Adaptometer

ADAPTOMETER (from Latin adaptare - to adapt and metron - measure), an instrument for determining the adaptation of the retina, based on the principle of determining the 'threshold of irritation' of the retina, i.e., determining the minimum visual perceptibility of the retina caused by precisely dosed light stimulation. The most precise is the Nagel adaptometer. It consists of a box 80 cm long, at one end of which are 3 lamps of 25 candles each, connected in sequence. The light from the lamps falls on a milky-white plate of 100 sq. cm, inserted at the other end of the box; this is the object of observation. The intensity of the light falling on the plate is dosed by a series of devices that allow reducing the light from the lamps to 1/1,000,000 of its original magnitude. Based on the amount of perceived light and the duration of adaptation, one can judge the course and state of adaptation in the subject being tested.