China
Africa
Explore chapters and articles related to this topic
Toxins in Neuro-Ophthalmology
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Visual side effects of digitalis are less common than cardiac or other noncardiac symptoms. The spectrum of toxicity varies and includes decreased visual acuity, central scotomas or visual field reduction, photopsia most pronounced in daylight, photophobia, blurry or snowy vision, visual hallucinations, diplopia and dyschromatopsia including xanthopsia (yellow vision), cyanopsia (blue vision) and chloropsia (green vision). Dyschromatopsia can remain asymptomatic and detected only by formal testing. The mechanism of ocular toxicity postulated to be Na+ K+ ATPase inhibition [37–39]. Most appropriate test to support a diagnosis of digoxin ocular toxicity is photopic and scotopic electroretinogram (ERG) seeking for b-wave-delayed implicit time and decreased b-wave amplitude.
Erythropsia and Chromatopsia: Case Study and Brief Review
Published in Neuro-Ophthalmology, 2021
Michael S. Vaphiades, Brendan D. Grondines, Christine A. Curcio
Chromatopsia is defined as the perceived increase in environmental hue, much the opposite of dyschromatopsia or achromatopsia.3 It may result from changes to normal photoreceptor cell distribution, their ability to communicate with post-synaptic neurons, or changes to the post-synaptic neurons themselves. The most common causes of acquired chromatopsia are drug effects. There are hundreds of drugs that may induce chromatopsia.8,9 The more familiar ones to clinicians include xanthopsia or yellow hue, commonly caused by digoxin, in therapeutic levels, which may also cause disturbance of colour discrimination more specifically tritanopia (blue-yellow colour blindness) and non-specific loss of colour discrimination.10 Cyanopsia, or a bluish tinge is commonly due to the inhibition of cone phosphodiesterase (PDE), a group of enzymes whose prominent function is regulating cyclic guanosine monophosphate levels and therefore rod and cone light response properties.11 Because of the presence of PDE5 in choroidal and retinal vessels, these medications increase choroidal blood flow and cause vasodilation of the retinal vasculature.12 Other than drug effects, chromatopsia also occurs after cataract extraction, retinal diseases, and medical illnesses like jaundice.13