• Users Online: 428
  • Home
  • Print this page
  • Email this page
Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 


 
 Table of Contents  
REVIEW ARTICLE
Year : 2022  |  Volume : 34  |  Issue : 1  |  Page : 12-18

Refractive Corneal surgeries: A Review


Jyothi The Lasik Vision Centre, Bengaluru, Karnataka, India

Date of Submission29-Jan-2022
Date of Decision30-Jan-2022
Date of Acceptance31-Jan-2022
Date of Web Publication21-Apr-2022

Correspondence Address:
Dr. Jyothi Vengalil Menon
Villa 141, Ferns Habitat, Doddenakundi, Bengaluru - 560 037, Karnataka
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/kjo.kjo_21_22

Rights and Permissions
  Abstract 

Refractive corneal surgeries are procedures for correction of refractive errors. Modern keratorefractive procedures include laser in situ keratomileusis, surface ablation, relatively newer refractive lenticule extraction, and corneal inlays. This article aims to present an overview of currently performed refractive corneal procedures. Basic aspects of patient selection, principles, advantages, limitations, complications, and clinical outcomes are discussed.

Keywords: Laser in situ keratomileusis, photorefractive keratectomy, refractive lenticule extraction, femtosecond lenticule extraction, small incision lenticule extraction


How to cite this article:
Menon JV. Refractive Corneal surgeries: A Review. Kerala J Ophthalmol 2022;34:12-8

How to cite this URL:
Menon JV. Refractive Corneal surgeries: A Review. Kerala J Ophthalmol [serial online] 2022 [cited 2022 Oct 6];34:12-8. Available from: http://www.kjophthal.com/text.asp?2022/34/1/12/343664




  Introduction and Methods Top


Refractive corneal surgeries modify the contour of the cornea to correct the refractive error. This can be done by using excimer laser ablation with or without flap, by femto laser, or by inserting corneal inlays. The field of refractive surgery has seen tremendous advances in the last two decades in terms of refinement in surgical techniques, advances in instrumentation, availability of newer diagnostic tools, and better understanding of corneal biomechanics.[1] This article aims to give an outline of the cornea-based options available in the armamentarium of refractive surgeon. Several studies have shown that modern keratorefractive procedures are efficient, safe, predictable, and stable for correction of refractive errors.[2],[3] Complications, though infrequent, can be further minimized by diligent patient selection and strict adherence to safety protocols.

Studies used in this article were obtained from PubMed search from January 2000 to January 2022. The filters applied were “abstract available,” “meta-analysis,” “randomized control trials,” “review,” and “systematic review.” The keywords used for search were “Refractive corneal surgery,” “Keratorefractive surgery,” “LASIK,” “PRK,” “Surface ablation,” “Refractive Lenticule Extraction,” “Presbyopia treatment,” and “Radial Keratotomy.”


  Patient Selection Top


To be a candidate for refractive corneal surgery, patients must be above 18 years of age with stable refraction and normal corneal topography. However, there are specific indications (albeit controversial) for performing refractive surgery in patients below 18 years. Studies have shown that refractive surgery improves visual acuity and stereopsis in children with anisometropic amblyopia and strabismus.[4],[5] The question remains as to the age at which to perform surgery and eligibility criteria to qualify for pediatric refractive surgery.


  Contraindications Top


The contraindications for performing refractive surgeries as per the FDA guidelines are discussed below.[1],[6]

Ocular contraindications

They include unstable refractive error, corneal ectatic disorders, herpetic keratitis, Avellino corneal dystrophy, cataract, and uncontrolled glaucoma. Patients with ocular allergies and dry eye are also relative contraindications.

Systemic contraindications

Pregnancy and lactation are absolute contraindications for refractive surgery. Patients on isotretinoin for acne must stop medication for at least 6 months prior to keratorefractive procedure. Uncontrolled diabetes mellitus or diabetes mellitus with ocular or systemic complications is a contraindication.[7]

Autoimmune disorders such as rheumatoid arthritis, Sjogren's syndrome, and SLE are relative contraindications. There are several studies indicating that patients with well-controlled autoimmune disorders have undergone refractive corneal surgeries with good visual outcomes.[8],[9] Primary Sjogren's disease is an exception to this. More studies are needed to address the role of laser refractive surgeries in patients with auto immune disease.

Preoperative evaluation for corneal refractive procedures

A comprehensive eye examination must be performed. Contact lens wearers must discontinue lenses for a minimum period of 2 weeks for soft lenses and 6 weeks for RGP lenses and longer in the presence of corneal warpage.

Special attention must be paid to deep set eyes and small palpebral fissure which can interfere with placement of speculum and microkeratome resulting in flap-related complications.

Accurate refraction must be performed both after cycloplegia and subjective correction. UCVA and BCVA must be recorded. Patients in presbyopia age group must be informed about near vision requirement after laser procedure and options for the same must be discussed.

Blepharitis and meibomanitis must be treated prior to surgery to avoid diffuse lamellar keratitis and infective keratitis.

Tear film evaluation is done. Several studies have documented that laser refractive surgeries can adversely affect tear film. Laser in situ keratomileusis (LASIK) is the worst offender in causing iatrogenic dry eye.[10],[11]

Corneal scars must be carefully looked for since they can cause artifacts on corneal imaging and interfere with creation of femto flaps.

Detailed posterior segment evaluation is performed and predisposing retinal lesions must be identified and treated.

Mesopic pupil size must be recorded, and the ablation zone must be bigger than mesopic pupil to avoid glare and haloes.[12],[13] Various pupillometers such as Colvard pupillometer are commercially available and give accurate pupil size in standard illumination conditions.[2]

Keratometry readings must be noted. It is important not to steepen the cornea more than 50D or flatten the cornea less than 35D as it can induce ocular aberrations. During microkeratome LASIK, cornea steeper than 46D is at risk for flap buttonholes and cornea flatter than 42D is at risk for free flap.

Tonometry must be recorded as patients with glaucoma pose a special challenge to refractive surgeons. Suction during flap creation can increase IOP. Reduction in corneal thickness can give fallacious IOP readings post refractive surgery. Steroids used postoperatively can increase IOP in steroid responders. All these factors must be considered prior to performing refractive surgery in a patient with glaucoma.[14],[15],[16]

Corneal pachymetry is measured using ultrasonic pachymetry or Orbscan or Pentacam. It is mandatory to leave a minimum residual stromal bed of 250 microns to maintain corneal stability. Current practice is to maintain residual stromal bed of 300 microns or 50% of original pachymetry whichever is higher. Percentage of tissue altered (PTA) is a recent metric used in screening patients considering flap thickness, ablation depth, and central corneal thickness. PTA higher or equal to 40% should be considered as a higher risk for post laser ectasia.[17],[18]

Corneal topography

Abnormal corneal morphology is by far the commonest cause of post-LASIK ectasia. Placido-based corneal topography is an excellent diagnostic tool to map anterior corneal surface and rule out conditions such as keratoconus and pellucid marginal degeneration. Orbscan is a hybrid system that uses Placido-based system and scanning slit system while Pentacam uses Scheimpflug imaging to scan the cornea. Both Orbscan and Pentacam give anterior and posterior corneal maps along with point-to-point pachymetry. These devices help to evaluate posterior elevation changes which are often the earliest changes in keratoconus. Belin Ambrosio display in Pentacam is a useful software to detect ectatic corneal conditions early.

Corneal biomechanics

Ocular response analyzer and Corvis ST are two systems that give an idea of corneal biomechanics indicated by corneal hysteresis (CH) and corneal resistance factor (CRF). A weaker cornea is more prone to ectasia following refractive procedure.[19]

Aberrometers (Wavefront analyzers) can measure higher order aberrations of the optical system of the eye which can be incorporated into the laser machine for correction.

OCT

Anterior segment OCT can give pachymetry and flap thickness which is useful while planning enhancements.


  Keratorefractive Procedures Top


Laser in situ keratomileusis

LASIK procedure consists of two steps: creation of corneal flap and excimer laser ablation.

Corneal flap can be created using a microkeratome or femto laser.[3]

Microkeratomes are manual or automated, geared or gearless, preassembled or assembled on the eye. Newer automated, gearless microkeratomes have increased the ease and safety of flap creation. Flap thickness can be 140, 160, 180, or 200 microns depending on the depth plate of microkeratome. Thinner flaps are safer due to increased residual stromal bed.

Flaps can also be created in a bladeless manner using water jet microkeratome.

In femto LASIK, femto laser creates the flap and refractive ablation is by excimer laser. Femto laser can make customized flaps of varying shape, thickness, and hinge position. Studies have indicated that femto flaps are more planar and predictable as compared to microkeratome flaps. However, the final visual outcomes after microkeratome LASIK and femto laser-assisted LASIK procedure appear to be similar.[20]

Excimer laser which corrects the refractive error has evolved from conventional broad-beam lasers to slit beam and finally modern flying spot lasers with spot size ranging from 0.5 to 0.9 mm. Smaller spot size produces a smoother stromal bed with a better ablation profile and translates into better outcome.

Eye trackers:

Excimer lasers have built in eye trackers that compensates for eye movements in X- and Y-axis during ablation. Modern eye trackers come with dynamic eye tracking, higher frequencies, and cyclotorsion control to actively track the pupil and ensure optimum centration during ablation with improved visual outcomes.

Types of laser in situ keratomileusis procedures

Depending upon patient's preexisting refractive parameters, LASIK procedure can be conventional, wavefront optimized, wavefront guided, or topography guided.

Conventional laser in situ keratomileusis surgery

Excimer laser does refractive ablation to correct refractive errors. During this process, prolate shape of cornea becomes oblate. This can induce higher order aberrations impacting the quality of vision in conventional LASIK procedure.

Wavefront-optimized laser in situ keratomileusis

In order to reduce the induced higher order aberrations, the laser spots are delivered in a predetermined and optimized manner on the cornea to reduce induced aberrations. This is known as wavefront-optimized LASIK and is a refinement over conventional LASIK.

Wavefront-guided laser in situ keratomileusis

The preexisting HOA of eye can be measured using aberrometers. Wavefront-guided LASIK (WFG) is customized to correct the patient's preexisting higher order aberrations. Studies have indicated that WFG LASIK appears to be better than conventional LASIK for treating eyes with higher order aberrations more than 0.30, in re-treatments, and in patients with large scotopic pupil size.[21],[22]

Topography-guided laser in situ keratomileusis

In patients with astigmatism, irregular cornea, decentered ablations, and preexisting corneal pathology, most of the aberrations arise from the cornea. In such eyes, it is difficult to capture reliable wavefront maps. The data obtained from corneal topography are used to perform[4] topography-guided LASIK to smoothen the irregular corneal surface and improve the quality of vision.[23],[24]

LASIK can be used to correct myopia up to 12D hyperopia up to 6D and astigmatism up to 6D, provided patient's keratometry and pachymetry values permit.

Sub-Bowman's keratomileusis

This procedure is thin-flap LASIK using 90-micron flap. It combines safety of photorefractive keratectomy (PRK) with minimum pain and speedy recovery of LASIK. Thinner flaps increase residual stromal bed, but they are difficult to handle and are prone for flap striae.[25]

Post laser in situ keratomileusis enhancements

Post LASIK enhancements can be treated by flap recut or lifting the flap and doing relaser, provided adequate RSB is present. Flap lift is preferred to flap cut. PRK is also an option. Some studies have shown that relifting the flap may result in more accurate refractive outcome as compared to PRK, but epithelial ingrowth is a risk.[26],[27],[28],[29]

Surface ablation

There has been a resurgence of surface ablation due to better pain control and use of mitomycin C. Surface ablation has less impact on corneal biomechanics as compared to LASIK with and no flap-related complications.[30] The epithelium is removed, and laser is applied on the bed consisting of Bowman's layer and anterior corneal stroma. 0.02% mitomycin C is applied on the corneal stroma. Epithelium may or may not be replaced. A bandage contact lens is placed to promote epithelial healing and to reduce pain. The following methods are used to separate epithelium

Photorefractive keratectomy

Mechanical scraping of epithelium is done in conventional PRK.

Laser-assisted subepithelial keratomileusis (LASEK)

Epithelium is removed using 20% alcohol and replaced after refractive ablation.

Epi-laser in situ keratomileusis

Microkeratome is used with a blunt blade to remove the epithelium that can be replaced.

With the use of bandage contact lens, studies have not conclusively demonstrated significant advantage with epithelium on or epithelium off methods.[31]

Trans-photorefractive keratectomy

Excimer laser is used to remove the epithelium followed by refractive ablation. This can be done in two ways. In “two-step trans-PRK,” epithelium is removed first by laser ablation followed by refractive ablation. In “one-step trans-PRK,” the epithelium removal and refractive ablation occurs sequentially as a single step significantly reducing the time taken.[32]

Surface ablation can be conventional, wavefront optimized, wavefront guided, or topography guided. Studies have shown that surface ablation with WFG treatment has better visual outcomes as compared to LASIK with WFG treatment.[33]

Advantages and limitations

Surface ablation is preferred in patients with deep set eyes, small palpebral fissures, flat or steep cornea, thin cornea, and in patients actively involved in contact sports. However, in patients actively involved in outdoor activities, there is an increased risk of haze due to ultraviolet light exposure. Problems faced in surface ablations are delayed visual recovery, postoperative pain, and early or late haze formation, especially with higher ablation depth. Pain can be managed by using bandage contact lens and oral NSAID. Application of 0.02% MMC after laser ablation on the stromal bed reduces haze allowing treatment of higher powers. Studies have shown that mitomycin at a concentration on 0.02% is safe for use on stromal bed after excimer laser ablation. While there is consensus on dose of mitomycin at 0.02%, there is no consensus on time of application which can vary from 12 s to 2 min. Doses less than 0.02% are less effective in preventing haze.[34],[35]

Refractive lenticule extraction

Refractive lenticule extraction is an all-femtosecond laser-based refractive technique. This procedure uses femto laser for refractive lenticule extraction. Two methods used are femtosecond lenticule extraction (FLEx) and small incision lenticule extraction (SMILE). FLEx requires the creation of a flap to remove the lenticule. SMILE is a flapless and minimally invasive procedure that extracts the lenticule from a small cornea incision. Currently, SMILE is used to correct myopia unto 10D and myopic astigmatism up to 6D. Studies have shown that SMILE has similar efficiency, predictability, and safety as compared to femtosecond LASIK. SMILE is minimally invasive with minimum pain and postoperative discomfort.[36],[37],[38],[39] Studies have indicated that SMILE may have a lesser impact on corneal biomechanics, and tear film as compared to LASIK.[40] Infrequent complications of SMILE include suction loss, lenticule tears, incision tears, epithelial ingrowth, diffuse lamellar keratitis, and residual refractive error. Surface ablation or CIRCLE procedure can be used for retreatment. In CIRCLE procedure, the lenticule is converted into a flap and laser is performed to correct the residual power.[41],[42],[43]

Presbyopia correction

Exciting developments are taking place in presbyopia correction, and various methods are currently available.[44]

The dominant eye is corrected for distance and non-dominant eye is corrected for near in presbyopia patients, when correcting for their refractive errors. The near vision correction by +1.5D is well tolerated.

PresbyLASIK is another option. PresbyLASIK is performed mono ocularly on the nondominant eye. In this procedure, in-built algorithms are used to make cornea multifocal to correct near vision. Mono-ocular biaspheric PresbyLASIK is reported to give good results in presbyopes.[45]

Corneal inlay is a new treatment modality for presbyopia. Corneal inlays are implanted in the anterior corneal stroma of the nondominant eye beneath the flap or beneath laser-created pockets. They improve the near vision by increasing the depth of focus. Synthetic and allogenic inlays have been described. Flexivue microlens, Kamra, and Raindrop inlays are some of the corneal inlays available.[46],[47]

Conductive keratoplasty

This is a laser-independent procedure used for correction of presbyopia and hyperopia. Radio frequency of 350 Hz is delivered into the peripheral corneal stroma to cause steepening of central cornea. Studies have shown conductive keratoplasty to be safe and effective for low-to-moderate hyperopia, hyperopic astigmatism, and presbyopia.[48],[49]

Radial keratotomy

Radial keratotomy (RK) was used to correct myopia by using corneal incisions to alter the shape of the cornea. Centripetal or centrifugal radial incisions are made in the cornea avoiding the central optical zone. The drawbacks of RK are variability in results and fluctuating vision. With the advent of lasers, RK has become outdated. Both LASIK and PRK with mitomycin C are useful in post RK residual errors.

Astigmatic keratotomy and limbal relaxing incisions

Astigmatic keratotomy (AK) is another technique used to correct corneal astigmatism usually prior to cataract surgery by placing corneal incision on the steep axis. Limbal relaxing incisions are made in the peripheral cornea just inside the limbus and are less likely to induce irregular corneal astigmatism. Femtosecond can be utilized for AK.

Intacs

Intacs are intracorneal ring segments. They are useful in correcting low myopia in patients with thin cornea or forme fruste keratoconus who are otherwise unsuitable for laser refractive procedure. Intacs are inserted creating corneal pockets using a mechanical technique or by creating channels using the femtosecond laser.

Complications of keratorefractive procedures

Cornea-based refractive surgeries have been refined over past two decades to yield safe, predictable, and excellent visual outcomes. Complications are infrequent and can happen during operative, immediate postoperative, and late postoperative period and can range from mild to vision threatening.

In microkeratome LASIK, flap complications such as suction loss with flap tear, free caps, buttonholes, flap striae, and rarely flap melt can occur. Decentered ablation and central islands can degrade the quality of vision.

Postoperative complications include residual refractive error, diffuse lamellar keratitis, and infectious keratitis epithelial ingrowth.

Dry eye can be troublesome and may need punctal plugs.

Femto procedure complications include vertical break through, opaque bubble layer, and transient light sensitivity.

In surface ablations, postoperative pain can make patients anxious. Delayed epithelial healing can occur. Corneal haze formation can degrade visual outcome.

Corneal ectasia

One of the dreaded complications of corneal refractive surgery is corneal ectasia. The cornea progressively becomes ectatic with reduction in best-corrected visual acuity. To a large extent, ectasia can be prevented by careful patient selection.

Risk factors for corneal ectasia

Abnormal corneal topography, high myopia, ablation depth above 75 microns, thin cornea, less residual stromal bed due to increased ablation, or thicker flap can lead to keratectasia.[50],[51],[52]

Studies have shown that postoperative corneal ectasia occurs at a lower rate in eyes undergoing PRK than LASIK and least of all in SMILE.[53] However, there are some recent reports of post SMILE ectasia.


  Clinical Outcomes Top


There are several studies and reviews on the safety, predictability, stability, and efficacy of various refractive surgeries. Most of these studies indicate excellent visual outcome with a few complications following laser vision correction. LASIK, PRK, and SMILE give safe, predictable, and comparable visual outcomes. Based on the current data, it is difficult to comment on the superiority of one technique over the other in terms of long-term visual outcomes.[54],[55],[56],[57],[58],[59],[60]


  Conclusion Top


Corneal refractive surgeries have come a long way from inception and provide excellent options to spectacle free vision. Various procedures are available to correct refractive errors. A thorough knowledge is essential to achieve best results and minimize complications. The results are encouraging, and the best is yet to come.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Ang M, Gatinel D, Reinstein DZ, Mertens E, Alió Del Barrio JL, Alió JL. Refractive surgery beyond 2020. Eye (Lond) 2021;35:362-82.  Back to cited text no. 1
    
2.
Wen D, McAlinden C, Flitcroft I, Tu R, Wang Q, Alió J, et al. Postoperative efficacy, predictability, safety, and visual quality of laser corneal refractive surgery: A network meta-analysis. Am J Ophthalmol 2017;178:65-78.  Back to cited text no. 2
    
3.
Sakimoto T, Rosenblatt MI, Azar DT. Laser eye surgery for refractive errors. Lancet 2006;367:1432-47.  Back to cited text no. 3
    
4.
Fecarotta CM, Kim M, Wasserman BN. Refractive surgery in children. Curr Opin Ophthalmol 2010;21:350-5.  Back to cited text no. 4
    
5.
Donahue SP. Long-term outcomes of photorefractive keratectomy for anisometropic amblyopia in children. Ophthalmology 2006;113:167-8.  Back to cited text no. 5
    
6.
Bower KS, Woreta F. Update on contraindications for laser-assisted in situ keratomileusis and photorefractive keratectomy. Curr Opin Ophthalmol 2014;25:251-7.  Back to cited text no. 6
    
7.
Simpson RG, Moshirfar M, Edmonds JN, Christiansen SM. Laser in-situ keratomileusis in patients with diabetes mellitus: A review of the literature. Clin Ophthalmol 2012;6:1665-74.  Back to cited text no. 7
    
8.
Chen TY, Chu DS. Refractive surgery for the patient with autoimmune diseases. Curr Opin Ophthalmol 2020;31:247-52.  Back to cited text no. 8
    
9.
Simpson RG, Moshirfar M, Edmonds JN, Christiansen SM, Behunin N. Laser in situ keratomileusis in patients with collagen vascular disease: A review of the literature. Clin Ophthalmol 2012;6:1827-37.  Back to cited text no. 9
    
10.
Denoyer A, Landman E, Trinh L, Faure JF, Auclin F, Baudouin C. Dry eye disease after refractive surgery: Comparative outcomes of small incision lenticule extraction versus LASIK. Ophthalmology 2015;122:669-76.  Back to cited text no. 10
    
11.
Toda I. Dry eye after LASIK. Invest Ophthalmol Vis Sci 2018;59:S109-15.  Back to cited text no. 11
    
12.
Salz JJ, Trattler W. Pupil size and corneal laser surgery. Curr Opin Ophthalmol 2006;17:373-9.  Back to cited text no. 12
    
13.
Fan-Paul NI, Li J, Miller JS, Florakis GJ. Night vision disturbances after corneal refractive surgery. Surv Ophthalmol 2002;47:533-46.  Back to cited text no. 13
    
14.
Shrivastava A, Madu A, Schultz J. Refractive surgery and the glaucoma patient. Curr Opin Ophthalmol 2011;22:215-21.  Back to cited text no. 14
    
15.
Bashford KP, Shafranov G, Tauber S, Shields MB. Considerations of glaucoma in patients undergoing corneal refractive surgery. Surv Ophthalmol 2005;50:245-51.  Back to cited text no. 15
    
16.
Ahmad M, Chocron I, Shrivastava A. Considerations for refractive surgery in the glaucoma patient. Curr Opin Ophthalmol 2017;28:310-5.  Back to cited text no. 16
    
17.
Santhiago MR. Percent tissue altered and corneal ectasia. Curr Opin Ophthalmol 2016;27:311-5.  Back to cited text no. 17
    
18.
Santhiago MR, Smadja D, Gomes BF, Mello GR, Monteiro ML, Wilson SE, et al. Association between the percent tissue altered and post-laser in situ keratomileusis ectasia in eyes with normal preoperative topography. Am J Ophthalmol 2014;158:87-95.e1.  Back to cited text no. 18
    
19.
Moshirfar M, Motlagh MN, Murri MS, Momeni-Moghaddam H, Ronquillo YC, Hoopes PC. Advances in biomechanical parameters for screening of refractive surgery candidates: A review of the literature, part III. Med Hypothesis Discov Innov Ophthalmol 2019;8:219-40.  Back to cited text no. 19
    
20.
Chen S, Feng Y, Stojanovic A, Jankov MR 2nd, Wang Q. IntraLase femtosecond laser vs. mechanical microkeratomes in LASIK for myopia: A systematic review and meta-analysis. J Refract Surg 2012;28:15-24.  Back to cited text no. 20
    
21.
Smadja D, Reggiani-Mello G, Santhiago MR, Krueger RR. Wavefront ablation profiles in refractive surgery: Description, results, and limitations. J Refract Surg 2012;28:224-32.  Back to cited text no. 21
    
22.
Alió JL, Piñero D, Muftuoglu O. Corneal wavefront-guided retreatments for significant night vision symptoms after myopic laser refractive surgery. Am J Ophthalmol 2008;145:65-74.  Back to cited text no. 22
    
23.
Ramamurthy S, Soundarya B, Sachdev GS. Topography-guided treatment in regular and irregular corneas. Indian J Ophthalmol 2020;68:2699-704.  Back to cited text no. 23
  [Full text]  
24.
Holland S, Lin DT, Tan JC. Topography-guided laser refractive surgery. Curr Opin Ophthalmol 2013;24:302-9.  Back to cited text no. 24
    
25.
Slade SG. Thin-flap laser-assisted in situ keratomileusis. Curr Opin Ophthalmol 2008;19:325-9.  Back to cited text no. 25
    
26.
Parikh NB. Management of residual refractive error after laser in situ keratomileusis and photorefractive keratectomy. Curr Opin Ophthalmol 2014;25:275-80.  Back to cited text no. 26
    
27.
Moshirfar M, Jehangir N, Fenzl CR, McCaughey M. LASIK enhancement: Clinical and surgical management. J Refract Surg 2017;33:116-27.  Back to cited text no. 27
    
28.
Chan C, Lawless M, Sutton G, Hodge C. Re-treatment in LASIK: To flap lift or perform surface ablation. J Refract Surg 2020;36:6-11.  Back to cited text no. 28
    
29.
Solaiman KA, Fouda SM, Bor'i A, Al-Nashar HY. Photorefractive keratectomy for residual myopia after myopic laser in situ keratomileusis. J Ophthalmol 2017:8725172. doi:10.1155/2017.  Back to cited text no. 29
    
30.
Taneri S, Zieske JD, Azar DT. Evolution, techniques, clinical outcomes, and pathophysiology of LASEK: Review of the literature. Surv Ophthalmol 2004;49:576-602.  Back to cited text no. 30
    
31.
Kalyvianaki MI, Kymionis GD, Kounis GA, Panagopoulou SI, Grentzelos MA, Pallikaris IG. Comparison of Epi-LASIK and off-flap Epi-LASIK for the treatment of low and moderate myopia. Ophthalmology 2008;115:2174-80.  Back to cited text no. 31
    
32.
Gadde AK, Srirampur A, Katta KR, Mansoori T, Armah SM. Comparison of single-step transepithelial photorefractive keratectomy and conventional photorefractive keratectomy in low to high myopic eyes. Indian J Ophthalmol 2020;68:755-61.  Back to cited text no. 32
[PUBMED]  [Full text]  
33.
Moshirfar M, Schliesser JA, Chang JC, Oberg TJ, Mifflin MD, Townley R, et al. Visual outcomes after wavefront-guided photorefractive keratectomy and wavefront-guided laser in situ keratomileusis: Prospective comparison. J Cataract Refract Surg 2010;36:1336-43.  Back to cited text no. 33
    
34.
Majmudar PA, Schallhorn SC, Cason JB, Donaldson KE, Kymionis GD, Shtein RM, et al. Mitomycin-C in corneal surface excimer laser ablation techniques: A report by the American Academy of Ophthalmology. Ophthalmology 2015;122:1085-95.  Back to cited text no. 34
    
35.
Thornton I, Xu M, Krueger RR. Comparison of standard (0.02%) and low dose (0.002%) mitomycin C in the prevention of corneal haze following surface ablation for myopia. J Refract Surg 2008;24:S68-76.  Back to cited text no. 35
    
36.
Kim P, Sutton GL, Rootman DS. Applications of the femtosecond laser in corneal refractive surgery. Curr Opin Ophthalmol 2011;22:238-44.  Back to cited text no. 36
    
37.
Marino GK, Santhiago MR, Wilson SE. Femtosecond lasers and corneal surgical procedures. Asia Pac J Ophthalmol (Phila) 2017;6:456-64.  Back to cited text no. 37
    
38.
Ganesh S, Brar S, Arra RR. Refractive lenticule extraction small incision lenticule extraction: A new refractive surgery paradigm. Indian J Ophthalmol 2018;66:10-9.  Back to cited text no. 38
[PUBMED]  [Full text]  
39.
Sachdev GS, Ramamurthy S. Decade – Long journey with small incision lenticule extraction: The learnings. Indian J Ophthalmol 2020;68:2705-10.  Back to cited text no. 39
  [Full text]  
40.
Kobashi H, Kamiya K, Shimizu K. Dry eye after small incision lenticule extraction and femtosecond laser-assisted LASIK: Meta-analysis. Cornea 2017;36:85-91.  Back to cited text no. 40
    
41.
Asif MI, Bafna RK, Mehta JS, Reddy J, Titiyal JS, Maharana PK, et al. Complications of small incision lenticule extraction. Indian J Ophthalmol 2020;68:2711-22.  Back to cited text no. 41
  [Full text]  
42.
Siedlecki J, Luft N, Mayer WJ, Siedlecki M, Kook D, Meyer B, et al. CIRCLE enhancement after myopic SMILE. J Refract Surg 2018;34:304-9.  Back to cited text no. 42
    
43.
Moshirfar M, Shah TJ, Masud M, Linn SH, Ronquillo Y, Hoopes PC Sr. Surgical options for retreatment after small-incision lenticule extraction: Advantages and disadvantages. J Cataract Refract Surg 2018;44:1384-9.  Back to cited text no. 43
    
44.
Stival LR, Figueiredo MN, Santhiago MR. Presbyopic excimer laser ablation: A review. J Refract Surg 2018;34:698-710.  Back to cited text no. 44
    
45.
Chan TC, Kwok PS, Jhanji V, Woo VC, Ng AL. Presbyopic correction using monocular bi-aspheric ablation profile (PresbyMAX) in hyperopic eyes: 1-year outcomes. J Refract Surg 2017;33:37-43.  Back to cited text no. 45
    
46.
Moshirfar M, Desautels JD, Wallace RT, Koen N, Hoopes PC. Comparison of FDA safety and efficacy data for KAMRA and Raindrop corneal inlays. Int J Ophthalmol 2017;10:1446-51.  Back to cited text no. 46
    
47.
Moarefi MA, Bafna S, Wiley W. A review of presbyopia treatment with corneal inlays. Ophthalmol Ther 2017;6:55-65.  Back to cited text no. 47
    
48.
Huang B. Update on nonexcimer laser refractive surgery technique: Conductive keratoplasty. Curr Opin Ophthalmol 2003;14:203-6.  Back to cited text no. 48
    
49.
Du TT, Fan VC, Asbell PA. Conductive keratoplasty. Curr Opin Ophthalmol 2007;18:334-7.  Back to cited text no. 49
    
50.
Ambrósio R Jr. Post-LASIK ectasia: Twenty years of a conundrum. Semin Ophthalmol 2019;34:66-8.  Back to cited text no. 50
    
51.
Soundarya B, Sachdev GS, Ramamurthy S, Dandapani R. Ectasia after keratorefractive surgery: Analysis of risk factors and treatment outcomes in the Indian population. Indian J Ophthalmol 2020;68:1028-31.  Back to cited text no. 51
[PUBMED]  [Full text]  
52.
Moshirfar M, Tukan AN, Bundogji N, Liu HY, McCabe SE, Ronquillo YC, et al. Ectasia after corneal refractive surgery: A systematic review. Ophthalmol Ther 2021;10:753-76.  Back to cited text no. 52
    
53.
Shah R. History and results; indications and contraindications of SMILE compared with LASIK. Asia Pac J Ophthalmol (Phila) 2019;8:371-6.  Back to cited text no. 53
    
54.
Lee JK, Chuck RS, Park CY. Femtosecond laser refractive surgery: Small-incision lenticule extraction vs. femtosecond laser-assisted LASIK. Curr Opin Ophthalmol 2015;26:260-4.  Back to cited text no. 54
    
55.
Han T, Shang J, Zhou X, Xu Y, Ang M, Zhou X. Refractive outcomes comparing small-incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis for high myopia. J Cataract Refract Surg 2020;46:419-27.  Back to cited text no. 55
    
56.
Hamam KM, Gbreel MI, Elsheikh R, Benmelouka AY, Ouerdane Y, Hassan AK, et al. Outcome comparison between wavefront-guided and wavefront-optimized photorefractive keratectomy: A systematic review and meta-analysis. Indian J Ophthalmol 2020;68:2691-8.  Back to cited text no. 56
  [Full text]  
57.
Vestergaard AH. Past and present of corneal refractive surgery: A retrospective study of long-term results after photorefractive keratectomy and a prospective study of refractive lenticule extraction. Acta Ophthalmol 2014;92 Thesis 2:1-21.  Back to cited text no. 57
    
58.
Zhang J, Feng Q, Ding W, Peng Y, Long K. Comparison of clinical results between trans-PRK and femtosecond LASIK for correction of high myopia. BMC Ophthalmol 2020;20:243.  Back to cited text no. 58
    
59.
Han T, Xu Y, Han X, Zeng L, Shang J, Chen X, et al. Three-year outcomes of small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for myopia and myopic astigmatism. Br J Ophthalmol 2019;103:565-8.  Back to cited text no. 59
    
60.
Gulmez M, Tekce A, Kamıs U. Comparison of refractive outcomes and high-order aberrations after small incision lenticule extraction and wavefront-guided femtosecond-assisted laser in situ keratomileusis for correcting high myopia and myopic astigmatism. Int Ophthalmol 2020;40:3481-9.  Back to cited text no. 60
    




 

Top
 
 
  Search
 
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

 
  In this article
Abstract
Introduction and...
Patient Selection
Contraindications
Keratorefractive...
Clinical Outcomes
Conclusion
References

 Article Access Statistics
    Viewed1246    
    Printed70    
    Emailed0    
    PDF Downloaded170    
    Comments [Add]    

Recommend this journal


[TAG2]
[TAG3]
[TAG4]