A comparison of contrast sensitivity and sweep visual evoked potential (sVEP) acuity estimates in normal humans.

PURPOSE: Several previous studies have demonstrated that for normal adult subjects the optotype acuity measured with charts is better than the acuity determined with the sweep visual evoked potential (sVEP) using gratings or checks. However, there is no difference in psychophysical measures of acuity with optotype or grating charts. Thus, it is unclear whether the acuity discrepancy between optotype charts and the sVEP result from the stimulus design or other methodological differences. The purpose of this experiment is to determine the relationship between acuities extrapolated from a contrast sensitivity function (CSF) that uses optotypes and the sVEP. METHODS: Normal subjects (N = 10) with acuity of 0.00 logMAR or better (ETDRS chart) were recruited for this study. Two commercially available systems were used to measure CSFs [i.e., the Beethoven System (Ryklin Software, NY) and the qCSF system (Adaptive Sensory Tech, CA)]. The stimuli for the Beethoven were sine wave gratings (0.75-18.50 cpd), and thresholds were determined with a 2-alternative forced choice (2-AFC) procedure combined with a staircase. The stimuli for the qCSF system were spatially filtered letters (10 possible letters, 10-AFC) with the letter sizes and contrasts determined by a Bayesian adaptive procedure. Visual acuity was determined by fitting the data with a double exponential equation and extrapolating the fit to a contrast sensitivity of one. The sVEP was obtained with the PowerDiva (Digital Instrumentation for Visual Assessment, version 3.5, CA). The stimuli were sine wave gratings (80% contrast, 3-36 cpd) counterphased at 7.5 Hz. The final acuity was the average of two estimates each derived from the average of 10 sweeps. RESULTS: The average logMAR chart (acuity converted to cpd), sVEP, Beethoven, and qCSF acuities were 36.6 ± 4.62 cpd (mean ± SD), 31.2 ± 4.59 cpd, 27.3 ± 7.38 cpd, and 27.6 ± 6.36 cpd, respectively. The logMAR chart acuity was significantly different from the other acuity estimates (all p values < 0.05). The sVEP, Beethoven, and qCSF acuities were not different from one another (all p values > 0.05). The Beethoven and the qCSF acuities had a good intraclass correlation coefficient (ICC = 0.85). CONCLUSIONS: Similar to previous publications, the sVEP acuity estimate was less than the optotype chart acuity. The acuity determined with the sVEP and the CSFs with letter and grating stimuli were not statistically different, suggesting that the difference in acuity with the sVEP and optotype charts does not result from stimulus differences. Other methodological differences must account for the discrepancy in sVEP and optotype chart acuity.

The objective visual acuity in normal adult C57BL/6J mice:assessment with sweep visually evoked potential / 眼科新进展

Objective To evaluate the reliability of sweep visual evoked potential (SVEP) for assessing the normal objective visual acuity in adult wild-type C57BL/6J mice.Methods A total of 6 wild C57BL/6J mice of either gender at 32-33 days of age were collected.After the mice were anesthetized,the recording electrode (a 2-mm diameter tungsten electrode) was placed at 3 mm lateral to lambda over the left cortex (contralateral to the stimulated right eyes) and advanced to 400 μm within the cortex,and the needle electrodes which placed in the forehead and tail served as the reference and the ground,accordingly.Left eyes (unstimulated eyes) were covered during the recording.The screen (mean luminance 25 cd · m-2) was placed 20 cm in front of the mice,thereby covering 100° (horizontal) × 82° (vertical) of the visual field.The mice were stimulated by vertically sinusoidal grating,which consisted of 11 spatial frequencies,stimulus contrast was 100％,and time frequency was 1 Hz;the entire sweep took 12 seconds (11 spatial frequencies + 1s pre-adaptation),and the values were averaged until the error bars for the data were stable.The VEP waveforms of visual cortex corresponding to the left and right eyes were recorded separately.At least 3-4 trials consisting of 20 events for different frequencies were averaged.Left and right eye were tested alternately.Then the coordinate system was established by using the spatial frequency logarithm as x-axis and the amplitude of the response obtained by the discrete Fourier analysis as y-axis,the objective visual acuity was obtained by extrapolation to zero amplitude of the linear regression through the 4 effective data points adjacent to noise.Results SVEP showed that the amplitude of N100 wave was maximal at a spatial frequency of 0.05 c · deg-1.With the increase of the stimulus spatial frequency progressively,SVEP decreased in amplitude and increased in latency.The cortical electrical signal could not be distinguished from noise at a spatial frequency of 0.65 c · deg-1.The average acuity of 6 mice was (0.56 ± 0.04) c · deg-1 for right eyes and (0.50 ± 0.04)c · deg-1 for left eyes respectively.There was no significant difference between the two eyes(P＞0.05);The visual evoked potential acuity of 12 eyes was (0.53 ±0.03)c ·deg-1.Conclusion SVEP could be used to estimate the mouse VEP acuity,which was closed to the behavioral visual acuity.However,the VEP acuity was more objective and accurate as well as time-saving.

Visuocortical bilirubin-induced neurological dysfunction.

This review addresses the question whether elevated levels of total serum/plasma bilirubin (TB) cause measurable neurological effects, specifically to visuocortical functioning. Past research in the area of vision and its relation to jaundice has taken advantage of flash visual-evoked potentials (VEPs). Using a steady state VEP, we developed preliminary data suggesting that children who had jaundice with TB levels between 10 and 25mg/dL, but who did not have kernicterus, have measurable changes in visual function, when compared to control infants who did not have jaundice. This non-invasive test offers information about vision thresholds, signal amplitudes, and suprathreshold changes after brain exposure to bilirubin. Here, we review this novel tool, the steady state VEP, and data suggesting that neurological changes occur in infants with moderately elevated TB levels.

Comparison of two methods of extrapolating sweep pattern visual evoked potential acuity / 中华实验眼科杂志

Background Sweep pattern visual evoked potential (SVEP) is an objective method of visual test.There is a clear correlation between SVEP acuity and subjective vision,but they are not identical.Recent studies showed that new regression method can improve the accuracy of SVEP acuity. Objective This trial was to investigate and compare the outcome between amplitude-spatial frequency (A-SP) regression method and amplitudelogVA (A-logVA) regression method in extrapolating the SVEP acuity.Methods SVEP was recorded in 113 eyes of 64 subjects using GT-2000 ( Guo Te,China) with the gratings of 10 different spatial frequency from 0.99 to 12.89 cpd as stimulus.The 1 13 eyes included cataract,glaucoma,corneal disease,optical neuropathy,retinal disease,ocular trauma,refractive error and normal eyes.The correlation were analyzed of SVEP acuity,decimal visual acuity and LogMAR visual acuity.The response were averaged and DFT on the monitor display.SVEP acuity was calculated by extrapolating 0 response amplitude.Results The correlation indices of decimal visual acuity curves obtained by the A-logVA function was 0.663,and that obtained by the A-SP function was 0.705.The positive correlation was seen between subjective decimal visual acuity and A-logVA decimal visual acuity (r =0.540,P＜ 0.01 ) and between subjective decimal acuity and decimal acuity calculated by the A-SP regression method (r=0.620,P＜0.01 ).SVEP decimal acuity calculated by the A-SP function regression method was significantly different from the that calculated by the A-logVA function regression method (Z =-8.688,P＜0.01 ).And the correlation indices of LogMAR visual acuity curves obtained by the A-logVA function was 0.733 and that obtained by the A-SP function was 0.715.The positive correlation was found between the subjective LogMAR acuity and that calculated by the A-SP regression method (r=0.700,P＜ 0.01 ) and between the subjective LogMAR acuity and LogMAR acuity calculated by the A-logVA regression method (r=0.710,P＜0.01 ).SVEP LogMAR acuity from A-SP function regression method was significantly different from the LogMAR acuity from A-logVA function regression method (Z=-8.748,P＜0.01 ).No significant differences of VA LogMAR were found in gender,eyes,type of disease and age(x2 =2.171,P=0.338;x2 =0.976,P=0.614;x2 =6.032,P=0.420;x2 =14.720,P=0.257 ).Conclusions SVEP can obtain the visual outcome in human.The amplitude-logVA function regression method is more accurate in extrapolating SVEP acuity.