The purpose of the present study was to establish normal electroretinogram (ERG) parameters using 56 normal eyes of four dog breeds common in Thailand: poodle, Labrador retriever, Thai ridgeback, and Thai Bangkaew. Standard ERG findings were bilaterally recorded using a handheld multi-species ERG unit with an ERG-jet lens electrode for 28 dogs under preanesthesia with diazepam, anesthesia with propofol, and anesthesia maintenance with isoflurane. There were significant differences in the mean values of ERG amplitudes and implicit times among the four dog breeds (p < 0.05) except for the b-wave implicit time of the photopic 30 Hz flicker response with 3 cd.s/m2 (p = 0.610). Out of the four breeds, Thai Bangkaew had the longest implicit time (p < 0.001) of scotopic low intensity responses, b-wave of scotopic standard intensity responses (3 cd.s/m2), a-wave of the higher intensity response (10 cd.s/m2), and a-wave of the photopic single flash response (3 cd.s/m2). For the b/a ratio, only the ratio of the Cone response was significantly different among the different breeds. In this summary, normal ERG parameters for four dog breeds were reported. Data from the investigation supported the hypothesis that determination of breed-specific limits of normality for ERG responses is necessary for individual clinics and laboratories.
Animals ; Dogs/genetics/*physiology ; Electroretinography/veterinary ; Reference Values ; Retina/*physiology

The Naka-Rushton equation of the form, R = R(max) I(n)/(I(n)+K(n)), has been used to describe the b-wave luminance-response function of the scotopic electroretinogram. Rmax is the asymptotic value of the b-wave amplitude as a function of stimulus luminance I, K is the luminance that produces a b-wave amplitude that is one-half R(max), and n is a dimensionless constant that controls the slope of the function. These three parameters are often used in research laboratories, since it can show selective changes in each parameter. The present study describes these parameters (R(max) = 354 +/- 28 uV, n = 0.80 +/- 0.06, log K = -2.26 +/- 0.15 log cd. sec/m2) and the values obtained from the derivative analysis of Naka-Rushton equation (Anastasi et al) in 20 normal pigmented rabbit eyes. However, Naka-Rushton equation accurately describes the function only at low to moderate flash luminances. At high flash luminances, a second amplitude increase appears in the function.
Animals ; *Dark Adaptation ; Electroretinography ; Light ; Rabbits ; Retina/*physiology

The Naka-Rushton equation of the form, R = R(max) I(n)/(I(n)+K(n)), has been used to describe the b-wave luminance-response function of the scotopic electroretinogram. Rmax is the asymptotic value of the b-wave amplitude as a function of stimulus luminance I, K is the luminance that produces a b-wave amplitude that is one-half R(max), and n is a dimensionless constant that controls the slope of the function. These three parameters are often used in research laboratories, since it can show selective changes in each parameter. The present study describes these parameters (R(max) = 354 +/- 28 uV, n = 0.80 +/- 0.06, log K = -2.26 +/- 0.15 log cd. sec/m2) and the values obtained from the derivative analysis of Naka-Rushton equation (Anastasi et al) in 20 normal pigmented rabbit eyes. However, Naka-Rushton equation accurately describes the function only at low to moderate flash luminances. At high flash luminances, a second amplitude increase appears in the function.
Animals ; *Dark Adaptation ; Electroretinography ; Light ; Rabbits ; Retina/*physiology

The optimal dark adaptation time of electroretinograms (ERG's) performed on conscious dogs were determined using a commercially available ERG unit with a contact lens electrode and a built-in light source (LED-electrode). The ERG recordings were performed on nine healthy Miniature Schnauzer dogs. The bilateral ERG's at seven different dark adaptation times at an intensity of 2.5 cd.s/m2 was performed. Signal averaging (4 flashes of light stimuli) was adopted to reduce electrophysiologic noise. As the dark adaptation time increased, a significant increase in the mean a-wave amplitudes was observed in comparison to base-line levels up to 10 min (p > 0.05). Thereafter, no significant differences in amplitude occured over the dark adaptation time. Moreover, at this time the mean amplitude was 60.30 +/- 18.47 microV. However, no significant changes were observed for the implicit times of the a-wave. The implicit times and amplitude of the b-wave increased significantly up to 20 min of dark adaptation (p > 0.05). Beyond this time, the mean b-wave amplitudes was 132.92 +/- 17.79 microV. The results of the present study demonstrate that, the optimal dark adaptation time when performing ERG's, should be at least 20 min in conscious Miniature Schnauzer dogs.
Animals ; Dark Adaptation/*physiology ; Dogs/*physiology ; Electroretinography/*veterinary ; Male ; Retina/*physiology ; Time Factors

In vertebrate visual system, information is firstly processed in retina. With the development of the multi-electrode recording technique, concerted activity has been extensively observed in retinal ganglion cells of different species. However, the role of concerted activity in visual information processing is still unclear and under debating. This article reviews the recent studies focused on concerted activity among retinal ganglion cells, discussing the issues about its category, detection and physiological function.
Animals ; Cell Communication ; physiology ; Humans ; Photic Stimulation ; Retina ; physiology ; Retinal Ganglion Cells ; physiology ; Visual Pathways ; physiology ; Visual Perception ; physiology

The aim of this study was to investigate the acute effects of ethanol administration on pattern-reversal visual evoked potential (VEP) and multifocal electroretinography (mfERG). Fifteen healthy subjects with no ocular or general disease were recruited. VEP (0.25° pattern sizes) and mfERG with 19 elements in two recording segments were performed before ethanol administration to obtain baseline for each participant. A few days later, the participants visited again for VEP and mfERG measurements after ethanol administration. Ethanol (0.75 g/kg) was administered orally over the course of 30 minutes. VEP and blood alcohol concentration were evaluated one hour after ethanol administration, and mfERG was conducted after pupil dilation. The Wilcoxon signed-rank test was used to compare parameter changes after randomized eye selection. The mean blood alcohol concentration was 0.034% ± 0.05% by volume. VEP revealed a P100 latency delay (109.4 ± 5.3; 113.1 ± 8.2; P = 0.008) after alcohol administration. The P1 implicit time of ring 1 on mfERG showed a trend of shortening after alcohol administration (37.9 ± 1.0; 37.2 ± 1.5; P = 0.048). However, the changes did not show statistical significance after Bonferroni correction. In conclusion, orally administrated ethanol (0.75 g/kg) appears to suppress the central nervous system, but it is not clear whether alcohol intake affects the retina.
Adult ; *Alcohol Drinking ; Electroretinography ; Evoked Potentials, Visual/*physiology ; Female ; Humans ; Male ; Retina/physiology

OBJECTIVE: To compare pattern-pulse multifocal visual evoked potential (PPmfVEP) with pattern-reversal multifocal visual evoked potential (PRmfVEP), and to investigate the symmetry of mfVEP between both eyes in normal individuals. METHODS: The multifocal Vision Monitor was used to observe the mfVEP. T-test and ANOVA were used to analyze P1 wave, amplitude and signal noise ratios (SNR) of two mfVEPs. RESULTS: The SNR and the P1 amplitude reached the maximum at the central visual field and decreased with the increase of eccentricity, and then decreased slowly. The amplitude of the PPmfVEP was significantly smaller than the PRmfVEP in the central retina, while in the peripheral retina the result was exactly the opposite. SNR and amplitude of the PRmfVEP showed no statistical difference in both eyes (P > 0.05). The variance of the amplitude at the same side of visual field was larger than that at the symmetrical visual quadrant. CONCLUSION mfVEP can reflect the visual function in different parts of retina objectively and exactly. PPmfVEP reflect the vision function of the central retina better than PRmfVEP. The stability of PPmfVEP is better than PRmfVEP in the central retina, while the result is opposite in the peripheral retina. The mfVEP is symmetrical in both eyes of the same individual.
Evoked Potentials, Visual/physiology* ; Humans ; Neurologic Examination ; Reference Values ; Retina ; Sensitivity and Specificity ; Visual Fields/physiology*

Research on how to totally or partially restore the vision has attracted more attention in the fields of neural engineering and tissue engineering. Neural interface and visual prosthesis offer alternative ways for partially repairing the visual impairment. The most widely used visual prosthetics are based on retinal stimulation. This article is a state-of-art review of the principles, technical details and the limitations of retinal prosthesis.
Blindness ; therapy ; Electric Stimulation ; Electrodes, Implanted ; Humans ; Prosthesis Design ; methods ; trends ; Retina ; physiology ; Visual Perception ; physiology

BACKGROUNDInner retinal oxygenation response (ΔPO(2)) is a worldwide study focus. However, the relevant reports on its radiological measurements are limited. In this study, magnetic resonance imaging (MRI), employing T1 weighted image (T1WI), was used to detect changes in ΔPO(2) following 100% oxygen inhalation in human subjects.

METHODSMRI was performed on a 1.5-T GE scanner system. After obtaining ophthalmologic data, eleven healthy individuals were given room air and 100% oxygen inhalation in order with different intervals. The MRI T1WI data were collected for 50 minutes. Data were analyzed with NIH IMAGE software.

RESULTSΔPO(2) was not panretinally uniform, and changes in oxygenation response were spatially inhomogeneous. During the initial phase (before 5 minutes) of 100% oxygen inhalation, preretinal vitreous water signals in the region of papilla optica increased rapidly. On the contrary, in other regions signals declined. In a later period (35 minutes), ΔPO(2) was panretinally fluctuated and increased slowly and attained homeostasis. After hyperoxia (45 minutes), delayed-enhancement of preretinal vitreous water signals in regions other than the papilla optica occurred, and then dropped down. There was no significant difference (P > 0.05) at any consecutive time point during and after hyperoixa.

CONCLUSIONSThese results reveal that hyperoxia can induce region-specific signal changes in preretinal vitreous water. Regulatory activity of the retinal vessel network may be the mechanism during 100% oxygen inhalation. Moreover, MRI is a valuable tool for investigating ΔPO(2) and exploring the mechanism of retinal oxygenation response physiologically or pathologically in vivo.

Adult ; Female ; Humans ; Magnetic Resonance Imaging ; methods ; Male ; Oxygen Consumption ; physiology ; Retina ; physiology ; Young Adult

OBJECTIVETo report a mathematical function that characterizes the double-pass line spread function (LSF) of the human eye. Determining analytical functions that represent the double-pass LSF is important because it allows modeling the optical performance of the eye.

METHODSOptical section retinal images, generated in normal human eyes using a modified slit-lamp biomicroscope, were analyzed to derive the double-pass LSF by plotting the intensity distribution of laser light reflected/ scattered from the vitreoretinal interface. Three mathematical functions (Lorentzian, Gaussian, exponential) were fitted to the double-pass LSF and the root mean square error (RMSE) was calculated to provide a measure of the goodness of fit.

RESULTSThe Lorentzian function provided the best representation of the double-pass LSF of normal human eyes. The full width at half maximum (FWHM) of the Lorentzian fitted curve was positively correlated with age, indicating that the double-pass LSF broadens with age. Furthermore, the goodness of fit of the Lorentzian function was significantly better in younger subjects as compared with older subjects, suggesting that the fitted function to the double-pass LSF may vary according to age.

CONCLUSIONThe results demonstrate an age-related change in the double-pass LSF width and the goodness of fit of the Lorentzian function.

Adult ; Aged ; Humans ; Mathematics ; Middle Aged ; Retina ; physiology ; Vision, Ocular ; physiology