OASC Bulletin 31
During this bulletin, we would like to cover the subject of Corneal Refractive Surgery for Aircrew. The submission is fairly heavy-going but it should serve to give you some guidance. As ever, if you need further information, you should contact your local AFCO. Please note that there seems to be an issue with the formatting of this message therefore some letter a's have been replaced for @ symbols for some reason.
Until quite recently Corneal Refractive Surgery (CRS) was not permitted in either existing aircrew or recruits, however increasing evidence has emerged, much of it from the USA, of the safety of CRS in the military flying environment. There are still hazards and problems associated with CRS which must be considered before embarking on surgery.
CRS may be performed by a number of methods. Photorefractive Keratectomy (PRK) involves the reshaping of the anterior corneal surface by photoablation using an ultraviolet excimer laser. The corneal epithelium is removed prior to treatment and grows back over the treated zone within 4-6 days. Laser Epithelial Keratomileusis (LASEK) is a modification of PRK where a thin flap of corneal epithelium is created. The underlying corneal stroma is ablated in the same way as PRK but the flap of epithelium is replaced and acts as a bandage lens. The visual outcome is very similar to PRK but pain and haze are reduced. Laser In-Situ Keratomileusis (LASIK) involves the cutting of an actual flap of corneal stromal tissue and ablating the underlying stromal bed, before replacing the flap. Disruption of the epithelial layer is kept to a minimum and this avoids the aggressive healing response that leads to the formation of haze. Pain is also minimised and visual recovery occurs within 1-2 days. For those with low levels of myopia, outcomes in terms of visual performance for all of these techniques are very similar.
It is impossible to guarantee the result of surgery as healing and scar formation vary however the final uncorrected visual acuity after PRK and LASEK is comparable 12 months after treatment; LASEK is associated with less pain and visual recovery is more rapid although LASEK does produce more intra-operative pain. The most common complications following surgery include dry eyes, haze and reduced best corrected visual acuity; more serious complications include infection, inflammation and problems with the corneal flap. Postoperative best uncorrected visual acuity has been reported at 6/12 or better (the minimum standard for pilot selection is 6/12 or better uncorrected in each eye) in 46-100% of eyes depending on the degree of initial short sightedness. It should be noted that postoperative 6/6 vision may be subjectively different from preoperative best corrected 6/6 vision due to a reduction in contrast sensitivity.
Aircrew are normally recruited at an age before ocular maturity when CRS may not provide long-term refractive stability. CRS is not recommended below the age of 21 for this reason; however aircrew recruits may be accepted subject to the following criteria:
(a) CRS by PRK, LASEK and LASIK only.
(b) A minimum of one year to have elapsed since surgery
(c) Minimum age at application of 22.
(d) Subject’s refraction to have been stable for at least 6 months.
(e) Recorded pre-operative refractive error must not exceed –5.00 to +2.00 dioptres in any meridian
(f) Post operative visual acuity within current aircrew visual recruitment limits
If the preceding criteria are met candidates are to be referred to the Consultant Adviser in Ophthalmology (RAF) for assessment by the Officer and Aircrew Selection Centre. OASC will continue to screen RAF candidates via corneal topography to identify those who have had undeclared CRS.
Corneal Refractive Surgery for Ground Branches
The following methods of surgical correction of long or short sightedness are considered suitable for candidates for ground branches on an individual, case by case basis:
(a) Photorefractive keratectomy (PRK)
(b) Laser epithelial keratomileusis (LASEK)
(c) Laser in-situ keratomileusis (LASIK)
(d) Intrastomal corneal rings (ICRs), otherwise known as Intrastomal corneal segments (ICSs).
Entry will not be considered for candidates who have undergone radial keratotomy (RK) or astigmatic keratotomy (AK). Documentary evidence must be produced to confirm that their preoperative refractive error was no more than +6.00 or -6.00 dioptres in either eye and the best spectacle corrected visual acuity no worse than 6/9 in either eye, in addition at least 12 months is to have elapsed since last surgery. There are to have been no significant visual side effects secondary to the surgery affecting daily activities or night vision and refraction is to be stable; as defined by two refractions performed on each eye at least 6 months apart, with no more than 0.50 dioptre difference in the spherical equivalent of either eye. Specialist visual function testing must have been carried out with satisfactory results at least 12 months following surgery, this is to include assessment of refraction, symmetry of visual acuity, high and low contrast sensitivity (with and without glare sources) or contrast acuity analysis, astigmatism, glare, corneal clarity, masked mild hypermetropia and night vision.
Please note that, although OASC will endeavour to answer generic questions that arise, we will not be engaging or commenting on individual cases. In those cases, the individual is advised to contact their nearest AFCO who will be able to deal with any queries. All information published is for information only.
Information regarding a career in the RAF can be found athttp://www.raf.mod.uk/careers
Last edited by OASC; 21st Jun 2011 at 15:02.