Direct Light Reflex Research Articles

Effect of Light Intensity on the Relative Afferent Pupillary Defect in Unilateral Neuro-ophthalmic Pathology.

Objective pupillometry with standardized light intensities allows a comprehensive assessment of the relative afferent pupillary defect in patients with unilateral neuro-ophthalmic pathology. This study aimed to determine the impact of varying light intensities on the grade of relative afferent pupillary defect in unilateral neuro-ophthalmic pathology vis-à-vis healthy controls. Monocular pupillary light reflexes of 20 controls (14 to 50 years) and 31 cases (12 to 72 years) with clinically diagnosed relative afferent pupillary defect were measured thrice using 1-second-long light pulses, followed by 3 seconds of darkness, at eight light intensities (6.4 to 1200 lux) using objective pupillometry. The relative afferent pupillary defect was quantified as the ratio of the percentage change in the direct light reflexes of the left and right eyes. Its change with light intensity was described using standard exponential fits. The median (25th to 75th interquartile range) defect score of 54.8% cases decreased from baseline values of 1.58 (1.25 to 1.87) for right eye pathology and 0.45 (0.39 to 0.55) for left eye pathology to saturation values of 1.18 (1.05 to 1.31) and 0.98 (0.95 to 1.06), respectively, at light intensities between 56.9 and 300.5 lux. Like controls (1.01 [1.00 to 1.06]), the defect scores of the remaining 45.2% cases were constant with light intensity at 1.23 (1.18 to 1.46) and 0.87 (0.86 to 0.89) for right and left eye pathologies, respectively. Relative afferent pupillary defects may decrease with test light intensity in a significant proportion of patients with unilateral neuro-ophthalmic pathology. This highlights the importance of objective pupillometry with standardization light intensities for clinical assessment of afferent pupillary defects.

Septic Cavernous Sinus Thrombosis (CST) with Blindness Caused by Odontogenic Infection – A Case Report

Introduction: Septic cavernous sinus thrombosis (CST) is a rare thrombosis, but severe, causing damage to all nerves inside the cavernous sinus. The incidence rate of CST is estimated at two to four per million people per year. The symptom usually varies, gradually worsening, making diagnosis harder and potentially making permanent disability. Early detection and prompt treatment are very important to lower the morbidity rate. Case: Tn. M had complained of multiple headaches attacks since 8 months ago before being admitted followed by diplopia. Complaints had worsened 3 months before with the loss of vision in the left eye. MRI showed left thrombosis sinus cavernous. The terrible headache was scaled 8-9 with VAS score. The patient’s left eye was found proptosis palpebra, with anisocoria and mydriasis followed by no direct light reflex also indirect light reflex, visual acuity of the left eye is no light response, whereas the patient’s right eye is normal. On the patient’s left eye was found gaze palsy sinistra. The abnormal blood result was leucocytosis and thrombocytosis. The patient was given fondaparinux once a day with a dose of 6000 units subcutaneously for 5 days. After that, the headache was decreased significantly. The patient underwent 5 tooth extraction done by mouth surgeon after being discharged. The patient was given 20 mg rivaroxaban per day for three weeks, then 10mg per day for three months, and evaluated with MRV again. Conclusion: CST is still very rare but very lethal and makes permanent disability on the patient. Through this case, we demonstrate the potential of tooth infection which leads to septic CST and caused ophthalmoplegia and blindness.

Visual Disturbances as an Early Important Sign of Brain Tumor: A Case Report

Purpose: to raise attention for careful evaluation of ocular signs and symptoms, especially mild visual disturbances, for early detection of brain tumors. Case Presentation: A 45-year-old woman presented with a one-month history of gradual vision loss in both eyes. There was also a history of headache for over a year before the vision loss symptom appeared. There was no history of trauma, ocular pain, eye redness, or lacrimation. The visual acuity (VA) of both the right and left eyes with the best-corrected visual acuity (BCVA) was 6/30. Confrontation visual field test of both eyes revealed unremarkable results upon examination. The intraocular pressures (IOP) of both eyes were 11 mm Hg. Anterior segment examination of both eyes was within normal limit except for the direct light reflexes were decreased. Relative afferent pupillary defect (RAPD) of both eyes was difficult to assess. Fundoscopy examination of both eyes revealed papilledema. The retinal fields and macula were normal bilaterally. Computerized tomography (CT) scan demonstrated a hyperdense and calcified lesion in the right frontal lobe. The dimensions of the lesion were measured as 69.9 x 52.1 mm. After contrast, the CT scan showed a strongly enhanced lesion with thickening of the right frontal bone. Both of the anterior horns of the lateral ventricle were pressed by the lesion. There was a midline shift to the left by approximately 14 mm. Both of the eyes were within normal limits. Conclusion: Blurred vision and other visual disturbances are common early symptoms in brain tumors, but diagnosis is not made till very late due to late presentation. Early detection of a brain tumor through ocular signs and symptoms and complete neuro-ophthalmic evaluation can help in early diagnosis and appropriate management of brain tumors.

Management of traumatic isolated unilateral oculomotor nerve palsy in the emergency department and literature review

Cranial nerve (CN) lesions are observed due to congenital, infectious, neoplastic formations, migraine and head trauma. Along with the patient's age, clinical findings and neuroradiological imaging studies guide the diagnosis. A 57-year-old female patient was brought to the emergency room (ER) by Emergency Medical Services (EMS) due to a motor vehicle accident. No medical history. She was conscious, cooperative and orientated. Vital findings were normal. She had ptosis in the left eye, loss in the direct light reflex, restricted medial movements and mydriasis were determined. Radiological examination is normal. The patient was hospitalized with the diagnosis of isolated 3rd cranial nerve palsy (OCNP). Isolated OCNP is a rare condition usually secondary to major trauma. In addition to, there may be isolated unilateral OCNP without any evidence of neuroimaging abnormality. Emergency physicians should be vigilant in such cases that should perform detailed neurological examination and clinical follow-up for the patient's complaints.

A Novel Method for Measuring the Pupil Diameter and Pupillary Light Reflex of Healthy Volunteers and Patients With Intracranial Lesions Using a Newly Developed Pupilometer.

Background: Physicians currently measure the pupil diameter and the pupillary light reflex with visual observations using a ruler and a traditional penlight, leading to possibly inaccurate and subjective assessments. Although a mobile pupillometer has been developed and is available in clinical settings, this device can only assess one pupil at a time. Hence, an indirect pupillary light reflex, including those under irradiation to the opposite side of pupil, cannot be evaluated. Consequently, we have developed a new automatic mobile pupilometer, the Hitomiru®, with Hitomiru Co., Ltd. (Tokyo, Japan). This device is a two-glass type pupilometer with a video recording system. The pupil diameter and light reflex of both pupils can be measured simultaneously; therefore, both indirect and direct light reflexes can be assessed.Purpose: To evaluate the clinical ability of the Hitomiru® pupilometer to assess the pupil diameter and the pupillary light reflex of healthy volunteers and patients with intracranial lesions in an intensive care unit (ICU).Methods: Twenty-five healthy volunteers and five ICU patients with intracranial lesions on only the left side were assessed using the Hitomiru® pupilometer. The protocol was as follows: infrared light was applied to both pupils, followed by visible light to the right pupil, infrared light to both pupils, visible light to the left pupil, and then infrared light to both pupils. All the intervals were 2 s, and the dynamics of pupil diameters on both sides were continuously recorded.Results: The healthy adults had approximately 0.5 mm anisocoria, miosis was harder, and mydriasis was less with increased age. There were several differences in miosis rates, miosis times, and mydriasis rates between the healthy adults and the patients with intracranial lesions with both direct irradiation and indirect irradiation.Conclusions: The initial trial estimated and digitally recorded direct and indirect light reflexes, including rapidity of miosis after direct and indirect lights on, and mydriasis after direct and indirect lights off. The Hitomiru® pupilometer was a useful device to digitally record and investigate the relationship between pupil reflexes and intracranial diseases.

IMPROVEMENTS IN A PATIENT WITH MILD TRAUMATIC BRAIN INJURY AND DYSLEXIA FOLLOWING MULTIMODAL NEUROREHABILITATION

Event Abstract Back to Event IMPROVEMENTS IN A PATIENT WITH MILD TRAUMATIC BRAIN INJURY AND DYSLEXIA FOLLOWING MULTIMODAL NEUROREHABILITATION Frederick R. Carrick1* and David J. Traster1* 1 Carrick Institute, United States Background: We describe a 60 year-old male who presented to a chiropractic neurology clinic with a history of mild traumatic brain injury. The patient experienced severe dyslexia, migraines, photophobia, hyperacusis, lack of steadiness, autonomic changes and right sided hypertonicity of musculature. Methods: Upon comprehensive neurologic examination the patient demonstrated bilaterally non-responsive pupils upon direct light reflex, absence of adduction on left eye upon convergence testing, absent visual optokinetic nystagmus in all directions, and inability to read due to oculomotor deficits. The patient participated in a five day program of neurorehabilitation involving specific oculomotor therapy as well as off-vertical-axis-rotation therapy. Results: The patient experienced a normalization of visual optokinetic nystagmus responses. The patient improved reading comprehension as a result of improved version and vergence integrity. Conclusion: Integrated neurorehabilitation utilizing oculomotor, vestibular and physical rehabilitation produced significant improvements in a patient with dyslexia. The authors suggest further investigation into neurorehabilitation with dyslexia. Keywords: Traumatic brain injury (TBI), Dyslexia, Neurorehabilitation, concussion, concussion rehabilitation Conference: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration, Orlando, Florida, United States, 10 Dec - 14 Dec, 2015. Presentation Type: Poster Presentation Topic: Case Reports for Poster Presentation Citation: Carrick FR and Traster DJ (2015). IMPROVEMENTS IN A PATIENT WITH MILD TRAUMATIC BRAIN INJURY AND DYSLEXIA FOLLOWING MULTIMODAL NEUROREHABILITATION. Front. Neurol. Conference Abstract: International Symposium on Clinical Neuroscience: TBI and Neurodegeneration. doi: 10.3389/conf.fneur.2015.58.00086 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 03 Sep 2015; Published Online: 02 Nov 2015. * Correspondence: Prof. Frederick R Carrick, Carrick Institute, Cape Canaveral, United States, drfrcarrick@post.harvard.edu Dr. David J Traster, Carrick Institute, Cape Canaveral, United States, dtraster3@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Frederick R Carrick David J Traster Google Frederick R Carrick David J Traster Google Scholar Frederick R Carrick David J Traster PubMed Frederick R Carrick David J Traster Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Bilateral Iris Atrophy after the Femtosecond Assisted Laser In Situ Keratomileusis Surgery.

Purpose. To report an unknown complication of laser in situ keratomileusis (LASIK) surgery. Case Presentation. A 28-year-old female presented with photophobia and glare to our eye service. She stated in her medical history that she had undergone femtosecond assisted LASIK surgery in both eyes 15 months ago and her symptoms started just after this surgery. On admission, her best-corrected visual acuity was 10/10 in both eyes. She had mydriatic pupils with no direct light reflex. Examination of the anterior segment revealed bilateral iris atrophy projecting within the LASIK ablation zone and a transillumination defect was remarkable on the slit lamp examination. Conclusion. We hypothesized that this condition may have been caused by the abnormally increased IOP that resulted in ischemia in the iris vascular plexus during the suction process of surgery.

Visual Disturbance Following Shunt Malfunction in a Patient With Congenital Hydrocephalus

A 25-year-old woman presented with complaints of nausea and headache. She had been treated with a ventriculoperitoneal shunt for hydrocephalus when she was 7 months old. Her bilateral optic discs showed moderate atrophy. Right visual acuity allowed only perception of hand movement and left visual acuity was 0.02 (1.2). Computed tomography (CT) showed mild ventricular dilation but no periventricular lucency. Intracranial pressure (ICP) was not high when the shunt valve was punctured. Her visual acuity deteriorated 5 days after the consultation. She was referred again 8 days after the first consultation. The bilateral optic discs were completely pale. Both pupils were dilated on admission, and the bilateral direct light reflexes were absent. The patient could slightly detect only green light stimulus. CT showed moderate enlargement of the ventricle. ICP was 47 cmH(2)O when the shunt valve was punctured. Shuntgraphy showed obstruction of the shunt at the distal end of peritoneal catheter. Emergent total shunt revision was performed. She could detect dark stimulus and the still-dilated left pupil had recovered direct light reflex on the next day. The visual acuity was 0.01 (0.7) on the left 6 months after the operation, although she was blind in the right eye and the bilateral optic discs were completely pale. Visual loss associated with shunt failure remains a major morbidity in shunted congenital hydrocephalus. Early diagnosis and shunt revision may allow visual recovery.

When is a retro-bulbar hemorrhage not a retro-bulbar hemorrhage?

Clinical symptoms and signs of a retro bulbar haemorrhage (RBH) or oedema are periorbital pain, proptosis, decreasing visual acuity, restriction of eye movement and loss of direct light reflex. When these findings occur after facial trauma the diagnosis is traditionally thought to be that of RBH. However in the senior author's experience RBH has rarely been the cause of such findings. Instead this has been due to retrobulbar oedema requiring a different management approach. We therefore wish to challenge the concept that acute proptosis in trauma is usually RBH as currently believed.

Establishment and pathophysiological observation of an experimental animal model of traumatic optic neuropathy

To establish an animal model of traumatic optic neuropathy (TON) that resemble to clinical state and study the mechanical principle and change of pathophysiology of its nerve injury for clinical diagnosis and treatment. New Zealand white rabbits were used as the research objects. The method introduced by Wang Yi was repeated and improved. Mild and severe animal models of TON were established by reformed Wang Yi operation separately. After the spring gun struck, all animals were observed on pupils and direct light reflex and received the examinations of pattern reversal visual evoked potentials (PR-VEP). The pathophysiology of normal and injury optic nerve was observed. After recovery from anesthesia, the mydriasis and disappearance or dullness of direct light reflex happened in all injured eyes. No brain contusion, infection, orbital fracture and death were found. One optic nerve was broken with complete tunica vaginalis. The latency and amplitude of injured eyes deteriorated gradually. In group B, the waves became flat rapidly. After injury, the optic nerve underwent 3 stages: edema, hyperplasia and atrophy. The pathomorphological changes of injured eyes in group B were more serious than that in group A in any time. The reformed operation can establish constant nerve injury with high success rate. In mildly injured eyes, the injury deteriorated gradually. However, part visual function remained. In severely injured eyes, the pathomorphological changes were irreversible sooner after struck, and the visual function lost completely. There is a good correlation between PR-VEP and pathomorphology. PR-VEP can guide the clinical diagnosis and treatment.

Establishing a cat model of acute optic nerve injury

Background In order to investigate the progress in optic nerve injury and the following regeneration and repair, many kinds of animal models of optic nerve injury have been established, such as models of acute and chronic ocular hypertension, compression, amputating wound, ischemia reperfusion or hypoxia, intravitreal injection of excitatory amino acids, etc. However, most of these models are established by squeezing intraorbital optic nerve, and suitable for ophthalmology, and there are fewer models suitable for the acute cranial contusion in neurosurgery. Objective To observe the changes of optic nerve after acute injury, and the characteristics of methods for establishing model of acute optic nerve injury in cats. Design A complete randomized grouping and controlled animal trial. Setting Department of Neurosurgery, General Hospital of Ji'nan Military Area Command of Chinese PLA. Materials Twenty-eight healthy adult cats, common degree, either sex, weighing 2.0–3.5 kg, were provided by the animal experimental center of Fudan University. The cats were randomly divided into control group ( n =3) and model group ( n =25), and 5 cats in the model group were observed at 6 hours and 1, 3, 7 and 14 days after injury respectively. JX-2000 biological signal processing system (Department of Physiology, Second Military Medical University of Chinese PLA, Shanghai); Inverted phase contrast microscope (Olympus); Axioplan 2 imaging microgram analytical system (Labsystems). Methods The experiments were carried out in the Department of Neurosurgery, General Hospital of Jinan Military Area Command of Chinese PLA from June 2004 to June 2005. The cats in the model groups were made into models of acute optic nerve injury: The cats were anesthetized, then the limbs were fixed in a lateral recumbent position. Pterion approach in human was imitated, the operative incision was made along the line between lateral canthus and tragus, and it could be seen deep along the skull base that white optic nerve (about 3 mm) went through optic foramen and entered into brain tissue. It was squeezed with noninvasive vascular clip for 20 seconds, then the clip was removed, and then the skull was closed after it was examined to be no bleeding. The size of bilateral pupils, direct and indirect light reflexes were observed postoperatively. Successfully established models were judged by larger operated pupil than controlateral one, disappearance of direct light reflex and the existence of indirect light reflex. No model establishment was performed in the control group. Each cat was tested with flash visual evoked potential (F-VEP) to observe the electrophysiological changes before and after experiment. All the cats in the control group and model groups were killed under anesthesia before model establishment and at 6 hours, 1, 3, 7 and 14 days after model establishment respectively, and the pathological changes of the optic nerve after injury were observed under electron microscope and light microscope. Main outcome measures VEP and the ultrastructural changes of optic nerve after acute optic nerve injury in both groups. Results All the 28 cats were involved in the analysis of results. ▪ VEP results: The VEP latencies were obviously different between the control group and model group at each time point ( P < 0.05), whereas there were no obvious differences among different time points in the model group ( P > 0.05). The VEP amplitudes were obviously different between the control group and model group at each time point ( P < 0.05), whereas there were no obvious differences among different time points in the model group ( P > 0.05). ▪ Ultrastructural changes of the optic nerve: Under electron microscope, normal optic nerve myelin sheath had complete structure, tramal plates were clear and arranged tightly, axolemma was complete, whereas the structures of endoneurium, myelin sheath, tramal plates, axolemma and axon were in disorders after optic nerve injury. Conclusion Models of acute optic nerve injury established by squeezing intracranial optic nerve with noninvasive vascular clip can be applied in studying intracranial acute optic nerve injury.

Cells in the pretectal olivary nucleus are in the pathway for the direct light reflex of the pupil in the rat

Extracellular microelectrode recordings from 148 single cells in the pretectum of the hooded rat were classified according to their temporal response properties to light stimulation of their retinal receptive fields. Fifty-six cells were classified as tonic-on cells, 22 cells were classified as tonic-off cells, and 53 cells were classified as phasic cells. Seventeen cells could not be assigned to one of these 3 groups. The diameters of the receptive field centers of the tonic-on pretectal cell were clustered about a mean of 31° and the temporal response of these cells was sustained. Constriction of the contralateral pupil was produced by electrical stimulation through the recording electrode at sites containing tonic-on pretectal cells, but not at sites containing tonic-off pretectal cells or phasic pretectal cells. For this reason, we argue that tonic-on cells are likely to mediate constriction in the light reflex of the rat's pupil. Receptive field maps together with electrolytic marking lesions at recording and stimulation sites showed that tonic-on pretectal cells are retinotopically organized and are aggregated in a strip running from the dorso-medial tip of the pretectum to the ventro-lateral boundary. The anatomical distribution of these cells is coextensive with the region known as the pretectal olivary nucleus (PO) in the rat 26,27. Using fine microelectrodes, recordings were obtained from 27 axons presumed origin (fibers). Of these, 14 were tonic-on, 10 were phasic, 2 were tonic-off, and 2 were unclassified. Recordings from tonic-on fibers were obtained near tonic-on pretectal cells, typically in the most dorsal light-responsiveness region of the pretectum. These fibers were activated by single pulse electrical stimulation of the optic chiasm. The mean receptive field center diameter of 6 tonic-on fibers was 10.1°, or about a factor of 3 less than that of pretectal tonic-on cells. The mean conduction velocity of 14 tonic-on fibers was 3.1 m/s. We argue that the tonic-on cells of the PO serve to integrate signals from tonic-on center retinal ganglion cells with adjacent receptive fields to provide signals for constriction of the pupil to neurons in the oculomotor nucleus.

The pupillary light reflex in normal subjects.

In 19 normal subjects the pupillary reflex to light was studied over a range of stimulus intensities by infrared electronic pupillography and analysed by a computer technique. Increasing stimulus intensity was associated with an increase in direct light reflex amplitude and maximum rate of constriction and redilatation. Latency from stimulus to onset of response-decreased with increasing stimulus intensity. The normal range for each of these parameters is given and the significance of these results in clinical pupillary assessment discussed.

Efferent fibers in the cervical sympathetic nerve influenced by light

Spontaneous electrical activity of single-fiber preparations isolated from the central stump of the cervical sympathetic nerve has been recorded, the discharge frequency of which was greatly modified by changing the intensity of light reaching the cat's eyes. These fibers showed the highest firing frequency during darkness and the lowest in light (sometimes complete inhibition) and a gradation of the response intermediate illumination values. Light stimulations ranged from 0 to 1500 lux. The close correlation between the discharge frequency of these fibers and at the light stimulus intensity suggested that the fibers originated from the Budge's ciliospinal center and were directed to the dilatator pupillae muscle. Analysis of these units, besides confirming the intervention of the sympathetic system in the development of the pupillary light reflex, corroborates the hypothesis of a larger participation of sympathetic nerves in the reflex response to darkness than in the response to light. The role of sympathetic nerves in the direct light reflex appeared larger than in the consensual one. The conduction velocities of the light-responsive components were in a range of 6 to 25 m/sec (usually between 10 and 15 m/sec) as determined by (i) the action potential evoked in the single-fiber preparations, (ii) the functional analysis of compound action potentials, and (iii) the use of the antidromic occlusion method on the whole cervical sympathetic nerve. Very small doses of Nembutal (5 mg/kg) greatly decreased the resting discharge of the sympathetic light-responsive fibers and completely abolished the response to darkness.

An investigation of the correlation between abnormal patterns of ocular microtremor and an abnormal pupil reflex in neurological patients

Twenty-two patients and 7 normal subjects at the Burdenko Institute of Neurosurgery, Moscow, have taken part in an investigation in which the direct light reflex to a brief flash, and the high-frequency microtremor of the eyes, have been recorded. The direct pupil reflex recordings obtained with a flash of 20 msec duration and 100 lux intensity at the plane of the pupil were registered from the right eye of each patient. Ocular microtremor recordings were obtained simultaneously from both eyes of 20 of the patients. A set of criteria of abnormality of ocular microtremor, as judged by visual examination of the records, is proposed by the authors. Abnormality of the pupil reflex is assessed in terms of the amplitude, latent period, and time course of the contraction and relaxation phases of the reflex. A strong correlation has been found between the occurrence of an abnormal ocular tremor record and an abnormal pupil reflex. On the basis of this correlation, the authors propose that ocular tremor recordings may be used in diagnosis as sensitive indicators of brain-stem dysfunction.

Mechanical study on the traumatic optic nerve injury.

Optic nerve injury or blindness after head trauma has well been known since the days of Hippocrates, and has still remained one of the serious posttaumatic sequelae. Statistically about 2% of head-injured persons suffer from the visual loss and are impelled to have limited social activites3). As the victims of traffic accidents are increasing every year, the studies about this problem are urgent. Clinical manifestations of the injury of the optic nerve have been well known. The reports of many institutions have shown almost the same results. The summaries are as follows3): There is a constant mode of trauma to make an injury. It occurs frequently in motorcycle accidents. Sometimes it occurs even in trivial accidents, where impact force is not always so large. The blow is usually given to the front of the head. Symptomatologically visual loss occurs immediately after the trauma and is limited usually to the eye on the ipsilateral side to the impact and spares the eye on the contralateral side. Diagnosis is guided from the loss of direct light reflex of the affected side. The fracture of the optic canal is often visualized in X-ray studies. Surgical intervention is not fully effective. From the pathological view point, there are so many therories as to the causative factors of the injury of the optic nerve. The fracture of the optic canal, the bleeding of the sheath of the optic nerve, and the tearing of nerve fibers are prominent among them. Fracture theory seems most attractive because the fracture of the optic canal is found in 60-90% cases in X-ray studies. So far, these clinical and pathological data have strongly suggested that mechanical factors play an important role to cause the lesion. However, there has never been a fundamental engineering study. Therefore in this paper, mechnical studies were performed to investigate the mechanism and to clarify the threshold of the impact force of the fracture of the optic canal, which is thought to be closely relevent to the ipsilateral optic nerve injury. The studies were made up of series of experiments.