Oscillatory potentials in electroretinogram as an early marker of visual abnormalities in vitamin A deficiency

Abstract

Abstract. Vitamin A deficiency (VAD) caused by malnutrition and certain intestinal diseases induces visual impairments, including night blindness and photoreceptor cell dysfunction as indicated by reduced a-and b-waves in an electroretinogram (ERG). The effects of VAD on the inner retinal layer cells, including amacrine and ganglion cells, remain to be elucidated. The functions of these cells are reflected in oscillatory potentials (OPs), another component of the ERG. The present study investigated inner retinal layer cell function in VAD rats by analyzing OPs. In the present study, VAD was induced by feeding Brown Norway rats a vitamin A deficient diet for 10 weeks. A reduced body weight and peri-papillary opacification indicative of papilledema without histopathological alterations were observed, which are considered early symptoms of VAD. At this stage, the ERG revealed reduced OPs as well as a-and b-waves at various intensities of light stimulation. Further analysis indicated that the ratio of the alterations in OPs was more significant than those of a-and b-waves. After 5 weeks of recovery, these changes returned to control levels. These results suggest that OPs are the most sensitive and early marker of VAD-associated visual impairment in the ERG. IntroductionRetinoids, derivatives of vitamin A (Vit A), have essential roles in visual phototransduction. In the initial step of visual phototransduction, conversion of 11-cis retinal to all-trans (AT) retinal occurs in photoreceptor cells subjected to light exposure. Vitamin A deficiency (VAD) reduces this activity and subsequent downstream reactions in photoreceptor cells. As a result, patients with VAD exhibit visual abnormalities, including abnormal dark adaptation and night blindness, which may eventually progress to a severe visual impairment (1-3). Consistent with these clinical symptoms, electroretinogram (ERG) recordings in humans with VAD show decreases in amplitudes or loss of a-and b-waves, which reflect the function of photoreceptor and bipolar cells, respectively (1,3). A previous study reported that a reduced a-wave and a partial reduction of b-wave are induced by feeding albino rats a Vit A deficient diet for 8 weeks, with disintegration of the outer segments of photoreceptor cells (4). In contrast to the established effects of VAD on the a-and b-waves in ERG and histological alterations in photoreceptors, the effects of VAD on oscillatory potentials (OPs) remain to be elucidated. OPs, which are components of the ERG, are considered to be generated by the inner retinal layer cells, including amacrine and ganglion cells (5) and the reduction of OPs is known to be associated with reduced contrast sensitivity in diabetic patients (6). VAD has also been reported to reduce contrast sensitivity (7). Therefore, although, to the best of our knowledge, there are no studies indicating that VAD directly affects the formation of OPs or the function of inner retinal layer cells, it was hypothesized that OPs in ERG recordings may be affected during a state of ...

Optical Coherence Tomography Assessment Before and After Vitamin Supplementation in a Patient With Vitamin A Deficiency

“…Although the effect of vitamin A deficiency on the inner layers of the retina remains unclear, a recent study in rats analyzed the effect of vitamin A deficiency in the oscillatory potentials of the electroretinogram (reflects the function of amacrine and ganaglion cells) and found a reduction of these potentials associated with vitamin A deprivation. 14 …”

The Role of Vitamin A in Retinal Diseases

“…The functional impairment may be demonstrated using electrophysiology [80][81][82]. Interestingly, S-cones were shown to be affected prior to the L and M cones [81].…”

“…Interestingly, hypovitaminosis A has also been associated with reversible ganglion cell thinning [83], the reason for which is not understood but may reflect other vitamin A roles in the retina. The functional impairment may be demonstrated using electrophysiology [80][81][82]. Interestingly, S-cones were shown to be affected prior to the L and M cones [81].…”

Electroretinogram Recording in Larval Zebrafish using A Novel Cone-Shaped Sponge-tip Electrode

“…Outer retinal function of larval zebrafish is thus established before 4 dpf, meaning that the ERG is measurable from this early age onwards. Because of the short experimental cycle and the high-throughput properties of the model, the ERG has been applied to larval zebrafish for functional assessment of disease models, analyzing color vision and retinal development, studying visual circadian rhythms and testing drugs 8,9,10,11,12 . However, current approaches for larval zebrafish ERG has some complexities that may make it harder to adopt.…”