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

OBJECTIVETo characterize dark-adapted and light-adapted oscillatory potentials (OPs) in human electroretinogram (EGR) elicited by flashing light stimulation of the same intensity.

METHODSDark- and light-adapted ERGs of normal eyes were studied. The frequency spectra of the extracted dark-adapted OPs and light-adapted OPs were analyzed by a fast Fourier transform. The peak frequency, latency and total power of the OPs were determined.

RESULTSThe averaged peak frequency, latency, and power of the dark-adapted OPs was 125.3∓9.93 Hz, 41.7∓3.56 ms, and 9.25∓5.55 (V·s)(2), as compared with 79.5∓6.79 Hz, 50.8∓5.36 ms, and 3.56∓2.18 (V·s)(2) for light-adapted Ops, respectively, showing significant differences in the parameters between dark- and light-adapted Ops (P<0.001).

CONCLUSIONSCompared with dark-adapted OPs, light-adapted Ops is characterized by a lower peak frequency and a lower power with a prolonged latency.

Adaptation, Ocular ; physiology ; Adult ; Dark Adaptation ; physiology ; Electroretinography ; methods ; Female ; Humans ; Male ; Oscillometry ; Retina ; physiology ; Young Adult

Light adaptation enables the vertebrate visual system to operate over a wide range of ambient illumination. Regulation of phototransduction in photoreceptors is considered a major mechanism underlying light adaptation. However, various types of neurons and glial cells exist in the retina, and whether and how all retinal cells interact to adapt to light/dark conditions at the cellular and molecular levels requires systematic investigation. Therefore, we utilized single-cell RNA sequencing to dissect retinal cell-type-specific transcriptomes during light/dark adaptation in mice. The results demonstrated that, in addition to photoreceptors, other retinal cell types also showed dynamic molecular changes and specifically enriched signaling pathways under light/dark adaptation. Importantly, Müller glial cells (MGs) were identified as hub cells for intercellular interactions, displaying complex cell‒cell communication with other retinal cells. Furthermore, light increased the transcription of the deiodinase Dio2 in MGs, which converted thyroxine (T4) to active triiodothyronine (T3). Subsequently, light increased T3 levels and regulated mitochondrial respiration in retinal cells in response to light conditions. As cones specifically express the thyroid hormone receptor Thrb, they responded to the increase in T3 by adjusting light responsiveness. Loss of the expression of Dio2 specifically in MGs decreased the light responsive ability of cones. These results suggest that retinal cells display global transcriptional changes under light/dark adaptation and that MGs coordinate intercellular communication during light/dark adaptation via thyroid hormone signaling.
Animals ; Mice ; Dark Adaptation ; Light ; Retina ; Retinal Cone Photoreceptor Cells/metabolism* ; Adaptation, Ocular ; Neuroglia/physiology* ; Cell Communication ; Thyroid Hormones

PURPOSE: To investigate the characteristics of the waveform generated by blue and red light stimulations in a dark-adapted electroretinogram (ERG) and those of cone responses in the dark-adapted condition. METHODS: The study subjects were 52 persons (88 eyes) with no previous medical history. The author recorded b-waves (rod response) with red light stimulation and the x-waves (dark-adapted cone response) that appeared before the b-waves. The author also recorded b-waves with blue light stimulation, which had the same amplitude as the b-waves from the red light stimulation. The differences with respect to age and gender were studied. Waveforms of the dark-adapted cone ERGs were recorded by using a digital subtraction technique. RESULTS: The x-wave always appeared before the b-wave with 0 dB (2.4 cd.s/m2) red stimulation. With blue stimulation, a b-wave equivalent to the b-wave stimulated with the red light of 0 dB intensity appeared at an average of -14.57 dB. The implicit time for the b-wave was delayed significantly for the male group. There were no significant differences between different age groups. The dark-adapted cone ERG demonstrated the waveform of a negative response followed by a series of oscillatory potentials (OPs) and a positive response. CONCLUSIONS: The cone responses were followed by the rod responses with red light stimulation of 0 dB in the dark-adapted ERG. The waveforms of the cone ERGs were obtained in dark adaptation with red and blue light stimulation.
Adolescent ; Adult ; Child ; Dark Adaptation/*physiology ; *Electroretinography ; Female ; Humans ; Male ; Middle Aged ; Photic Stimulation/*methods ; Retina/*physiology