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Eye shifts are made basically by two kinds of movements - slow and fast. One should examine eye movements recordings to be evident in this (Fig. 5).

Fig. 5. Recording type of eyes movements (horizontal component) with fixation of a steady dot (right eye) by a subject. Upper recording - right eye, lower one - left eye. Beam deviation upwards corresponds to eye movement to the right, downwards - to the left. Vertical line - 1°calibration, horizontal line - 1 sec time, t - interval between saccades, A - saccadic amplitude

Eye fast movements recorded as vertical straight and thin lines were named "saccades" (originated from the old French term which means "a sail flap"). As the record shows, there are quite many saccades - two and more per second. Saccades of both right and left eyes are absolutely synchronous and of the same amplitude. The saccades are also oriented in same direction, Such a big number of saccades means that an eye's visual axis, or "the top of the Eiffel tower", changes its direction every half a second. Thus basing on this, one may conclude that the eye is constantly scanning the environment.



Individual differences.

Eye movements are individually very specific.

Fig. 6. Recording samples of eye movements with fixation of a steady dot (a=2'): 1 - П-form type, 2 - saccadic type, 3 - optokinetic type, 4 - drift type, 5 - explosive type

Nevertheless we distinguish five basic types of movements. The so-called П-type (Fig. 6, recording 1) is met rather often. In this case, saccade appears on a steady background of eye slow movements, and the next saccade turns the eye to the initial position in a certain time, finally recorded the Russian letter "П". This type of eye movements is most commonly met which is natural for well-balanced individuals. The П-type used to be common among shortsighted people.

Saccadic type (Fig. 6, recording 2) is demonstrated by many saccades appearing on a changing background of eye slow movements. The saccades themselves differ in amplitude and occur with ups and downs (skips) between them. The saccadic type is more natural with excitable persons.

Some patients demonstrated majority of saccades which mostly oriented in the same direction ((Fig. 6, recording 3). We named this type of eye movements optokinetic, which is a common thing for individuals with latent strabismus. In this case, some other defects of visual system may be probable.

Drift type of eye movements with few saccades and wide deviations of a movement slow component ((Fig. 6, recording 4, is ) normal for calm and phlegmatic individuals. Outburst type was considered as a separate one characterized by a saccadic series followed with a pause of 3-4 sec. ((Fig. 6, recording 5). This type is a very rare phenomenon. According to our studies, the described type is demonstrated by individuals suffering from mental diseases in a latent form.

Type of eye movements is permanent and remains stable, perhaps, for the whole life of an individual. It is easy to determine specific connection between a particular recording of eye movements and an individual who is under observation. We consider eye movements to be an easy way of person identification, perhaps even better than using fingerprints. In the nearest future one will probably invent a coded lock that will get unlocked with the help of an owner's sight into an entrance door peephole. Looking at the typical eye movements one could not help remembering Goethe's words:

"One's image of the World is different, it's true;
there's so much sense in it - for me and you"