The Establishment Of Equiluminance Turning Curve For Chromatic Visual Evoked Potential And It's Application In Chromatic-Visual-Function Detection

Partâ… A Model of Equiluminance Turning Curve for Chromatic Visual Evoked PotentialColor vision is one of the important visual functions of human.Color vision deficiency may directly affect visual detection and discrimination,as well as color discrimination per se.There are three parallel visual pathways.M-pathway is fast conducting and has a broad spectral sensitivity,and specialized for processing transient information.Thus, M-pathway has photopic luminosity function in which the sum of L- and M-cone signals(L+M pathway).And,M-pathway is sensitive to stimuli with low spatial and high temporal frequencies.The P pathway on other hand,is slower and good at process fine details,therefore,it is more sensitive to higher spatial and lower temporal frequencies,and process red-green(R-G) information in which L- and M-cone signals are antagonistic(L-M pathway).The function of the K pathway is partly contributed to blue-yellow(B-Y) information in which S-cones are opposed by a combined L+M-cone signal(S-(L+M) pathway).It is well acknowledged that visual evoked potentials(VEP) are useful for investigating the physiology and pathophysiology of the human visual system,including the visual pathways and the visual cortex.VEPs can be used effectively in association with psychophysics to study both normal and abnormal visual function. According to the different characteristic of the three pathways,we use high temporal frequency chromatic VEP stimulation for congenital red-green color deficiency through L+M pathway and we use low temporal frequency stimulation for acquired color vision deficiency through chromatic pathway.Establish the LMS color space and transfer the tristimulus values from CIE XYZ color space to LMS color space,and then find the equiluminance for normal and color defects from formula.Partâ…¡A Study on Equiluminance of Chromatic Visual Evoked Potential in Congenital Color Vision DeficiencyPurposeTo research a novel method of the quantitative measurement for color vision deficiencies.MethodsWe recorded Chromatic Visual evoked potential to red/green stimuli to separate different forms of anomalous color vision objectively.Stimuli were red/green reversing sinusoidal gratings(1 cyc/deg).Using a stepwise procedure,the luminances of the red and green parts were varied in steps in opposite direction,while the hue of individual squares and space-averaged luminance were held constant."Equiluminance turning curve" were established according to measurements at the each luminance conditions.ResultsThe VEP test of 36 normals and 16 congenital color vision deficiencies showed that the subjective equiluminance of normals was reached at a luminance ratio red/(red + green) = 0.50.At that point,the VEP amplitude reduced to the lowest.In 16 color anomalous subjects the VEP-dip positions were at different luminance ratio.Which means these dips were shifted compared to normal and the dip position were corresponded to the predicted luminance ratios obtained by calculations using the Smith-Pokorny transformation.Thus the equiluminance may allow objective assessment of color vision deficiencies.ConclusionsThe method overcomes the limits of all the traditional subjective methods used in clinical practice,fulfills the impersonal and quantitative requirements in color vision deficiencies test.Except that it distinguishes the dichromats and the anomalous trichromats efficiently,it also makes a foundation for the future research of color vision deficiencies.Partâ…¢Relationship of Chromatic Visual Evoked Potential and the Changes of Foveal Photoreceptor Layer in Central Serous Chorioretinopathy Patients PurposeThe purpose of this study is to investigate the relative involvement of chromatic and achromatic visual subsystems in central serous chorioretinopathy(CSC),and to correlate changes in the function of these subsystems with the changes of the foveal photoreceptor layer using Fourier domain optical coherence tomography(FD-OCT).Methods29 patients with CSC and 29 age-matched control subjects were tested and compared.Equiluminance was established psychophysically for each subject with heterochromatic flicker photometry(HFP).Equiluminant red-green(R-G),blue-yellow (B-Y),and yellow-black(Y-Bk) sinusoidal gratings(1 cyc/deg) presented in a pattern onset(100ms)-offset(400ms) mode.We measured the distance between the internal limiting membrane(ILM) and the external limiting membrane(ELM),and the length of the longest outer segment(OS) in 29 CSC eyes and 29 normal eyes on FD-OCT image.ResultsVEP mean latency was delayed significantly in CSC patients compared to controls. The VEP delay was greater for chromatic than for achromatic stimuli.Retinal thickness from ILM to ELM was associated significantly and selectively with B-Y VEP latency (r=-0.40,p=0.032).ConclusionsThe results are consistent with data which indicate the loss of photoreceptors in CSC resulting in a reduced thickness of the outer nuclear layer.Additionally,they are consistent with data which indicate that the photoreceptor loss is relatively greater in cones and,especially,the blue cones.