Elimination of the color discrimination impairment along the blue–yellow axis in patients with hypothyroidism after treatment with levothyroxine as assessed by the Farnsworth–Munsell 100 hue test.

Our previous study has shown that individuals with untreated hypothyroidism display significantly higher partial error scores (√PES) along the blue–yellow axis compared to the red–green axis than normal individuals using the Farnsworth–Munsell 100 hue test [J. Opt. Soc. Am. A 37, A18 (2020)]. We wished to determine how color discrimination may change when hypothyroidism has been treated to the point of euthyroidism. Color discrimination was reassessed for 17 female individuals who had undergone treatment for hypothyroidism, and the results were compared with 22 female individuals without thyroid dysfunction. No statistically significant difference was found in the total error score (√TES) for the first and second measurements for both groups (𝑝>0.45). The √PES for the hypothyroid group improved significantly in the previously impaired color regions after the treatment. Color discrimination defects found in untreated hypothyroidism can be negated with treatment of the condition over an appropriate time period.