Practical Considerations When Designing Refractive Surgery Policies

 

1. Refractive Restrictions

It is necessary to limit the range of refractive errors accepted for certain occupations to avoid the increased risk of pathology and optical effects associated with high refractive errors. Those with low levels of refractive error are deemed unsuitable for certain occupations due to the health and safety issues associated with poor unaided vision should their refractive correction be dislodged, (e.g. police force). Such individuals could be accepted if they had undergone a successful refractive surgery procedure.

Any recruiting restrictions placed on refractive surgery patients should be based on visual performance rather than other factors such as refractive error. The majority of individuals who have undergone a refractive surgery procedure will have excellent visual quality. Of the few who suffer a reduction in visual performance, it is rarely related to the size of their pre-operative refractive error. It is worth remembering that the risk of retinal detachment increases with increasing myopia and that reducing the refractive error does not affect this risk (Burton, 1989).

 

2. Recovery times

For myopia below –6.00D, the refraction tends to stabilise within 3-6 months of PRK and 1-3 months following LASIK. However, it can take up to 12 months for the visual performance to recover fully, particularly under conditions of low illumination. RK is generally not recommended due to the diurnal variation in visual performance and the reduction in ocular integrity.

 

3. Assessment of applicants with a history of refractive surgery

An examination to consider the suitability of a refractive surgery patient for a particular profession should include:

A slit lamp examination to confirm that the eye has returned to normal and that there is no significant loss of corneal transparency.

Refraction, topographic examination and pachymetry to screen for keratectasia. The candidate should provide details of their pre-operative refractive error and if possible details such as their post-operative corneal thickness and the nature of any complications that may have occurred during or following the procedure.

Candidates should have their visual performance assessed using a technique sensitive to the presence of scattered light and aberrations. The Snellen letter chart is inadequate alone but a low contrast logMAR chart or contrast sensitivity test provides some information.

Candidates should not be considered until all medication has ceased.

 

4.  
Detection of Laser Surgery

Applicants to professions that do not allow refractive surgery have been known to attempt to avoid disclosure of their ocular history. Radial keratotomy cases are easily identified since the radial scars are permanent. The detection of those who have undergone photorefractive keratectomy is more problematic because the corneal signs generally disappear once the initial stromal haze has subsided. LASIK tends to result in a faint C-shaped ring but this can fade completely in some patients. Possible methods for screening out candidates who have undergone a corneal refractive procedure include pachymetry and topography. However, measurements of the central corneal thickness vary significantly within the normal population, (Price et al., 1999) with a mean central thickness of 550nm but a range of 472 to 651nm. Since the cornea also thickens to some extent following both PRK and LASIK, pachymetry is a surprisingly insensitive method of identifying those who have undergone refractive surgery. The use of corneal topography maps to identify cases of refractive surgery has also been considered. Schallhorn et al. (Schallhorn et al., 1998) examined the sensitivity of topography to detect refractive surgery and found that even experienced observers exhibited only 77% sensitivity. Others have demonstrated an artificial neural network for recognition of corneal topography patterns after myopic refractive surgery with 99% accuracy, 99% sensitivity and 100% specificity (Smolek and Klyce, 2001). It is likely that topography in combination with a proven neural network would provide a more suitable test for screening candidates but topography alone would be insufficient.

However, if a quick and reliable method was available for detecting reduced visual performance post-refractive surgery, it is debatable whether there would be a need to screen candidates for previous refractive surgery, as long as they met the visual standard

 

© British Society for Refractive Surgery and Catharine Chisholm