Features of Visual Dysfunctions in Patients with Primary Hypothyroidism and Thyrotoxicosis

Abstract

Purpose: to study the prevalence and nature of visual dysfunctions in patients with primary hypothyroidism and thyrotoxicosis.Material and methods. The material for this study was the results of a survey of 54 patients (108 eyes) with thyroid dysfunctions: 32 people (64 eyes) with primary untreated hypothyroidism and 22 people (44 eyes) with primary untreated thyrotoxicosis. Static automated perimetry and dedicated shortwave infrared (blue-yellow) perimetry were performed. The average total value of the photosensitivity of each (n = 74) tested point of the field of view was analyzed, the topography of the location of focal defects was studied, and the severity of impairments to photosensitivity was assessed by aggregate signs.Results. Reliably high sensitivity (92.6 %) and specificity (50.0 %) of short-wave infrared perimetry in relation to static automated perimetry were revealed. In thyroid dysfunctions, the prevalence of optic neuropathy reaches 93 % according to the data of short-wave infrared perimetry versus 7 % of static automated perimetry. It is manifested by a diffuse decrease in light sensitivity to blue stimulus with an increase in the depth of depression from the center to the periphery in both types of thyroid dysfunction. Against this background, with primary hypothyroidism, focal defects appeared in the form of first-order scotomas, and with primary thyrotoxicosis, second-order scotomas. Scotomas were located at the periphery of the central visual field, 20–30° from the fixation point. In the analyzed groups, high average group indices of the maximum corrected visual acuity were established, which allows us to speak about the safety of the photopic (cone) component of the visual analyzer.Conclusion. The pattern of photosensitivity disorders, the topography of the location of the loci of local defects revealed by the short-wave infrared perimetry, indicate that the earliest signs of optical neuropathy are manifested at the level of photoreceptors — selectively in the S-cones. Decreased sensitivity to blue stimulus (440 nm) refers to an acquired color anomaly called tritanopia; which can be present with high visual function, is most often associated with a decrease in the number of S-cones and a deficiency of retinol (the source of cyanolab synthesis).