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Wednesday / March 20.
HomemistoryThe Final Verdict LASIK put to the Ultimate Test

The Final Verdict LASIK put to the Ultimate Test

A recent study highlights that 96 per cent of pilots in active service for the US Armed Forces reported that their visual acuity improved after LASIK surgery. These people have the highest visual acuity needs of any individual. There couldn’t be a more stringent test. Is it now time to finally put to rest the irrational fear and fear-mongering about the safety of LASIK in appropriately screened patients?

For naval pilots within a defence group – those who fly ultra-fast planes and land them on aircraft carriers in challenging weather conditions in countries involved in war – good vision is clearly a matter of life or death.

Understandably then, in past decades, many highly competent young men and women, intent on pursuing a career in the armed services, have been turned away, just because their vision has let them down.

Fortunately, times have changed and so have the advances in refractive surgery. These advances have enabled these talented individuals to pursue their dreams in the armed services with more precise vision than they could ever have imagined.

What puzzles me, as an active outdoor true believer in refractive surgery, is that despite improvements in corneal and lenticular refractive surgery, the uptake remains very low

In America, armed forces personnel are able to undergo free refractive surgery on a priority basis as part of the Warfighter Refractive Eye Surgery Programme (WRESP).

WRESP is a significant medical program, which was started after numerous large studies were completed to assess the impact of refractive surgery on actively deployed military personnel. The US armed forces’ two preferred methods of refractive surgery are ASLA – also referred to as Photorefractive Keratectomy (PRK) –
and Laser in situ keratomileusis (LASIK).

I came across one of these studies recently, when preparing a lecture on the ‘Alphabet Soup of Refractive Surgery’ for Super Sunday, a conference hosted by the Optometry Association Australia’s NSW division in June. The study, by Tanzer et al, looked at the outcomes of LASIK on naval aviators1 – an occupation, I would argue, that has the highest visual needs of any, with the possible exception of micro-surgeons.

Specifically, the study looked at visual outcomes, safety and higher-order aberrations following LASIK. It was carried out at two naval sites and included over 600 eyes, mainly with myopia (548).

The findings were significant:

  • 98.3 per cent of the myopic eyes achieved a 6/6 or 20/20 result.
  • 40 per cent of myopic and mixed myopic eyes gained at least one line of corrected Snellen acuity. The results amongst the hyperopes was not quite as dramatic but still excellent with 95.7 per cent achieving 6/6 (20/20). Two myopic eyes lost two lines of corrected visual acuity.
  • 95.6 per cent of pilots believed the surgery had helped their effectiveness as naval aviators and a whopping 99.6 per cent would recommend it to their friends.1

This study is significant in a number of ways. Firstly, if the US Navy thinks this surgery is safe for its aviators who fly multimillion dollar jets, then the irrational fear and fear-mongering about the safety of LASIK in appropriately screened patients should be put to rest.

Secondly the visual outcomes are excellent, and again for appropriately selected patients, the most likely visual outcome is 6/6 (20/20).

Mental State Linked to Satisfaction

The advantage of performing studies in active servicemen and women is that the follow-up is excellent. If a soldier, sailor or marine is ordered to be somewhere for an examination, you know they will show up. This makes the conclusions drawn from data mined in these studies very powerful.

Another interesting study that caught my eye published in the Journal of Cataract and Refractive Surgery2 looked at the role of depressive symptoms in patient satisfaction with visual quality after laser in situ keratomileusis. Basically this study on 370 active servicemen found what many ophthalmic surgeons and optometrists suspected; that there was a link between preoperative mental state and postoperative satisfaction.

Patients completed the Armstrong Laboratory Survey Depression scale preoperatively and a questionnaire for visual quality and satisfaction postoperatively.

Patients with higher levels of depressive symptoms had 3.0 times higher odds (95 per cent confidence interval [CI], 1.2 to 7.4) of being less satisfied than those with low levels of depressive symptoms one month after LASIK (P <or= .02).

G Force and the White Rabbit

Perhaps my favourite, though slightly disconcerting, study looked at the effect of G force on the LASIK flap.3 In this study New Zealand white rabbits underwent LASIK surgery and were then strapped into the cockpit of a flight stimulator before undergoing a rapid-sequence ejection at 9GZ (nine times the force of gravity). While it was pleasing to see that the LASIK flaps were not affected by the experience, it was unclear how it affected the rabbits themselves.

Success Brings Disadvantages Too

The success of the Warfighter programme has also come at a logistic price for the US armed forces. A New York Times article (June 2006) described a new problem for the US Navy arising from the improved functionality of active and would-be pilots: “Aging fighter pilots can now remain in the cockpit longer, reducing annual recruiting needs. And recruits whose bad vision once would have disqualified them from the special forces are now eligible, making the competition for these coveted slots even tougher.”

The author went on to state that as a result: “For generations, Academy graduates with high grades and bad
eyes were funnelled into the submarine service. But in the five years since the Naval Academy began offering free eye surgery to all midshipmen, it has missed its annual quota for supplying the navy with submarine officers every year.”

Perhaps that’s not a bad problem to have.

An Australian Perspective

Like many ophthalmologists in Australia, I provide a consulting and surgical service to our armed service personnel.

Refractive surgery has been available to certain armed forces personnel in Australia for over a decade. Funding has been provided for those in specific roles such as SAS and Naval Divers. Strict screening and follow-up guidelines have been put in place to ensure optimal function prior to a return to active duty.

One of the patents I have worked with was a 39-year old Australian Naval Pilot. The Naval Pilot was referred to Vision Eye Institute for assessment of possible refractive surgery. He was flying helicopters and found that not only was his astigmatism disconcerting, he found that the spectacles prescribed affected his visual field. He was an active sportsman who enjoyed surfing and soccer.

The naval pilot had moderate astigmatism, but corrected to 6/6 in both eyes. I discussed with him the risks and benefits of the surgery and stressed the impact that any adverse event would have on his ability to fly helicopters.

At this point of time pilots in Australia must have ASLA (PRK) although studies such as the one mentioned above may lead to a change in these rules.

The Lieutenant proceeded to bilateral sequential ASLA surgery and by three months, he had achieved unaided visual acuity of 6/6 in each eye. He underwent his compulsory six-month review and was cleared to fly as visual standards one without glasses. He continues to fly helicopters for the Royal Australian
Navy and enjoys his surfing and soccer without the need for glasses.

So, Why the Hesitation?

Since 2009 improvements in intraocular lens surgery safety and predictability have resulted in increased uptake of refractive lens exchange, especially in hyperopic patients (see Figure 1). Yet despite this evolution, LASIK still makes up just two thirds of the surgical procedures I perform.

What puzzles me, as an active outdoor true believer in refractive surgery, is that despite improvements in corneal and lenticular refractive surgery, the uptake remains very low.

Since LASIK was first introduced to Australia in 1991 only an estimated 2-3 per cent of the eligible population have taken up the surgical option.

I imagine the reasons for this low uptake are multifactorial: contact lenses have continued to improve and for many patients, spectacles are not only perfectly acceptable, they are a fashion accessory.

Refractive surgery is neither perfectly safe nor perfectly predictable and I think the premature promotion of some technologies such as “Intracor” and corneal inlays, which have subsequently proven to be less than adequate, have muddied the refractive waters. Furthermore, the nomenclature surrounding the “alphabet soup” of refractive surgery is confusing for patient and medical professional alike.

Cost is also a barrier for many patients, especially in these uncertain economic conditions. Patients quite reasonably want some certainty surrounding their investment. However, for many people it is the fear of a catastrophic event that stops them from proceeding. In reality this risk for LASIK is extremely low but for many people, the fact that it could happen is enough.

Hopefully, published studies such as the LASIK one conducted by the US Armed Services will finally convince those eye care professionals who remain hesitant, and their patients, of the life changing results that can be achieved from this most common of surgeries.

Flap, Zap and Put it Back

LASIK remains the most common refractive surgical procedure in the world. It involves the creation of a 110um cornel flap with a femtosecond laser, the re-shaping of the cornea with an excimer laser and then the replacement of the flap.

I hesitate to quote the oft used short-hand for the technique; “Flap, Zap and put it back”. This phrase certainly captures the basic surgical steps but belittles the sophisticated nuances of the surgery and makes it sound both perfectly simple and perfectly safe.

While I would argue that LASIK is a safe procedure – I’ve had it done, myself – I would also assert that it is neither perfectly safe nor perfectly predictable. However, it is very accurate, especially for low to moderate levels of myopia… and the Visual recovery is rapid.

Prof. Gerard Sutton is Professor of Corneal Surgery and Refractive Surgery in Sydney, a consultant to the Royal Australian Navy and specialises in refractive, cataract and corneal surgery.

References

1. Laser in situ keratomileusis in United States Naval aviators. Tanzer DJ, Brunstetter T, Zeber R, Hofmeister E, Kaupp S, Kelly N, Mirzaoff M, Sray W, Brown M, Schallhorn S. J Cataract Refract Surg. 2013 May 8 [Epub ahead of print] From the Navy Surgery Center (Naval Medical Center, San Diego, California, and the Navy Refractive Surgery Center (Sray), Naval Medical Center, Portsmouth, Virginia, USA.)

2. (J Cataract Refract Surg. 2009 Feb) by Morse et al.Cornea 2003 Mar;22(2):142-5.

3. Laser in situ keratomileusis flap stability during simulated aircraft ejection in a rabbit model. Goodman RL, Johnson DA, Dillon H, Edelhauser HF, Waller SG.