Abstract
Abstract: :
Purpose:To have more understanding of electrical properties about ocular tissues, the impedances of the tissues of pig’s eye were measured. Methods:Impedances of cornea, lens, vitreous, retina, RPE + sclera were measured in laboratory 2 hours after pig’s eyes were enucleated at the butchery. The eyes were kept in icebox during transportation. Source signal was sinusoidal with fixed amplitude of 0.2 V and frequency was varied from 100 to 2.2 kHz. This signal was fed in a buffer operational amplifier. The output of the amplifier was connected in series with a resistor of 510 ohm and then linked to a plate Pt electrode. The contact area of the electrode to the tissue was 2.5 mm x 4 mm. Tissue was put on a gold plate, which had area of 6 mm x 6 mm that served as return loop for current. All the tissues were modeled as a resistor in parallel with a capacitor. By measuring the amplitudes and phases, the impedances of the tissues were obtained. Constant room temperature– control and tissue moist keeping were particularly concerned during the experiment. Results:The impedance, which contains resistance and capacitance of each tissue shows hyperbolic decayed profile with respect to frequency. The magnitudes of impedance for cornea, lens, vitreous, retina, RPE + sclera change from 2890 ± 300, 2750 ± 490, 4530 ± 520, 2220 ± 750, 1870 ± 220 ohms to 430 ± 50, 1170 ± 450, 3410 ± 480, 540 ± 140 and 500 ± 50 ohms/(10 mm2) respectively when the frequency varies from 100 Hz to 2200 Hz. The capacitances of these tissues are all in the range of 0.05 to 1.0 uF in which the capacitance of retina is larger. Conclusions:The impedance measurement for different ocular tissues can be a help for us to have more understanding of the electrical properties of these tissues. Further more these data may also be applicable to the electrophysiological studies in the associated field.
Keywords: computational modeling • electrophysiology: non–clinical