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R. Shinder, B. C. Szirth, W. He, L. P. Frohman, R. E. Turbin; Amplitude, Latency and Constriction/Dilation Velocity of an Afferent Pupillary Defect as Measured With a Pupillometer. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5538.
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© ARVO (1962-2015); The Authors (2016-present)
The Neuroptics pupillometer is a device measuring pupillary response to a graded light source over a standard ambient background. Amplitude, latency, maximum constriction velocity (MCV), mean constriction velocity (CV), and dilation velocity (DV) are recorded. We attempt to quantify the asymmetry of the pupillary reflex (relative afferent pupillary defect, RAPD) in various optic nerve diseases using pupillometry measurements.
Pupillometry in each eye of 14 consecutive patients with an RAPD by swinging flashlight test were reviewed in a pilot analysis comparing ischemic to other optic neuropathies. The RAPD was also quantified in log units using neutral density filters placed over the more reactive pupil.
Mean amplitude of constriction in normal pupils (5.36 -> 3.14 mm, 41%) was more rapid than in pupils with an RAPD (5.05 -> 3.39 mm, 33%)(p=.006). Trends not reaching significance with this small sample size included MCV (5.78 for normal, 4.40 mm/sec for RAPD) (p=.117) and CV (2.28 for normal, 1.9 mm/sec for RAPD) (p=.236). Latency of constriction (.22 for normal, .23 sec for RAPD) and DV (1.05 for normal, .99 mm/sec for RAPD) were similar in both groups. The abnormally reacting pupil caused by ischemic optic neuropathy (ION) displayed a slower MCV (2.92 vs 5.23 mm/sec)(p=.039) and CV (1.22 vs 2.29 mm/sec) (p=.039). Trends not meeting significance included amount of constriction (23% vs 31%) (p=.204) and DV (.74 vs .98 mm/sec) (p=.423) compared to non-ischemic causes. Latency of constriction was similar among both groups.
Comparison of the difference in percentage amplitude constriction may allow the detection of an RAPD using the pupillometer, and comparison of maximum constriction velocity and mean constriction velocity may differentiate the RAPD in ischemic from other etiologies of RAPD. Although the case numbers were small in this pilot, they provide rationale to conduct additional pupillometry on 100 consecutive patients with an RAPD identified in the next 3 months that should help elucidate how disease type affects pupillometric parameters.
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