Studies of the mechanisms of visual analyzer adaptation in remote space missions are of paramount importance in the domain of space medicine. Pathogenesis of ocular nerve edema, the fundamental symptom of space-flight associated neuro-ocular syndrome (SANS), remains unclear. One of the hypothesized SANS trigger is a change of the pressure gradient in the sclera lattice coat of the membrane due to fluctuations of both the intracranial and intraocular pressures in the absence of gravity. This work extended the previous studies of ocular hydrodynamics during 5-day simulation of the microgravity body effects by dry immersion. We present the results of intraocular hydrobalance analysis after 21-d DI with participation of 8 male subjects at the age of 24 to 35 years. Data of electron tonography and diurnal intraocular pressure measurements were correlated with the fluid balance dynamics. Ocular hydrodynamics disbalance was registered in 80 % of the subjects. Tonography revealed clinically significant changes in 25 % of the subjects. These results enabled determination of the degree and character of ocular hydrodynamics autoregulation in the condition of compensatory body hypohydration.