The Movement of Soft Contact Lenses on the Human Eye Exposed to +Gz Acceleration,
DEFENCE AND CIVIL INST OF ENVIRONMENTAL MEDICINE DOWNSVIEW (ONTARIO)
Pagination or Media Count:
Aircrew in the Canadian Forces who require optical correction are required to wear conventional spectacles. The use of contact lenses would alleviate many problems posed by eyeglasses. Concern has been expressed that contact lenses may slip excessively, or be lost from the eye under conditions of increased Gz. Experienced contact lens wearers were exposed to Gz in the DCIEM centrifuge. Each subject was wearing a pair of 15 millimeter soft contact lenses. Each lens was marked with a 12 millimeter white cross to facilitate observation of movement. Movement of the lenses was filmed with a high-speed LOCAM camera with telephoto lens. The resulting film was projected and the magnified movement along the -z axis was measured using the iris as a reference. These measurements were then corrected to real values. Each subject was examined with a slit lamp before and after Gz exposures for objective evaluation of fit and movement of the lenses. It was observed that the soft contact lenses were displaced along the -z axis with increasing Gz in most cases. After being displaced at peak G the lenses did not immediately return to their original position with reduction of G. It was further observed from the film that at no time was lens slippage great enough to prevent a subject from receiving optical correction. The amount of slippage between subjects is highly variable. Blinking action and facial tensing also affect the amount of movement.
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