OBJECTIVES: To explore the composition characteristic of event related potential （ERP） in different visual acuity levels, and to provide theoretical basis for the objective assessment of visual acuity. METHODS: Monocular stimulus was performed on 16 selected subjects. The subjects were required to look straight at the screen ahead and count the amount of stimuli from different directions. The pictures of optotype stimulus which corresponding to three different visual acuity levels were showed in the center of the screen. The ERP results were recorded separately. RESULTS: （1） The P₁ amplitudes of match stimuli recorded under the supra-threshold visual acuity level were higher than that of match stimuli recorded under the threshold and sub-threshold visual acuity levels. There was no significant difference between the P₁ amplitudes of match stimuli recorded under the threshold and sub-threshold visual acuity levels. The tendency of conflict stimuli was similar to that of match stimuli under three visual acuity levels. （2） In the 340-500 ms post-stimulus range, P₃₀₀ component was found under supra-threshold and threshold visual acuity levels; no P₃₀₀ component was found in corresponding time window under sub-threshold visual acuity. The differences of P₃₀₀ amplitudes among three visual acuity levels were statistically significant. The amplitudes from high to low were the supra-threshold, threshold and sub-threshold visual acuity levels. CONCLUSIONS ERP can be a potential new method for the objective assessment of visual acuity in forensic medicine.
Adult ; Evoked Potentials ; Evoked Potentials, Visual ; Humans ; Photic Stimulation ; Visual Acuity/physiology* ; Visual Perception

To investigate the effect of illumination on visual acuity and visual field in eyes with multifocal intraocular lens (IOL), the near and far visual acuity of the eyes with multifocal implants were compared to those of the eyes with monofocal implants in the diminished illumination, and the visual fields of two groups were also compared by the different target size and intensity. The near and far visual acuity of the eyes with multifocal implants were significantly decreased as compared to those of the eyes with monofocal implants under diminished illumination, and the visual field of the multifocal implanted eyes also significantly decreased as compared to that of the monofocal implanted eyes by the reduction of spot size and intensity. From the above results, it is assumed that the bifocal separation of incident light to two simultaneous focal points in the multifocal implants causes more decreased visual acuity and narrower visual field in the diminished illumination as compared to that of the eyes with monofocal implants.
Adult ; Cataract Extraction ; Female ; Humans ; *Lenses, Intraocular ; Light ; *Lighting ; Male ; Visual Acuity/*physiology ; Visual Fields/*physiology

OBJECTIVE: To establish an acuity inspection system with sweep pattern visual evoked potential (SPVEP) so as to provide the evidence for acuity objective inspection. METHODS: Based on the domestic sweep pattern visual evoked apparatus, sections of hardware were reformed and a manipulation program possessing false random control software was compiled. The SPVEP acuity for the 78 eyes (10 normal eyes, 10 ametropia eyes, 48 prevalence eyes, 10 false ametropia eyes) was estimated with our acuity objective inspection system, then compared with the E visual acuity of those eyes by statistical procedure. RESULTS: There was a close correlation between the SPVEP acuity and E visual acuity for 78 eyes (r2 = 0.946). CONCLUSION SPVEP acuity inspection system can be applied to estimate objective acuity.
Evoked Potentials, Visual/physiology* ; Forensic Medicine/methods* ; Humans ; Vision Tests/methods* ; Visual Acuity/physiology*

OBJECTIVEThe objective of this article was to review the current advances in diagnostic methods for Acanthamoeba keratitis (AK).

DATA SOURCESData used in this review were retrieved from PubMed (1970-2013). The terms "Acanthamoeba keratitis" and "diagnosis" were used for the literature search.

STUDY SELECTIONData from published articles regarding AK and diagnosis in clinical trials were identified and reviewed.

RESULTSThe diagnostic methods for the eight species implicated in AK were reviewed. Among all diagnostic procedures, corneal scraping and smear examination was an essential diagnostic method. Polymerase chain reaction was the most sensitive and accurate detection method. Culturing of Acanthamoeba was a reliable method for final diagnosis of AK. Confocal microscopy to detect Acanthamoeba was also effective, without any invasive procedure, and was helpful in the early diagnosis of AK.

CONCLUSIONClinically, conjunction of various diagnostic methods to diagnose AK was necessary.

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

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

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*

OBJECTIVES: To study the effect of different attentional conditions on the event-related potential （ERP） components generated by the visual information stimuli related to visual acuity, and provide a theoretical reference for clinical forensic visual objective evaluation. METHODS: With visual acuity optotypes as normal form of visual information stimuli, 15 volunteers as study subjects were supposed to account the visual acuity optotypes under the attentional condition of visual stimuli. Furthermore, the subjects were required to listen to the storytelling carefully under the non-attentional condition of visual stimuli, and after the examination, they needed to answer the story-related questions. All the EEG results of two different attentional conditions from the subjects were recorded by 32 channel ERP system. RESULTS: Under two attentional conditions, P₁ and P₃₀₀ components were evoked by the visual acuity optotypes on supra-threshold and threshold visual acuity levels, while only P₁ component were evoked by the visual acuity optotypes on sub-threshold levels. In the ERP waveforms evoked by the visual acuity optotypes on supra-threshold, P₁ and P₃₀₀ amplitudes under attentional condition were larger than that under non-attentional condition. CONCLUSIONS Attentional conditions can influence the detection of visual acuity. P₃₀₀ component can be used to distinguish the visual acuity levels with supra-threshold and sub-threshold under non-attentional condition.
Attention/physiology* ; Electroencephalography ; Evoked Potentials ; Evoked Potentials, Visual ; Humans ; Visual Acuity

OBJECTIVES: To analyze the Nogo-P3 component of event-related potential (ERP) in the process of visual acuity processing, to provide electrophysiological evidence for objective evaluation of visual acuity. METHODS: Twenty-six subjects with no other ocular diseases except for ametropia were recruited, and all subjects had uncorrected visual acuity both eyes 1/10 (evaluated using Monoyer chart). Block letter E with different visual angles and directions were used as graphic stimuli. The Go/Nogo paradigm was used for ERP studies. The visual angle of Go stimulation angle was 1°15', Nogo stimuli were 1°15', 55', 24' and 15'. The visual acuity test was performed on each of the two naked eyes separately in all subjects, and the characteristics of the Nogo-P3 component were analyzed. RESULTS: The latency of Nogo-P3 showed no difference between the stimuli of 1°15' and 55', and between Nogo stimulation angle 24' and 15'. There was significant difference between Nogo stimulation angle 1°15' and 24', and between Nogo stimulation angle 1°15' and 15' (P<0.05). There was significant difference between Nogo stimulation angle 55' and 24', and between Nogo stimulation angle 55' and 15' (P<0.05). No significant differences were observed in the Nogo-P3 amplitude among Nogo stimulation. CONCLUSIONS In the Go/Nogo paradigm, Nogo-P3 can reflect the cognitive response of subjects to Nogo stimulation, which can be used for objective evaluation of visual acuity.
Electroencephalography ; Evoked Potentials/physiology* ; Humans ; Photic Stimulation ; Reaction Time/physiology* ; Refractive Errors ; Visual Acuity

OBJECTIVE: To compare the vision objectively assessed by SPVERA with the illiterate E Acuity in normal subjects. METHODS: The effect of artificially induced image defocusing on visual acuities (Vas) measured by SPVEP and illiterate E chart measurement was studied in 14 normal subjects. SPVEP was recorded using vertical gratings of 8 different spatial frequencies ranging from 0.235 9 to 30.203 2 c/deg. The responses were averaged and displayed through the discrete Fourier transform on the monitor display. SPVERA was determined by extrapolating the PVER amplitude -spatial frequency function to baseline. SPVERA was compared with illiterate E visual acuity measured under the same conditions of optical defocus. RESULTS: With moderate defocusing (<+1.0 diopter (D),VA > 0.42), the SPVERA were equal to or poorer than the illiterate E visual acuity. With more defocus (> +2.0 diopter (D), VA < 0.3),the SPVERA became better than the illiterate E chart Visual Acuity. The correlation between the two acuities was r2 = 0.919. CONCLUSION SPVERA and the illiterate E visual acuity correlated to a certain degree. We conclude that the SPVERA is effective in estimating vision objectively.
Adult ; Evoked Potentials, Visual/physiology* ; Female ; Fourier Analysis ; Humans ; Male ; Middle Aged ; Pattern Recognition, Visual/physiology* ; Photic Stimulation ; Vision Disorders/physiopathology* ; Vision Tests/methods* ; Visual Acuity/physiology*