Biomedical subjects

John L Keltner

Publications and source records attributed to John L Keltner.

14 recordsLinked to original sources

PubMed2006

The association between glaucomatous visual fields and optic nerve head features in the Ocular Hypertension Treatment Study.

PURPOSE: To determine the association between change from baseline in the optic nerve head (ONH) and the visual field (VF) during follow-up of ocular hypertension participants in the Ocular Hypertension Treatment Study. DESIGN: Longitudinal randomized clinical trial. PARTICIPANTS: One hundred sixty-eight eyes of 152 ocular hypertensive participants ages 40 to 80 years. METHODS: Cox hazard models were applied to 3232 eyes, which included 81 eyes that reached a study end point by developing a glaucomatous VF (VF end point) and 128 eyes that reached a study end point by developing an optic disc change (optic disc end point). MAIN OUTCOME MEASURES: Primary open-angle glaucoma end point as determined by changes in the VF or optic disc. RESULTS: Forty-one eyes reached an end point by both VF and optic disc criteria; 40 eyes reached only a VF end point, and 87 reached only an optic disc end point. Times to reach isolated disc or field end points were similar. Visual field end points were more likely (P<0.0001) in eyes that showed the following ONH features: an ONH hemorrhage, thinning of the optic disc rim, or enlargement of the horizontal cup-to-disc (C/D) ratio. Optic disc end points were more likely (P<0.0001) in eyes that showed the following VF features: some evidence of a nasal step or a partial arcuate VF defect, or an increase in the pattern standard deviation (PSD). CONCLUSIONS: Both the VF and the optic disc must be monitored with equal diligence, because either may show the first evidence of glaucomatous damage. Changes in the ONH based on stereophotographic observation (rim thinning, hemorrhage, or a slight increase in C/D ratio) and VF changes (evidence of a nasal step/partial arcuate defect or an increase in PSD) suggest that these cases have an increased risk of developing glaucoma. Confirmation of such subtle findings should be sought through repeat testing and correlation with other clinical results.

Adult↗

PubMed2006

Leber hereditary optic neuropathy possibly triggered by exposure to tire fire.

We report three members of one family, a mother and two daughters aged 4 and 7 years, who developed visual loss from Leber hereditary optic neuropathy within a 19-month period. All three had been exposed to smoke from two large rubber tire fires within the previous 24 months, suggesting the possibility of an epigenetic triggering factor.

Adult↗

PubMed2006

Asymmetries and visual field summaries as predictors of glaucoma in the ocular hypertension treatment study.

PURPOSE: To evaluate whether baseline visual field data and asymmetries between eyes predict the onset of primary open-angle glaucoma (POAG) in Ocular Hypertension Treatment Study (OHTS) participants. METHODS: A new index, mean prognosis (MP), was designed for optimal combination of visual field thresholds, to discriminate between eyes that developed POAG from eyes that did not. Baseline intraocular pressure (IOP) in fellow eyes was used to construct measures of IOP asymmetry. Age-adjusted baseline thresholds were used to develop indicators of visual field asymmetry and summary measures of visual field defects. Marginal multivariate failure time models were constructed that relate the new index MP, IOP asymmetry, and visual field asymmetry to POAG onset for OHTS participants. RESULTS: The marginal multivariate failure time analysis showed that the MP index is significantly related to POAG onset (P < 0.0001) and appears to be a more highly significant predictor of POAG onset than either mean deviation (MD; P = 0.17) or pattern standard deviation (PSD; P = 0.046). A 1-mm Hg increase in IOP asymmetry between fellow eyes is associated with a 17% increase in risk for development of POAG. When threshold asymmetry between eyes existed, the eye with lower thresholds was at a 37% greater risk of development of POAG, and this feature was more predictive of POAG onset than the visual field index MD, though not as strong a predictor as PSD. CONCLUSIONS: The MP index, IOP asymmetry, and binocular test point asymmetry can assist in clinical evaluation of eyes at risk of development of POAG.

Antihypertensive Agents↗

PubMed2006

In vivo imaging of the photoreceptor mosaic in retinal dystrophies and correlations with visual function.

PURPOSE: To relate in vivo microscopic retinal changes to visual function in patients who have various forms of retinal dystrophy. METHODS: The UC Davis Adaptive Optics (AO) fundus camera was used to acquire in vivo retinal images at the cellular level. Visual function tests consisting of visual fields, multifocal electroretinography (mfERG), and contrast sensitivity were measured in all subjects by using stimuli that were coincident with areas imaged. Five patients with different forms of retinal dystrophy and three control subjects were recruited. Cone densities were quantified for all retinal images. RESULTS: In all images of diseased retinas, there were extensive areas of dark space between groups of photoreceptors, where no cone photoreceptors were evident. These irregular features were not seen in healthy retinas, but were apparent in patients with retinal dystrophy. There were significant correlations between functional vision losses and the extent to which these irregularities, quantified by cone density, occurred in retinal images. CONCLUSIONS: AO fundus imaging is a reliable technique for assessing and quantifying the changes in the photoreceptor layer as disease progresses. Furthermore, this technique can be useful in cases where visual function tests provide borderline or ambiguous results, as it allows visualization of individual photoreceptors.

Adolescent↗

PubMed2005

Normal visual field test results following glaucomatous visual field end points in the Ocular Hypertension Treatment Study.

OBJECTIVE: To compare the occurrence of normal visual field (VF) test results following 2 vs 3 consecutive, abnormal, reliable test results in the Ocular Hypertension Treatment Study. METHODS: The Ocular Hypertension Treatment Study is a prospective, multicenter follow-up study as part of a longitudinal randomized clinical trial. Sixty-four (68 eyes) of 1636 participants developed a VF primary open-angle glaucoma (POAG) end point. We compared the proportion of normal VF test results after a VF POAG end point among eyes whose VF abnormality was confirmed by 2 (n = 9 eyes) vs 3 (n = 59 eyes) consecutive, abnormal, reliable VF test results. RESULTS: The proportion of VF test results that were normal subsequent to a VF POAG end point in eyes whose abnormality was confirmed by 2 consecutive, abnormal, reliable test results was significantly higher (73 [66%] of 110) compared with eyes whose abnormality was confirmed by 3 consecutive, abnormal, reliable test results (46 [12%] of 381) (P = .01). CONCLUSIONS: A VF POAG end point confirmed by 3 consecutive, abnormal, reliable VF test results appears to have greater specificity and stability than either 1 or 2 consecutive, abnormal, reliable VF test results. However, some eyes whose VF POAG end point was confirmed by 3 consecutive, abnormal, reliable test results nonetheless had 1 or more normal test results on follow-up.

Adult↗

PubMed2005

Characteristics of the normative database for the Humphrey matrix perimeter.

PURPOSE: The Humphrey Matrix (Carl Zeiss Meditec, Dublin CA; Welch-Allyn, Skaneateles, NY) is a high-spatial-resolution perimeter that uses frequency-doubling stimuli. It incorporates an efficient test strategy that assumes that age, eccentricity, and test procedure type have only small effects on sensitivity. The results used to create the normative database for the perimeter were examined, to see whether these assumptions were met and to examine the form of the normative data. METHOD: Visual fields were measured (Matrix 30-2, 24-2, 10-2 and Macula patterns) in >275 subjects judged to be normal by a battery of clinical procedures. The right eye was always tested first. RESULTS: Sensitivity decreased by approximately 0.7 dB per age decade across all eccentricities; sensitivity decreased with eccentricity, typically by <5 dB at the most peripheral points tested. Although there was no systematic difference in sensitivity between the 30-2 and 24-2 tests, the Macula test sensitivities were typically 1 dB higher than for the 10-2 test. Sensitivity in the left eye was slightly lower than in the right, with the difference being significantly greater in the temporal visual field. In most test locations, the 95% confidence interval of normal sensitivity was approximately 6 dB below the median sensitivity. CONCLUSIONS: The performance of the test strategy in the Matrix perimeter is appropriately matched to the response characteristics of the normal population. The finding of a spatially nonuniform difference in sensitivity between left and right eyes is attributable to light-adaptation differences between the eyes. This effect is accounted for in the perimeter's normative database.

Adolescent↗

PubMed2004

Neurologic impairment 10 years after optic neuritis.

BACKGROUND: Participants enrolled in the Optic Neuritis Treatment Trial have been observed for more than a decade to assess the relationship between optic neuritis and the development of clinically definite multiple sclerosis. OBJECTIVE: To assess neurologic disability 10 to 12 years after an initial episode of optic neuritis. DESIGN: Longitudinal follow-up of a clinical trial. SETTING: Fourteen Optic Neuritis Treatment Trial clinical centers performed standardized neurologic examinations, including an assessment of neurologic disability. PARTICIPANTS: One hundred twenty-seven patients who had developed clinically definite multiple sclerosis. MAIN OUTCOME MEASURES: Functional Systems Scale and Expanded Disability Status Scale. RESULTS: The disability of most patients was mild, with 65% of patients having an Expanded Disability Status Scale score lower than 3.0. The degree of disability appeared to be unrelated to whether the baseline magnetic resonance imaging scan was lesion-free or showed lesions (P =.51). Among patients with baseline lesions, the degree of disability was unrelated to the number of lesions that were present on the scan (P =.14). Two patients died owing to severe multiple sclerosis, one of whom had no lesions revealed on the baseline scan. CONCLUSION: Most patients who develop clinically definite multiple sclerosis following an initial episode of optic neuritis will have a relatively benign course for at least 10 years.

Adult↗

PubMed2004

Visual function more than 10 years after optic neuritis: experience of the optic neuritis treatment trial.

PURPOSE: To assess visual function more than 10 years after an episode of optic neuritis in patients enrolled in the Optic Neuritis Treatment Trial. DESIGN: Longitudinal follow-up of a randomized clinical trial. METHODS: Vision testing included measures of visual acuity, contrast sensitivity, and visual field. Quality of life was assessed with the National Eye Institute Visual Function Questionnaire. RESULTS: Examinations were completed on 319 patients. In most patients, visual function test results in the eyes that experienced optic neuritis at study entry ("affected eyes") were normal or only slightly abnormal after 9.9 to 13.7 years. Visual acuity in the affected eyes was >or=20/20 in 74%, 20/25 to 20/40 in 18%, <20/40 to 20/200 in 5%, and <20/200 in 3%. On average, visual function was worse in patients with multiple sclerosis (MS) than in those without MS. Recurrent optic neuritis in either eye occurred in 35% of patients. Such attacks were more frequent in patients with MS (P <.001). The National Eye Institute Visual Function Questionnaire scores were lower when visual acuity was abnormal and when MS was present. CONCLUSIONS: Most patients retained good to excellent vision more than 10 years after an attack of optic neuritis. Recurrences were more frequent in patients with MS.

Adolescent↗

PubMed2003

Classification of visual field abnormalities in the ocular hypertension treatment study.

OBJECTIVES: (1) To develop a classification system for visual field (VF) abnormalities, (2) to determine interreader and test-retest agreement, and (3) to determine the frequency of various VF defects in the Ocular Hypertension Treatment Study. METHODS: Follow-up VFs are performed every 6 months and are monitored for abnormality, indicated by a glaucoma hemifield test result or a corrected pattern SD outside the normal limits. As of January 1, 2002, 1636 patients had 2509 abnormal VFs. Three readers independently classified each hemifield using a classification system developed at the VF reading center. A subset (50%) of the abnormal VFs was reread to evaluate test-retest reader agreement. A mean deviation was calculated separately for the hemifields as an index to the severity of VF loss. MAIN OUTCOME MEASURES: A 97% interreader hemifield agreement. RESULTS: The average hemifield classification agreement (between any 2 of 3 readers) for 5018 hemifields was 97% and 88% for the 1266 abnormal VFs that were reread (agreement between the first and second classifications). Glaucomatous patterns of loss (partial arcuate, paracentral, and nasal step defects) composed the majority of VF defects. CONCLUSION: The Ocular Hypertension Treatment Study classification system has high reproducibility and provides a possible nomenclature for characterizing VF defects.

Antihypertensive Agents↗

PubMed2003

High- and low-risk profiles for the development of multiple sclerosis within 10 years after optic neuritis: experience of the optic neuritis treatment trial.

OBJECTIVE: To identify factors associated with a high and low risk of developing multiple sclerosis after an initial episode of optic neuritis. METHODS: Three hundred eighty-eight patients who experienced acute optic neuritis between July 1, 1988, and June 30, 1991, were followed up prospectively for the development of multiple sclerosis. Consenting patients were reassessed after 10 to 13 years. RESULTS: The 10-year risk of multiple sclerosis was 38% (95% confidence interval, 33%-43%). Patients (160) who had 1 or more typical lesions on the baseline magnetic resonance imaging (MRI) scan of the brain had a 56% risk; those with no lesions (191) had a 22% risk (P<.001, log rank test). Among the patients who had no lesions on MRI, male gender and optic disc swelling were associated with a lower risk of multiple sclerosis, as was the presence of the following atypical features for optic neuritis: no light perception vision; absence of pain; and ophthalmoscopic findings of severe optic disc edema, peripapillary hemorrhages, or retinal exudates. CONCLUSIONS: The 10-year risk of multiple sclerosis following an initial episode of acute optic neuritis is significantly higher if there is a single brain MRI lesion; higher numbers of lesions do not appreciably increase that risk. However, even when brain lesions are seen on MRI, more than 40% of the patients will not develop clinical multiple sclerosis after 10 years. In the absence of MRI lesions, certain demographic and clinical features seem to predict a very low likelihood of developing multiple sclerosis. This natural history information is a critical input for estimating a patient's 10-year multiple sclerosis risk and for weighing the benefit of initiating prophylactic treatment at the time of optic neuritis or other initial demyelinating events in the central nervous system.

Acute Disease↗

PubMed2002

Multifocal electroretinogram: age-related changes for different luminance levels.

BACKGROUND: Age-related changes in the first-order multifocal electroretinogram (mfERG) responses were measured for two different luminance levels (200 and 700 cd.m(-2)). The relative contribution of optical and neural factors to senescent change in response was evaluated. METHODS: Data were obtained from one eye of each of 71 normal phakic subjects, age 9-80 years. The mfERG responses were recorded with the 7" stimulus-refractor unit (EDI) and VERIS 4.3 using the following protocol: bipolar contact lens, 103 hexagons, consecutive stimulation with 200 and 700 cd.m(-2), pupils > or =6 mm, amplification of 10(5), filter cut-offs at 10 and 300 Hz. RESULTS: Age-correlated decreases in amplitude and response density and increases in P1 implicit time were found for both luminance levels. The mean response density (nV.deg(-2)) was higher for the 700 cd.m(-2) stimulus, but the rate of change with age was not significantly different from that obtained with the 200 cd.m(-2) stimulus. Implicit time was not significantly different for the two light levels, nor was the rate of change with age. The decrease in response density and the increase in implicit time with age were significant across all retinal regions, dividing the 50 deg stimulus into six concentric rings. Age-related change in response density was greatest for the central retina and decreased with increasing retinal eccentricity. CONCLUSION: Log mfERG response changes linearly as a function of age. Analyses of the effects of reduced ocular media transmission and increased stray light, along with ancillary data obtained from pseudophakes, imply that age-related changes in the mfERG are due to both optical and neural factors.

Adolescent↗

PubMed2002

The Ocular Hypertension Treatment Study: a randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma.

BACKGROUND: Primary open-angle glaucoma (POAG) is one of the leading causes of blindness in the United States and worldwide. Three to 6 million people in the United States are at increased risk for developing POAG because of elevated intraocular pressure (IOP), or ocular hypertension. There is no consensus on the efficacy of medical treatment in delaying or preventing the onset of POAG in individuals with elevated IOP. Therefore, we designed a randomized clinical trial, the Ocular Hypertension Treatment Study. OBJECTIVE: To determine the safety and efficacy of topical ocular hypotensive medication in delaying or preventing the onset of POAG. METHODS: A total of 1636 participants with no evidence of glaucomatous damage, aged 40 to 80 years, and with an IOP between 24 mm Hg and 32 mm Hg in one eye and between 21 mm Hg and 32 mm Hg in the other eye were randomized to either observation or treatment with commercially available topical ocular hypotensive medication. The goal in the medication group was to reduce the IOP by 20% or more and to reach an IOP of 24 mm Hg or less. MAIN OUTCOME MEASURES: The primary outcome was the development of reproducible visual field abnormality or reproducible optic disc deterioration attributed to POAG. Abnormalities were determined by masked certified readers at the reading centers, and attribution to POAG was decided by the masked Endpoint Committee. RESULTS: During the course of the study, the mean +/- SD reduction in IOP in the medication group was 22.5% +/- 9.9%. The IOP declined by 4.0% +/- 11.6% in the observation group. At 60 months, the cumulative probability of developing POAG was 4.4% in the medication group and 9.5% in the observation group (hazard ratio, 0.40; 95% confidence interval, 0.27-0.59; P<.0001). There was little evidence of increased systemic or ocular risk associated with ocular hypotensive medication. CONCLUSIONS: Topical ocular hypotensive medication was effective in delaying or preventing the onset of POAG in individuals with elevated IOP. Although this does not imply that all patients with borderline or elevated IOP should receive medication, clinicians should consider initiating treatment for individuals with ocular hypertension who are at moderate or high risk for developing POAG.

Administration, Topical↗

PubMed2002

The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open-angle glaucoma.

BACKGROUND: The Ocular Hypertension Treatment Study (OHTS) has shown that topical ocular hypotensive medication is effective in delaying or preventing the onset of primary open-angle glaucoma (POAG) in individuals with elevated intraocular pressure (ocular hypertension) and no evidence of glaucomatous damage. OBJECTIVE: To describe baseline demographic and clinical factors that predict which participants in the OHTS developed POAG. METHODS: Baseline demographic and clinical data were collected prior to randomization except for corneal thickness measurements, which were performed during follow-up. Proportional hazards models were used to identify factors that predicted which participants in the OHTS developed POAG. RESULTS: In univariate analyses, baseline factors that predicted the development of POAG included older age, race (African American), sex (male), larger vertical cup-disc ratio, larger horizontal cup-disc ratio, higher intraocular pressure, greater Humphrey visual field pattern standard deviation, heart disease, and thinner central corneal measurement. In multivariate analyses, baseline factors that predicted the development of POAG included older age, larger vertical or horizontal cup-disc ratio, higher intraocular pressure, greater pattern standard deviation, and thinner central corneal measurement. CONCLUSIONS: Baseline age, vertical and horizontal cup-disc ratio, pattern standard deviation, and intraocular pressure were good predictors for the onset of POAG in the OHTS. Central corneal thickness was found to be a powerful predictor for the development of POAG.

Administration, Topical↗

PubMed2002

Baseline visual field characteristics in the ocular hypertension treatment study.

PURPOSE: The Ocular Hypertension Treatment Study (OHTS) seeks to evaluate the safety and efficacy of topical ocular hypotensive medication in preventing or delaying the onset of visual field loss and/or optic nerve damage in ocular hypertensive subjects at risk for developing primary open-angle glaucoma. This study evaluates the baseline visual field test characteristics (visual field status, reliability properties, etc.) of patients who underwent eligibility visual field testing for entry to the OHTS. DESIGN: Cross-sectional study of baseline data as part of a longitudinal randomized clinical trial. PARTICIPANTS: Two thousand eight hundred nineteen ocular hypertensive individuals, aged 40 to 80 (mean age, 55). METHODS: Subjects underwent at least two Humphrey Field Analyzer Program 30-2 Full Threshold visual field examinations in both eyes for study eligibility. A third examination was performed if a prior test was abnormal, questionable, or unreliable. For final eligibility, two sets of visual field examinations had to meet OHTS criteria for reliability and had to be classified as "normal." All OHTS visual field tests of potential subjects were submitted for eligibility assessment to the OHTS Visual Field Reading Center. MAIN OUTCOME MEASURES: The percentage of visual fields that were normal and reliable according to OHTS criteria. RESULTS: Of the subset of 2304 subjects who completed the eligibility assessments, 1828 (79%) were OHTS-eligible based on visual field test requirements. A third eligibility test was required for 11% of all eyes because of unreliable, questionable, or abnormal test results. With the 33% fixation loss cutoff in the OHTS, 97% of all eligibility visual field examinations were reliable and 3% were unreliable. The most frequent cause (69.5%) of unreliability was excessive fixation losses. CONCLUSIONS: Permitting one repeat test after an abnormal or unreliable test allowed an extra 560 patients to be "eligible" for the study based on visual field tests. A clinical screening review of otherwise normal and reliable tests was not restrictive. The adoption of a 33% fixation loss cutoff significantly reduced the number of required retests and prevented study rejection of 89 patients.

Adult↗