To study the effect of extrinsic controls on blinking
by examining blink parameters and tear stability among adapted soft contact lens (CL) wearers performing tasks that require varying amounts of visual concentration.
The Demographic Questionnaire, Contact Lens Dry Eye
Questionnaire, and Current Symptoms Questionnaire were completed by 15 adapted soft CL wearers (nine females). Three 55 s simultaneous measurements of tear film
stability via retroillumination and blinking
were obtained with a slit-lamp biomicroscope and 200 Hz video camera while subjects listened to music and played a video game with and without their habitual CLs. Interblink interval (IBI) and blink amplitude (BA) were calculated. The area of break-up (AB) was calculated for the retroillumination image before each blink. The Current Symptoms Questionnaire was completed four times throughout testing.
With the game compared to music, IBI was significantly longer and BA significantly decreased without CLs (p ≤ 0.001). With CLs, the IBI did not significantly change between tasks but the BA significantly decreased (p = 0.100). The AB significantly increased with CL and the game (paired t-test, p ≤ 0.001). The BA was significantly correlated with self-reported severity of dry eye
for all testing scenarios (Spearman r ≥ 0.5579, p < 0.0001) and several symptom measures (Spearman r ≥ 0.6262, p < 0.0001). The AB was significantly correlated with symptom measures including bothersome discomfort for the game with and without CLs (Spearman r ≥ 0.5064, p < 0.0001).
During tasks requiring concentration, the IBI increased (blink rate decreased) and many blinks were incomplete without CLs. With CLs, tear film
instability increased. Blinking
frequency also increased, but it remained high when subjects played the game, and symptoms of ocular irritation increased. This suggests that wearing soft CLs, even when fully adapted, provides enough extrinsic ocular surface stimulation to override internal controls and affect blink parameters.