Sensitivity to stimulus onset and offset in the S-cone pathway

AbstractPrevious work [Vassilev, А., Mihaylova, M., Racheva, K., Zlatkova, M., & Anderson, R. S. (2003). Spatial summation of S-cone ON and OFF signals: Effects of retinal eccentricity. Vision Research, 43, 2875–2884; Vassilev, A., Zlatkova, M., Krumov, A., & Schaumberger, M. (2000). Spatial summation of blue-on yellow light increments and decrements in human vision. Vision Research, 40, 989–1000] has shown that spatial summation of brief S-cone selective stimuli depends on their polarity, increments or decrements, suggesting involvement of S-ON and OFF pathways, respectively. This assumption was tested in two experiments using a modified two-color threshold method of Stiles to selectively stimulate the S-cones. In the first experiment we measured detection threshold for small 100ms S-cone selective increments and decrements presented within three types of temporal window, rectangular, ramp onset/rapid offset and rapid onset/ramp offset. The ramp-onset threshold was higher than the ramp-offset threshold regardless of stimulus sign. In the second experiment we measured reaction time (RT) with near-threshold stimuli spatially coincident with the background to avoid spatial contrast. RT distribution for S-cone selective 500ms increments and decrements was unimodal and followed stimulus onset. An increase of stimulus duration to 1000 and 2000ms resulted in the appearance of responses following stimulus offset. The results suggest that, for brief S-cone selective increments or decrements, the human visual system is more sensitive to stimulus onset than to stimulus offset. Only for longer stimuli is the offset important, probably due to slow adaptation at a postreceptoral level

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 (>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

The Effect of Induced Intraocular Stray Light on Recognition Thresholds for Pseudo-High-Pass Filtered Letters

PURPOSE: The Moorfields Acuity Chart (MAC)—comprising pseudo-high-pass filtered “vanishing optotype” (VO) letters—is more sensitive to functional visual loss in age-related macular degeneration (AMD) compared to conventional letter charts. It is currently unknown the degree to which MAC acuity is affected by optical factors such as cataract. This is important to know when determining whether an individual's vision loss owes more to neural or optical factors. Here we estimate recognition acuity for VOs and conventional letters with simulated lens aging, achieved using different levels of induced intraocular light scatter. METHODS: Recognition thresholds were determined for two experienced and one naive participant with conventional and VO letters. Stimuli were presented either foveally or at 10 degrees in the horizontal temporal retina, under varying degrees of intraocular light scatter induced by white resin opacity-containing filters (WOFs grades 1 to 5). RESULTS: Foveal acuity only became significantly different from baseline (no filter) for WOF grade 5 with conventional letters and WOF grades 4 and 5 with VOs. In the periphery, no statistical difference was found for any stray-light level for both conventional and VOs. CONCLUSIONS: Recognition acuity measured with conventional and VOs is robust to the effects of simulated lens opacification, and thus its higher sensitivity to neural damage should not simultaneously be confounded by such optical factors. TRANSLATIONAL RELEVANCE: The MAC may be better able to differentiate between neural and optical deficits of visual performance, making it more suitable for the assessment of patients with AMD, who may display both types of functional visual loss

Case Report: Changes in Spatial Summation for Chromatic Stimuli in a Patient with Hypothyroidism Due to Autoimmune Thyroiditis Before and After Treatment with Levothyroxine.

Introduction: Acquired hypothyroidism is associated with a wide range of deficits including visual effects. Investigating colour vision mediated by S-cones has shown potential to detect diseases such as glaucoma or diabetes, however, studies of colour vision in hypothyroidism are scarce. Case presentation: In the present study we report spatial summation data of a patient with hypothyroidism due to autoimmune thyroiditis tested with S-cone specific stimuli. The area of complete spatial summation (Ricco’s area) is believed to reflect neural convergence and has been widely used to study structural changes to compensate for cell loss. We measured Ricco’s area before and after treatment with levothyroxine. Colour contrast thresholds were measured as a function of stimulus area in the retinal periphery, under S-cone isolating conditions. Ricco’s area was determined from the Threshold vs Area curve for either blue (S-cone increments) or yellow (S-cone decrements) stimuli. The patient’s data before treatment showed enlarged Ricco’s area (3 to 10 times larger) only for yellow stimuli compared to participants without hypothyroidism. After a treatment with levothyroxine and having reached euthyroidism, Ricco’s area decreased significantly (p < 0.05) for yellow stimuli, but remained unchanged for blue stimuli (p = 0.177). A second subject without hypothyroidism, who participated in both experiments did not show any significant differences for either blue (p = 0.081) or yellow stimuli (p = 0.78). Conclusion: The observed increase in Ricco’s area in hypothyroidism may be related to increased convergence to compensate for ganglion cell dysfunction. The results suggest that this process can be reversible after treatment. Examination of the S-cone system provides the potential to monitor this condition

Factors Affecting The Attitudes Of Students From Nurse And Midwifery For Professional Realization In The Field Of Child Health

Introduction: One of the most pressing problems in the health care system in recent decades is the shortage of nurses. A smaller and smaller share of the new graduates chose to work in the field of children's health. Students' attitudes towards professional realization can be significantly influenced during their training in a clinical setting. Therefore, the study of the factors influencing the readiness of student nurses and midwives to work with children is of great scientific and practical importance.Objective: To study the factors influencing the attitudes of students majoring in nurse and midwife for professional realization in the field of children's health.Material and methods: Analysis of literature sources, documentary, and survey method, through an online survey published on a specialized platform for online completion via the Internet. The opinion of 53 students majoring in Nursing and Midwifery at Medical Universities in the country was studied. The study was conducted in the period January - February 2021.Results and discussion: A significant part of the future nurses declare preparedness for professional realization in the field of children's health (74.50%). Among the surveyed students, the largest share of those wishing to work in Nurseries (24.40%), Children's Department and Neonatology (22.20%). Half of the respondents indicated that they were worried about working with children (51.10%), and according to 65.40% of them it was provoked by fear that they would cause them pain. The motivational factors for working with children are love for children, the positive energy that they radiate and the desire to help kids – which are our future. Negative attitudes about working with children are determined by the inability to cope with child suffering and the inability to communicate with children.Conclusion: The positive attitude of the future nurses and midwives for professional realization in the field of children's health is a guarantee for the successful solution of the problem with the shortage of specialists