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Version: 1.0

Publication Date: June 16, 2017

Report Length: 16 Pages

CADTH RAPID RESPONSE REPORT: SUMMARY WITH CRITICAL APPRAISAL

Laser Eye Surgery for Vision Correction: A Review of Clinical Effectiveness and Guidelines

SUMMARY WITH CRITICAL APPRAISAL Laser Eye Surgery for Vision Correction 2

Authors: Rob Edge, Charlene Argez

Cite As: Laser eye surgery for vision correction: a review of clinical effectiveness and guidelines. Ottawa: CADTH; 2017 Jun. (CADTH rapid response report:

summary with critical appraisal).

ISSN: 1922-8147 (online)

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Context and Policy Issues

Refractive error (ametropia) is a common condition resulting in decreased visual acuity.

Patients are treated and symptoms can be corrected with eyeglasses, contact lenses, or

surgery.1 Eyeglasses are the simplest and safest means of refractive error correction.

1

Laser eye surgeries are a subset of surgical procedures used to correct most common

refractive errors and are the most frequently performed procedures for low to moderate

near-sightedness (myopia).1 Photorefractive keratectomy (PRK), was developed over 20

years ago, and subsequently wavefront-guided laser in situ keratomileusis (LASIK) has

become the most commonly performed keratorefractive procedure. Other procedures are

variations of PRK and include laser epithelial keratomileusis (LASEK) and epi-LASIK.1 Long

term studies demonstrate excellent safety, efficacy, and stability of these procedures with

long term refractive stability for far-sighted (hyperopic) patients less certain than for myopic

patients.1-3

Some concern remains regarding the stability of post-surgical refractive error which is

reflected in post-surgical waiting periods for refractive surgery patients applying for some

occupations with visual acuity requirements in Canada.4 This report aims to retrieve and

review the clinical effectiveness evidence for laser eye surgery as compared to eyeglasses

and no treatment for patients with new vision correction requirements and those with

unstable visual acuity requiring a change to current refractive correction. Additionally, this

report aims to retrieve and review evidence-based guidelines associated with laser eye

surgery for first responders and patients with occupational requirements for high visual

acuity.

Research Questions

1. What is the clinical effectiveness of laser eye surgery in adults newly requiring vision

correction and those with unstable visual acuity requiring a change to current refractive

correction?

2. What are the evidence-based guidelines associated with laser vision correction in first

responders or in persons required to maintain a high visual acuity?

Key Findings

No literature was identified that specifically examined laser eye surgery patients with a new

requirement for vision correction. Additionally, no studies were identified that compared

laser eye surgery to eyeglasses or no treatment. The lack of comparative efficacy evidence

was also reported by one included health technology assessment published in 2013 that

conducted a systematic literature search without search date limitations. One identified

meta-analysis did not define the refractive stability of patient in the included studies. This

meta-analysis found extrapolation of data from large observational studies suggested

microbial keratitis would be less common in wavefront-guided laser in situ keratomileusis

(LASIK) patients than in contact lens wearers over the course of ten years. One set of

guidelines with recommendations for laser eye surgery were identified. These guidelines

did not have recommendations specific to patients with first responder or high visual acuity


occupational requirements but included unstable refraction in a list of laser eye surgery

contraindications.

Methods

Literature Search Methods

A limited literature search was conducted on key resources including PubMed, The

Cochrane Library, University of York Centre for Reviews and Dissemination (CRD)

databases, ECRI, Canadian and major international health technology agencies, as well as

a focused Internet search. No filters were applied to limit the retrieval by study type. Where

possible, retrieval was limited to the human population. The search was also limited to

English language documents published between January 1, 2012 and May 18, 2017.

Rapid Response reports are organized so that the evidence for each research question is

presented separately.

Selection Criteria and Methods

One reviewer screened citations and selected studies. In the first level of screening, titles

and abstracts were reviewed and potentially relevant articles were retrieved and assessed

for inclusion. The final selection of full-text articles was based on the inclusion criteria

presented in Table 1.

Table 1: Selection Criteria

Population Adults requiring vision correction (e.g., either those newly requiring glasses or those with worsening vision who already are wearing glasses)

Intervention Laser eye surgery (including but not limited to, laser-assisted-in-situ keratomileusis [LASIK], photo refractive keratectomy [PRK], Wavefront etc.)

Comparator Q1: Corrective Lenses; no treatment Q2: No comparator

Outcomes Q1: Clinical effectiveness and safety (e.g., long term harms and benefits/outcomes, loss of vision correction/maintenance of visual acuity, having to wear glasses despite having surgery, success rates [potential harms of surgery], etc.) Q2: Guidelines for first responders or those requiring a high visual acuity for their job (e.g., police, military, firefighters, pilots, etc.)

Study Designs Health technology assessments, systematic reviews, meta-analyses, randomized controlled trials, non-randomized studies, and evidence-based guidelines.

Exclusion Criteria

Articles were excluded if they did not meet the selection criteria outlined in Table 1, they

were duplicate publications, or were published prior to 2012.

Critical Appraisal of Individual Studies

The included systematic review was critically appraised using the Assessing the

Methodological Quality of Systematic Reviews (AMSTAR) tool,5, while guidelines were

assessed with the AGREE II instrument.6 The included HTA was also evaluated using

AGREE II as this instrument had more applicable quality-related domains.6 Summary


scores were not calculated for the included studies; rather, a review of the strengths and

limitations of each included study were described, narratively.

Summary of Evidence

Quantity of Research Available

A total of 425 citations were identified in the literature search. Following screening of titles

and abstracts, 421 citations were excluded and four potentially relevant reports from the

electronic search were retrieved for full-text review. Eight potentially relevant publications

were retrieved from the grey literature search. Of these potentially relevant articles, nine

publications were excluded for examination of an irrelevant population, while three

publications met the inclusion criteria and were included in this report. Appendix 1

describes the PRISMA flowchart of the study selection.

Additional references of potential interest are provided in Appendix 5.

Summary of Study Characteristics

One meta-analysis (MA),7 one health technology assessment (HTA),

2 and one set of

evidence-based guidelines1 were identified that met the selection criteria, although no

identified studies fulfilled all criteria exactly. A summary of included study characteristics is

provided in Appendix 2.

Study Design

The MA, published in 2017, examined the incidence of one adverse event outcome by

comparative MA of large (minimum sample size of 1000) observational studies.7 The HTA

was published in 2013 and examined the efficacy, effectiveness, and safety of refractive

eye surgery through a systematic literature search of available evidence.2 The guidelines

published by the American Academy of Ophthalmology in 2013 were designed as

interpretations of the best identified evidence by committees of knowledgeable health

professionals.1

Country of Origin

The MA was written by authors in the USA. The country of origin for included studies was

not reported.7 The HTA was authored in Belgium and searched articles published in Dutch,

English, French, and German.2 The included guidelines were published in the USA.

1

Patient Population, Intervention, and Comparators

The MA did not specify inclusion of studies where patients had a new requirement for

refractive correction or stable refraction, and it is the only identified study that directly

compared corrective lenses to laser eye surgery. Studies included in the MA examined

three different types of contact lenses, soft daily wear contact lenses, soft extended use

contact lenses, and rigid gas permeable lenses. Different contact lenses were compared to

each other, and compared to LASIK in this MA. Identified studies ranged from 1017 to 639

000 patients.7

The HTA was aimed at examining refractive eye surgery for adult patients with myopia,

hyperopia and/or astigmatism. Studies that investigated other medical conditions such as

cataract, presbyopia, glaucoma, corneal disease, and eye injuries were excluded from the

HTA. Patient criteria did not specify a new requirement for refractive correction or patients


with specific occupational vision requirements. Interventions of interest in the HTA were

eyeglasses, contact lenses, laser refractive surgery, and intraocular lenses. The HTA

included a systematic literature search to identify studies evaluating refractive eye surgery

as compared to eyeglasses or contact lenses.2

The guidelines identified and included in this report define the patient population of interest

as individuals beyond the amblyogenic age with refractive errors.1 Interventions of interest

in these guidelines were eyeglasses, contact lenses, orthokeratology, and refractive

surgery for myopia, astigmatism, presbyopia, or hyperopia.1

No studies were identified that specifically examined a patient population with a change in

visual acuity requiring new or a change to current refractive correction, and no guidelines

were identified with specific recommendations for first responder patient populations or

patient populations with occupational requirements for visual acuity or firearms proficiency.

No studies were identified that examined outcomes of any laser eye surgery to control

patients receiving no treatment.

Outcomes

The MA was focused on examining the frequency of a single outcome, microbial keratitis

infection.7 Microbial keratitis is the most serious risk of contact lens use and can lead to

vision loss even if appropriately managed.1 When included studies provided culture-proven

and presumed infection case numbers the analysis used presumed infection case

numbers.7

The primary visual acuity outcomes searched for in the HTA were the need for glasses or

contact lenses, the ratio or the mean postoperative uncorrected visual acuity (UCVA) to the

mean preoperative best spectacle corrected visual acuity (BCVA), UCVA 20/20, and

refraction within 0.5 diopters (D) of target refraction. Secondary visual acuity outcomes

included in the search were UCVA 20/40, and refraction within 1 D of target refraction. The

HTA also searched for quality of life and safety outcomes.2

The guidelines did not include a systematic literature search, however the formulated

recommendations cite outcomes of corneal infection, acuity outcomes, quality of life, patient

perceptions and expectations, side effects, and complications.1

Summary of Critical Appraisal

A tabulated summary of the critical appraisal of included literature is provided in Appendix

3.

The MA7 provided details on the systematic literature search used to identify included

studies, however the authors did not present the results of the literature selection process.

The MA provided information on data extraction methodology however this was not done in

duplicate. A focused purpose and scope was a strength of the included MA, as was the

provided discussion on the limitations of the study, and the lack of potential COI. The MA

was limited by the identification of low quality study designs (case series and survey

studies), lack of critical appraisal of these studies, and no assessment of statistical

heterogeneity. The use of presumed infection case numbers from included studies is a

potential source of bias.

The included HTA was comprehensive and had many strengths including an explicit scope

and purpose, involvement of stakeholders and external experts, well described


methodology, a literature search and selection methodology that included languages other

than English with selection done in duplicate, and a described data extraction methodology.

An economic assessment of laser eye surgery was also conducted in the included HTA.

Limitations of the HTA included an undefined target audience, acknowledged potential

COIs, and a lack of a specific discussion on the limitations of the HTA.2

The included guidelines had a broad focus that was defined along with a purpose and a

target audience. Stakeholders and external experts were involved the development of the

included guidelines. The recommendations are clearly identifiable, linked to supporting

evidence, and graded. The guidelines also included some information on guideline

implementation, patient assessment, and information on cost-effectiveness. Limitations of

the guidelines include a literature search methodology that was reported to be detailed

elsewhere and was unavailable for review, a lack of guideline development methodology,

no specific discussion on the limitations of the guidelines, and acknowledged potential

COIs.1

Summary of Findings

A summary of findings is also provided in Appendix 4.

What is the clinical effectiveness of laser eye surgery in adults newly requiring vision

correction and those with unstable visual acuity requiring a change to current refractive

correction?

The included MA did not define the patient population as having a new requirement for

vision correction, as having stable vision, or if it was a mixed patient population. The

analysis presents data supporting a less frequent occurrence over 10 years of presumed

microbial keratitis in patients who received LASIK as compared to patients who wear any

examined contact lens type. Over five years patients wearing soft contact lenses and daily

wear contact lenses also experienced a greater frequency than LASIK patients, and only

soft contact lens wearers would experience a greater frequency of microbial keratitis than

LASIK patients in the first year following surgery. Both patients wearing daily wear soft

contacts and patients wearing rigid gas permeable contact lenses experienced a

statistically significant less frequent infection occurrence (P < 0.05) during the first year

following LASIK. These findings remain relatively unchanged when a 10% retreatment or

enhancement rate for LASIK patients is accounted for.7

The HTA from 2013 conducted a systematic literature search and did not find any

systematic reviews or RCTs that evaluated refractive eye surgery as compared to

eyeglasses or contact lenses. The HTA also did not identify studies that reported outcomes

of dependence on corrective lenses. The HTA noted safety considerations that flap

complications can occur with LASEK and LASIK, while PRK and LASEK can be associated

with more pain. Dry eyes was reported as the leading adverse event associated with LASIK

however the symptoms resolve six months following surgery.2

What are the evidence-based guidelines associated with laser vision correction in first

responders or in persons required to maintain a high visual acuity?

The identified guidelines did not formulate recommendations specific to first responders or

persons required to maintain high visual acuity. Relevant recommendations and statements

from the included guidelines are quoted and provided in Appendix 4, Table 7. One strong

recommendation based upon moderate evidence included information on patient selection


for refractive surgery that did not include criteria for refractive stability, however a list of

refractive surgery contraindications included unstable refraction.

Limitations

No evidence directly addressing the selection criteria was identified for this review.

Evidence from the identified MA may be from an irrelevant or mixed population as the

patient population was not sufficiently defined.

Conclusions and Implications for Decision or Policy Making

No studies were identified that specifically examined patient populations with a new

requirement for refractive correction or patient populations with changing vision correction

requirements. Additionally, no studies were identified that specifically examined first

responder patient populations or patient populations with occupational requirements for

visual acuity or firearms proficiency. As reported in the included guidelines,

contraindications for refractive surgery include unstable refraction.1 Another set of

guidelines, not sufficiently evidence-based for inclusion in this report, also report refractive

stability as a criteria for patient selection.8 The lack of evidence identified in this report on

refractive surgery for patients with a new refractive correction requirement may be a

reflection of this patient selection criteria. Two additional studies of potential interest

examined US military personnel (See Appendix 5, Table 8). Patient inclusion criteria for

both studies included stable refraction for 12 months, neither included comparative efficacy

to corrective lenses or to untreated patients.9,10

The included literature did not provide an

evidence-basis for the inclusion of stable refraction as part of a laser eye surgery patient

selection criteria.

An MA was identified that examined studies of populations that may have included patients

with new vision correction requirements. When results from observational studies were

extrapolated over ten years, the MA found that LASIK patients experienced less frequent

microbial keratitis as compared to patients using different types of contact lenses.7

No studies were identified that examined laser eye surgery as compared to eyeglasses or

to control patients receiving no treatment. The included HTA conducted a systematic

literature without limitations on publication date that also did not identify evidence

comparing clinical efficacy of laser eye surgery to corrective lenses.2


References

1. AAO Refractive Management/Intervention PPP Panel, Hoskins Center for Quality Eye Care. Refractive errors & refractive surgery PPP - 2013 [Internet]. San Francisco (CA): American Academy of

Ophthalmology; 2013 Jul [cited 2017 May 24]. Available from: https://www.aao.org/preferred-practice-pattern/refractive-errors--surgery-ppp-2013

2. Obyn C, Smit Y, Post P, Kohn L, Defourny N, Christiaens W, et al. Correction of refractive errors of the eye in adults part 2: laser surgery and intraocular lenses [Internet]. Brussels (BE): Belgian Health Care Knowledge Centre (KCE); 2013 [cited 2017 May 24] (KCE reports; no. 215). Available from:

http://kce.fgov.be/sites/default/files/page_documents/KCE_215_refractive_eye_surgery.pdf

3. O'Brart DP, Shalchi Z, McDonald RJ, Patel P, Archer TJ, Marshall J. Twenty-year follow-up of a randomized prospective clinical trial of excimer laser photorefractive keratectomy. Am J Ophthalmol. 2014 Oct;158(4):651-63.

4. Hovis JK. Canadian vision standards - 2016 [Internet]. Ottawa (ON): Canadian Association of Optometrists; 2016 [cited 2017 May 24]. Available from:

https://opto.ca/sites/default/files/resources/documents/canadian_vision_standards_2016_hovis_en.pdf

5. Shea BJ, Grimshaw JM, Wells GA, Boers M, Andersson N, Hamel C, et al. Development of AMSTAR: a measurement tool to assess the methodological quality of systematic reviews. BMC Med Res Methodol [Internet]. 2007 [cited 2017 May 24];7:10. Available from:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1810543/pdf/1471-2288-7-10.pdf

6. Brouwers M, Kho ME, Browman GP, Burgers JS, Cluzeau F, Feder G, et al. AGREE II: advancing guideline development, reporting and evaluation in healthcare. CMAJ [Internet]. 2010 [cited 2017 May 24]Dec;182(18):E839-E842. Available from:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3001530/pdf/182e839.pdf

7. Masters J, Kocak M, Waite A. Risk for microbial keratitis: Comparative metaanalysis of contact lens wearers and post-laser in situ keratomileusis patients. J Cataract Refract Surg. 2017 Jan;43(1):67-73.

8. Corneal refractive surgery: standards & guidelines [Internet]. Edmonton (AB): College of Physicians and

Surgeons of Alberta; 2012 Sep [cited 2017 May 24]. Available from: http://cpsa.ca/wp-content/uploads/2015/03/Corneal_Refractive_Surgery_Standards.pdf

9. Sia RK, Ryan DS, Stutzman RD, Pasternak JF, Eaddy JB, Logan LA, et al. Wavefront-guided versus wavefront-optimized photorefractive keratectomy: clinical outcomes and patient satisfaction. J Cataract Refract Surg. 2015 Oct;41(10):2152-64.

10. Sia RK, Ryan DS, Edwards JD, Stutzman RD, Bower KS. The U.S. Army Surface Ablation Study: comparison of PRK, MMC-PRK, and LASEK in moderate to high myopia. J Refract Surg. 2014 Apr;30(4):256-64.

https://www.aao.org/preferred-practice-pattern/refractive-errors--surgery-ppp-2013https://www.aao.org/preferred-practice-pattern/refractive-errors--surgery-ppp-2013http://kce.fgov.be/sites/default/files/page_documents/KCE_215_refractive_eye_surgery.pdfhttps://opto.ca/sites/default/files/resources/documents/canadian_vision_standards_2016_hovis_en.pdfhttps://opto.ca/sites/default/files/resources/documents/canadian_vision_standards_2016_hovis_en.pdfhttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC1810543/pdf/1471-2288-7-10.pdfhttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC3001530/pdf/182e839.pdfhttp://cpsa.ca/wp-content/uploads/2015/03/Corneal_Refractive_Surgery_Standards.pdfhttp://cpsa.ca/wp-content/uploads/2015/03/Corneal_Refractive_Surgery_Standards.pdf


Appendix 1: Selection of Included Studies

421 citations excluded

4 potentially relevant articles retrieved for scrutiny (full text, if available)

8 potentially relevant reports retrieved from other sources (grey

literature, hand search)

12 potentially relevant reports

9 reports excluded for examination of an irrelevant population.

3 reports included in review

425 citations identified from electronic literature search and screened


Appendix 2: Characteristics of Included Publications

Table 2: Characteristics of Included MA

Author, Publication Date

Study Design Population Intervention Comparator(s) Outcomes

Masters, 20177 MA of case series

and survey studies with over 1000 patients

Patients undergoing LASIK or wearing contact lenses

LASIK or contact lenses

none Incidence of microbial keratitis

LASIK = laser in-situ keratomileusis; MA = meta-analysis

Table 3: Characteristics of Included HTA/Guidelines

Origin, Publication Date

Interventions of Interest

Evidence Levels and Recommendation Grading Target Population

Belgian Health Care Knowledge Centre, 2013

2

Eyeglasses, contact lenses, laser refractive surgery, intraocular lenses

Used GRADE to assess quality of evidence (criteria provided in another source): GRADE evidence profile High - RCT Moderate Low Observational study Very Low

Level decreases one to two categories for: Risk of bias Inconsistency Indirectness Imprecision Publication bias Level increases one to two categories for: Large magnitude of effect Evidence of dose-response Accounting for confounding factors

Not explicitly stated

American Academy of Ophthalmology, 2013

1

Eyeglasses, contact lenses, orthokeratology, refractive surgery for myopia, astigmatism, presbyopia, and hyperopia

Levels of Evidence Individual studies 1++: High quality MAs, systematic reviews of RCTs or RCTs

with very low bias risk 1+: Well conducted MAs, systematic reviews of RCTs or RCTs

with low bias risk 1-: MAs, systematic review of RCTs or RCTs with high bias risk 2++: High quality systematic reviews of case control or cohort

studies with very low bias risk 2+: Well conducted case control or cohort studies with low bias

risk 2-: Case control or cohort studies with high bias risk and/or

significant risk that relationship is not causal 3: non-analytic studies 4: expert opinion

Body of evidence: Good quality: Further research is very unlikely to change our

confidence in the estimate of effect

American Academy of Ophthalmology members, and other ophthalmologists


Origin, Publication Date

Interventions of Interest

Evidence Levels and Recommendation Grading Target Population

Moderate quality: Further research is likely to have an

important impact on our confidence in the estimate of effect and may change the estimate Insufficient quality: Further research is very likely to have an

important impact on our confidence in the estimate of effect and is likely to change the estimate Any estimate of effect is very uncertain Grades of Key Recommendations: Strong Recommendation: Used when the desirable effects of

an intervention clearly outweigh the undesirable effects or clearly do not Discretionary Recommendation: Used when the trade-offs are

less certain-either because of low-quality evidence or because the evidence suggests that desirable and undesirable effects are balanced

MA = meta-analysis; RCT = randomized controlled trial


Appendix 3: Critical Appraisal of Included Publications

Table 4: Strengths and Limitations of Meta-Analysis using AMSTAR5

Strengths Limitations

Masters, 20177

Systematic literature search methodology described with inclusion/exclusion criteria and search terms Data extraction methodology described Studies in the analysis examined a large number of patients Tabulated study characteristics Focused purpose and scope Discussion on study limitations Statement of no COIs

No duplication of study selection or data extraction No details on literature selection process No critical appraisal of included studies Included studies were case series and survey studies only No reporting of statistical heterogeneity

COI = conflict of interest

Table 5: Strengths and Limitations of HTA/Guidelines using AGREE II6

Strengths Limitations


Explicit scope and purpose

Stakeholder and external experts involved in guideline

development

HTA development methodology described

Search methodology described and included Dutch, English,

French, and German language literature

Literature search methodology detailed including

inclusion/exclusion criteria

Literature selection and critical appraisal were done in

duplicate by independent reviewers

Data extraction methodology described Provided an economic assessment of refractive eye surgery

Unclear target audience

Acknowledged potential COIs of individual authors

No specific discussion on limitations of this HTA


Explicit target audience, scope, and purpose

Stakeholder and external experts involved in guideline

development

Recommendations clearly identifiable, linked to supporting

evidence, and graded

Guidance on recommendation implementation and patient

assessment

Information on cost-effectiveness

Literature search methodology detailed in alternate source

Guideline development methodology not detailed

Acknowledged potential COIs of individual authors

No specific discussion on limitations of the guidelines

COI = conflict of interest; HTA = health technology assessment;


Appendix 4: Main Study Findings and Authors Conclusions

Table 6: Summary of Findings of Included Studies

Main Study Findings Authors Conclusion

Masters, 20177

Annualized incidence of microbial keratitis infection DW soft contact lenses (8 studies, 2.1M patients)

Incidence per 10 000 (95% CI): 3 (2, 5) Soft contact lenses (8 studies, 239k patients)

Incidence per 10 000 (95% CI): 17 (14, 20) RGP contact lenses (8 studies, 885k patients)

Incidence per 10 000 (95% CI): 1 (0, 2) Post LASIK (9 studies, 670k patients)

Incidence per 10 000 (95% CI): 5 (4, 7) Microbial Keratitis incidence rate difference per 10 000 patients assuming 10% LASIK retreatment rate At 1 year (95%CI) DW soft contact lenses vs LASIK: -2.6 (-4.7, -0.4) (P = 0.0229) Soft contact lenses vs LASIK: 11.5 (8.0, 15.0) (P < 0.0001) RGP contact lenses vs LASIK: -4.7 (-6.6, -2.8) (P < 0.0001)

At 5 year (95%CI) DW soft contact lenses vs LASIK: 10.5 (7.1, 13.9) (P < 0.0001) Soft contact lenses vs LASIK: 80.8 (73.9, 87.7) (P < 0.0001) RGP contact lenses vs LASIK: 0.0 (-2.5, 2.5) (P = 0.9968)

At 10 year (95%CI) DW soft contact lenses vs LASIK: 26.9 (22.4, 31.3) (P < 0.0001) Soft contact lenses vs LASIK: 167.8 (158.2, 177.4) (P < 0.0001) RGP contact lenses vs LASIK: 5.8 (2.8, 8.9) (P = 0.0005)

The risk for microbial keratitis associated with soft contact lens wear over time seems to be higher than that after LASIK. Although more studies comparing complications after LASIK versus contact lens wear are needed, this study shows that in terms of microbial keratitis risk there might be a benefit for some patients, specifically extended-wear contact lens users, to have LASIK. (p73) Further comparisons looking at vision loss, dry eye, flap complications, and other complications of each modality should be performed to fully describe the safety and efficacy of contact lenses in relation to LASIK and refractive surgery in general. (p72)

CI = confidence interval; DW = daily wear; RGP = rigid gas permeable; LASIK = laser in-situ keratomileusis


Table 7: Relevant Recommendations and Statements of Included HTA/Guidelines

Relevant Study Findings and Statements


Comparative efficacy evidence availability:

This systematic review did not identify any systematic reviews or RCTs that evaluated refractive eye surgery versus spectacles or contact lenses (i.e. usual care). (p17) Direct comparisons of refractive surgery with usual care (spectacles or contact lenses) were not identified, nor were data on spectacle independency available. (p 28) The primary goal of the patients undergoing refractive surgery is to reduce their dependency on glasses or contact lenses. Yet the most commonly reported effectiveness measures in the scientific literature are visual acuity (e.g. UCVA 20/20) and the residual refractive error (e.g. correction within 0.5 D). These clinical parameters respectively measure the efficacy and precision of the correction technique. They can be proxies for glasses/contact lenses dependency after surgery although they do not perfectly distinguish between patients who still need a (partial) correction or not. (p39) Safety Conclusions:

Flap problems occur with LASEK and LASIK. PRK and LASEK are associated with more pain. Glares and halos are frequently reported with laser treatments (p40) Experts reported that dry eyes may be the leading adverse effect after LASIK, though mean symptoms and severity return to pre-operative levels at 6 months after surgery (p40)


Evidence-based Recommendations:

Strong recommendation, moderate evidence: Before refractive surgery, corneal topography should be evaluated for evidence of irregular astigmatism, corneal warpage, or abnormalities suggestive of keratoconus or other corneal ectasias. All of these conditions may be associated with unpredictable refractive outcomes, and keratoconus and the ectasias may be associated with ectasia progression following keratorefractive surgery. Strong recommendation, good evidence: Patients should be informed that there is a risk for night-vision symptoms after keratorefractive surgery. Statements:

Refractive Surgery Contraindications: (p 20) 1

Unstable refraction Certain abnormalities of the cornea Insufficient corneal thickness for the proposed ablation depth Significant cataract Uncontrolled glaucoma Uncontrolled external disease Uncontrolled autoimmune or other immune-related disease Unrealistic patient expectations Eyeglasses are the simplest and safest means of correcting a refractive error; therefore, eyeglasses should be considered before contact lenses or refractive surgery. A patients eyeglasses and refraction should be evaluated whenever visual symptoms develop. (p11)


Appendix 5: Additional References of Potential Interest

Table 8: Relevant statements from additional references of potential interest

Sia et al., 20159 The study included active-duty U.S. service members age 21 years or older with myopia or myopic

astigmatism ranging from -1.00 to -10.00 diopters (D) of manifest spherical equivalent (SE), manifest refractive cylinder up to 4.00 D, stable refraction for at least 12 months, and corrected distance visual acuity (CDVA) of 20/20 or better in both eyes. (p2153) No statements regarding the use of corrective lenses post-operatively or regarding operation of firearms.

Sia et al., 201410

A total of 167 active duty U.S. Army personnel, age 21 years or older with moderate to high myopia (defined as manifest spherical equivalent [MSE] of -4.00 D or greater) and corrected distance visual acuity (CDVA) of 20/20 or better in both eyes, were included in the study. All patients demonstrated refractive stability for at least 12 months prior to surgery. (p2) No statements regarding the use of corrective lenses post-operatively or regarding operation of firearms.

Canadian Vision Standards

4

Vision requirements for engagement in the Royal Canadian Mounted Police (2016) 4

Uncorrected visual acuity. 6/18 in each eye; or 6/12 in the better eye and 6/30 in the worse eye. Corrected visual acuity. 6/6 in the better eye and 6/9 in the worse eye. Refractive Surgery. Candidates who have undergone corneal refractive surgery to meet these vision requirements must demonstrate that refractive error has remained stable for 1 month for LASIK and 3 months for PRK. There are no problems with contrast sensitivity and glare. (p3)

Corneal Refractive Surgery

8

From the College of Physicians and Surgeons of Alberta (2012) 8.

A pre-operative evaluation by an ophthalmologist or optometrist registered in Alberta, which includes the following determinations: 1. absence of contraindications due to systemic and ocular disease; 2. refractive stability over time and especially after rigid contact lens removal; and 3. corneal topography, pachymetry and complete slit lamp and dilated fundoscopic examination (p12)

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