[Comparative studies of twilight vision with the Mesoptometer I and II and the Nyktometer].

In 44 persons (19 to 39 years old, visual acuity better than 1.0), mesopic vision and sensitivity to glare were measured under binocular conditions by means of Mesoptometer I and Mesoptometer II (Oculus) and Nyktometer (Rodenstock). No differences were found between the two mesoptometers, but the nyktometer provided significantly worse results (a difference of 2-3 numbers). Mesopic vision was improved by minus glasses in 20% of the cases (Mesoptometer I), in 39% (Mesoptometer II) or in 50% (Nyktometer). The last instrument evoked the greatest amount of accomodation ("instrument myopia"). The best instrument for testing mesopic vision and sensitivity to glare under natural conditions was Mesoptometer I. Equal results were obtained by Mesoptometer II. Because of the easy handling and reduced reliability of the results, the nyktometer can only be recommended for screening examinations.