Laser Eye Surgery Research Paper

Small incision lenticule extraction (SMILE) versus laser in-situ keratomileusis (LASIK): study protocol for a randomized, non-inferiority trial

1Singapore National Eye Centre, Singapore, Singapore

2Singapore Eye Research Institute, Singapore, Singapore

3Department of Ophthalmology, National University Health System, Singapore, Singapore

4Department of Clinical Sciences, Duke-NUS Graduate Medical School, Singapore, Singapore

Corresponding author.

Marcus Ang: gs.moc.oohay@nhasucram; Donald Tan: gs.ten.cificap@tdcens; Jodhbir S Mehta: moc.liamg@athemdoj

Author information ►Article notes ►Copyright and License information ►

Received 2012 Feb 13; Accepted 2012 May 31.

Copyright ©2012 Ang et al.; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

This article has been cited by other articles in PMC.

Abstract

Background

Small incision lenticule extraction or SMILE is a novel form of ‘flapless’ corneal refractive surgery that was adapted from refractive lenticule extraction (ReLEx). SMILE uses only one femtosecond laser to complete the refractive surgery, potentially reducing surgical time, side effects, and cost. If successful, SMILE could potentially replace the current, widely practiced laser in-situ keratomileusis or LASIK. The aim of this study is to evaluate whether SMILE is non-inferior to LASIK in terms of refractive outcomes at 3 months post-operatively.

Methods/Design

Single tertiary center, parallel group, single-masked, paired-eye design, non-inferiority, randomized controlled trial. Participants who are eligible for LASIK will be enrolled for study after informed consent. Each participant will be randomized to receive SMILE and LASIK in each eye. Our primary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> −3.00 diopter (D)) at a tertiary eye center in terms of refractive predictability at 3 months post-operatively. Our secondary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> −3.00 D) at a tertiary eye center in terms of other refractive outcomes (efficacy, safety, higher-order aberrations) at 3 months post-operatively. Our primary outcome is refractive predictability, which is one of several standard refractive outcomes, defined as the proportion of eyes achieving a postoperative spherical equivalent (SE) within ±0.50 D of the intended target. Randomization will be performed using random allocation sequence generated by a computer with no blocks or restrictions, and implemented by concealing the number-coded surgery within sealed envelopes until just before the procedure. In this single-masked trial, subjects and their caregivers will be masked to the assigned treatment in each eye.

Discussion

This novel trial will provide information on whether SMILE has comparable, if not superior, refractive outcomes compared to the established LASIK for myopia, thus providing evidence for translation into clinical practice.

Keywords: Refractive surgery, Laser in situ keratomileusis, Small incision lenticule extraction

Background

Laser in-situ keratomileusis (LASIK) is the current laser refractive procedure of choice to treat myopia. The advantages of LASIK include early postoperative improvement and stabilization of visual acuity, minimal postoperative patient discomfort, and the possibility of enhancement in the future [1]. However, side effects such as dry eyes, reduced vision in low lighting conditions, and visual distortions such as glare and haloes can still occur in up to 1% to 2% of cases; while flap-related complications, inflammation, or infection, though rare, can have serious consequences [2,3].

Femtosecond lasers have been widely used in LASIK to fashion a corneal flap, which is followed by corneal ablation using a separate excimer laser [4]. The advantages of femotosecond or ‘bladeless’ LASIK over microkeratome LASIK flaps are reduced postoperative dry-eye symptoms, reduced likelihood of flap dislocation, and reduced incidence of buttonholes or free caps [2,3]. Recently, refractive lenticule extraction (ReLEx) has been introduced as a single laser refractive procedure without the use of an excimer laser [5-8]. Small incision lenticule extraction (SMILE) is a variation of ReLEx that requires no retractable flap, thus reducing surgical time, reduced patient inconvenience from moving from one laser to another, and, potentially, more accurate ablation [8].

A review of current literature reveals that there are few studies available to validate the outcome of ReLEx or SMILE, which has obtained CE Mark approval in 2009 but yet to be approved by the United States FDA [5-8]. Initial clinical results have been promising, which found that postoperative refractive outcomes after ReLEx were comparable to LASIK with few complications [9,10]. However, there are currently no randomized controlled trials comparing both surgical procedures. We have also conducted preliminary clinical and experimental studies with promising results and confirmed the safety and efficacy of ReLEx [11].

Non-inferiority trials are used to compare standard treatment with a new treatment that is expected to have some advantages such as greater predictability, less side effects, or greater improvement in quality of life [12,13]. LASIK, which is the current gold standard for corneal refractive surgery, already produces good visual outcomes with refractive predictability. As we do not expect to see a great improvement to the results from the already established LASIK, we aim to demonstrate that SMILE is just as good in terms of visual outcome in this randomized non-inferiority trial.

Methods/Design

Study objective and hypotheses

In this study we aim to demonstrate that the refractive predictability of SMILE is not inferior to the established procedure (LASIK) to treat myopia. Refractive predictability is one of several standard refractive outcomes, defined as the proportion (number) of eyes achieving a postoperative spherical equivalent (SE) within ±0.50 diopter (D) of the intended target. Our primary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> −3.00 D) at a tertiary eye center in terms of refractive predictability at 3 months postoperatively. Our secondary hypothesis (stated as null) in this non-inferiority trial would be that SMILE differs from LASIK in adults (>21 years old) with myopia (> −3.00 D) at a tertiary eye center in terms of other refractive outcomes (efficacy, safety, higher-order aberrations) at 3 months postoperatively.

Trial design

This trial is a single tertiary center, parallel group, single-masked, paired-eye design, non-inferiority, randomized controlled trial. We will use a paired-eye study design, with subjects randomly assigned to undergo one procedure in each eye (SMILE in one eye, LASIK in the other eye). All procedures will be performed in the SNEC Refractive Center by the same fully qualified refractive surgeons, who are co-investigators in this study. Each surgeon has performed more than 30 similar surgeries and 20 cases of SMILE to ensure that each surgeon is adept at performing this procedure. After randomization and random allocation to treatment group, each subject will undergo either SMILE or LASIK in one eye, followed by LASIK or SMILE in the fellow eye on the same day (either the left or right eye will be randomized to decide which eye is operated on first). We have obtained ethics approval from our Institutional Review Board (CIRB Ref No: 2011/109/A) and this trial has been registered (Clinical Trials Registration NCT01216475).

Participants and recruitment

All participants with bilateral myopia will be recruited at the Singapore National Eye Center (SNEC) with the inclusion and exclusion criteria detailed in Table ​1. All subjects will be recruited and provide written informed consent that explains the details of the trial, interventions, and study protocol in accordance with the principles of the Declaration of Helsinki.

Table 1

Inclusion and exclusion criteria for trial participants

Surgical interventions

SMILE procedure

Each SMILE procedure will be performed using an established, described technique [7]. After application of topical anesthesia, standard sterile draping, and insertion of the speculum, the patient’s eye will be centered and docked with the curved interface cone before application of suction fixation. The laser will then be activated for photo-dissection in the following sequence: first the posterior surface of the refractive lenticule (spiral in), then the lenticule border is created. The anterior surface of the refractive lenticule (spiral out) is then formed which extended beyond the posterior lenticule diameter by 0.5 mm to form the anterior flap and is followed by a rim cut. We will use the following FS laser parameters: 120 μm flap thickness, 7.5 mm flap diameter, 6.5 mm optical zone of lenticule, 145 nj of power with side cut angles at 90°. A superior hinge, 50° in cordal length, will be made in all cases. The spot distance and tracking spacing are 3/3 μm for the lenticule, 2.5/2.5 μm for the lenticule side cut, 3/3 μm for the flap, and 2/2 μm for the flap side cut. After the suction is released, a Siebel spatula (Rhein Medical, Heidelberg, Germany) is inserted under the flap near the hinge before the flap is separated and reflected. The edge of the refractive lenticule is separated from the stromal bed with a sinsky hook and the posterior border of the lenticule gently separated with the Siebel spatula. The lenticule is then grasped with non-toothed serrated forceps through the small incision.

LASIK procedure

Each LASIK procedure will be performed using a standard, established technique. Under topical anesthesia and standard draping, a lid speculum is used to retract the eyelids, and polyvinyl acetate surgical spears (Ivalon, New London, CT) to dry the conjunctival fornices. A superiorly hinged 120/140 μm thick flap will be created using the Visumax femtosecond laser (Carl Zeiss). Excimer laser ablation is then performed using Wavelight Allegretto WAVE Eye-Q 400 Hz excimer laser (Wavelight GmbH, Alcon, Fort Worth, TX, USA). After ablation, the flap will be carefully repositioned, and postoperative medications are commenced.

Outcomes

We plan to use standard primary and secondary outcomes measures at 3 months postoperatively, which are reported in any assessment refractive surgical technique and standard outcomes in refractive studies. Measurements and outcomes are based on visual acuity (VA) and refraction that are performed by trained refractive optometrists and are repeatedly tested to ensure accuracy and reproducibility. Our primary outcome measure is refractive predictability, which is defined as the proportion number of eyes achieving a postoperative spherical equivalent (SE) within ±0.50 D of the intended target.

Secondary outcome measures include: (1) Efficacy: defined as the proportion number of eyes achieving a unaided visual acuity (UAVA) of 20/20 or better postoperatively; (2) Safety: defined as the proportion number of eyes that lost or gained one or more lines of postoperative best-corrected visual acuity (BCVA) relative to the preoperative BCVA; (3) Higher-order aberrations (HOAs): measured using the Bausch and Lomb Technolas Zywave aberrometer with Zywave software version 4.45 (ZYOPTIX Diagnostic Workstation, Bausch & Lomb); (4) Contrast sensitivity: tested using the Vision Contrast Test System (VCTS) chart (VCTS 6500 contrast sensitivity chart) in six spatial frequencies.

Sample size

As this is a paired design, non-inferiority trial with a binary outcome, we calculate the required sample size using the maximum likelihood method for large sample proposed by Nam (1997) [14]. A review of current literature reveal that the reported refractive predictabilities in LASIK and SMILE range from 78.2% to 96.7% [1,14,15] and from 90.0% to 95.6%, [5-8], respectively. The results from our own audit department estimate our refractive predictability at 82% for LASIK (2011, unpublished). We therefore assumed the refractive predictabilities in LASIK and SMILE in this study are 82% and 92%, respectively. Thus, a sample of 67 subjects (134 eyes) will be sufficient to confirm non-inferiority with a power of ≥80% and at a 5% significance level using a 10% non-inferiority margin, which is the clinically significant difference from our preliminary data. To account for a lost to follow-up rate of 5%, 70 subjects will be recruited.

Randomization and blinding

The random allocation sequence will be generated by a computer with no blocks or restrictions, and implemented by concealing the number-coded surgery within sealed envelopes until just before the procedure. This randomization process will be performed by a research assistant masked to the study subjects and participants will be enrolled by co-investigator surgeons who will assign participants to their groups after opening the sealed envelope, that is each subject will receive a different procedure in each eye at random. In this single-masked trial, subjects and their caregivers will be masked to the assigned treatment in each eye. Both procedures will be performed within the SNEC Refractive Suite, using the femtosecond laser machine. Clinically, it is impossible to detect any difference between each procedure postoperatively to the untrained eye without the slit-lamp microscope. While the surgeons cannot be masked as they will be performing the intervention, the outcome assessors such as nurses, research assistants, and trained optometrists will also be masked to the assigned treatment to improve the objectivity of the research outcomes, as well as to minimize bias. In the event of adverse events (please see below), a code-breaking envelope for each subject will be available.

Data collection

All patients will have data collection forms outlining each follow-up visit and data to be collected at each visit, which include visual acuity, refraction results, clinical examination findings, and the outcome measures as described above. All data will be securely stored in the SNEC Refractive Suite and then entered into a password-secure desktop computer locked within the Singapore Eye Research Institute, with data back-up into hard drives done daily. Only the named investigators will have access to the research data. All data access will be monitored and controlled by the PI. At the end of the study, the research data will be entered by the research assistant and stored for up to 5 years in compliance with any integrity issues that may arise from any subsequent publications. Following that time period the data will be kept under the control of the PI.

Adverse events

All subjects will be monitored during enrolment into the study for adverse events. All adverse events or serious adverse event (SAE) will be reported to both the centralized institution review board and institution heads (Singhealth) according to the guidelines (http://research.singhealth.com.sg).

Statistical analyses

Demographic and baseline information will be described, and eye-specific characteristics will be described for each treatment. To study the non-inferiority of SMILE to LASIK, a 90% confidence interval of the difference in predictability between the two treatments (LASIK minus SMILE) will be constructed by a method using score intervals with continuity correction (method #10 in Newcombe RG, 1998) [15]. If the upper limit of the 90% confidence interval does not exceed the pre-defined non-inferiority margin of 5%, non-inferiority is confirmed. Similarly, for each of the two secondary outcomes, efficacy, and safety, a 90% confidence interval of the difference between the two treatments using the above-mentioned method will be constructed and then compared with a non-inferiority margin of 5%. Assuming the other secondary outcome, HOA, follows a normal distribution, a 90% confidence interval of the difference between the two treatments will be constructed through a paired t-test, and then compared with a non-inferiority margin of 10%. We would not be performing any interim analyses due to the short duration of follow-up for each outcome measure.

Discussion

In this non-inferiority trial, we aim to demonstrate that SMILE is just as good as LASIK in terms of refractive outcome, as we do not expect to see a great improvement to the results from the already established LASIK procedure. Moreover, this trial may show that SMILE has additional benefits, such as reduction in higher-order aberrations that leads to better quality of vision. On the other hand if we use a superiority trial design with a small sample size that fails to demonstrate any difference between LASIK and SMILE, would be inconclusive since it does not necessarily prove equivalence. Thus we use a non-inferiority trial design to compare our primary and secondary outcomes.

Despite its proven efficacy, LASIK still requires the use of two laser machines: one for the flap creation and another for the excimer ablation. This increases the cost as well as the surgical time for the procedure. SMILE uses only one laser machine, thus potentially reduces surgical time and cost. Moreover, SMILE does not involve any flap creation, which potentially reduces risk of side effects such as dry eyes. For these reasons, SMILE is potentially a new, improved form of refractive surgery, which may supersede LASIK and change clinical practice. There is also potentially a positive impact on healthcare as surgical time and costs are reduced with this new, ‘all-in-one’ laser procedure. Moreover, the needs for enhancements or retreatment are higher in patients with high myopia, a common condition in Singapore. SMILE can be used to treat high myopia without the extra costs involved in visual rehabilitation following LASIK enhancement.

More importantly, in the longer term we propose that SMILE may potentially develop into a reversible surgical procedure. Unlike LASIK which uses an excimer laser to ablate or destroy corneal tissue, SMILE cuts and removes a piece of corneal lenticule, which may be stored and replaced into the cornea at a later time. This is important as we can potentially reverse the refractive procedure many years later when the patient’s myopia decreases and presbyopia sets in. The ability to re-implant the cornea lenticule allows for treatment of corneal ectasia, reversal or monovision, or even the possibility of a presbyopic implant. We have done preliminary studies to demonstrate corneal lenticule viability after ReLEx [16]; and in an experimental animal study, we demonstrated proof of principle of a reversible corneal refractive procedure for the first time (unpublished). We were able to successfully store and re-implant an autologous stromal lenticule into rabbit eyes with minimal resultant inflammation and no signs of rejection after 28 days. This is important as we can potentially reverse the refractive procedure when the patient develops presbyopia. The ability to re-implant the cornea lenticule allows for treatment of corneal ectasia, reversal of myopia, monovision or even the possibility of a presbyopic implant.

In conclusion, this non-inferiority clinical trial that compares SMILE and LASIK will help to determine if this new refractive procedure, SMILE, has equal or better visual and refractive outcomes compare to the traditional LASIK for treatment of myopia. Results of this trial will likely impact clinical practice with potentially further development into novel techniques for re-implantation and reversibility.

Abbreviations

LASIK, Laser in-situ keratomileusis; ReLEx, Refractive lenticule extraction; SMILE, Small incision lenticule extraction.

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

All authors (MA, DT, JSM) participated in the design of the study, performed the statistical analysis, participated in its coordination, and helped to draft the manuscript. All authors read and approved the final manuscript.

Acknowledgements

The authors thank Mr. Lim Chun Fan for statistical expertise.

References

  • Sugar A, Rapuano CJ, Culbertson WW, Huang D, Varley GA, Agapitos PJ, de Luise VP, Koch DD. Laser in situ keratomileusis for myopia and astigmatism: safety and efficacy: a report by the American Academy of Ophthalmology. Ophthalmology. 2002;109:175–187. doi: 10.1016/S0161-6420(01)00966-6.[PubMed][Cross Ref]
  • Salomao MQ, Wilson SE. Femtosecond laser in laser in situ keratomileusis. J Cataract Refract Surg. 2010;36:1024–1032. doi: 10.1016/j.jcrs.2010.03.025.[PMC free article][PubMed][Cross Ref]
  • Moshirfar M, Gardiner JP, Schliesser JA, Espandar L, Feiz V, Mifflin MD, Chang JC. Laser in situ keratomileusis flap complications using mechanical microkeratome versus femtosecond laser: retrospective comparison. J Cataract Refract Surg. 2010;36:1925–1933. doi: 10.1016/j.jcrs.2010.05.027.[PubMed][Cross Ref]
  • Kim P, Sutton GL, Rootman DS. Applications of the femtosecond laser in corneal refractive surgery. Curr Opin Ophthalmol. 2011;22:238–244. doi: 10.1097/ICU.0b013e3283477c9c.[PubMed][Cross Ref]
  • Sekundo W, Kunert K, Russmann C, Gille A, Bissmann W, Stobrawa G, Sticker M, Bischoff M, Blum M. First efficacy and safety study of femtosecond lenticule extraction for the correction of myopia: six-month results. J Cataract Refract Surg. 2008;34:1513–1520. doi: 10.1016/j.jcrs.2008.05.033.[PubMed][Cross Ref]
  • Blum M, Kunert K, Schroder M, Sekundo W. Femtosecond lenticule extraction for the correction of myopia: preliminary 6-month results. Graefes Arch Clin Exp Ophthalmol. 2010;248:1019–1027. doi: 10.1007/s00417-009-1293-1.[PubMed][Cross Ref]
  • 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;95:335–339. doi: 10.1136/bjo.2009.174284.[PubMed][Cross Ref]
  • Shah R, Shah S, Sengupta S. Results of small incision lenticule extraction: all-in-one femtosecond laser refractive surgery. J Cataract Refract Surg. 2011;37:127–137. doi: 10.1016/j.jcrs.2010.07.033.[PubMed][Cross Ref]
  • Krueger RR, Juhasz T, Gualano A, Marchi V. The picosecond laser for nonmechanical laser in situ keratomileusis. J Refract Surg. 1998;14:467–469.[PubMed]
  • Ratkay-Traub I, Ferincz IE, Juhasz T, Kurtz RM, Krueger RR. First clinical results with the femtosecond neodynium-glass laser in refractive surgery. J Refract Surg. 2003;19:94–103.[PubMed]
  • Ang M, Chaurasia S, Angunawela RI, Poh R, Riau AK, Tan D, Mehta J. Femtosecond Lenticule Extraction (FLEx): clinical results, interface evaluation and intraocular pressure variation. Invest Ophthalmol Vis Sci. 2012;53:1414–1421. doi: 10.1167/iovs.11-8808.[PubMed][Cross Ref]
  • Christensen E. Methodology of superiority vs. equivalence trials and non-inferiority trials. J Hepatol. 2007;46:947–954.[PubMed]
  • Turan FN, Senocak M. Evaluating “superiority”, “equivalence” and “non-inferiority” in clinical trials. Ann Saudi Med. 2007;27:284–288. doi: 10.4103/0256-4947.51490.[PubMed][Cross Ref]
  • Nam JM. Establishing equivalence of two treatments and sample size requirements in matched-pairs design. Biometrics. 1997;53:1422–1430. doi: 10.2307/2533508.[PubMed][Cross Ref]
  • Newcombe RG. Improved confidence intervals for the difference between binomial proportions based on paired data. Stat Med. 1998;17:2635–2650. doi: 10.1002/(SICI)1097-0258(19981130)17:22<2635::AID-SIM954>3.0.CO;2-C.[PubMed][Cross Ref]
  • Mohamed-Noriega K, Toh KP, Poh R, Balehosur D, Riau A, Htoon HM, Peh GS, Chaurasia SS, Tan DT, Mehta JS. Cornea lenticule viability and structural integrity after refractive lenticule extraction (ReLEx) and cryopreservation. Mol Vis. 2011;17:3437–3449.[PMC free article][PubMed]

Articles from Trials are provided here courtesy of BioMed Central

This post is a response to two questions: What do you do? and Why aren’t you wearing your glasses?

I’m a sociologist of science and technology. I’m interested in how scientists know what they know. I look at how successful technologies move from magical to mundane while failed ones are written out of history. I try to teach my students to think critically about new science and technology: to ask who wins, who loses and who should decide. As well as the scientific data, I want to know what it means for people to live with difficult, uncertain knowledge and disruptive technologies.

Partly following a distinguished tradition of self-experimentation, but mostly in an effort to steal a march on my mid-life crisis, I recently became intimate with a technology of mind-boggling, eye-watering (of which more later) awesomeness. For the person undergoing it, laser eye surgery feels for a short time like the oddest thing in the world. But, if the social mainstream is mapped by The Simpsons (as good a guide as any, I reckon) then the procedure has become exceedingly normal. Over the last twenty years, during which more than a million people in the UK have had the treatment, it has featured in two Simpsons episodes. In the first, Homer is envisioning a future in which Bart encounters a blind Ned Flanders. Flanders explains: ‘I never should’ve had that trendy laser surgery. It was great at first but, you know, at the ten-year mark your eyes fall out.’

Three episodes later, in a moment of classic Simpsons amnesia, Homer is trying to avoid having to choose glasses. The optometrist suggests surgery, adding. ‘I must warn you it’s an experimental procedure and we still don’t know the long-term effe…’ at which point Homer interrupts her: ‘Less yapping, more zapping!’

I share the excitement as well as the fear. It’s an ambivalence that is common in public attitudes to technology. We yearn for technological solutions to our problems and yet we know that they can disappoint. We worry that we will become dependent on things that we never knew we needed. Technologies normally don’t change our lives in the ways we are promised and, if they do, we take their benefits for granted. The risks, meanwhile, are impossible to fully foresee. Critics of technology are right to call it a social experiment.

My motivation for taking part in this experiment is hypocritical. I couldn’t get on with contact lenses. I used to tell people that I was, like John Hegley (see his poem ‘glasses good, contact lenses bad’), a militant spectacle-wearer. But I don’t believe any person with glasses can completely lose the image of Piggy, the boy from Camberley who loses first his glasses and then his life in Lord of The Flies. Clearly vanity is a part of it, but I am under no illusion that glasses have been the thing holding me back. I don’t know if or how my life will be different without glasses, but the idea of a machine – not just any machine; a laser, that most futuristic of machines – being able to melt my eyeball into a more perfect shape excites me in a very shallow way. For all our ambivalence and in full recognition of its power to change our lives, we embrace technology without much critique. Innovators are the masters of our universe. We adopt their products not just because we are being utilitarian but also because we find them fascinating. Being modern is about embracing novelty, even if it is for novelty’s sake.

Like 2.5 billion other people in the world, I am naturally short-sighted. This ‘epidemic of myopia’ would, in the absence of any solution, be considered part of the normal variation of human beings. But, with technological enhancements, it becomes a defect that can be corrected. My ametropic eyes (whose lenses focus incoming light so that it misses my retina) yearn to be emmetropic ones. For the last twenty years, my glasses have done the job of refocusing the light. Take them away, and the eye itself needs to be given a new lens (like a contact lens) or reshaped.

Laser eye surgery, properly known as LASIK (Laser-Assisted in Situ Keratomileusis), began in the 1980s. The idea of fiddling around inside people’s eyes in order to correct their vision was not new, but a new technology had made precise eye engineering possible. Excimer lasers had been around for a few years. The idea was that, if such a laser could be precisely tuned, it could melt away bits of the tissue on the surface of eye, changing its curve. A scientist at IBM, Rangaswamy Srinivasan, had revealed the possibility of ‘ablative photodecomposition’, the precise etching of living tissue using lasers. The question was how to demonstrate that it could work on people’s eyes. Opthalmologists like Stephen Trokel at Columbia had used lasers on the eyes of dead animals, then human cadavers, then live animals, but animals are notoriously bad at reading eye charts.

Human tests began with blind volunteers. In 1989, Marguerite McDonald published the results of one such study in which a blind young woman had agreed to have experimental laser surgery. Weeks after the surgery, much to the surprise of the researchers, the woman regained her sight. It appeared that her blindness was more psychological than physiological. The study became the accidental first success story of laser eye surgery.

In 1988, a volunteer name Alberta Cassady became the first officially sighted person to have an eye lasered. Cassady needed her eye removed because of a tumour on her eye socket and asked if it would be useful for any tests. McDonald recounts how ‘we got permission to rush her out past all the apes… and do a treatment’, which, in her case, turned her perfect eye into a longsighted one. When Cassady’s eye was removed, the opthamologists could see that the lasers had done the job, removing tiny bits of the cornea without scarring the eyeball.

A later innovation led to what became known as the ‘flap and zap’. Rather than just blasting the eye and letting its fragile surface slowly heal, surgeons began slicing into the cornea, peeling back a layer, using the laser and then replacing the flap to act as a bandage. This procedure, despite its grotesque beginnings, has now become the norm. It is reliable and easily replicated. With machines that can precisely map an individual’s eyeball and target a laser to remould it, laser surgery has become largely automated and extremely lucrative for eye doctors.

I turn up for a consultation, with the Simpsons echoing in my mind, ready to ask about the dangers. To calm my Ned Flanders worry, a leaflet reassures me that ‘becoming blind from laser eye surgery is an extremely improbable consequence’. I tell my students that there is no such thing as ‘safe’, only ‘safe enough’, but I can’t quite shake the ‘extremely improbable’. The UK’s health regulator NICE says that it’s safe and effective ‘in appropriately selected patients’. But the Daily Mail aren’t the only ones to dig up cautionary anecdotes. In the US, former Food and Drug Administration official Morris Waxler has waged a campaign against the treatment, claiming that it causes unacknowledged side effects and is unregulated. Such controversies attract the attention of sociologists because they force the various people involved to make their arguments explicit. But, weighing them against the millions of other data points, I am willing to set aside my professional scepticism.

It is easy to fixate on technological risks. But we should also cast a critical eye on the benefits of a technology and how they are shared. Laser eye surgery, although it promises to return people to normality, can be considered a human enhancement. As with other enhancements, from blood doping to modafinil, it introduces ethical questions – will it exacerbate social inequality? Is there a line between therapy and enhancement? Should we be searching for perfection anyway?

On entering the eye clinic, I am sold a vision of a life free from glasses. I am told that I will be ‘free to run’, whatever that means. The literature on the tables is full of stories from rock climbers and actors, once encumbered by glasses, now fulfilling their true potential. The guarantee is that my eyesight will be 20/20 or my money back. 20/20, it turns out, is nothing special. It is a gloriously vague metric of mediocrity. If you have 20/20 vision, you can see at 20 feet what a normal human being sees at 20 feet (the distance you sit away from the letters at the optician’s), begging the question of what counts as normal during an ‘epidemic of myopia’. The magazines hint at going beyond this workable imperfection. They talk about ‘life with HD vision’. Some birds of prey apparently have 20/2 vision. I’ll aim for that.

I’m played a video in which the company’s chief scientist – let’s call him Chuck – tells me what an exciting day it is and how passionate he is about eyes. He tells stories of life-saving eye surgery and schemes to deliver glasses to people in poor countries. Chuck says that the technology they use was originally developed for the Hubble Space Telescope. He is on a video, so I can’t interrupt him (Didn’t Hubble have blurred vision and need glasses as soon as it was launched?) Chuck tells me, without acknowledging the contradiction, that the technology is bleeding-edge new but also reassuringly old and therefore safe as houses.

New eye machines on offer in the clinic promise more perfect perfection. ‘Wavefront-guided LASIK’ will map the miniscule contours of my dysfunctional eyeballs so that the laser can smooth out every crease. According to its web site, the STAR S4 IR machine algorithmically ‘Calculates the ablation torsional angle from multiple matching reference points’ as it steers its robotic laser. But first, I must get my eyes mapped. A Pentacam machine measures my cornea while I concentrate on a spinning bar. The next machine involves staring into something like an X-Wing targeting computer. Then I look at a picture of a hot air balloon above a desert highway. A tiny puff of air is bounced off my eyeball to measure the pressure inside my eye. All of these machines are in standard-issue desktop grey-cream. I’m then given a very old-fashioned eye test – guessing letters and trying to draw out tiny differences between patterns of dots. Congratulations, I’m told, I can have eye surgery.

Then Chuck is back on screen, only this time he’s less excited. He tells me that my eyes will take some time to recover and they will be dry for a few weeks. And they will still age. In a decade or so, my new superpowers will fade and I will need reading glasses. Chuck then reassures me that he has lasered his own wife and daughter.

Before I go, I’m told the price. Apparently the offer in the window was only for people who had pretty good eyes to begin with. Mine are a tougher challenge. Given that computers and lasers will be doing the hard work and the whole thing will take two minutes, I am unsure why this justifies the price bump. Whatever. Less yapping, more zapping.

On the day of the operation, I meet the surgeon. His job title seems rather grand considering he will be playing magician’s assistant alongside an automated laser, whose instructions have been provided by another machine. Nevertheless he is eminently qualified and maintains an old-school paternalism as he tells me that my stupid eyeballs are poorly suited to the flap-and-zap. Instead, he recommends a similar, more painful operation with a longer recovery time. He tells me that it’s my choice but, reading the subtext, I have no option. Translating his expertise in relative risks into something meaningful would require me to do a degree in opthamology, and I need to get on.

I am whisked into the operating theatre, where I am underwhelmed by the performance: no gown, no scrubbing up, no sense of occasion. There is a period of five minutes where it all gets a bit Clockwork Orange. My eyeballs are numbed and the lids forced open with tiny clamps while a drop of solvent dissolves the top layer of the cornea. Then the lasers, making a noise like a Geiger counter, do their thing, the surgeon puts on a contact lens as a sort of bandage, and it’s done. The laser has taken tissue away from the middle of my cornea, making it flatter, refocussing the light onto my retina. But, because of my astigmatism – a non-spherical eyeball – the laser also corrected for this, as well as ironing out all of the ‘microprescription’ lumps and bumps.

I am given a minibar of eye drops to administer once the anaesthetic wears off. Just before putting on my sunglasses to stumble home, I catch a hint of crystal clear vision. Then things blur. But this an iatrogenic blur rather than one of deformity, and I am told that it will pass as my eyes heal over the next few days. On my eyes’ journey back to normality, they feel as though they are being dragged through a pool of chlorinated onions. I close my eyes while my corneas mend and realise that my ethical concerns have evaporated. I don’t worry that others are missing out on this rather pointless procedure. I don’t feel enhanced, nor did I feel that my glasses had disabled me before. If anything, I feel a bit less special, a bit boring. I harbour a lingering question as to whether the surgeon who stood by while the laser did its thing might have had other dreams in mind when he qualified, but I console myself that he probably does more worthy things too.

As the fog breaks and clarity returns, I am still in search of justification. I am not the people in the magazines who are desperate to escape their glasses because they are professionally extreme - rock climbers – or professionally vain – actors, TV presenters. The one benefit I hit upon is that I can now tuck a pencil behind my ear like my Grandpa used to. Maybe I should stop being a sociologist of science and take up some activity that would be impossible in glasses, like cycling in the rain, diving for pearls or running for leader of the Labour party?

0 Thoughts to “Laser Eye Surgery Research Paper

Leave a comment

L'indirizzo email non verrà pubblicato. I campi obbligatori sono contrassegnati *