Color Vision in the Gas Station Workers of Isfahan City: A Quantitative Analysis With the Farnsworth D15 Color Test

Background and Objectives: The color vision evaluation of gas station workers in Isfahan City. Methods: This cross-sectional comparative study was performed on workers at gas stations in Isfahan; all the workers were men. The participants were divided into two 40-people groups of exposure and non-exposure (the members of the fuel sales department). The participants had better vision than 8/10 and no underlying problems or eye disease. Besides, examination, including color vision was performed for all subjects. Color vision was assessed using the D15 test under high to medium light conditions. Also, the color vision test was performed monocularly. Then, the obtained data were analyzed using SPSS V. 22. Results: The two study groups significantly differed in terms of color vision impairment index (P <0.001). Also, more color vision defects were seen in the group exposed to gasoline. The color confusion index (as the indicator of color vision defects) were 1.485 and 1.129 in exposure and non-exposure to gasoline groups, respectively. Thus, color vision defects were significantly higher in the exposure to gasoline group, compared with the control group. Conclusion: The results of this study showed a difference in color vision index between the two groups. Therefore, long-term exposure to organic solvents, such as gasoline in fuel stations may cause color vision loss.

Progressive Cone-Dystrophy, Cone-Rod Dystrophy, and Rod-Cone Dystrophies

Cone-rod dystrophies are retinopathies in which cones are mainly affected and rod-cone dystrophies (retinitis pigmentosa) are retinopathies in which rods are mainly affected. The most common symptoms in cone-rod dystrophies are a progressive decrease in central vision and color vision loss. The most common symptoms in rod-cone dystrophies are night blindness and progressive narrowing in the visual field. The common point in both diseases is photoreceptor cell apoptosis and death resulting from genetic damage. The aim of this review is to present up-to-date and recent literature information on cone-rod and rod-cone dystrophies.

Cone photoreceptor classification in the living human eye from photostimulation-induced phase dynamics

Human color vision is achieved by mixing neural signals from cone photoreceptors sensitive to different wavelengths of light. The spatial arrangement and proportion of these spectral types in the retina set fundamental limits on color perception, and abnormal or missing types are responsible for color vision loss. Imaging provides the most direct and quantitative means to study these photoreceptor properties at the cellular scale in the living human retina, but remains challenging. Current methods rely on retinal densitometry to distinguish cone types, a prohibitively slow process. Here, we show that photostimulation-induced optical phase changes occur in cone cells and carry substantial information about spectral type, enabling cones to be differentiated with unprecedented accuracy and efficiency. Moreover, these phase dynamics arise from physiological activity occurring on dramatically different timescales (from milliseconds to seconds) inside the cone outer segment, thus exposing the phototransduction cascade and subsequent downstream effects. We captured these dynamics in cones of subjects with normal color vision and a deuteranope, and at different macular locations by: (i) marrying adaptive optics to phase-sensitive optical coherence tomography to avoid optical blurring of the eye, (ii) acquiring images at high speed that samples phase dynamics at up to 3 KHz, and (iii) localizing phase changes to the cone outer segment, where photoactivation occurs. Our method should have broad appeal for color vision applications in which the underlying neural processing of photoreceptors is sought and for investigations of retinal diseases that affect cone function.

Multifocal and full-field electroretinogram changes associated with color-vision loss in mercury vapor exposure

We evaluated the color vision of mercury-contaminated patients and investigated possible retinal origins of losses using electroretinography. Participants were retired workers from a fluorescent lamp industry diagnosed with mercury contamination (n= 43) and age-matched controls (n= 21). Color discrimination was assessed with the Cambridge Colour Test (CCT). Retinal function was evaluated by using the ISCEV protocol for full-field electroretinography (full-field ERG), as well as by means of multifocal electroretinography (mfERG). Color-vision losses assessed by the CCT consisted of higher color-discrimination thresholds along the protan, deutan, and tritan axes and significantly larger discrimination ellipses in mercury-exposed patients compared to controls. Full-field ERG amplitudes from patients were smaller than those of the controls for the scotopic responseb-wave, maximum response, sum of oscillatory potentials (OPs), 30-Hz flicker response, and light-adapted cone response. OP amplitudes measured in patients were smaller than those of controls for O2 and O3. Multifocal ERGs recorded from ten randomly selected patients showed smaller N1–P1 amplitudes and longer latencies throughout the 25-deg central field. Full-field ERGs showed that scotopic, photopic, peripheral, and midperipheral retinal functions were affected, and the mfERGs indicated that central retinal function was also significantly depressed. To our knowledge, this is the first demonstration of retinal involvement in visual losses caused by mercury toxicity.