaboration with Dr Kurtz and his associates to develop the laser parameters for use in corneal refractive surgery.25 Laser pulses of ultrashort duration of the order of 10−15 seconds were focused 150–200 microns below the epithelial surface and delivered in a spiral pattern. Tissue dissection was achieved best at pulse energies ranging from 4 µJ to 8 µJ and spot separations of 10–15 microns.
The first Food and Drug Administration (FDA) approved femtosecond laser for ophthalmological use was IntraLase Pulsion. It was approved in the year 2000 for lamellar corneal surgery and became commercially available for creation of corneal flap in LASIK surgery by 2001. The laser spots were delivered in a spiral pattern. The earlier models were of the low frequency and high energy. The first generation IntraLase Pulsion femtosecond laser 5(Abbott Medical Optics) had a frequency of only about 10 kHz. With technological advancements, higher frequencies and lower energies were targeted. This translated to greater cutting speeds, more efficient tissue cutting and less spill-over effect on the adjacent tissue. The second and third generation IntraLase laser systems had a frequency of 15 kHz and 30 kHz, respectively, while the energy delivered lowered to 2.9 µJ and 1.7 µJ. The lower energy systems require closer spacing of the laser spots. The fifth generation IntraLase femtolaser received FDA approval in 2008 for FS-LASIK (Femtosecond-LASIK). It had a planar applanation system with a frequency of 150 kHz and could create a flap in about 10 seconds.
In 2007, VisuMax laser (200 kHz) was approved for its laser microkeratome function by the FDA. The currently available VisuMax laser (Carl Zeiss Meditec AG) has a frequency of 500 kHz with each pulse conveying energy of about 150 nJ. The laser spots have 1 μm diameter and are placed at a distance of 2–5 μm in a spiral pattern. The VisuMax laser, unlike the IntraLase, has a curved applanation surface which causes less corneal distortion and minimizes intraocular pressure (IOP) spikes. The other femtosecond laser systems approved for femto-LASIK include the Femtec (Technolas Perfect Vision), Femto LDV (Ziemer Ophthalmic Systems AG), and Wavelight FS200 (Alcon Surgical).
The femtosecond laser technology has evolved from the early laser systems with a low repetition rate (10 kHz) which needed higher energy to operate, to the newer devices having a higher repetition rate (as high as 500 kHz), with lesser energy utilization, shorter procedure duration and better surface quality.26 In addition to refractive surgery, femtosecond lasers have found applications in tunnel creation for intracorneal ring segments (INTACS), astigmatic keratotomy, keratoplasty (both penetrating and lamellar) and cataract surgery.
The femtosecond lasers were a major advancement over the microkeratome in being able to make thinner flaps which were more precise and thus, associated with fewer flap-related complications and corneal biomechanical changes.27
In the year 2000, Holger et al. used Ti-sapphire femtosecond laser in porcine eyes to create corneal flaps and stromal lenticules. They observed enhanced precision of stromal cuts with pulse energies of 1–2 µJ (lower than that used by Kurtz et al.), spot size of 5–10 microns and spot separation of 8 microns. The thermal alteration of adjacent tissue was of the order of only 1 micron.28 Subsequently, in 2003, Heisterkamp et al. successfully demonstrated the use of femtosecond laser in rabbit corneas for creation of the anterior corneal flap and stromal lenticule, which was extracted after lifting the flap. They proposed femtosecond laser to be a suitable replacement for both microkeratome and excimer laser.296
In 2003, Ratkay-Traub et al. published the clinical results of use of femtosecond neodymium-glass laser on human eyes. It was used to create the corneal flap, perform keratomileusis and create channels for intrastromal ring segments. Comparable results were observed between FS-LASIK and microkeratome-LASIK. Femtosecond laser created precise stromal cuts with additional advantages over the mechanical methods.30
The evolution of refractive lenticule extraction marked the next major breakthrough in the field of refractive surgery. Sekundo et al. introduced the technique of FLEx in 2008, which involved a femtosecond laser-assisted creation of a flap as well as a refractive lenticule. The femtosecond laser flap was lifted akin to the LASIK flap, and the underlying refractive lenticule was dissected from the stromal bed and extracted.31 At present, the VisuMax (Carl Zeiss Meditec, Jena, Germany) laser platform is the only commercially available system that allows refractive lenticule creation. Though the new procedure of refractive lenticule extraction was observed to be safe and efficacious, it did not lead to a decrease in the flap-related complications.32 There was a need for superior procedures that eliminated the need for a corneal flap. This led to the evolution of small incision lenticule extraction (SMILE) in 2010. Sekundo et al. described the creation of an intrastromal refractive lenticule that could be extracted through two small side-cut incisions of 80° chord length, placed 180° apart. Although the lenticule dissection and extraction is more challenging, the technique is associated with a significantly decreased incidence of microstriae and dry eyes as well as an improved internal structural stability. SMILE became available for commercial use in 2011.33
The initial VisuMax laser system used for SMILE had a frequency of 200 kHz. The new 500 kHz VisuMax femtosecond laser received the FDA approval for SMILE in September 2016. It is currently approved to treat myopia ranging from −1.00 D to −8.00 D of myopia, with less than or equal to −0.50 D cylinder and manifest refraction spherical equivalent (MRSE) less than or equal to −8.25 D. It is not yet approved for treating astigmatism or hyperopia. Currently, trials are ongoing to evaluate the safety and efficacy of SMILE in higher degrees of myopia, as well as astigmatism and hyperopia.
 
CONCLUSION
Femtosecond laser technology was introduced in the field of refractive surgery in 2001 for the creation of lamellar corneal flaps to allow subsequent excimer laser ablation. The initial high-energy, low pulse femtolaser systems have evolved to present day low energy, high-pulse systems with enhanced precision and minimum collateral damage. The most recent innovation of flapless intrastromal lenticule extraction has marked a significant leap forward, with the elimination of flap-related complications, improved biomechanical stability and a better-preserved ocular surface. With further 7technological advancements, the refractive applications of this procedure will expand to encompass all types of refractive error with minimum complications and optimal outcomes.
REFERENCES
  1. Meyer-Schwickerath G. Light Coagulation. St. Louis, Missouri: CV Mosby Company;  1960.
  1. Palanker DV, Blumenkranz MS, Marmor MF. Fifty years of ophthalmic laser therapy. Arch Ophthalmol. 2011;129:1613–9.
  1. Schawlow AL, Townes CH. Infrared and optical masers. Phys Rev. 1958;112(6): 1940–9.
  1. Maiman TH. Stimulated optical radiation in ruby. Nature. 1960;187:493–4.
  1. Zaret MM, Breinin GM, Schmidt H, et al. Ocular lesions produced by an optical maser (laser). Science. 1961;134:1525–6.
  1. Bridges WB. Laser oscillation in singly ionized argon in visible spectrum. Appl Phys Lett. 1964;4:128.
  1. Krueger RR, Rabinowitz YS, Binder PS. The 25th anniversary of excimer lasers in refractive surgery: historical review. J Refract Surg. 2010;26(10):749–60.
  1. Bahrawy ME, Alió JL. Excimer laser 6th generation: state of the art and refractive surgical outcomes. Eye Vis (Lond). 2015;2:6.
  1. Belin, MW. Evaluating Emerging Refractive Technologies. Int Ophthalmol Clin. 2002;42:1–18.
  1. Sato T, Akiyama K, Shibata H. A new surgical approach to myopia. Am J Ophthalmol. 1953;36:823–9.
  1. Barraquer JI. Queratomileusis para la corrección de la miopía. Arch Soc Amer Oftal Optom. 1964;5:27.
  1. Swinger CA, Krumeich J, Cassiday D. Planar lamellar refractive keratoplasty. J Refract Surg. 1986;2:17.
  1. Ruiz LA, Rowsej JJ. In situ keratomileusis. Invest Ophthalmol Vis Sci. 1988;29:392.
  1. Reinstein DZ, Archer TJ, Gobbe M. The history of LASIK. J Refract Surg. 2012;28(4):291–8.
  1. Srinivasan R, Wynne JJ, Blum SE. Far-UV photoetching of organic material. Laser Focus. 1983:62–66.
  1. Cotliar AM, Schubert HD, Mandel ER, et al. Excimer laser radial keratotomy. Ophthalmology. 1985;92(2):206–8.
  1. Marshall J, Trokel S, Rothery S, et al. An ultrastructural study of corneal incisions induced by an excimer laser at 193 nm. Ophthalmology. 1985;92(6):749–58.
  1. McDonald MB, Liu JC, Byrd TJ, et al. Central photorefractive keratectomy for myopia: Partially sighted and normally sighted eyes. Ophthalmology. 1991;98:1327–38.
  1. Pallikaris IG, Papatzanaki ME, Siganos DS, et al. A corneal flap technique for laser in situ keratomileusis—Human studies. Arch Ophthalmol. 1991;109(12):1699–1702.
  1. Ito M, Quantock AJ, Malhan S, et al. Picosecond laser in situ keratomileusis with a 1053-nm Nd:YLF laser. J Refract Surg. 1996;12(6):721–8.
  1. Krueger RR, Juhasz T, Gualano A, et al. The picosecond laser for nonmechanical laser in situ keratomileusis. J Refract Surg. 1998;14(4):467–9.
  1. Krueger RR, Quantock AJ, Juhasz T, et al. Ultrastructure of picosecond laser intrastromal photodisruption. J Refract Surg. 1996;12(5):607–12.

  1. 8 Stern D, Schoenlein RW, Puliafito CA, et al. Corneal ablation by nanosecond, picosecond, and femtosecond lasers at 532 and 625 nm. Arch Ophthalmol. 1989;107(4):587–92.
  1. Kurtz RM, Horvath C, Liu HH, et al. Lamellar refractive surgery with scanned intrastromal picosecond and femtosecond laser pulses in animal eyes. J Refract Surg. 1998;14(5):541–8.
  1. Juhasz T, Loesel FH, Kurtz RM, et al. Corneal refractive surgery with femtosecond lasers. IEEE J Select Topics Quantum Electron. 1999;5:902–10.
  1. Hjortdal J, Nielsen E, Vestergaard A, et al. Inverse cutting of posterior lamellar corneal grafts by a femtosecond laser. Open Ophthalmol J. 2012;6:19–22.
  1. Callou TP, Garcia R, Mukai A, et al. Advances in femtosecond laser technology. Clin Ophthalmol. 2016;10:697–703.
  1. Lubatschowski H, Maatz G, Heisterkamp U, et al. Application of ultrashort laser pulses for intrastromal refractive surgery. Graefe' Arch Clin Exp Ophthalmol. 2000;238:33–9.
  1. Heisterkamp A, Mamom T, Drommer W, et al. Photodisruption with ultrashort laser pulses for intrastromal refractive surgery. Laser Phys. 2003;13(5):743–8.
  1. Ratkay-Traub I, Ferincz IE, Juhasz T, et al. First clinical results with the femtosecond neodynium-glass laser in refractive surgery. J Refract Surg. 2003;19(2):94–103.
  1. Sekundo W, Kunert K, Russmann CH, et al. First efficacy and safety study of femtosecond lenticule extraction for the correction of myopia. J Cataract Refract Surg. 2008;34:1513–20.
  1. Blum M, Kunert KS, Engelbrecht C, et al. Femtosecond lenticule extraction (FLEx) - Results after 12 months in myopic astigmatism. Klin Monbl Augenheilkd. 2010;227:961–5.
  1. Sekundo W, Kunert KS, Blum M. Small incision corneal refractive surgery using the small incision lenticule extraction (SMILE) procedure for the correction of myopia and myopic astigmatism: results of a 6-month prospective study. Br J Ophthalmol. 2011;95(3):335–9.