The relationships between eye movements and head movements of the primate during gaze shifts are analyzed in detail in the present paper. Applying the mechanisms of neurophysiology to engineering domain, we have improved the robot eye-head coordination. A bionic control strategy of coordinated head-eye motion was proposed. The processes of gaze shifts are composed of an initial fast phase followed by a slow phase. In the fast phase saccade eye movements and slow head movements were combined, which cooperate to bring gaze from an initial resting position toward the new target rapidly, while in the slow phase the gaze stability and target fixation were ensured by the action of the vestibulo-ocular reflex (VOR) where the eyes and head rotate by equal amplitudes in opposite directions. A bionic gaze control model was given. The simulation results confirmed the effectiveness of the model by comparing with the results of neurophysiology experiments.
Bionics ; Eye Movements ; physiology ; Fixation, Ocular ; physiology ; Head Movements ; physiology ; Humans ; Ocular Physiological Phenomena ; Orientation ; Photic Stimulation ; Reflex, Vestibulo-Ocular ; physiology ; Saccades ; physiology

An application of digital signal processor (DSP) in the visual electrophysiology record system is presented in this paper. The system's design and implementation are described in detail. Results of its simulation and the clinical experiments are acceptable.
Adult ; Algorithms ; Computer Simulation ; Diagnosis, Computer-Assisted ; instrumentation ; methods ; Electrophysiology ; instrumentation ; methods ; Equipment Design ; Evoked Potentials, Visual ; physiology ; Female ; Humans ; Ocular Physiological Phenomena ; Signal Processing, Computer-Assisted ; Software Design ; Vision, Ocular

PURPOSE: We report a case of cortical blindness due to transient cerebral ischemia associated with general anesthesia. METHODS: A 45 year-old woman complained of bilateral visual loss after emergent incision and drainage for the treatment of extensive pyogenic abscess around the left mandibular space causing severe respiratory distress, and transient cerebral ischemia due to difficult tracheal intubation. At first ophthalmologic examination, 8 days after the operation, visual acuity was hand movement. Functions of external ocular muscles, blinking reflex, accommodation, pupillary light reflex, color vision test, intraocular pressure, and the findings of anterior segment, optic nerve and fundus were normal. Humphrey visual field examination showed nonspecific visual field defect, and pattern visual evoked potential examiantion showed flattening of waveforms. Both brain magnetic resonance imaging and electroencephalography were normal. However, brain single positron emission computerized tomography demonstrated general decrease of blood perfusion in the cerebrum including the occipital lobes. RESULTS: Without any specific treatment, her vision improved gradually, and 6 weeks after operation, it was 0.4 in the right and 0.7 in the left eye. After 3 months, it was 0.9, and no other abnormal ocular findings were noted on both eyes. CONCLUSIONS: Cortical blindness can occur by transient cerebral ischemia associated with general anesthesia, and its visual prognosis may be good.
Abscess ; Anesthesia, General* ; Blindness, Cortical* ; Blinking ; Brain ; Cerebrum ; Color Vision ; Drainage ; Electroencephalography ; Electrons ; Evoked Potentials, Visual ; Female ; Hand ; Humans ; Intraocular Pressure ; Intubation ; Ischemic Attack, Transient ; Magnetic Resonance Imaging ; Middle Aged ; Muscles ; Occipital Lobe ; Optic Nerve ; Perfusion ; Prognosis ; Reflex ; Visual Acuity ; Visual Fields

PURPOSE: Sildenafil citrate (Viagra(R)) acts as a relatively specific inhibitor of the type 5 phosphodiesterase isoenzyme (PDE5) in the corpus cavernosum. But, it also has a mild inhibitory effect on PDE6 in the retinal photoreceptor. Therefore, we studied the ocular side effects of sildenafil. METHODS: We tested the visual acuity, intraocular pressure, color vision, visual evoked potential (VEP), electroretinogram (ERG), anterior segment and fundus appearance. All tests were done before and after medication of 50 mg and 100 mg sildenafil, respectively. RESULTS: There was no significant effect of sildenafil on visual acuity, intraocular pressure, color vision, VEP, anterior segment and fundus appearance. ERG changes after 50 mg sildenafil were not significant. The a-wave amplitude of the maximal combined response after 100 mg sildenafil showed significant changes (p=0.021). The b-wave amplitude of the maximal combined response after 100 mg sildenafil showed changes with borderline significance (p=0.059). CONCLUSIONS: In considering the fact that even single dose of 100 mg sildenafil showed changes on ERG, it seems that retinal function in patients receiving sildenafil for a longer period, especially in patients with underlying vascular abnormalities should be monitored by clinical and electrophysiologic tests.
Citric Acid ; Color Vision ; Eating* ; Evoked Potentials, Visual ; Humans ; Intraocular Pressure ; Photoreceptor Cells, Vertebrate ; Retinaldehyde ; Visual Acuity ; Sildenafil Citrate

PURPOSE: The purpose of the present study was to investigate various visual function tests for early detection of ethambutol-induced ocular toxicity. METHODS: A prospective study of 20 eyes of 10 patients being treated with ethambutol was conducted. Visual acuity, visual field, color vision, fundus examination, contrast sensitivity, optical coherence tomography (OCT), and pattern-visual evoked potential (VEP) were assessed. Examinations were performed prior to therapy and every month for 5 months after treatment. VEP was performed every other month. The mean values of each parameter at each month were compared with the baseline examination and a p-value of <0.05 was considered significant. In addition, a greater than 2 standard deviation (SD) change in each parameter from the mean values at baseline was considered as an ocular toxicity induced change in each individual eye. RESULTS: On OCT, a significant increase of the average retinal nerve fiber layer thickness was detected after 4 months of therapy. VEP showed an increased mean latency of the P100 wave after 2 and 4 months of therapy. However, a greater than 2 SD change from the mean values of the baseline was not observed on OCT, while 30% (6/20) of the eyes showed more than a 2 SD increase in VEP latency. Visual acuity, color vision, fundus, contrast sensitivity, and visual field were not affected in any patients. CONCLUSIONS: The authors of the present study consider VEP as a sensitive test to detect early toxicity of ethambutol. VEP can be helpful in identifying subclinical ocular toxicity, especially in the high-risk patients.
Color Vision ; Contrast Sensitivity ; Ethambutol ; Evoked Potentials ; Evoked Potentials, Visual ; Eye ; Humans ; Nerve Fibers ; Prospective Studies ; Retinaldehyde ; Tomography, Optical Coherence ; Visual Acuity ; Visual Fields

BACKGROUNDElectroencephalogram (EEG) activity in normal subjects and epileptic patients is often closely related to the eye's status such as eye opened (EO), eye closure (ECL) and eyes closed (EC). ECL is the period immediately after closing of the eyes and only lasts for less than 3 seconds if the eyes remain closed. EC is the period as long as the eyes are closed. Epileptiform changes on EEG induced by ECL or EC are called the changes of ECL sensitivity (ECLS) or EC sensitivity (ECS). ECLS occurs mainly but not exclusively in photosensitive patients and ECS has been seen rarely in photosensitive patients. This study aimed to investigate the relationships among ECLS, ECS, photosensitivity and epilepsy syndromes in children.

METHODSEEG records from child patients in the EEG Department of Peking University First Hospital during the period of May 2005 to May 2007 were examined for the presence of ECLS or ECS. Open-close eye tests and intermittent photic stimulations were carried out during video-EEG monitoring for examining ECLS, ECS and photosensitivity.

RESULTSBased on ECLS and ECS on their EEGs, 30 patients were divided into ECLS group (16 cases) and ECS group (14 cases). There were more boys than girls in the two groups. The mean age of initial detection of ECLS and ECS was 10 years, and the average onset age of seizures was 9 years. The epilepsy syndromes in the ECLS group included idiopathic photosensitive occipital lobe epilepsy, Panayiotopoulos syndrome, symptomatic occipital lobe epilepsy, juvenile myoclonic epilepsy, juvenile absence epilepsy, eyelid myoclonia with absences, epilepsy with grand mal on awakening and pure photosensitive epilepsy with mainly generalized tonic clonic seizures. Those in the ECS group were juvenile myoclonic epilepsy, idiopathic photosensitive occipital lobe epilepsy, Panayiotopoulos syndrome and Gastaut type-idiopathic children occipital epilepsy. Photosensitivity was detected in 88% of patients with ECLS and 29% of patients with ECS.

CONCLUSIONSECLS and ECS are relatively common in females. Comparing with ECS, ECLS is found in more epilepsy syndromes. However, ECS and ECLS could exist in the same epilepsy syndrome. ECLS and ECS can be associated or dissociated with photosensitivity. The rate of ECLS with photosensitivity is higher than that of ECS with photosensitivity, suggesting that mechanisms for ECLS, ECS and photosensitivity may be different but correlated.

Adolescent ; Child ; Child, Preschool ; Electroencephalography ; Epilepsy ; physiopathology ; Female ; Humans ; Male ; Ocular Physiological Phenomena ; Photic Stimulation

PURPOSE: To report an extremely rare case of optic nerve involvement in Miller-Fisher syndrome. CASE SUMMARY: A 74-year-old woman presented to our clinic with decreased visual acuity in both eyes. Such symptoms started 1 month prior to her visit, after sudden onset of left-side motor power weakness and dysphasia. Following the initial symptoms, our patient consecutively experienced worsening dysphagia, ptosis, and lateral gaze limitation. We confirmed the diagnosis as Miller Fischer syndrome with a positive anti-GQ1b antibody serology. She received immunoglobulin treatment for 5 days in other departement. She visited our clinic due to continuing diplopia, decrease of visual acuity and gait disturbance. On initial examination, the corrected visual acuity was 0.5 in both eyes. Ptosis of both eyelids, esodeviation, limitation in ocular movement was noted. The fundoscopic examinations revealed relatively pale optic disc. There was decrease in color vision in both eyes. The visual evoked potential test showed low amplitude and delayed latency in P100 wave in both eyes. Two months after her initial visit to our department her symptoms started to improve, and after 4 months all the initial problems resolved completely and her corrected visual acuity checked out to be 0.8 in both eyes and VEP abnormality was recovered. CONCLUSIONS: It is extremely uncommon for Miller Fisher syndrome to involve the optic nerve. We present such a case of a 74-year-old woman whose symptoms improved 4 months after its first attack with treatment.
Aged ; Aphasia ; Color Vision ; Deglutition Disorders ; Diplopia ; Esotropia ; Evoked Potentials, Visual ; Eye ; Eyelids ; Female ; Gait ; Humans ; Immunoglobulins ; Miller Fisher Syndrome ; Optic Nerve ; Visual Acuity

PURPOSE: To assess the clinical usefulness of the pressure phosphene tonometer (Proview(R)) compared with the Goldmann applanation tonometer. METHODS: Ninety four eyes of 50 patients, aged from 3rd decade to 6th decade and with intraocular pressure (IOP) ranging from 9 to 21 mmHg, were measured by Proview(R) 5 times each. The average of these values was compared with the value measured with the Goldmann applanation tonometer. Twenty eyes of 10 patients, aged from 3rd decade to 4th decade, were trained repeatedly and measured again by the same method after 1 month. RESULTS: IOP measured by Proview(R) was statistically higher than that with the Goldmann applanation tonometer (p<0.05). The difference between the two measurements for patients in their 5th and 6th decades was more than in their 3rd and 4th decades. Nevertheless, the measurement difference decreased and the correlation coefficient increased between the devices in the repeatedly trained group (r=0.923). CONCLUSIONS: In measuring IOP, the pressure phosphene tonometer (Proview(R)) is not suitable in elderly or newly adapted patients, but it provides significant values in young and repeatedly trained group.
Aged ; Humans ; Intraocular Pressure ; Phosphenes*

Authors studied characteristics of ERG b-wave and oscillatory potential, which can be applied to ERG protocol for clinical purposes. Following conclusions were obtained from the ERG test performed on 20 normal men(40 eyes) during dark adaptation and light adaptation time, under the conditions where other factors were equal. 1. In the scotopic ERG test, 88%(364/414uv) of maximum b-wave amplitude in 30 minutes were obtained in first 1 minute of dark adaptation. By using this shortening scotopic protocol for the acquired retinal disease, sufficient result can be expected without the over 20 minutes dark adaptation. 2. In the photopic ERG test, if over 30 minutes dark adaptation time were given, it would take at least 15 minutes to reach the regular initial photopic value. Therefore, it is recommended that photopic ERG test be done before the scotopic ERG test. 3. In the oscillatory potential test, light adaptation time has little effect on summed photopic oscillatory potential amplitudes and implicit time. Summed scoto pic oscillatory potential amplitude reaches the highest 1 minute after the dark adaptation. Therefore, it is recommended that to obtain higher amplitude and more sensitive test result, oscillatory potential test be done 1 minute after the dark adaptation.
Adaptation, Ocular* ; Dark Adaptation* ; Retinal Diseases

PURPOSE: To compare the intraocular pressure (IOP) measured by the pressure phosphene tonometer (PPT) and the Goldmann applanation tonometer (GAT) according to the feedback of the IOP measured by GAT and the use of the dominant hand during the measurement. METHODS: In a group of 40 eyes of 40 normal subjects in their twenties and thirties without diagnostic specificity, IOP was measured with PPT three times by themselves and with the GAT by one examiner on 3 different days. In 20 eyes of the feedback group, the subjects were informed of their IOP measured by GAT and were allowed to measure with PPT again. In each group, half of the eyes (20 eyes) were assigned to use the dominant hand to measure the IOP (dominant group) and the other half (20 eyes) were assigned in the other way (nondominant group). RESULTS: In feedback, nonfeedback and dominant groups, comparison of the first day showed statistically significant differences of mean IOP. But on the third day, there were no significant differences among all 4 groups and there were significant correlations. There was a stronger correlation between the two methods in the feedback group (r=0.721) than in the nonfeedback group. The correlation coefficient of all 40 eyes was 0.605 (p<0.001). CONCLUSIONS: PPT has a strong correlation with GAT in the range of normal IOP and is thought to be more useful as a self tonometer for the measurement of both eyes with the periodical measurement of IOP by GAT in clinics.
Hand ; Intraocular Pressure* ; Phosphenes* ; Sensitivity and Specificity