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Lenworth N Johnson

Publications and source records attributed to Lenworth N Johnson.

11 recordsLinked to original sources
PubMed2006

Development and validation of a computerized expert system for evaluation of automated visual fields from the Ischemic Optic Neuropathy Decompression Trial.

BACKGROUND: The objective of this report is to describe the methods used to develop and validate a computerized system to analyze Humphrey visual fields obtained from patients with non-arteritic anterior ischemic optic neuropathy (NAION) and enrolled in the Ischemic Optic Neuropathy Decompression Trial (IONDT). The IONDT was a multicenter study that included randomized and non-randomized patients with newly diagnosed NAION in the study eye. At baseline, randomized eyes had visual acuity of 20/64 or worse and non-randomized eyes had visual acuity of better than 20/64 or were associated with patients refusing randomization. Visual fields were measured before treatment using the Humphrey Field Analyzer with the 24-2 program, foveal threshold, and size III stimulus. METHODS: We used visual fields from 189 non-IONDT eyes with NAION to develop the computerized classification system. Six neuro-ophthalmologists ("expert panel") described definitions for visual field patterns defects using 19 visual fields representing a range of pattern defect types. The expert panel then used 120 visual fields, classified using these definitions, to refine the rules, generating revised definitions for 13 visual field pattern defects and 3 levels of severity. These definitions were incorporated into a rule-based computerized classification system run on Excel(R) software. The computerized classification system was used to categorize visual field defects for an additional 95 NAION visual fields, and the expert panel was asked to independently classify the new fields and subsequently whether they agreed with the computer classification. To account for test variability over time, we derived an adjustment factor from the pooled short term fluctuation. We examined change in defects with and without adjustment in visual fields of study participants who demonstrated a visual acuity decrease within 30 days of NAION onset (progressive NAION). RESULTS: Despite an agreed upon set of rules, there was not good agreement among the expert panel when their independent visual classifications were compared. A majority did concur with the computer classification for 91 of 95 visual fields. Remaining classification discrepancies could not be resolved without modifying existing definitions. Without using the adjustment factor, visual fields of 63.6% (14/22) patients with progressive NAION and no central defect, and all (7/7) patients with a paracentral defect, worsened within 30 days of NAION onset. After applying the adjustment factor, the visual fields of the same patients with no initial central defect and 5/7 of the patients with a paracentral defect were seen to worsen. CONCLUSION: The IONDT developed a rule-based computerized system that consistently defines pattern and severity of visual fields of NAION patients for use in a research setting.

Automation↗
PubMed2006

Facilitation as well as inhibition of the blink reflex by a visual prepulse requires intact striate cortex.

OBJECTIVE: The role of visual cortex in modulation of the human eye blink reflex was assessed. METHODS: Participants were 13 patients with unilateral striate cortex damage. Nonreflexogenic gratings were presented in their intact or blind hemifield prior to white noise or air puff blink-eliciting stimuli. RESULTS: Inhibition of reflex amplitude was observed at asynchronies ranging from about 120 to 600ms for visible but not invisible prepulses. Facilitation by intact-hemifield gratings was observed for (1) the latency of the acoustic blink reflex, (2) the amplitude of the disynaptic cutaneous blink reflex, R1, and (3) the latency of voluntary hand-grip reactions to the reflexogenic stimuli. These facilitatory effects were absent on trials with blind-hemifield prepulses. CONCLUSIONS: An intact V1 is required for prepulse facilitation as well as inhibition. SIGNIFICANCE: These results extend a popular model of sensorimotor gating deficits in schizophrenia.

Adolescent↗
PubMed2004

Neuroretinitis in patients with multiple sclerosis.

PURPOSE: To present a case series of three patients with neuroretinitis associated with multiple sclerosis. DESIGN: Retrospective, noncomparative, consecutive, interventional case series. PARTICIPANTS: Thirty-five consecutive patients with neuroretinitis. METHODS: The records of 35 consecutive patients with neuroretinitis were reviewed for prior, concurrent, or subsequent development of multiple sclerosis. MAIN OUTCOME MEASURES: Presentation, clinical course, and diagnosis of multiple sclerosis. RESULTS: Three of 35 patients (8.6%) with neuroretinitis were diagnosed with multiple sclerosis by the McDonald criteria. One of the three patients underwent brain biopsy that further confirmed multiple sclerosis. Neuroretinitis in the three patients occurred after the diagnosis of multiple sclerosis. All three patients with multiple sclerosis had been treated with interferon beta before or concurrently with the development of neuroretinitis. CONCLUSIONS: Neuroretinitis can be an associated manifestation of multiple sclerosis. The possible association between neuroretinitis and interferon beta warrants further investigation.

Adult↗
PubMed2004

The clinical spectrum of amiodarone-associated optic neuropathy.

PURPOSE: To describe the clinical spectrum of amiodarone-associated optic neuropathy. METHODS: Observational cases series and review. RESULTS: Of 55 cases, the median interval for onset of optic neuropathy was four months after initiating amiodarone; 88% occurred within 12 months. Seven (13%) patients were asymptomatic. Twenty-two (40%) patients presented with sudden visual loss, while 26 (47%) had insidious loss of vision. Visual acuity ranged from 20/15 to light perception; 10 (18%) patients had legal blindness with visual acuity of 20/200 or worse. Visual field loss was present in 91% of cases. Color vision loss was present in eight (40%) of 20 cases. Optic disc edema was present in 85% of cases, while eight (15%) patients had retrobulbar optic neuropathy, without evidence of disc edema. Optic disc edema resolved over a median time of three months. Five patients had raised intracranial pressure on lumbar puncture. CONCLUSION: We were able to classify amiodarone-associated optic neuropathy into five clinical categories with respect to temporal characteristics and optic nerve appearance: insidious-onset (43%), acute-onset (28%), retrobulbar (13%), increased intracranial pressure (8%), and delayed-progressive onset (8%). Most cases of optic neuropathy commenced within 12 months of initiating amiodarone, with the median onset being four months. Over 10% of patients will have no visual symptoms at the onset. Ophthalmologic examinations within the first 12 months--and particularly within four months of initiating amiodarone--should improve early detection of amiodarone-associated optic neuropathy.

Aged↗
PubMed2003

Hallucinating the past: a case of spontaneous and involuntary recall of long-term memories: perspectives on the hemispheric organization of visual memory.

This paper presents the unique case of a patient who developed palinopsias and formed visual hallucinations, representing spontaneous recall of memories from a discrete 10-year time period. The visual phenomena began shortly after the initiation of prophylactic whole-brain radiation therapy, following the removal of a metastatic adenocarcinoma in the region of the right cuneus. The most striking feature of this patient's hallucinations is the composition: memories from a discrete 10-year time period from about 30 years ago. This case provides further evidence to support the theory of a contralateral and hemispheric organization of visual memory. We propose that visual memory traces formed nearly three decades ago were spontaneously recalled in the form of hallucinations and palinopsias. It is noteworthy that the region of the brain most affected by the tumor and subsequent radiation therapy is postulated to permit perception of mental imagery. To our knowledge, no other case involving hallucination of 30-year-old memories has been reported.

Adenocarcinoma↗
PubMed2003

Visual function in patients with optic nerve pallor (optic atrophy).

This cross-sectional study assessed the relationship between the degree of optic nerve pallor (optic atrophy) and visual function. Using a set of "gold standard" stereoscopic slides, the severity of optic atrophy for 270 eyes, each having sustained a bout of optic neuropathy, was graded. Good visual acuity was found in 55/86 (64.0%) mild, 54/119 (45.4%) moderate, and 21/65 (32.3%) marked optic atrophy eyes. Good visual field was found in 6/28 (21.4%) mild, 4/43 (9.3%) moderate, and 2/28 (7.1%) marked optic atrophy eyes. Good color vision was found in 31/46 (67.4%) mild, 12/62 (19.4%) moderate, and 7/31 (22.6%) marked optic atrophy eyes. A significant rank correlation was observed between optic atrophy and visual acuity (P < 0.001; rs = 0.356), visual field (P < 0.001; rs = -0.398), and color vision (P < 0.001; rs = -0.492). As the graded severity of optic atrophy increases, the proportion of eyes with good visual function decreases. Visual field, rather than visual acuity or color vision, appears to be a better indicator of the severity of visual loss, when optic atrophy is present.

Cross-Sectional Studies↗
PubMedDate not supplied

Repeated intervals of high-dose corticosteroid: an overlooked therapy in multiple sclerosis.

The rate of conversion to multiple sclerosis is about 6% per year for five years after the first episode of optic neuritis. While the new MS agents have garnered much attention as promising agents to prevent MS relapses, an overlooked therapy is pulse high-dose corticosteroid (10 mg per kg or greater) as an intervention to delay or prevent the development of MS. Data from Optic Neuritis Treatment Trial (ONTT) and other studies underscore the need to investigate the efficacy of high-dose corticosteroid in MS.

Adjuvants, Immunologic↗