ERG analyses were carried out to evaluate the changes in the electrical activity of the retina between the right and left eye of control, diabetic, diabetic+CMV, and diabetic+IGFBP-3 NB animals [4] (link), [20] (link). Briefly, rats were dark-adapted overnight and ERG responses were recorded from both eyes together using platinum wire corneal electrodes, forehead reference electrode, and ground electrode in the tail. Pupils were dilated using 1% tropicamide solution (Alcon). Methylcellulose (Celluvise; Allergan, Irvine, CA) drops were applied as well to maintain a good electrical connection and body temperature was maintained at 37°C by a water-based heating pad. ERG waveforms were recorded with a bandwidth of 0.3–500 Hz and samples at 2 kHz by a digital acquisition system and were analyzed a custom-built program (MatLab). Statistics was done on the mean ±SD amplitudes of the a- and b- wave of each treatment group, including oscillatory potentials. Comparisons were made between the right (OD) and left eyes (OS).
Intraocular pressure (IOP) was measured monthly using a tonometer (TonoLab, Colonial Medical Supply, Franconia, NH). Briefly, the tip of the probe of the tonometer was placed at the cornea of the eye. During measurements, the tip of the probe hit the cornea six times and gave the IOP reading of that eye.
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