Intracranial hypertension following epidural blood patch.
Explore the source record for details and available documents.
Acetazolamide↗
Biomedical subjects
Joseph F Rizzo
Publications and source records attributed to Joseph F Rizzo.
Scanning laser polarimetry of edematous and atrophic optic nerve heads.
OBJECTIVE: To determine if scanning laser polarimetry (SLP) measures form birefringence of the retinal nerve fiber layer (RNFL). METHODS: Consecutive patients with either acute unilateral disc edema or chronic diffuse unilateral disc atrophy underwent SLP using the GDx Nerve Fiber Analyzer (Laser Diagnostic Technologies Inc, San Diego, Calif). The former group had peripapillary RNFL edema, presumably with no change in form birefringence elements, while the latter had optic nerve atrophy, presumably with a loss of birefringence elements in the RNFL. A subset of patients with acute unilateral disc edema who subsequently developed disc atrophy had repeated SLP at 6 months. Intereye and intertest comparisons of 6 SLP parameters representative of RNFL thickness were performed using the paired t test. RESULTS: In the acute unilateral disc edema group (n = 28), none of the SLP parameters were significantly increased in affected vs fellow eyes. In the chronic unilateral disc atrophy group (n = 30), all SLP parameters were significantly decreased in affected vs fellow eyes (P<.001). Patients with disc edema who had a follow-up SLP demonstrated significant declines of all parameters in the affected eyes (P<.007) but no change in SLP parameters in unaffected eyes. CONCLUSION: Scanning laser polarimetry measures form birefringence properties of the RNFL, but not necessarily the RNFL thickness.
Acute Disease↗
Optic neuropathy secondary to sub-tenon anesthetic injection in cataract surgery.
Explore the source record for details and available documents.
Aged↗
Retinal arterial wall plaques in Susac syndrome.
PURPOSE: To demonstrate retinal arterial wall plaques (RAWPs) in patients with Susac syndrome, a disorder that consists of the triad of branch retinal artery occlusion, encephalopathy, and hearing loss. The clinician may misinterpret these RAWPs as emboli. DESIGN: Observational case series. METHODS: Four patients (one man and three women, aged 21-38 years) were examined and followed. RESULTS: Four patients with Susac syndrome had RAWPs in association with branch retinal artery occlusions. They were present in six of eight eyes. The plaques were yellow to yellow-white and located usually away from retinal bifurcations. Retinal arterial wall plaques occur at the midarteriolar segments, whereas Hollenhorst plaques occur at vascular bifurcations. Four of six eyes had resolution of the plaques. CONCLUSIONS: Retinal arterial wall plaques may occur with branch retinal artery occlusions in Susac syndrome. This finding should help the clinician who is struggling to make a diagnosis in a patient with an enigmatic encephalopathy and/or hearing loss. These plaques may resolve over time.
Adult↗
Perceptual efficacy of electrical stimulation of human retina with a microelectrode array during short-term surgical trials.
PURPOSE: This work is part of a feasibility assessment of a retinal prosthesis as a means to restore vision to patients with blindness caused by retinitis pigmentosa. The primary goal was to assess the concordance of the form of induced perception and the pattern of electrical stimulation of the retina, and the reproducibility of the responses. METHODS: Five volunteers with severe retinitis pigmentosa and one with normal vision were studied. A companion paper in this issue provides details on demographics, visual function, surgical methods, general stimulation strategy, and data analysis. Volunteers were awake during surgery while a 10-microm-thick, microfabricated electrode array was placed on the retina. The array was connected to extraocular current sources that delivered charges to 50-, 100-, and 400-microm-diameter electrodes. Negative control trials were randomly included. Perceptual quality was judged by the similarity between the form of stimulation and perception (i.e., accuracy) and the reproducibility of responses. RESULTS: Only 1 of 40 control tests yielded a false-positive result. On average, volunteers 3, 5, and 6 reported percepts that matched the stimulation pattern 48% and 32% of the time for single- and multiple-electrode trials, respectively. Two-point discrimination in the best cases may have been achieved in two blind subjects using (center-to-center) electrode separation of 600 and 1960 microm. Reproducibility was achieved 66% of the time in the blind subjects. By comparison, in the normal-sighted subject, perceptual form was reported accurately 57% of the time, with 82% reproducibility, and two-point discrimination may have been achieved in one trial with 620-microm electrode spacing and in two trials each with 1860- and 2480-microm electrode spacing. In subjects 5 and 6, perceptual size was inconsistently related to the charge, although relatively large differences in charge (median: 0.55 microcoulombs [microC]) between two trials produced differently sized percepts. Longer stimuli did not produce rounder percepts. CONCLUSIONS: Single percepts induced by single-electrode stimulation were relatively small, but the form of percepts, especially after multielectrode stimulation, often did not match the stimulation pattern, even in a normal-sighted volunteer. Reproducible percepts were more easily generated than those that matched the stimulation pattern.
Adult↗
Methods and perceptual thresholds for short-term electrical stimulation of human retina with microelectrode arrays.
PURPOSE: To report methods for performing epiretinal electrical stimulation with microfabricated electrode arrays and determining perceptual thresholds on awake human volunteers during acute surgical trials. METHODS: Four hypotheses were tested: (1) epiretinal stimulation can be performed during acute experiments without obviously damaging the retina or degrading vision or the health of the eye; (2) perception can be obtained 50% of the time in blind patients with charge densities below published safety limits; (3) the minimal charge needed to induce perception would be higher in patients with more severe retinal degeneration; and (4) threshold charge would be lower at shorter stimulus durations. Five subjects with severe blindness from retinitis pigmentosa and one with normal vision (who underwent enucleation of the eye because of orbital cancer) were studied. Electrical stimulation of the retina was performed on awake volunteers by placing a single 250-microm diameter handheld needle electrode or a 10-microm thick microfabricated array of iridium oxide electrodes (400-, 100-, or 50-microm diameter) on the retina. Current sources outside the eye delivered charge to the electrodes. Assessment of damage was made by observing the clinical appearance of the eyes, comparing pre- and postoperative visual acuity, obtaining retinal histology in one case, and comparing perceptual thresholds with published safety limits. RESULTS: No clinically visible damage to the eye or loss of vision occurred. Even at sites removed from stimulation, histology revealed swollen photoreceptor inner and outer segments, which were believed to be nonspecific findings. Percepts could not be reliably elicited with 50-microm diameter electrodes using safe charges in one blind patient. With the two larger electrodes, only the normal-sighted patient had thresholds at charge densities below 0.25 and 1.0 millicoulombs (mC)/cm(2) for 400- and 100-microm diameter electrodes, respectively, which is one seemingly reasonable estimate of safety derived from the product of charge per phase and charge density per phase. In blind patients, thresholds always exceeded these levels, although most were close to these limits in patient 6. The range of charge density thresholds with the 400- microm electrode in blind patients was 0.28 to 2.8 mC/cm(2). The normal-sighted patient had a threshold of 0.08 mC/cm(2) with a 400-microm electrode, roughly one quarter of the lowest threshold in the blind patients. Strength-duration curves obtained in two blind patients revealed the lowest threshold charge at the 0.25- or 1.0-ms stimulus duration. CONCLUSIONS: Threshold charge densities in severely blind patients were substantially higher than that in a normal-sighted patient. Charge densities in blind patients always exceeded one seemingly reasonable estimate of safe stimulation. The potential adversity of long-term stimulation of the retina by a prosthesis has yet to be determined.
Adult↗
Thresholds for activation of rabbit retinal ganglion cells with an ultrafine, extracellular microelectrode.
PURPOSE: To determine electrical thresholds required for extracellular activation of retinal ganglion cells as part of a project to develop an epiretinal prosthesis. METHODS: Retinal ganglion cells were recorded extracellularly in retinas isolated from adult New Zealand White rabbits. Electrical current pulses of 100- micro s duration were delivered to the inner surface of the retina from a 5- micro m long electrode. In about half of the cells, the point of lowest threshold was found by searching with anodal current pulses; in the other cells, cathodal current pulses were used. RESULTS: Threshold measurements were obtained near the cell bodies of 20 ganglion cells and near the axons of 19 ganglion cells. Both cathodal and anodal stimuli evoked a neural response in the ganglion cells that consisted of a single action potential of near-constant latency that persisted when retinal synaptic transmission was blocked with cadmium chloride. For cell bodies, but not axons, thresholds for both cathodal and anodal stimulation were dependent on the search method used to find the point of lowest threshold. With search and stimulation of matching polarity, cathodal stimuli evoked a ganglion cell response at lower currents (approximately one seventh to one tenth axonal threshold) than did anodal stimuli for both cell bodies and axons. With cathodal search and stimulation, cell body median thresholds were somewhat lower (approximately one half) than the axonal median thresholds. With anodal search and stimulation, cell body median thresholds were approximately the same as axonal median thresholds. CONCLUSIONS: The results suggest that cathodal stimulation should produce lower thresholds, more localized stimulation, and somewhat better selectivity for cell bodies over axons than would anodal stimulation.
Action Potentials↗
Sneeze-induced visual and ocular motor dysfunction.
PURPOSE: The purpose of this report is to describe two neuroophthalmic complications that are related by their temporal association with a sneeze. DESIGN: We describe observational case reports of two patients. METHODS: Both patients were examined, and their conditions were diagnosed and treated according to standard indications for each neuroophthalmic condition. RESULTS: The first case describes a patient who had previously undergone intracranial surgery, including removal of the clivus and later developed a trochlear nerve paresis after a sneeze. The second case describes a patient who repeatedly demonstrates transient decreased perfusion to his right central retinal artery and an associated afferent papillary defect after sneezing. CONCLUSION: The mechanical and hemodynamic forces involved in sneezing are formidable and may cause permanent cranial neuropathy or temporarily alter ocular blood flow in certain patients.
Adult↗
Use of magnetic resonance imaging to differentiate optic neuritis and nonarteritic anterior ischemic optic neuropathy.
OBJECTIVE: To determine if magnetic resonance imaging (MRI) of the optic nerves obtained during the acute phase can distinguish patients with optic neuritis (ON) from those with nonarteritic anterior ischemic optic neuropathy (NAION). DESIGN: Retrospective, neuroradiologic, observational study. PARTICIPANTS: Sixty-four patients diagnosed as having either ON or NAION who were diagnosed by clinical criteria and imaged by MRI. METHODS: Demographic information on the MRI scans was masked and the patients were presented randomly and in a blinded fashion to a neuroradiologist (JDR) for determination of abnormalities. Reproducibility was assessed by presenting 10 of the scans a second time to the same neuroradiologist. MAIN OUTCOME MEASURES: The presence or absence and location of abnormal MRI signals of the optic nerve. RESULTS: Evaluation of reproducibility revealed identical interpretations of the ten scans submitted a second time. The optic nerve was abnormal in the clinically affected eye in 31 of the 32 ON patients but in only 5 of the 32 NAION patients. Thirty of the 31 ON patients who received gadolinium had enhancement, and 27 of the 32 ON patients had increased short T(1) inversion recovery signal in the clinically affected optic nerve. The five NAION patients with abnormal scans in the clinically affected eye had increased short T(1) inversion recovery signal, and in two of these, there also was enhancement of the optic nerve. For the ON patients, enhancement involved the entire length of the intraorbital optic nerve in 18 cases and the intracranial segment of the optic nerve in 19 cases. CONCLUSIONS: Our study shows that MRI scanning of the optic nerve shows significantly different results between patients clinically diagnosed with either ON or NAION.
Acute Disease↗
Orbital apex syndrome: a rare presentation of extramedullary hematopoiesis: case report and review of literature.
We describe a case of compressive neuropathy in the orbital apex due to extramedullary hematopoiesis (EMH). A 64-year-old man with Polycythemia Rubra Vera developed unilateral visual loss, proptosis, complete ophthalmoplegia, and facial paresis. Bone marrow biopsy showed myelofibrosis. Magnetic resonance imaging demonstrated enhancement at the orbital apex and subtle optic canal narrowing. Decompression of the optic nerve with biopsy of surrounding bone showed EMH. The patient received a course of radiation without benefit. We suggest including the diagnosis of EMH of the orbital apex bones in the differential diagnosis of patients with myeloproliferative disorders who develop an orbital apex syndrome.
Facial Paralysis↗
Combined vitrectomy lens and contact electrode for erg recording during surgery.
Explore the source record for details and available documents.
Animals↗
Neuro-ophthalmologic complications of cataract surgery.
Neuro-ophthalmologic complications from cataract surgery are uncommon and include central nervous system toxicity, binocular diplopia, traumatic optic neuropathy and ischemic optic neuropathy. Retrobulbar blocks may be accidentally injected into the subarachnoid space with diffusion to the brainstem. This leads to cardiovascular, respiratory, and mental status compromise. Most patients have complete recovery with adequate support. Post-operative, binocular diplopia may occur secondary to anisometropia or previously unrecognized misalignment. Periocular injection may cause paresis or fibrosis of extraocular muscles. Anterior or posterior ischemic optic neuropathy can occur in the first 6 weeks after cataract surgery with or without periocular injection. The risk to the other eye is high with subsequent contralateral cataract extraction. Post-operative vision loss associated with direct traumatic needle injury is recognized immediately. Therefore, an orbital MRI may be warranted for a patient with an optic neuropathy in the first 24 hours after cataract surgery using periocular anesthesia. If evidence of needle injury is present on neuroimaging, a trial of steroids should be considered.
Aged↗