Biomedical subjects

Chris A Johnson

Publications and source records attributed to Chris A Johnson.

At least 19 recordsLinked to original sources

PubMed2007

The results of screening frequency doubling technology perimetry in different locations of the community.

PURPOSE: To determine the effect of screening location on the frequency of abnormal test results with Frequency Doubling Technology (FDT) perimetry. DESIGN: Retrospective cross-sectional study. METHODS: The Vision Screening Outreach Project conducted FDT testing in community sites surrounding Portland, Oregon. The sites were separated into a specific location type: health care clinics, work sites, senior centers, festivals/fairs, food banks/shelters, and other locations. These locations were compared for differences in the proportion of screening failures. MAIN OUTCOME MEASURES: Screening failure (defined as a repeatable, abnormal FDT result in either eye). RESULTS: There were 9052 participants from 211 locations in Oregon and Washington. On initial FDT testing, the right and left eye had abnormal results in 18% (1654/9052) and 21% (1918/9052) of participants. Of those with abnormal FDT results, approximately 30% of eyes reverted to normal on repeat testing. Overall, 13% of participants were screening failures. Screening failure was highly associated with age (P<0.001). After controlling for age, participants at senior centers (P<0.001) were most likely to be screening failures and participants at work sites (P=0.006) were least likely to be screening failures when compared with health clinics. CONCLUSIONS: An investigator should repeat an initially abnormal FDT result when screening with FDT. Age and the location of testing influence the probability of a screening failure. Screening in senior centers is most likely to result in screening failure. However, only a randomized controlled trial can determine the true benefit of FDT screening in these locations.

Adolescent↗

PubMed2006

Frequency doubling technology perimetry in normal children.

PURPOSE: To test visual field thresholds of normal children with frequency doubling technology (FDT) perimetry to quantify testing times and reliability characteristics in a pediatric population and to determine whether current methods of stratifying adult threshold values need revision for children. DESIGN: Prospective cross-sectional study. METHODS: Ninety-four children, ages 5 to 17 years, were recruited from local pediatric clinics and the general community and were tested at one center. Children likely to have abnormal visual fields or abnormal test taking ability because of ophthalmic, neurologic, or behavioral problems were excluded. Children were asked to perform a threshold FDT visual field with each of their eyes. Threshold results were gathered, analyzed, and compared with the standards that have been established for tests in adults. Results were validated by testing a further 72 children, with the same protocol, at a different center. RESULTS: For children older than 14 years, threshold mean deviation values were within normal limits according to the adult normative database that is used currently in FDT perimetry. Below 15 years of age, mean deviations for normal children decreased with decreasing age. The best linear fit was given by a mean deviation of -11.43 +/- 0.82 dB x age (R2 = 0.18; P < 10(-5)). CONCLUSION: This research establishes a normative model for pediatric visual field testing with FDT and, by a comparison of threshold results for normal children to established adult norms, provides evidence that parameters for normal sensitivity must be revised for children younger than 15 years.

Adolescent↗

PubMed2006

Comparison of the ASA, MOBS, and ZEST threshold methods.

The modified binary search, or MOBS, technique is an adaptive, non-parametric procedure for estimating thresholds [Tyrrell, R. A, & Owens, D. A. (1988). A rapid technique to assess the resting states of eyes and other threshold phenomena: the modified binary search (MOBS). Behavior Research Methods, Instruments, and Computers, 20, 137-141.], which has recently been incorporated into a commercially available perimeter. Information regarding the performance of this technique is limited, however. We performed Monte Carlos simulations on the MOBS procedure, as well as on a Zippy Estimation by Sequential Testing, or ZEST, procedure (King-Smith, Grigsby, Vingrys, Benes & Supowit, 1994) and an Accelerated Stochastic Approximation, or ASA, procedure (Kesten, 1958) for comparison. The efficiency, convergence probability, and robustness to false positive and false negative responses were determined. Differences between the three procedures typically were small, the most prominent being the number of presentations required to estimate threshold.

False Negative Reactions↗

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

Repeatability of normal multifocal VEP: implications for detecting progression.

PURPOSE: To assess the repeatability of the multifocal visual evoked potential (mfVEP) and to compare it with the repeatability of standard automated perimetry (SAP) in the same group of 50 normal controls retested after 1 year. Our second aim was to assess the repeatability of false alarm rates determined previously for the mfVEP using various cluster criteria. METHODS: Fifty individuals with normal vision participated in this study (33 females and 17 males). The age range was 26.7 to 77.9 years and the group average age (+/- SD) was 51.4 (+/- 12.1) years. Pattern-reversal mfVEPs were obtained using a dartboard stimulus pattern in VERIS and two 8-minute runs per eye were averaged. The average number of days between the first and second mfVEP tests was 378 (+/- 58). SAP visual fields were obtained within 17.4 (+/- 20.3) days of the mfVEP using the SITA-standard threshold algorithm. Repeatability of mfVEPs and SAP total deviation values were evaluated by calculating point-wise limits of agreement (LOA). Specificity (1-false alarm rate) was evaluated for a range of cluster criteria, whereby the number and probability level of the points defining a cluster were varied. RESULTS: Point-wise LOA for the mfVEP signal-to-noise ratio (SNR) ranged from 2.0 to 4.3 dB, with an average of 2.9 dB across all 60 locations. For SAP, LOA ranged from 2.4 to 8.9 dB, with an average of 4.0 dB (excluding the points immediately above and below the blind spot). Clusters of abnormal points were not likely to repeat on either mfVEP or SAP. When an mfVEP abnormality was defined as the repeat presence (confirmation) of a 3-point (P < 0.05) cluster anywhere within a single hemifield, only 1 (of 200) monocular hemifield was deemed abnormal. Although the LOA of the mfVEP were similar throughout the field, the limited dynamic range of SNR at superior field locations will limit the ability to follow progression in "depth" at those locations. CONCLUSIONS: Repeatability of the mfVEP was slightly better than SAP visual fields in this group of controls with a 1-year retest interval. This suggests that progression in early stages should be more easily detectable by mfVEP. However, in certain field locations (eg, superior periphery), the relatively more narrow dynamic range of the SNR of the mfVEP may limit detection of progression to just 1 event. Confirmation of a 3-point cluster abnormality is highly suggestive of a true defect on the mfVEP.

Adult↗

PubMed2006

Normal age-related sensitivity loss for a variety of visual functions throughout the visual field.

PURPOSE: The purpose of this study is to compare the rate of age-related decline, the magnitude of practice effects, and test-retest variability among normal subjects using six different tests of visual function. METHODS: One hundred normal subjects aged between 20 and 85 were enrolled in the study. Six visual field test procedures were used consisting of standard automated perimetry (SAP), short wavelength automated perimetry (SWAP), temporal modulation perimetry (TMP), frequency-doubling technology perimetry (FDT), detection acuity perimetry (DAP),and resolution acuity perimetry (RAP). To facilitate direct comparison, the results for each test were divided by that test's estimated dynamic range. RESULTS: Of the three tests used clinically most commonly, SWAP exhibited the greatest aging and practice effects and test-retest variability followed by FDT with SAP exhibiting the least. RAP was the most variable test followed by TMP. CONCLUSIONS: These results should be taken into account when evaluating glaucomatous loss using different functional tests and when comparing the performance, predictive power, and speed of detection of the different tests.

Adult↗

PubMed2006

Evaluation of decision rules for frequency-doubling technology screening tests.

PURPOSE: Frequency-doubling technology (FDT) perimetry has shown promise as a screening test for glaucoma. This study investigates different possible decision rules for FDT screening by applying them to groups of normal and glaucoma subjects. METHODS: Within three centers, 218 subjects (aged 15-88 years; 78 with glaucoma, 140 without ocular disease) were each tested twice with the screening program of the FDT perimeter. The subjects consisted of 140 normal subjects with no evidence of glaucoma or other ocular disease likely to affect the visual field and 78 subjects with a diagnosis of glaucoma and no other ocular disease. Fifteen decision rules were applied to the data to compare their sensitivity and specificity. RESULTS: Estimated specificities of the different decision rules ranged from 78% to 99%, although with this sample size, the confidence intervals for these estimates are quite large. Estimated sensitivities ranged from 40% to 72%. Suggested criteria for distinguishing normal subjects from those with glaucoma seem to be either a cluster of two or more adjacent locations abnormal at the p < 2% level with at least one location confirmed or a single location very abnormal (p < 1%) and confirmed. CONCLUSIONS: Specificity was clearly improved by confirming an apparently abnormal test result by repeating the screening test outweighing the resultant small loss in sensitivity. These findings provide useful information for making an informed choice of decision rules for FDT screening results.

Adolescent↗

PubMed2006

Scotoma mapping by semi-automated kinetic perimetry: the effects of stimulus properties and the speed of subjects' responses.

PURPOSE: The study aimed firstly to determine the effects of stimulus variables on the detection of a scotoma border and, secondly, to study the reproducibility of the method during semi-automated kinetic perimetry. METHODS: The size of the physiological blind spot in 18 young normal subjects was measured with a video-campimetric device, the Tübingen computer campimeter (TCC). Kinetic stimuli of two different sizes and at four different levels of luminance were presented. Examinations were repeated within 2 weeks. Measurements were corrected for individual response times and the area of the blind spot was computed. The effects of stimulus strength and size and the repeatability of blind spot measurements were evaluated by an analysis of variance. RESULTS: The physiological blind spot showed significant inter- and intraindividual variations in size (least square means ranging from 17 to 49 square degrees), with a standard deviation of 6.8 square degrees. The measured size of the blind spot increased as a function of decreasing stimulus value, by reducing either the relative brightness or the size of stimuli. Use of a correction for each subject's speed of responses nearly halved the level of random variance. The temporal sequence of measurements (the order in which they were performed) had no apparent effect on the calculated values of blind spot size. CONCLUSIONS: Semi-automated kinetic perimetry can determine the size of the physiological blind spot with good repeatability in young, normal subjects. Determination of each individual's speed of response and inclusion of this variable in the calculations reduced variance of the measure significantly. This study confirmed the presence of considerable interindividual differences in the size of the physiological blind spot.

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

Assessment of false positives with the Humphrey Field Analyzer II perimeter with the SITA Algorithm.

PURPOSE: To evaluate the effects of false-positive (FP) response errors on mean deviation (MD), pattern standard deviation (PSD), glaucoma hemifield test (GHT), and test duration in the Humphrey Field Analyzer's (HFA II) Swedish Interactive Threshold Algorithm (SITA; Carl Zeiss Meditec, Inc., Dublin, CA). METHODS: Five individuals with glaucoma (ages 52, 63, 69, 77, and 78 years) and five individuals with normal, healthy eyes (ages 25, 34, 43, 45, and 52 years), participated in the study. Each subject was experienced in automated perimetry and performed multiple, monocular baseline SITA-standard (SITA-S) 24-2 visual field tests. In addition, normal subjects completed SITA-S 24-2 field examinations in which known frequencies of FP error were introduced (0%, 5%, 10%, 20%, or 33% frequency). Likewise, the subjects with glaucoma completed visual field examinations with 0%, 20%, and 33% error introduced during the test. RESULTS: Reported FP errors were significantly lower than the introduced frequency of error. The SITA algorithm more accurately identified FP errors when the MD and PSD diverged from normal. Test duration increased as introduced error frequencies increased. The Statpac single-field analyses indicated that two thirds of the tests with introduced errors produced a "low-patient-reliability" determination. CONCLUSIONS: HFA II SITA-S underestimates patients' FP errors, particularly among normal patients. High FP error frequencies can have adverse effects on MD and PSD, leading clinicians and researchers to an inaccurate determination of the amount and severity of visual field loss.

Adult↗

PubMed2005

Quantitation of cardiolipin molecular species in spontaneously hypertensive heart failure rats using electrospray ionization mass spectrometry.

Electrospray ionization mass spectrometry has previously been used to probe qualitative changes in the phospholipid cardiolipin (CL), but it has rarely been used in a quantitative manner. We assessed changes in the amount of individual molecular species of cardiac CL present in a model of congestive heart failure using 1,1',2,2'-tetramyristoyl cardiolipin as an internal standard. There was a linear relationship between the ratio of the negative molecular ion ([M-H]-) current from four different CL reference standards and the [M-H]- from the internal standard, as a function of the concentration of CL molecular species. Therefore, this internal standard can be used to quantitate many naturally occurring CL molecular species over a wide range of CL concentrations. Using this method, changes to individual molecular species of CL in failing hearts from male spontaneously hypertensive heart failure rats were examined. CL isolated from cardiac mitochondria was compared with left ventricular tissue to demonstrate the feasibility of extracting and quantitating CL from either mitochondrial or tissue samples. The acyl chain composition of individual CL molecular species was identified using tandem mass spectrometry. In animals with heart failure, the major cardiac CL species (tetralinoloyl) decreased significantly, whereas other minor CL species were significantly increased.

Animals↗

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

Psychophysical investigation of ganglion cell loss in early glaucoma.

PURPOSE: To evaluate ganglion cell loss in early glaucoma using a variety of psychophysical tests and to identify optimal perimetric technique(s) for detection of early glaucomatous visual function loss. METHODS: Five perimetric tests, short wavelength automated perimetry (SWAP), temporal modulation perimetry (TMP), frequency doubling technology perimetry (FDT), detection acuity perimetry (DAP), and resolution acuity perimetry (RAP) were compared in their ability to discriminate between normal individuals and patients with early glaucoma or glaucoma suspects. Comparisons were also made by their ability to produce repeatable defects. The tests examined different visual functions that are likely to be mediated by different retinal ganglion cell subpopulations, thereby permitting examination of hypotheses of ganglion cell death in early glaucoma. RESULTS: All visual field tests demonstrated high performance in separating glaucoma patients from normal individuals. SWAP, TMP, FDT, and DAP provided the greatest discrimination between normal individuals and high- and low-risk glaucoma suspects. However, SWAP, TMP, and FDT obtained better consistency across the various analysis approaches (global indices and pointwise) than DAP and RAP. Of all the test types, FDT exhibited the highest proportion of repeatable abnormal test locations, with poor confirmation rates achieved by DAP and RAP. CONCLUSION: The performance of SWAP, FDT, and TMP suggests that these test types may all be suitable for detection of early loss of visual function in glaucoma. Ganglion cell subpopulations with lower levels of redundancy and/or those with larger cell sizes offer the most parsimonious explanation for earliest ganglion cell losses occurring in glaucoma.

Cell Death↗

PubMed2005

Predictive value of frequency doubling technology perimetry for detecting glaucoma in a developing country.

PURPOSE: To determine the feasibility and diagnostic precision of Frequency Doubling Technology (FDT) perimetry as a method to detect glaucoma in rural villages of a developing country. DESIGN: Cross-sectional study. METHODS: Testing included FDT perimetry (C-20-5 screening protocol), tonometry, anterior segment biomicroscopy, and dilated ophthalmoscopy in 296 rural, non-English speaking residents of Southern India over 35 years old. Participants repeated the FDT if they had a location with reduced sensitivity or an unreliable result. We defined an abnormal FDT as one location of reduced sensitivity present on both the initial and repeat examination. We determined the diagnostic precision of FDT separately for a glaucomatous optic disc, a cup to disc ratio (C/D) > or = 0.7, and a C/D > or = 0.8. RESULTS: Ninety-three percent of subjects were able to complete the test satisfactorily. With repeat FDT testing, 37% of eyes with abnormal FDT results subsequently converted to normal and 67% of eyes with unreliable results subsequently became reliable. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for a glaucomatous optic disc were 7%, 87%, 13%, 76%, and 69%, respectively; for a C/D > or = 0.7, they were 0%, 87%, 0%, 91%, and 81%, respectively; and for a C/D > or = 0.8, they were 0%, 87%, 0%, 99%, and 87%, respectively. CONCLUSION: Clinicians can use FDT perimetry to rapidly screen for glaucoma in rural villages of a developing country. FDT testing had high specificity and negative predictive value, but low sensitivity and positive predictive value. The low sensitivity suggests that FDT has limited applicability as the sole test for glaucoma screening in this population. Repeat testing of FDT results that are unreliable or suspected of being abnormal is beneficial for this screening procedure.

Adult↗

PubMed2005

Vision requirements for driver's license examiners.

PURPOSE: The purpose of this study was to determine the vision requirements for licensing and registration examiners (LREs) of motor vehicle drivers in the state of California. METHODS: A comprehensive investigation was conducted that included a literature review, consideration of the Americans with Disabilities Act, analysis of materials with a subject matter expert panel, an overview of visual function tests, a formal job analysis, job audits and site visits to licensing offices, analysis of accidents and critical incidents, performance of simulation studies, and a review and evaluation of all materials collected during the study. RESULTS: Based on this analysis, three visual functions (best-corrected visual acuity, peripheral visual field extent, and color vision) were determined to be important for performing the essential job functions of an LRE. It was recommended that LREs demonstrate a best-corrected visual acuity of at least 20/20 in each eye, a peripheral visual field of at least 100 degrees diameter of horizontal and vertical extent in each eye (with no evidence of scotomas or pathologic areas of nonseeing within the visual field), and color vision capabilities that permit a passing score on the Farnsworth Panel D-15 color vision test. DISCUSSION: The findings of this investigation provide a strong basis for specifying and justifying vision requirements for performing essential job functions for an LRE in the state of California.

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↗

PubMed2005

Evaluation of the structure-function relationship in glaucoma.

PURPOSE: While glaucoma is evaluated on the basis of structural and functional test results, the spatial relationship between structure and function is not well defined. This study produces a topographical map to demonstrate how sectors of the optic nerve head (ONH) are related to locations in the visual field, using empiric cross-sectional patient data. METHODS: One hundred nine subjects with healthy eyes and 166 subjects with diagnosed or suspected glaucoma (one test per patient) were evaluated using a retina tomograph and white-on-white standard automated perimetry (SAP). The tomograph ONH images were divided into 36 sectors; and the sector rim areas normalized to account for changes in the total rim area. These were then correlated with SAP thresholds. For each visual field location, a map was produced indicating the strength of correlation between the normalized sector rim areas and thresholds. RESULTS: The highest correlation between a sector's normalized rim area and a SAP location's sensitivity was 0.520. Twenty-seven of the 52 non-blind spot SAP locations exhibited a correlation greater than 0.2 with at least one ONH sector. Locations in the superior hemifield were usually best correlated with the polar inferior temporal sectors of the ONH; locations in the inferior hemifield were usually best correlated with the polar superior temporal sectors of the ONH. CONCLUSIONS: A map relating regions of the ONH to SAP test locations has been produced. This map may be useful in elucidating the structure-function relationship, particularly for cases of localized glaucomatous loss.

Aged↗

PubMed2005

Causes of visual impairment and common eye problems in Northwest American Indians and Alaska Natives.

OBJECTIVES: Little information exists regarding the causes of visual impairment and the most common eye problems in American Indians/Alaska Natives. METHODS: We randomly sampled American Indians/Alaska Natives older than 40 years from 3 tribes within the Northwest region. RESULTS: We found a higher prevalence of visual impairment and normal-tension glaucoma, as well as a lower prevalence of ocular hypertension, in American Indians/Alaska Natives compared with previous results in other racial/ethnic groups. CONCLUSIONS: American Indians/Alaska Natives have a need for vision correction. Future interventions in American Indians/Alaska Natives should include providing spectacles for refractive error, detecting glaucoma, and preventing visual impairment from age-related maculopathy and cataracts.

Adult↗