November 2019

REFRACTIVE

Research Highlight
Examining long-term refractive results in the military


by Maxine Lipner EyeWorld Senior Contributing Writer


Dr. Cason performing refractive surgery on a member of the military
Source: John Cason, MD

 

Investigators in a recent study evaluated how military personnel who had PRK or LASIK fared in the long term, finding that nearly half continued to enjoy 20/20 vision for a mean of 8.2 years after refractive surgery.1
The study was a retrospective look at the many refractive surgery cases the military handles. “In the Department of Defense, we do about 40,000 patients per year, and in the Navy, it’s just shy of 10,000 cases per year,” said John Cason, MD. “We’re doing all of this refractive surgery and have been since 1993 when Dr. [Steven] Schallhorn first started doing the procedures here in San Diego.”

Operational importance

Unlike civilian patients who may have personal reasons for undergoing refractive procedures, in the military it is done primarily for operational reasons, Dr. Cason said. “For us, it’s a medical readiness issue so we can deploy to austere environments,” he said, adding that even when it comes to flying an airplane, a contact lens is not good enough since this could fall out. Likewise, wearing spectacles may interfere with protective equipment, such as the seal of a gas mask. In short, the military perceives refractive surgery as a very noble cause, Dr. Cason stressed. “In general, we view our uncorrected vision as a means to be able to see the enemy before the enemy sees us,” he said.
It is incumbent on the military to make sure that the results are not only safe and effective in the short term but also the long term. While short-term studies indicate that 97–98% of patients enjoy 20/20 acuity, there are not many refractive studies in general that examine the long-term effects, with most going out 2–3 years, Dr. Cason said. One exception is a study2 by Rosman et al. that examined 10-year data on PRK, Dr Cason noted, adding that it showed similar results to the recent study and thus indicates that the cornea was very stable after refractive surgery.

Military long view

The recent study by Dr. Cason and coinvestigators included 160 eyes followed up for a period as long as 17 years. “The average drift was about 1/10th of a diopter per year,” Dr. Cason said, adding that this could be due to lenticular thickness changes or to shifts of axial length.
The fact is that such changes vary among patients. If it is lenticular changes, lifestyle can play a role, Dr. Cason pointed out. A patient presenting with diabetes who spends a lot of time outdoors exposed to UV light and who is a smoker could potentially face advanced lenticular changes faster than someone who has a healthier diet and lifestyle. The fact that half of patients still have 20/20 or better vision not only speaks to the long-term stability of the procedure but also to the healthier regimen in general of the patients included in the study.
Dr. Cason discussed the Rosman et al. study further, noting that it found 41% of eyes in the PRK group and 42.5% of eyes in the LASIK group were within 1 D of intended correction 10 years after surgery. “For anyone doing refractive surgery, you can look at this study, the Rosman et al. study, and some other shorter-term studies and feel fairly confident that refractive surgery is safe and effective,” Dr. Cason said. “It improves the quality of life for our patients and is relatively long-lasting, withstanding the normal aging changes that occur as we get older.”
In Dr. Cason’s view, the minimal changes that occur over the long term bode well for refractive surgery. “Considering the normal aging changes that still occur as we get older, it’s impressive that the refractive results are so good in the long term,” he concluded.

About the doctor

John Cason, MD
Naval Medical Center
San Diego

References

1. Godiwalla RY, et al. Long-term outcomes of refractive surgery performed during the military. Mil Med. 2019. Epub ahead of print.
2. Rosman M, et al. Comparison of LASIK and photorefractive keratectomy for myopia from –10.00 to –18.00 diopters 10 years after surgery. J Refract Surg. 2010;26:168–76.

Relevant financial interests

Cason: None

Contact information

Cason
: john.b.cason.mil

Examining long-term refractive results in the military Examining long-term refractive results in the military
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