Chloroquine is now uncommonly used in favor of its derivative hydroxychloroquine. In the United States, hydroxychloroquine is most often used for its anti-inflammatory effects in rheumatology and dermatology. Clinical trials cancer chloroquine Chloroquine plus proguanil side effects Our results suggest that chronic exposure to hydroxychloroquine is associated with thinning of the perifoveal inner retinal layers, especially in the ganglion cell and inner plexiform layers, even in the absence of functional or structural clinical changes involving the photoreceptor or retinal pigment epithelial cell layers. The choroidal vasculature supplies the outer one-third of the inner nuclear layer, outer plexiform layer, outer nuclear layer, photoreceptors, and RPE. Because of this division of the blood supply to the retina, ischemic choroidal vascular lesions and ischemic lesions attributed to the retinal vasculature produce different histologic pictures. Figure 2a and 2b this classic representation of Plaquenil toxicity is a preservation of the outer retinal layers subfoveally with perifoveal loss of the IS/OS junction on both sides of the fovea. Perifoveal IS/OS junction loss is associated with perifoveal outer retinal thinning, resulting in an ovoid appearance in the central retina, creating the flying saucer sign. While early toxicity may be asymtomatic, patients with more advanced stage of toxicity may complain of color vision changes or paracentral scotomas. Its toxic effects on the retina are seen in the macula. Plaquenil and thinning outer nuclear layer of retina Comparison of Screening Procedures in Hydroxychloroquine Toxicity, Neurosensory Retina Hydroxychloroquine retinopathy cumulative dose Thinning of the peripapillary retinal nerve fiber layer pRNFL and ganglion cell + inner plexiform layer GCIP, observed on optical coherence tomography OCT, are known to be accelerated in MS, even in the absence of optic neuritis, which is common in MS. Retinal Layer Thinning in MS Advances With Disease Progression. How to Succeed in Plaquenil Screenings. CLINICAL SCIENCES High-Speed Ultra–High-Resolution Optical.. Rats exposed to a 12 h lightdark cycle at 32 footcandles show thinning of the outer nuclear layer of the central superior retina midway between the ora ciliaris retinae and the optic nerve. From the normal 12 layers at 6 months of age, the cellularity shows progressive reduction to 10, 8, or 6 nuclei or less by 9, 18, and 24 months, respectively. The inner retinal layers are significantly thicker and hyperreflective from the acute infaract. After the initial acute phase of the retina artery occlusion, the swollen inner retinal layers will start to atrophy. OCT scans will display thin inner retinal layers with fairly normal outer retinal layers. The pathogenic effect of plaquenil is the induction of lysosomal dysfunction in photoreceptors and retinal pigment epithelium RPE cells. A lysosome is a membrane-bound organelle found in the cytoplasm of most cells and it contains hydrolytic enzymes that function in intracellular digestive processes.