PRK effective for night vision goggle use

WASHINGTON — Photorefractive keratectomy can improve uncorrected visual acuity and visual resolution when night vision goggles are in use. According to a study published in the March issue of Ophthalmology, the procedure does not cause a loss of visual resolution.

Prem Subramanian, MD, PhD, and colleagues here at the Walter Reed Army Medical Center had 38 eyes of 19 patients undergo photorefractive keratectomy (PRK) for myopia and astigmatism. All patients were active-duty U.S. Army Special Forces soldiers. Follow-up was 3 months. Preoperative and postoperative uncorrected and best corrected visual resolutions through night vision goggles were assessed using a high-contrast tribar chart presented at four light levels. All patients had been trained in night vision goggle use before testing.

Uncorrected visual acuity at the 3-month postop was 20/20 or better in 33 eyes (86.8%). No eye lost 2 or more lines of best corrected visual acuity. Preoperative and postoperative low-contrast acuity showed no significant differences at all levels of resolution. Preoperative visual resolution through night vision goggles decreased systematically with decreasing night sky condition. Postoperatively, night vision goggle performance equaled or exceeded preoperative performance with best correction.

“This improvement may result in soldiers functioning better in a field environment, since their dependence upon and maintenance of glasses and contact lenses would be reduced. In fact, use of glasses or contact lenses can limit or even preclude use of night vision devices, as well as chemical protective masks,” Dr. Subramanian said.

The researchers also suggested testing patients postoperatively with more challenging tasks, “such as firing at a rifle range under night conditions to provide an additional means of assessing the effects of refractive surgery on the ability of soldiers to carry out their military missions.”