EVALUATION OF MIDTERM STABILITY OF NIGHT-VISION TESTS

Background: Dark adaptation rate, scotopic retinal sensitivity and con trast sensitivity under mesopic conditions, but not visual acuity, hav e been shown to be directly related to the ability to identify militar y targets at night. These parameters can be used to select personnel f or specific military tasks demanding excellent night vision, as well a s to assess pharmacological effects on night vision. Purpose: To evalu ate the midterm (2 to 6-week period) stability of night Vision tests b ased on assessment of the above parameters. Methods: Dark adaptation r ate, scotopic retinal sensitivity and contrast sensitivity under mesop ic conditions were studied in 16 young volunteers during a 6-week peri od. Results: Tests of scotopic retinal sensitivity (after 30 min of da rk adaptation) exhibited high reproducibility and a low fluctuation ra te, with a high correlation between values at week 0 and at 2-week int ervals during the following 6 weeks of the study (rs (week 0 to week 6 ) = 0.81, p = 0.0001). The reproducibility of mesopic contrast sensiti vity tests (average of 1.5, 3, 6 and 12 cycles per degree (cpd)) was f air (rs (week 0 to week 2) = 0.67, p = 0.0045), whereas that of dark a daptation rate tests was poor. Conclusions: In View of the reproducibi lity characteristics of these night vision tests, assessment of night vision ability in pilots and military person nel, as well as assessmen t of pharmacological effects on night vision, may be based on scotopic retinal sensitivity (after 30 min of dark adaptation) and contrast se nsitivity under mesopic conditions (average of 1.5, 3, 6 and 12 cpd).