Spectral Sensitivity Measured with Electroretinogram Using a Constant Response Method

Abstract

A new method is presented to determine the retinal spectral sensitivity function S(λ) using the electroretinogram (ERG). S(λ)s were assessed in three different species of myomorph rodents, Gerbils (Meriones unguiculatus), Wistar rats (Ratus norvegicus), and mice (Mus musculus). The method, called AC Constant Method, is based on a computerized automatic feedback system that adjusts light intensity to maintain a constant-response amplitude to a flickering stimulus throughout the spectrum, as it is scanned from 300 to 700 nm, and back. The results are presented as the reciprocal of the intensity at each wavelength required to maintain a constant peak to peak response amplitude. The resulting S(λ) had two peaks in all three rodent species, corresponding to ultraviolet and M cones, respectively: 359 nm and 511 nm for mice, 362 nm and 493 nm for gerbils, and 362 nm and 502 nm for rats. Results for mouse and gerbil were similar to literature reports of S(λ) functions obtained with other methods, confirming that the ERG associated to the AC Constant-Response Method was effective to obtain reliable S(λ) functions. In addition, due to its fast data collection time, the AC Constant Response Method has the advantage of keeping the eye in a constant light adapted state.

Challenging a Myth and Misconception: Red-Light Vision in Rats

“…Most importantly, the rat retina does not only respond to high intensity red light, but low intensity red light of 1 mcd × s/m 2 (scotopic) and 1 cd × s/m 2 (photopic) already yield significant retinal responses and thus is sensitive to red light especially in scotopic conditions. The photopic spectral sensitivity function of rats peaks at 500 nm, accompanied by a smaller peak at 361 nm, corresponding to the absorption maxima of M-and UV-cones, respectively [13]. Therefore, both, the decrease in amplitude and the higher response threshold for red-light-induced retinal activity is in accordance with the spectral sensitivity function S(λ) proposed by de Farias Rocha et al [13].…”

“…Retinal function is typically assessed by electroretinography (ERG), where the sum field potential changes evoked by light stimuli are measured, which consist of a negative a-wave, followed by a positive b-wave (representing hyperpolarization and depolarization of photoreceptors and ON-bipolar cells, respectively). Photopic spectral sensitivity curves of image-forming photoreceptors of rats and mice have recently been determined by a constant response ERG, where response amplitudes were kept constant by adjusting light intensities throughout the UV-visible spectrum (300 to 700 nm) [13]. These measurements revealed two sensitivity peaks in rats at 362 and 502 nm, corresponding to the peak absorption wavelengths of their UV-and M-cones [13].…”

“…Photopic spectral sensitivity curves of image-forming photoreceptors of rats and mice have recently been determined by a constant response ERG, where response amplitudes were kept constant by adjusting light intensities throughout the UV-visible spectrum (300 to 700 nm) [13]. These measurements revealed two sensitivity peaks in rats at 362 and 502 nm, corresponding to the peak absorption wavelengths of their UV-and M-cones [13]. No significant responses to long wavelength light (above 620 nm) were detected [13].…”

“…These measurements revealed two sensitivity peaks in rats at 362 and 502 nm, corresponding to the peak absorption wavelengths of their UV-and M-cones [13]. No significant responses to long wavelength light (above 620 nm) were detected [13]. In addition to rods and cones, light is also perceived by the non-image forming intrinsically photosensitive retinal ganglion cells (ipRGCs) located in the inner retina.…”

Estudo eletrofisiológico de modelo animal para retinopatia da prematuridade

“…Como ilustrado no nomograma de sensibilidade espectral (Figura 3), os bastonetes apresentam pico de sensibilidade espectral em 498 nm e banda beta sensível ao UV (Toda et al , 1999). Os cones são divididos em dois tipos, com picos de sensibilidade em comprimentos de ondas curtos (360 nm, em roxo) e médios (509 nm, em verde) e possibilitando, desta maneira, visão fotópica dicromática Williams, 2007;Rocha et al, 2016;Weick;Demb, 2011). Eles estão organizados em duas faixas na retina: na porção ventral encontram-se os cones S e, na dorsal, os cones M, com uma faixa central de cones que coexpressam opsinas tanto para comprimentos curtos quanto por médios (Lukáts et al, 2005).…”