Biomedical subjects

Randy H Kardon

Publications and source records attributed to Randy H Kardon.

25 records · Page 2Linked to original sources

PubMed2002

Greater pupillary escape differentiates central from peripheral visual field loss.

OBJECTIVE: To test whether pupil escape observed during a constant light stimulus was greater in eyes with central visual field loss compared to eyes with peripheral visual field loss and normal eyes. DESIGN: Comparative, observational case series. PARTICIPANTS: Twenty-seven normal subjects, 5 patients with central field loss, 11 patients with peripheral field loss, and 8 patients with combined loss (central and peripheral visual field loss) were tested. METHODS: A dual-channel infrared pupillograph was used to simultaneously record the right and left pupil diameters at a rate of 60 Hz to characterize the initial, phasic pupil contraction, and the sustained, or prolonged, pupil contraction in response to a 5-second light stimulus. Full-field light stimuli with a diameter of 30 degrees were presented to each eye at seven different intensities. MAIN OUTCOME MEASURES: The amplitude of the phasic pupil contraction was compared with the amplitude of the sustained pupil contraction at the four brightest intensities (slope of phasic versus sustained contraction) in the normal eyes and in eyes with visual field loss in the center and the periphery. RESULTS: The sustained pupillary contraction showed a statistically greater reduction in proportion to the phasic component in eyes with central field loss compared to those with peripheral field loss, combination central and peripheral field loss, and normal eyes. CONCLUSIONS: Afferent neurons from the central retina normally contribute a substantial component to the sustained pupil response. Eyes with central field loss can be distinguished from eyes with peripheral field loss by a relatively greater loss of the sustained response, causing greater pupil escape. This study showed that pupil movements in response to a nonperimetric full-field light stimulus may provide some degree of mapping of retinotopic sensitivity. This information may be of use in interpreting the pupillary movements during the swinging flashlight test and may help predict the pattern of visual field loss.

Humans↗

PubMed2002

Visual improvement with corticosteroid therapy in giant cell arteritis. Report of a large study and review of literature.

OBJECTIVES: (1) To report the incidence and extent of visual improvement achieved by high-dose systemic corticosteroid treatment in eyes with visual loss due to giant-cell arteritis (GCA). (2) To understand the cause of the discrepancies between visual improvement revealed by routine visual acuity (VA) and by the central visual field in kinetic perimetry. (3) To review critically the contradictory literature on the effectiveness of corticosteroid therapy on visual recovery in GCA and to attempt to reconcile differences in the reported results. METHODS: Clinical data were collected systematically on 84 consecutive patients (114 eyes) with visual loss, all of whom had GCA confirmed by temporal artery biopsy and treated by us with high-dose systemic corticosteroid therapy. The patients were treated between 1974 and 1999 and data were compiled retrospectively. All patients underwent a detailed visual and ophthalmic evaluation at the initial visit and at every follow-up. This included visual field testing (with a Goldmann perimeter). All were treated with systemic corticosteroid therapy (intravenous followed by oral in 41 patients and oral only in 43 patients). RESULTS: Visual loss was due to anterior ischaemic optic neuropathy (91%), central retinal artery occlusion (10.5%), cilioretinal artery occlusion (10%), and/or posterior ischaemic optic neuropathy (4%), either alone or in different combinations. Improvement in both VA (>or= 2 lines) and central visual field was found in only five (4%) eyes of five patients (three treated with intravenous and two with oral steroid therapy). Improvement in VA >or= 2 lines but not in the central visual field was found in seven eyes (in six patients). Visual improvement was seen in 7% of 41 patients treated initially with intravenous steroids versus 5% (p = 0.672) of 43 patients treated with oral steroids only. Comparison of patients with visual improvement in both VA and fields versus those with no improvement suggested a shorter interval (p = 0.065) between onset of visual loss and start of therapy in the improved patients. CONCLUSIONS: In our study, only 4% of eyes with visual loss due to GCA improved, as judged by improvement in both VA and central visual field (by kinetic perimetry and Amsler grid). The data also suggest that there is a better (p = 0.065) chance of visual improvement with early diagnosis and immediate start of steroid therapy. Improvement in VA without associated improvement in the central visual field or Amsler grid may simply represent a learned ability to fixate eccentrically with more effective use of remaining vision: this factor could help explain a number of reported cases in the literature of improved VA after steroid treatment for GCA. To prevent further visual loss in either eye and for management of systemic manifestations of GCA, all patients must be treated on a long-term basis with adequate amounts of systemic corticosteroids.

Aged↗

PubMed2002

Characterization of the pupil light reflex, electroretinogram and tonometric parameters in healthy rat eyes.

PURPOSE: To characterize the pupil light reflex (PLR), electroretinographic (ERG) and tonometric parameters in healthy rat eyes. METHODS: Brown Norway rats were used for experiments. The PLR was evaluated with a computerized pupillometer (n = 27), ERGs were recorded simultaneously from both eyes (n = 27) and IOP was measured with a Tonopen (n = 15). RESULTS: The analysis of the PLR parameters confirmed that the consensual PLR had a significantly smaller amplitude (0.1-0.2 mm; p = 0.03) and an increased latency time (p = 0.001) compared to the direct PLR. Electroretinography revealed an a-wave amplitude of 207.2 +/- 13 microV with a latency of 25.6 +/- 0.7 ms, and a b-wave 554.3 +/- 24.5 microV with a latency of 21.4 + 1.8 ms. The flicker ERG recording revealed amplitudes of 40.6 +/- 2.4 microV. Tonometry measurements revealed that isoflurane, but not halothane, anesthesia suppressed the IOP (non-anesthetized: 25.3 +/- 1.0 mmHg; 1% halothane + 30% NO: 26.2 +/- 1.1 (p > 0.1); 1% isoflurane + 30% NO: 20.1 + 1.6 (p < 0.05)). CONCLUSIONS: Consensual PLR in rats has a relative deficit compared to the direct PLR. Isoflurane anesthesia has a suppressive effect on the IOP in healthy rat eyes.

Anesthetics, Inhalation↗

PubMed2002

Papilledema as the presenting manifestation of spinal schwannoma.

A 63-year-old woman with headache, blurred vision, bilateral optic disc edema, and normal cranial magnetic resonance imaging scan underwent lumbar puncture that revealed an elevated opening pressure (290 mm water), a protein level of 114 mg/dl, and mild pleocytosis. Spinal magnetic resonance imaging later demonstrated a sacral tumor, which proved to be a schwannoma with sarcoid-like features. After surgical removal of the tumor, the patient's manifestations resolved. This case emphasizes that low spinal cord tumors can cause elevated intracranial pressure without causing markedly elevated cerebrospinal fluid protein or cells, or any myelopathic manifestations, perhaps by obstructing sacral cerebrospinal drainage. Comprehensive spine imaging should be a part of the evaluation of a patient with papilledema who has normal brain imaging but abnormal spinal fluid constituents.

Female↗

PubMed2002

Childhood-onset chronic inflammatory demyelinating polyradiculoneuropathy with cranial nerve involvement.

A 17-year-old male presented with chronic diplopia and generalized motor weakness. He was previously diagnosed with chronic inflammatory demyelinating polyradiculoneuropathy and acute disseminated encephalomyelitis in childhood. Cranial magnetic resonance imaging (MRI) revealed a rarely reported finding of thickening and enhancement of multiple cranial nerves. Nerve conduction studies and electromyography showed peripheral nerve demyelination with axonal involvement. There was improvement in the clinical examination, MRI, and electrophysiologic studies after combined corticosteroid and plasma exchange therapy. We review the clinical presentation, course, and response to therapy among children with chronic inflammatory demyelinating polyradiculoneuropathy, with specific emphasis on the frequency and pattern of cranial nerve involvement.

Adolescent↗

PubMedDate not supplied

Neuro-ophthalmic manifestations of hemangiopericytoma.

PURPOSE: To describe the neuro-ophthalmic presentations of a rare intracranial tumor, hemangiopericytoma. METHODS: Retrospective multicenter case series. RESULTS: The neuro-ophthalmic and radiographic features of hemangiopericytoma are reviewed. The clinical presentation may mimic meningioma and the pre-operative distinction between meningioma and hemangiopericytoma is important because the evaluation, management, treatment, and prognosis differ significantly for the two lesions. CONCLUSION: We report five cases of intracranial hemangiopericytoma and review the neuro-ophthalmic findings of this uncommon entity.

Adult↗

PubMedDate not supplied

Abnormal multifocal electroretinogram (mfERG) in ethambutol toxicity.

OBJECTIVE: To report the abnormal multifocal electroretinogram (mfERG) findings in two cases of presumed ethambutol toxicity. DESIGN: Retrospective observational case series. PARTICIPANTS: Two patients with ethambutol toxicity and visual loss. TESTING: Multifocal electroretinography. MAIN OUTCOME MEASURE: Waveform measurements on multifocal electroretinography. RESULTS: Two patients with bilateral visual loss due to ethambutol toxicity underwent mfERG testing that disclosed both diffuse and central field loss compatible with retinal dysfunction as a contributing mechanism to the visual field loss. CONCLUSION: Ethambutol toxicity affects not only the optic nerve but probably other retinal elements based upon abnormal mfERG findings.

Aged, 80 and over↗