Retinal Toxicity Induced by Chemical Agents

Abstract

Vision is an important sense for humans, and visual impairment/blindness has a huge impact in daily life. The retina is a nervous tissue that is essential for visual processing since it possesses light sensors (photoreceptors) and performs a pre-processing of visual information. Thus, retinal cell dysfunction or degeneration affects visual ability and several general aspects of the day-to-day of a person's lives. The retina has a blood-retinal barrier, which protects the tissue from a wide range of molecules or microorganisms. However, several agents, coming from systemic pathways, reach the retina and influence its function and survival. Pesticides are still used worldwide for agriculture, contaminating food with substances that could reach the retina. Natural products have also been used for therapeutic purposes and are another group of substances that can get to the retina. Finally, a wide number of medicines administered for different diseases can also affect the retina. The present review aimed to gather recent information about the hazard of these products to the retina, which could be used to encourage the search for more healthy, suitable, or less risky agents.

Keywords: cell death; medicinal; medicinal herbs; natural products; neurotoxicity; pesticides; retina.

Figure 1

Schematic figure showing the areas affected by the pesticides. Effects in retinal vascularization and RPE are showed in the eye draw whereas in neural retina are represented in retinal scheme.

Figure 2

Schematic figure showing the areas affected by some drugs. Alterations in retinal vessels and RPE are represented in the eye whereas impact in retinal cell are showed in the retinal scheme.

Figure 3

Fundus image: white arrow shows a concentric epithelial degeneration around the fovea, called bull’s eye maculopathy.

Figure 4

Hydroxychloroquine toxicity: white arrow shows presence of parafoveal zone of hyperfluorescence on fluorescein angiography.

Figure 5

Multimodal imaging: (a) infrared light retinography shows confluent plaques of chorioretinal atrophy in posterior pole, with the macular area more preserved; (b) OCT shows marked impairment of the outer neurosensory retinal layer, retinal pigmented epithelium, and perifoveal choroid. Diffuse thinning is seen with marked atrophy of the outer nuclear layer, external limiting membrane, and ellipsoid zone. Diffusely increased posterior light reflectance demonstrates associated retinal pigmented epithelium atrophy. The foveal area maintains normal architecture but shows slightly increased internal reflectivity of the outer nuclear layer.

Figure 6

Tamoxifen retinopathy: (a) fundus autofluorescence image showing no abnormality; (b) optical coherence tomography: white arrow demonstrates ellipsoid foveal zone disruption and external limiting membrane hyperreflectivity.