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Analysis of eye hydrodynamics on the basis of tests with a mechanical load applied
Author(s) -
STEIN A,
LYUBIMOV G,
MOISEEVA I,
IOMDINA E,
NAZARENKO L
Publication year - 2012
Publication title -
acta ophthalmologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.534
H-Index - 87
eISSN - 1755-3768
pISSN - 1755-375X
DOI - 10.1111/j.1755-3768.2012.2653.x
Subject(s) - outflow , intraocular pressure , mechanics , glaucoma , mathematics , materials science , ophthalmology , physics , medicine , meteorology
Purpose To use the results of tonography and other measurements on the mechanically loaded eye for obtaining information about its hydraulic system. Methods We carried out tests of two types: standard 4 min tonography using a digital indentation tonograph Glautest‐60 and discrete IOP measurements for up to 20 min after the load was removed. The experimental data were processed on the basis of our model of the eyeball as an elastic water‐filled shell, which makes it possible to correctly estimate the individual elastic properties. The entire pressure vs. time tonography curve was used. Results We introduce two parameters measurable from tonography: the IOP stabilization time and the limiting pressure in the loaded eye (the standard processing method yields one parameter). This and comparison with other data, including those available from literature, enabled us to test different hypotheses that specify the model and make it possible to calculate the hydraulic characteristics, e.g., the outflow facility coefficient. It is shown that the set of assumptions commonly used in processing the tonography data is inconsistent with the facts. The most intriguing are the apparent increase in the output (episcleral vein) pressure and the presence in the system of two characteristic times. Possible mechanisms to which these observations can be attributed are the pressure dependence of the outflow resistance and the capacitance of the outflow system. Conclusion Under mechanical actions, in the hydraulic system of the eye substantial changes occur. The correct interpretation of these, strongly individual, changes may be important for diagnostics. Tonography may be a useful tool but the method of processing its data needs modification.