tion of contraction. Most of the investigators (Duke-Elder, 1949; Lowenstein and Loewenfeld, 1958, 1963; Shaknovitch; Talbot, 1938; Tschirren, 1947; Walsh, 1910; Weiler, 1910) agreed that the latency period of pupil contraction ranges from 0.2 to 0.3 second. Some authors, however, have reported shorter latency periods; for example, Fuchs (1903) reported 0.12 second, Dolének (1960) 0.126 to 0.295 second, and Gradle and Eisendraht (1923) 0.1875 second. At the other end of the time scale, von Arlt (1869) found the pupillary latency period to be 0.492 second and Donders (1864) 0.400 second.
There have been relatively few studies relating the pupillary latency period to other physiological factors. Schlesinger (1913) stated that it increased upon repeated stimulation; Loewenfeld and Lowenstein (1963) have maintained that it may vary among individuals and in the same individual under different experimental conditions.
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| Figure 1. Diagram of pupillary reflex to light stimulus (after Lowenstein and Loewenfeld). L.P.=Latent Period in pupillary contraction. |
