The eye’s optical system creates a limit as to how wide and deep the laser ablation should be, i.e., the wider the ablation, the deeper the laser must ablate into the cornea, which may result in delayed healing and prolonged visual recovery. The development of new lasers allows the creation of a wider ablation zone while removing the least amount of tissue. Studies have shown that this reduces problems with night vision and other side effects associated with laser refractive surgery.
Laser technology that provides variable optical zone sizes and beam shapes with scanning capabilities allows the eye surgeon greater flexibility in developing a more personalized laser vision procedure.
A spot laser may be adjusted so minimal spherical aberrations are produced and a larger optical zone is created. Results from clinical trials indicate that 67% of eyes had UCVA of 20/16 or better and 25%
had 20/12.5 or better. Additionally, there was an overall improvement in nighttime visual function and night driving, which is achieved by preserving the optical zone size and better shaping of the ablation
profile.
During traditional LASIK, the corneal fl ap is created with a mechanical microkeratome manipulated by the surgeon’s hand. While this method has worked well over the years, the performance of these devices can be unpredictable and is the source of a majority of surgical complications. These diffi culties result in irregularities in thickness between the central and peripheral areas of the fl ap that can induce postoperative astigmatism.
The IntraLase Femtosecond Laser Keratome, which received FDA approval in December 1999, is the fi rst blade-free technology for creating the corneal flap.
The laser keratome beam passes into the cornea at a predetermined depth, producing a precise cut that is reportedly more accurate than the microkeratome. Corneal fl aps made with the laser keratome appear to adhere more tightly to the corneal bed at the end of the procedure, which may eliminate problems with long-term fl ap displacement. A reported disadvantage to this new technology is that surgical time is increased, leaving the stroma exposed several minutes longer, which has led to reported complaints of photophobia and eye irritation for up to two days after surgery.
While it may take longer (4 to 7 days) to recover good vision, the approach appears to be associated with a lower incidence of dry eyes, corneal complications, and enhancement procedures compared with
traditional LASIK.
The FAA requires that civil airmen with refractive surgical procedures (e.g., PRK, LASIK) discontinue fl ying until their eyecare specialist has determined that their vision is stable and there are no signifi cant
adverse effects or complications. The airman should submit one of two documents to the FAA (a report from their eyecare specialist or “Report of Eye Evaluation” [FAA-8500-7]). These reports can be
submitted directly to the Aerospace Medical Certifi cation Division when released from care, or to their Aviation Medical Examiner during their next fl ight physical. This report should state:
“. . . . that the airman meets the visual acuity standards and the report of eye evaluation indicates healing is complete, visual acuity remains stable, and the applicant does not suffer sequela, such as glare intolerance, halos, rings, impaired night vision, or any other complications. . . .”
(Guide for Aviation Medical Examiners, July 2005)
If you are a pilot contemplating refractive surgery, consult an eye care specialist to determine if you are a good candidate for laser refractive surgery. Although the FAA and most major air carriers allow laser
refractive surgery, professional aviators should consider how it could affect their occupational and certifi cation status. As with any invasive procedure, there are many variables that can infl uence the
fi nal outcome. You should understand all risks as well as the benefits before electing to have a procedure performed that could compromise your visual performance in the cockpit.
No comments:
Post a Comment