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M. Yu, M.L. Thomas, R. Peter, B. Ridley, E.R. Hotchkiss, M.B. Russo; Relationship Between Some Parameters of Pupil-Light Reflection and Adaptation Light Level . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4077.
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Purpose: To investigate the relationship between some parameters of pupillary light reflex and the adaptation illuminance for further application of pupillary light reflex. Methods: The latency of constriction, the amplitude of constriction and the initial amplitude of pupil were measured in the dominant eyes of 23 normal subjects (18-35 years old) with FIT 2003 oculometer (Pulse Medical Instruments, Rockville, Maryland, USA) under 4 adaptation illuminances. The stimulating flash was generated by a group of LED from which luminance was automatically modulated according to the initial diameter of pupil at the beginning of stimulation to keep the luminous flux constant in the eye. The epoch of the stimulating flash was 250 ms. The viewing distance of the stimulating LED was 95 mm. The corneal illuminances for adaptation were 5, 60, 400 and 630 Foot Candles (Ft-cd) respectively. The measurements were taken after 20 minutes of adaptation for each illuminance level. Results: Corresponding to the corneal illuminance of 5, 60, 400 and 630 Ft-cd, the latencies of constriction were 281±18, 287±15, 278±15 and 278±14 ms respectively; the amplitudes of constriction were 1.14±0.24, 1.07±0.23, 0.659±0.146 and 0.639±0.176 mm respectively; and the initial diameters of pupil were 5.56±1.10, 5.55±1.13, 4.27±0.56 and 3.99±0.51 mm respectively. The amplitude of constriction decreased linearly with the increase of corneal illuminance from 5 to 400 Ft-cd. The amplitude of constriction and the initial diameter of pupil decreased significantly when the corneal illuminance was increased from 60 to 400 Ft-cd. Conclusions: In this preliminary analysis, the amplitude of constriction and the initial amplitude of pupil changed with the adaptation level significantly in the adaptation light range from 60 to 400 Ft-cd. Therefore, the adaptation status must be considered when quantitatively measuring the parameters of pupillary light reflex in this adaptation illuminance range.
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