Interventional procedures consultation document - photorefractive (laser) surgery for the correction of refractive error
NATIONAL INSTITUTE FOR CLINICAL EXCELLENCE
Interventional Procedure Consultation Document
Photorefractive (laser) surgery for the correction of refractive errors
The National Institute for Health and Clinical Excellence is examining photorefractive (laser) surgery for the correction of refractive errors and will publish guidance on its safety and efficacy to the NHS in England, Wales and Scotland. The Institute's Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisors, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about photorefractive (laser) surgery for the correction of refractive errors.
This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:
Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.
The process that the Institute will follow after the consultation period ends is as follows.
For further details, see the Interventional Procedures Programme manual, which is available from the Institute's website (www.nice.org.uk/ipprogrammemanual).
Closing date for comments: 23 August 2005
Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.
Current evidence on photorefractive (laser) surgery for the correction of refractive errors suggests that it is adequately safe and efficacious for use in selected patients with mild or moderate myopia. Evidence shows that it is less efficacious in patients with severe myopia and hyperopia.
|1.2||Clinicians wishing to undertake photorefractive (laser) surgery for the correction of refractive errors should ensure that patients understand the benefits and potential risks of the procedure, including failure to achieve the expected improvement in unaided vision, other visual disturbances, corneal infection and flap complications. These risks should be weighed against the alternatives of wearing spectacles or contact lenses. In addition, use of the Institute's Information for the public is recommended.|
|1.3||Clinicians should audit and review clinical outcomes of all patients who have photorefractive (laser) surgery for the correction of refractive errors. Further research will be useful and clinicians are encouraged to collect longer term follow-up data.|
Clinicians should have adequate training before performing these procedures. The Royal College of Ophthalmologists has produced standards for laser refractive surgery (www.rcophth.ac.uk/scientific/docs/RefractiveSurgeryStandardsDec2004.pdf).
|2.1.1||Photorefractive (laser) surgery is used to treat refractive errors such as myopia, astigmatism and low degrees of hyperopia.|
Refractive errors are usually corrected by wearing spectacles or contact lenses. Surgical treatments have been developed to improve myopia, hyperopia and astigmatism by re-shaping the cornea.
|2.2||Outline of the procedure|
|2.2.1||In photorefractive surgery, corneal re-shaping is achieved using excimer laser ablation. Excimer laser techniques include photorefractive keratectomy (PRK), laser epithelial keratomileusis (LASEK) and laser in-situ keratomileusis (LASIK).|
PRK involves the removal of the corneal epithelium by surgical dissection and excimer laser ablation of a calculated amount of the stromal bed of the cornea. LASEK is a modification of PRK; it uses dilute alcohol to loosen the corneal epithelium before lifting it from the treatment zone as a hinged sheet and then replacing it at the end of the procedure. In LASIK, a flap is created with a microkeratome; this is lifted during laser ablation and then repositioned.
A systematic review of the published evidence on these procedures was commissioned by the Institute.
|2.3.2||In seven randomised controlled trials (RCTs) included in the review, there were no significant differences in the proportion of eyes achieving the predicted refractive outcome between the three procedures for myopia or myopic astigmatism. Data from more than 2000 eyes treated with PRK for myopia showed that a median of 69% of eyes had achieved within 0.5 D of their intended correction, and that 89% had achieved within 1.0 D. Data from case series of more than 1800 eyes undergoing LASEK for myopia or astigmatism showed that a median of 75% of eyes were within 0.5 D and a median of 92% of eyes were within 1.0 D of their intended correction at 3 to 6 months follow-up. Data from eyes treated with LASIK for myopia or astigmatism showed that 77% (7309/9542) were within 0.5 D and 91% (8109/8885) were within 1.0 D of their intended correction at 3 to 12 months. One RCT found LASEK to be significantly more accurate than PRK for eyes with hyperopia.|
Final uncorrected visual acuity was similar for all three techniques. For more details, refer to the sources of evidence (see Appendix).
Ectasia, a condition which can result in corneal thinning, is a serious complication related to refractive surgery and can lead to loss of vision. Data from the review estimated the risk of ectasia following LASIK as a median of 0.2% (range 0 to 0.87%, overall rate of 40/10,806 eyes). However, many of the affected eyes may have been selected inappropriately for LASIK treatment, and with careful patient selection the rate might have been lower. Rates of ectasia were not reported following PRK, and very little information was reported about LASEK, with no cases of ectasia described in one case series of 171 eyes.
|2.4.2||In eyes treated for myopia, loss of best spectacle-corrected visual acuity was seen in a median of 0.5% (0-20.5%) of eyes treated with PRK, 0% (0-8.2%) of eyes treated with LASEK and 0.6% (0-3%) of eyes treated with LASIK. Patients with high myopia were more likely to lose two or more lines of best spectacle-corrected visual acuity than those with moderate to low myopia.|
|2.4.3||Flap complications may occur during LASIK and LASEK, requiring conversion to PRK or postponement of ablation (with LASIK), and occasionally there may be loss of best spectacle-corrected visual acuity. Epithelial in-growth was reported in LASIK in a median of 1.3% (0.0 to 4.4%) of eyes.|
|2.4.4||Microbial keratitis was only reported in LASIK studies and occurred in 0.0 to 0.16% of eyes. This incidence was similar to, or less than, that reported for contact lens wearers.|
|2.4.5||Other patient-reported problems included visual difficulty in low light conditions, corneal haze, light halos and problems with glare. The occurrence of significant corneal haze was reported following all three procedures (in 0.0 to 31% of eyes treated with PRK, 0 to 25% with LASEK and 0 to 2% with LASIK). Glare and night vision difficulties were less common after LASIK. For more details, refer to the sources of evidence (see Appendix).|
|2.5.1||These procedures can make it more difficult to detect glaucoma and to measure accurately the intraocular lens power required for cataract surgery. Techniques are available to address these difficulties, provided it is known that photorefractive surgery has previously been done.|
Chairman, Interventional Procedures Advisory Committee
|Appendix:||Sources of evidence|
The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.
Available from: www.nice.org.uk/ip320review
This page was last updated: 03 February 2011