OBJECTIVES: To study the virtual reality-pattern visual evoked potential (VR-PVEP) P100 waveform characteristics of monocular visual impairment with different impaired degrees under simultaneous binocular perception and monocular stimulations. METHODS: A total of 55 young volunteers with normal vision (using decimal recording method, far vision ≥0.8 and near vision ≥0.5) were selected to simulate three groups of monocular refractive visual impairment by interpolation method. The sum of near and far vision ≤0.2 was Group A, the severe visual impairment group; the sum of near and far vision <0.8 was Group B, the moderate visual impairment group; and the sum of near and far vision ≥0.8 was Group C, the mild visual impairment group. The volunteers' binocular normal visions were set as the control group. The VR-PVEP P100 peak times measured by simultaneous binocular perception and monocular stimulation were compared at four spatial frequencies 16×16, 24×24, 32×32 and 64×64. RESULTS: In Group A, the differences between P100 peak times of simulant visual impairment eyes and simultaneous binocular perception at 24×24, 32×32 and 64×64 spatial frequencies were statistically significant (P<0.05); and the P100 peak time of normal vision eyes at 64×64 spatial frequency was significantly different from the simulant visual impairment eyes (P<0.05). In Group B, the differences between P100 peak times of simulant visual impairment eyes and simultaneous binocular perception at 16×16, 24×24 and 64×64 spatial frequencies were statistically significant (P<0.05); and the P100 peak time of normal vision eyes at 64×64 spatial frequency was significantly different from the simulant visual impairment eyes (P<0.05). In Group C, there was no significant difference between P100 peak times of simulant visual impairment eyes and simultaneous binocular perception at all spatial frequencies (P>0.05). There was no significant difference in the P100 peak times measured at all spatial frequencies between simulant visual impairment eyes and simultaneous binocular perception in the control group (P>0.05). CONCLUSIONS VR-PVEP can be used for visual acuity evaluation of patients with severe and moderate monocular visual impairment, which can reflect the visual impairment degree caused by ametropia. VR-PVEP has application value in the objective evaluation of visual function and forensic clinical identification.
Humans ; Evoked Potentials, Visual ; Vision, Ocular ; Vision, Binocular/physiology* ; Vision Disorders/diagnosis* ; Virtual Reality

There are irreversible eyeball structural changes in high myopic patients. These changes include axial length, corneal radius, anterior chamber depth, fundus degeneration, macula thickness, etc. There is a close relationship between the damage degree of visual function and these changes. The incidence of complications, such as vitreous opacity, posterior vitreous detachment, cataract, glaucoma, posterior staphyloma and retina detachment, is also highly related to the myopia diopter. More and more researches have indicated that the myopia diopter and the level of visual function are affected by multiple factors. It is promising to detect all of these changes by different kinds of methods, and to assess visual function through these changes. By clarifying these changes, it is also useful to distinguish traumatic damage from disease to provide evidence for forensic assessment of eye injuries.
Eye/physiopathology* ; Forensic Medicine ; Humans ; Myopia/pathology* ; Vision, Ocular/physiology*

OBJECTIVETo report a mathematical function that characterizes the double-pass line spread function (LSF) of the human eye. Determining analytical functions that represent the double-pass LSF is important because it allows modeling the optical performance of the eye.

METHODSOptical section retinal images, generated in normal human eyes using a modified slit-lamp biomicroscope, were analyzed to derive the double-pass LSF by plotting the intensity distribution of laser light reflected/ scattered from the vitreoretinal interface. Three mathematical functions (Lorentzian, Gaussian, exponential) were fitted to the double-pass LSF and the root mean square error (RMSE) was calculated to provide a measure of the goodness of fit.

RESULTSThe Lorentzian function provided the best representation of the double-pass LSF of normal human eyes. The full width at half maximum (FWHM) of the Lorentzian fitted curve was positively correlated with age, indicating that the double-pass LSF broadens with age. Furthermore, the goodness of fit of the Lorentzian function was significantly better in younger subjects as compared with older subjects, suggesting that the fitted function to the double-pass LSF may vary according to age.

CONCLUSIONThe results demonstrate an age-related change in the double-pass LSF width and the goodness of fit of the Lorentzian function.

Adult ; Convergence, Ocular ; physiology ; Eyeglasses ; Female ; Humans ; Male ; Myopia ; physiopathology ; Vision, Binocular ; physiology

This review summarizes objective assessment of visual function using visual electrophysiology. Objective assessment of visual acuity using pattern visual evoked potential (PVEP) and sweep pattern visual evoked potential (SPVEP), objective assessment of visual field using multifocal visual evoked potential (MVEP).
Electrophysiology ; Evoked Potentials, Visual ; Humans ; Photic Stimulation ; Vision Tests/methods* ; Vision, Ocular/physiology* ; Visual Acuity/physiology* ; Visual Field Tests ; Visual Pathways/physiology*

Cerebral Cortex ; growth & development ; physiology ; Evoked Potentials, Visual ; physiology ; Humans ; Infant, Newborn ; Infant, Premature ; growth & development ; Sensory Thresholds ; physiology ; Vision, Ocular ; physiology ; Visual Acuity ; physiology ; Visual Perception ; physiology

In the literatures on the human vision physiology and physics, there were reports about space resolution limit of 1' visual angle, frequency resolution limit of 5 nm and time resolution limit of 0.1" of human vision. However, there has been no report about the contrast resolution limit of human vision,especially the report of measuring method and result about the contrast resolution limit of human vision based on the modern digital image processing. Here we report a modern method for measuring the contrast resolution limit of human vision based on computer digital image processing technology, and we present the measured results and their mathematical models. The function relationships of contrast resolution limit varying with background gray in a photopic or a scotopic sights were illuminated respectively. It can be expected that such investigations with regard to human vision will establish the physiological foundation of the theories and techniques in hiding bodies and hiding figures (stealth), in anti-hiding bodies and anti-hiding figures, in the night vision system independent of infrared, as well as in their relative industries.
Algorithms ; Contrast Sensitivity ; physiology ; Female ; Humans ; Image Processing, Computer-Assisted ; methods ; Male ; Models, Theoretical ; Vision, Ocular ; physiology ; Young Adult

OBJECTIVES: To study the characteristic of contrast visual evoked potentials （CVEP） in patients with ocular trauma. METHODS: Sixty patients defined as ocular trauma by forensic clinical examination in our center were selected, and split into 0.2-0.3 （Group A）, 0.3-0.5 （Group B） and ≥0.5 （Group C） according to the best corrected visual acuity. The variation characteristics of wave amplitude and latency of CVEP under 100%, 25% and 10% contrast were observed and analyzed statistically. RESULTS: （1） Under the same contrast, the wave amplitude of P₁₀₀ decreased with the decrease of stimulus perspective. （2） Under the same stimulus perspective, the wave amplitude of P₁₀₀ decreased with the decrease of contrast （P<0.05）. （3） Under the contrast of 100% and 25% with the same stimulus perspective （except 100% 7' perspective stimulus）, the difference between group A and group B had no statistical significance （P>0.05）. Between group A and group C, group B and group C, the wave amplitude of P₁₀₀ gradually increased with the increase of vision （P<0.05）. Under the contrast of 10% with 15' stimulus perspective, the wave amplitude of P₁₀₀ increased with the increase of vision （P<0.05）. （4） Under the same contrast with the same stimulation perspective, the latency of P₁₀₀ wave shortened with the increase of vision, while the difference had no statistical significance （P>0.05）. Under the same stimulus perspective, the latency of P₁₀₀ wave was prolonged with the decrease of contrast （P>0.05）. CONCLUSIONS CVEP may become one of the possible methods for the evaluation of contrast visual acuity.
Evoked Potentials, Visual/physiology* ; Eye Injuries/physiopathology* ; Humans ; Pattern Recognition, Visual/physiology* ; Photic Stimulation ; Vision, Ocular ; Visual Acuity

OBJECTIVE: To bring forward a new method for automatic measurement of the translation and rotation of the eye movement. METHODS: A centroid method, edge filter, and ellipse fitting were used to get the accurate position of the eye center. The rotation angle of the eye was determined by Fourier-Translation arithmetic operators. RESULTS: The simulation image test and initial clinical experiment obtained a good precision. CONCLUSION This method can eliminate the influence of eyelid overlapping and illumination, which can measure the 3-dimensional eye movement accurately.
Electronic Data Processing ; Electronystagmography ; methods ; Eye Movements ; Humans ; Imaging, Three-Dimensional ; methods ; Models, Anatomic ; Models, Biological ; Nystagmus, Optokinetic ; physiology ; Reflex, Vestibulo-Ocular ; physiology ; Video Recording ; Vision, Ocular

The retinotopic topography of area 17 in cats was measured by optical imaging based on intrinsic signals. When stimulated with two neighboring gratings oriented orthogonally each other, which were positioned respectively in the upper and lower visual fields, one piece of cortex that had the retinal projection corresponding to the area around the border of the two stimulus gratings became blurred in the resultant function orientation map, because the neurons in this site received excitatory signals from both the horizontal and the vertical gratings via indirect ways. This functional map of the same cortex was compared with that elicited only by a horizontal or vertical grating stimulation in the whole visual field. Accordingly, the accurate position of the retinotopic eccentricity of the cortex in visual field can be demarcated by calculating the cross correlation coefficient of the two functional maps. Furthermore, compared with the electrophysiological measure of receptive fields of single cortical neurons, the retinotopic eccentricities revealed by optical imaging were identical. This experiment provides a fast and relatively accurate method to calculate the retinotopic eccentricities in a large cortical area of the visual cortex.
Animals ; Brain Mapping ; methods ; Cats ; Evoked Potentials ; Retina ; physiology ; Tomography, Optical ; Vision, Ocular ; physiology ; Visual Cortex ; physiology ; Visual Pathways ; physiology ; Visual Perception ; physiology