Actually, the numerous studies of the different visual functions were done in Outer Space as well as during the modeling of the flight conditions. This way the primary attention was paid to the study of the following parameters of the visual system: visual acuity, chromatic and contrast sensitivity, accommodation and convergence (Y.P. Petrov, 1969, O.O. Riumin, 1980; A.P. Ginsburg, J. Vahderploeg., 1985; L.P. Zverev., I.G. Ovechkin., O.O. Riumin, 1996). It was found the visual acuity being highly stable and does not change during the flight (E.V. Khrunov, L.S. Khachaturiantz, V.A. Popov, 1974). The same data were obtained in the experimental researches in the modeling of the haemodynamic shifts typical for the weightlessness (J.H Kilp., Heublen , 1984).

At the same time, some investigations demonstrated the negative dynamics of the parameters of the accommodation and convergence, as well as the asthenopic symptoms in cosmonauts even at the beginning of the flight (Y.P. Petrov, 1969). Those symptoms were not progressed and some investigators did not obtain them at all and followed the conclusion on the stability of the accommodation during the flight (O.O. Riumin, 1980).Also, the studies of the color vision and color discrimination in cosmonauts (A.L. Kitaev-Smik, 1969; L.P. Zverev., I.G. Ovechkin., O.O. Riumin, 1996) showed the absence of the valuable variations of the mentioned parameters under the given condition. The results of the contrast sensitivity examinations in the spaceship’s crew during the flight demonstrated the 14-16 % decrement (A.P. Ginsburg, J. Vahderploeg, 1985) which believed by the authors can’t be the reason of the reduction in functional condition of the cosmonaut.

So, the analysis of the sources in the area from one hand let us draw the conclusion that the variations of the main visual functions of the cosmonaut during the flight are insignificant and are practically in the range of the physiological norm. From the other hand, the range of the investigations in outer space was obviously insufficient and was limited by the restricted set of the traditional methods.

PURPOSES

To develop the PC-based System of Connected Methods of the functional condition investigations on the different levels of the visual system’s (VS) organisation and to study variations of the cosmonaut’s VS parameters in the space vehicle "Soyuz" and on the board of the orbital piloted complex "Mir".

METHODS

The special PC-notebook program named "Ocular-complex" realizing the extended system of psychophysical methods of VS investigation was used. The functional core of the program was constituted by the “Ocular” program, Color Campimetry methods (Nesteruk L.I., 1992; Nesteruk L.I., 1994; Nesteruk L.I, Shamshinova A.M., Endrichovsky S.E., 1995; Nesteruk L.I., 1997; Shamshinova A.M., Endrichovsky S.N., Nesteruk L.I., Yacovlev A.A., 1997).

The following visual tests were realized there:

1. Visual Acuity verification in achromatic (standard) and colored (red on blue, green on purple and blue on yellow) tables.
2. Luminance Sensitivity Threshold (LST) detection in the Central Part of the Visual Field (CPVF). Color Campimetry (“Ocular” program), CPVF range from -10⁰ to +10⁰, red stimuli on achromatic background with luminance being equal to 0.1 cd/m2.
3. Colored combinations of LST studies. Color Campimetry (“Ocular” program), CPVF range from -10⁰ to +10⁰, red stimuli on blue background with luminance being equal to 2.0 cd/m2.
4. Rhythm's acquisition and reproduction’s dynamics after the complicated visual stimulation. “Ocular-Rhythmic” program (Nesteruk L.I, Malova J.V., 1994). The Subject was presented by 10 visual flashes of about 1 second interval between them (simple rhythm); the flashes had changed stochastically the shape (square, circle), size (1⁰ - 5⁰), position (0⁰ - 10⁰ from the center on the screen). The task was to remember the interval and to reproduce one by pressing any bottom on the keyboard for 50 times.
5. "Simple" cognitive functions investigation after the visual stimulation of varied spatial and temporal complexity. “Ocular-Gnostic” program. The Subject was instructed to press a sum (0-9) of 3 numbers (0-3) presented stochastically on the screen but equidistant from it’s center (5⁰); the size of the stimuli was equal to 2⁰; the time of the numbers exposition varied from 1 to 0.2 seconds. The coefficient of the correct answers in dependence of the exposition time was registered.

The Cosmonaut - Researcher Y. Baturin had performed visual tests every day, except of the 1st day on the Station "Mir". Pre- and after- expedition studies also were done including one right after the landing and during 1 week of adaptation.

The processing of the data of the present investigation was performed by the PC-package “Statistica”.

RESULTS

It was shown for acuity of vision being stable during the experiment (before, during and after the flight) except of the 9^th day of the flight, when only colored combinations (green on purple) demonstrated the negative dynamics for 50%, 10% and 10% in 3 examinations during the time interval of 8 hours.

The statistically significant achromatic and colored LSTs (“Ocular”) both was found to be increased during the flight in comparison with ones detected before and after the flight and was shown to have the different gradient in the center and paracenter of the visual field (Fig.4, 5, 6). The LST’s maximum during the flight (minimum sensitivity) was detected in 4-5 and 12-13 days. The LST’s minimum (maximum sensitivity) was detected in 8-9 days of the flight, after which the LST’s dynamics was negative till the end of the flight. After 1 week of adaptation (4, 6 and 8 days) the LST parameters reached the pre- flight level. That was not found the statistically significant difference between LST parameters before and after the flight.

Figure 4. LST Integral Coefficient	Figure 5. Achromatic LST	Figure 6. Colored LST

Rhythm's acquisition and reproduction dynamics (“Ocular-Rhythmic”) after the complicated visual stimulation (Fig.7, 8, 9) demonstrated the maximum time’s precision of reproduction (Mean Value) on the the 9^th - 10^th day of the flight, which has the statistically significant difference in comparison with the values before and after flight. At the same time the variability of reproduction (Standard Deviation) was also maximal, and the stability (inverse to the Gradient) of those parameters during the flight was minimal. It should be noted here that the Gradient was negative except of 2-3th days of the flight (in the Spaceship), 15^th day (before landing) and at the end of the 1^st week of adaptation after the flight.

Figure 7. Mean Value of reproduction's time interval	Figure 8. Standart Deviation of reproduction's time interval	Figure 9. Gradient of reproduction's time interval

"Simple" cognitive functions investigation (“Ocular-Gnostic”) after the complicated visual stimulation (Fig. 10) was found to have the maximal value of the coefficient in the flight (9^th - 10^th day, Station “Mir”), not in the earth based ones. Interestingly, the statistically significant difference of the coefficient was found only between ones before the flight and during the presence of the cosmonaut on the Station. No significant difference was found not only before and after the flight, but in the flight and after the flight too.

	Figure 10. The Coefficient of correct answers in "Simple" cognitive functions investigation

DISCUSSION

That was pointed out the data of the previous investigations on the visual functions in the real and modeled cosmic flight had demonstrated the absence of the principal shifts in the VS's functional condition of a cosmonaut. At the same time it is believed to be obvious, that the factors of the cosmic flight should make a significant influence on the VS. Those factors are known to cause the valuable changes in the following physiological (and connected psychological) processes: the start of the pathogenetic mechanisms in the general blood support system connected with haemodynamical effects of the weightlessness and hypodynamia as well as with the variations of the functional condition of the central and peripheral nervous system. Even the shape of the eyeball is changing when the weightlessness (tended to be more spherical).

The subjective reports of the cosmonauts as well as one of the cosmonaut - researcher Y. Baturin show sometimes the dramatic changes in vision.

The reason of the drawn contradictories might be seen in the following:

1. the traditional methods of the study of the functional condition of the VS during the cosmic flight oriented first to the examination of the accommodative – refractive system of the eye;
2. the methods applied for the evaluation of the condition of the sensory and gnostic levels are not sensitive and specific enough;
3. VS was not investigated as a whole functional subsystem of the organism under the conditions of the cosmic flight;
4. the principal impossibility of the interpretation of the results of applied methods in the correspondence to the levels of the VS’s organization.

The results of the present investigation show that an alternative approach to the solution of the given problem can be found using the "Ocular-complex" system, realizing psychophysical methods of investigation correspondent to the different levels of the VS’s organization (Nesteruk L.I., 1992; Nesteruk L.I., 1994; Nesteruk L.I, Shamshinova A.M., Endrichovsky S.E., 1995; Nesteruk L.I., 1997).

The interesting fact demonstrated with the "Ocular-complex" is the reliable difference in the functional condition of the VS before, during and after the space flight. This difference could be characterized as a negative dynamics during the space flight, which has a distinctive character showed by all the 5 applied tests, correspondent to the various levels of the VS. The improvement of major parameters about the 9^th day of the flight is correspondence with the data obtained on the cardio-vascular, respiratory and other functional systems (E.V. Khrunov, L.S. Khachaturiantz, V.A. Popov, 1974; C.L. Fisher, J.Degianni, 1982). The parameters of the tests during the 1^st week of the after flight adaptation was tended to rich the ones obtained before the flight, which is also supported with investigations of other functional systems.

The analysis of the results shows the evidence on the high stability of the visual acuity, the integrated parameter of the VS, to the influence of the damaging factors in the space flight. The study of the LSTs (Color Campimetry) in the central and paracentral parts of the VF on the achromatic and colored background let us reveal the tendency to the reliable decrement of the light and color sensitivity during the flight in comparison with the earth – based ones. It should be noted the presence of the 2 peaks of LSTs (decrements of the sensitivity) in the 4-5 and the 12-13 days of the flight. The best sensitivity (lowest LSTs) during the flight was registered in 8-9 days, which however were lower than one before the flight.

The remarkable fact of the improving of the coefficient of the “Simple” cognitive functions (“Ocular-Gnostic”) as well as it’s mounting to the maximum value during the flight, in comparison with the earth - obtained one, might appoint on the optimal level of the VS’s adaptation and on the best VS’s central part performance.

Analyzing the dynamics of the mentioned parameters the assumption could be drawn here on the some rhythmical, oscillatory character of the VS functioning under the space flight conditions, manifested in the periodical variations in the functional condition of the neuro- receptor and cortical levels of the VS.

Unfortunately, the insufficiency of the experimental material, restricted by the time of the flight as well as the number of investigations, does not let us to follow the mentioned tendency in time, and also to explain it from the point of the haemodynamical shifts happened in the organism under the weightlessness condition.

CONCLUSIONS

1. The reliable variations of the functional condition of the VS of the cosmonaut were detected before during and after the space flight by means of the "Ocular-complex" program.
2. Five tests of the "Ocular-complex" demonstrate principally different character of the parameter's variations, what can appoint on the detection by the complex of the various properties (levels) of the VS.
3. The data of the "Ocular-complex" tests correlate with the ones obtained on the other functional systems in the organism's adaptation during and after the flight.
4. The battery of the "Ocular-complex" tests can be recommended as the basic for the evaluation of the VS's functional condition in outer space.

ASKNOWLEGEMENT

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