To analyze brightness, contrast, and color balance of digital versus film retinal images in a multicenter clinical trial, to propose a model image from exemplars, and to optimize both image types for ...evaluation of age-related macular degeneration (AMD).
The Age-Related Eye Disease Study 2 (AREDS2) is enrolling subjects from 90 clinics, with three quarters of them using digital and one quarter using film cameras. Image brightness (B), contrast (C), and color balance (CB) were measured with three-color luminance histograms. First, the exemplars (film and digital) from expert groups were analyzed, and an AMD-oriented model was constructed. Second, the impact of B/C/CB on the appearance of typical AMD abnormalities was analyzed. Third, B/C/CB in AREDS2 images were compared between film (156 eyes) and digital (605 eyes), and against the model. Fourth, suboptimal images were enhanced by adjusting B/C/CB to bring them into accord with model parameters.
Exemplar images had similar brightness, contrast, and color balance, supporting an image model. Varying a specimen image through a wide range of B/C/CB revealed greatest contrast of drusen and pigment abnormalities against normal retinal pigment epithelium with the model parameters. AREDS2 digital images were more variable than film, with lower correspondence to our model. Ten percent of digital were too dim and 19% too bright (oversaturated), versus 1% and 4% of film, respectively. On average, digital had lower green channel contrast (giving less retinal detail) than film. Overly red color balance (weaker green) was observed in 23% of digital versus 8% of film. About half of digital (but fewer film) images required enhancement before AMD grading. After optimization of both image types, AREDS2 image quality was judged as good as that in AREDS (all film).
A histogram-based model, derived from exemplars, provides a pragmatic guide for image analysis and enhancement. In AREDS2, the best digital images matched the best film. Overall, however, digital provided lower contrast of retinal detail. Digital images taken with higher G-to-R ratio showed better brightness and contrast management. Optimization of images in the multicenter study helps standardize documentation of AMD (ClinicalTrials.gov NCT00345176).
Accommodation dynamics in aging rhesus monkeys Croft, Mary Ann; Kaufman, Paul L; Crawford, Kathryn S ...
American journal of physiology. Regulatory, integrative and comparative physiology,
12/1998, Volume:
275, Issue:
6
Journal Article
Peer reviewed
1 Department of Ophthalmology
and Visual Sciences, Wisconsin Regional Primate Research Center,
University of Wisconsin, Madison, Wisconsin 53792; and
2 Department of Ophthalmology,
Columbia ...University, New York, New York 10032
Accommodation, the mechanism by which the
eye focuses on near objects, is lost with increasing age in humans and
monkeys. This pathophysiology, called presbyopia, is poorly understood. We studied aging-related changes in the dynamics of accommodation in
rhesus monkeys aged 4-24 yr after total iridectomy and midbrain implantation of an electrode to permit visualization and stimulation, respectively, of the eye's accommodative apparatus. Real-time video
techniques were used to capture and quantify images of the ciliary body
and lens. During accommodation in youth, ciliary body movement was
biphasic, lens movement was monophasic, and both slowed as the
structures approached their new steady-state positions.
Disaccommodation occurred more rapidly for both ciliary body and lens,
but with longer latent period, and slowed near the end point. With
increasing age, the amplitude of lens and ciliary body movement during
accommodation declined, as did their velocities. The latent period of
lens and ciliary body movements increased, and ciliary body movement
became monophasic. The latent period of lens and ciliary body movement
during disaccommodation was not significantly correlated with age, but
their velocity declined significantly. The age-dependent decline in
amplitude and velocity of ciliary body movements during accommodation
suggests that ciliary body dysfunction plays a role in presbyopia. The age changes in lens movement could be a consequence of increasing inelasticity or hardening of the lens, or of age changes in ciliary body motility.
presbyopia
OBJECTIVE To characterize functional and anatomic sequelae of a bleb induced by subretinal injection. METHODS Subretinal injections (100 μL) of balanced salt solution were placed in the ...superotemporal macula of 1 eye in 3 cynomolgus macaques. Fellow eyes received intravitreal injections (100 μL) of balanced salt solution. Fundus photography, ocular coherence tomography, and multifocal electroretinography were performed before and immediately after injection and again at intervals up to 3 months postinjection. Histopathologic analyses included transmission electron microscopy and immunohistochemistry for glial fibrillary acidic protein, rhodopsin, M/L-cone opsin, and S-cone opsin. RESULTS Retinas were reattached by 2 days postinjection (seen by ocular coherence tomography). Multifocal electroretinography waveforms were suppressed post–subretinal injection within the subretinal injection bleb and, surprisingly, also in regions far peripheral to this area. Multifocal electroretinography amplitudes were nearly completely recovered by 90 days. The spectral-domain ocular coherence tomography inner segment–outer segment line had decreased reflectivity at 92 days. Glial fibrillary acidic protein and S-cone opsin staining were unaffected. Rhodopsin and M/L-cone opsins were partially displaced into the inner segments. Transmission electron microscopy revealed disorganization of the outer segment rod (but not cone) discs. At all postinjection intervals, eyes with intravitreal injection were similar to baseline. CONCLUSIONS Subretinal injection is a promising route for drug delivery to the eye. Three months post–subretinal injection, retinal function was nearly recovered, although reorganization of the outer segment rod disc remained disrupted. Understanding the functional and anatomic effects of subretinal injection is important for interpretation of the effects of compounds delivered to the subretinal space. CLINICAL RELEVANCE Subretinal injection is a new potential route for drug delivery to the eye. Separating drug effects from the procedural effects is critical.
Background: Latinos have one of the highest rates of visual impairment associated with eye disease in the United States. Although little is known about the prevalence and risk of undetected eye ...disease (UED) in this population, it is known that Latinos encounter disproportionate barriers in accessing health care, which may influence the burden of UED. Objective: To estimate the burden and to evaluate factors associated with UED among Latinos, a majority of whom were Mexican-American. Research Design: Population-based, cross-sectional study. A detailed interview and eye examination were performed on participants. Subjects: A sample of 6357 Latinos (95% of whom had Mexican ancestry), aged ≥40, in 6 census tracts in Los Angeles, California. Main Outcome Measure: UED (macular degeneration, glaucoma, diabetic retinopathy, cataract, and refractive error) was defined as those persons with eye disease and no reported history of that eye disease. Results: Fifty-three percent (3349 of 6357) of the participants had eye disease. Sixty-three percent (2095 of 3349) of them had UED. Major risk factors for UED included older age odds ratio (OR): 4.7 (age ≥80), having diabetes mellitus (OR: 3.3), never having had an eye examination (OR: 2.4), being uninsured (OR: 1.6), lower educational attainment (OR: 1.4), and low acculturation (OR: 1.3). Conclusions: These findings provide evidence of the burden of UED among Latinos. Interventions that address the modifiable risk factors (lack of insurance, never having had an eye examination, etc.) may improve detection of eye disease and decrease the burden of visual impairment in this high-risk minority population.
Presence and severity of age-related cataract was determined in adults 43 to 84 years of age in Beaver Dam, Wisconsin. Duplicate photograph gradings for nuclear sclerosis (n = 1160), cortical ...opacities (n = 1159), and posterior subcapsular cataract (n = 1137) were performed. There are five levels of nuclear sclerosis. Exact agreement occurred in 64.7% of the cases; agreement within one category in 99.8%. For cortical opacities, graders estimate involved area in nine segments of the lens. When the continuous scale is divided into 12 categories of severity, exact agreement varied between 73.5 and 82.4%; for agreement within one category, rates varied between 84.6 and 89.9%. For posterior subcapsular cataracts, exact agreement for involvement of the central circle occurred in 95.0% and agreement within one category occurred in 97.7%. Intraobserver comparisons disclosed similar concordance. These grading schemes are semiquantitative, reproducible, and can be performed for the large numbers of photographs from population-based studies.
Ocular biometric parameters and accommodative amplitude were measured by various techniques in 100 normal emmetropic human subjects age 18-70 yr. Anterior chamber depth decreased and lens thickness ...increased linearly over the entire age group. Accommodative amplitude declined linearly until a stable nadir was reached at about age 50 yr. The respective slopes and intercepts of the age-dependent decline in anterior chamber depth were essentially the same for measurements made independently by optical pachmetry, A-scan ultrasonography, and slit-lamp Scheimpflug photography. The age-dependent increase in lens thickness differed in slope and intercept for measurements made by photography and ultrasonography if the generally accepted lenticular sound velocity was assumed for all subjects. However, if putative lenticular sound velocity was adjusted for age, the relationships given by the two techniques were essentially identical. Total anterior segment length (defined as the distance between the anterior corneal and posterior lens surfaces), vitreous cavity length (distance between the posterior lens and anterior retinal surfaces), and total globe length were all independent of age. This constellation of findings indicates that the human lens grows throughout adult life while the globe does not, that thickening of the lens completely accounts for shallowing of the anterior chamber with age, but that the posterior surface of the lens remains fixed in position relative to the cornea and retina.
To compare gradings of lesions associated with age-related macular degeneration (AMD) from digital and stereoscopic film images.
Instrument validation study.
Sixty-two subjects (124 eyes) with ...varying degrees of AMD, including no AMD.
Images of the optic disc and macula were taken using a 45 degrees digital camera (6.3 megapixels) through dark-adapted pupils and pharmacologically dilated pupils. In addition, 30 degrees stereoscopic retinal film images were taken through pharmacologically dilated pupils of the same eyes. All images were graded for drusen size, type, and area; pigmentary abnormalities; geographic atrophy; and neovascular lesions using the modified Wisconsin Age-Related Maculopathy Grading System. Exact agreement and unweighted kappa scores were calculated for paired gradings resulting from digital and film images.
Agreement between gradings obtained from stereoscopic slide transparencies and digital nonstereoscopic images.
Exact agreement between gradings of digital and stereoscopic film images taken through pharmacologically dilated pupils was 91% (kappa = 0.85) for the categories of none, early AMD, and late AMD. Exact agreement for gradings of digital images taken through dark-adapted pupils compared with gradings of film images was 80% (kappa = 0.69). Exact agreement for gradings of digital images captured through dark-adapted and pharmacologically dilated pupils was 86% (kappa = 0.78). In addition, kappa scores for agreement between different approaches for individual lesions were moderate to almost perfect.
Gradings resulting from high-resolution digital images, especially when the pupil is pharmacologically dilated, are comparable with those resulting from film-based images. We conclude that digital imaging of the retina is useful for epidemiological studies of AMD.
To estimate the prevalence and risk factors of obesity in a sample of primarily urban Mexican Americans (the fastest growing segment of the US population), and to examine the association between ...obesity and co-morbid conditions.
Subjects were participants from a cross-sectional, population-based prevalence study. Data were collected on 6038 noninstitutionalized self-identified Latinos of primarily Mexican American ancestry age > or = 40 years from six census tracts in Los Angeles County, California. Obesity was defined having a body mass index > or = 30.0 kg/m2.
The overall prevalence of obesity was 50% (females 54% vs males 43%, P < .0001). Stepwise logistic regression analyses revealed that obesity was positively associated with being a former smoker (OR 1.5, P = .0009), being unemployed (OR 1.5, P < .0001), and with female sex (OR 1.3, P = .02). Obesity was negatively associated with being single or divorced (OR .8, P = .014), being a current smoker (OR .6, P < .0001), and with age > or = 70 years (OR .4, P < .0001). After adjusting for sex and age, obesity was significantly associated with the following systemic comorbidities: hypertension, heart failure, arthritis, diabetes, angina, back pain, and asthma (P < .01).
Because of the high prevalence of obesity and its associated systemic co-morbidities, an evaluation of current intervention programs is needed to determine the most effective approach to help decrease the prevalence of obesity and the risk of associated co-morbidities in this the fastest growing segment of the US population.
Accommodation dynamics in aging rhesus monkeys CROFT, M. A; KAUFMAN, P. L; CRAWFORD, K. S ...
American journal of physiology. Regulatory, integrative and comparative physiology,
12/1998, Volume:
44, Issue:
6
Journal Article
Peer reviewed
Accommodation, the mechanism by which the eye focuses on near objects, is lost with increasing age in humans and monkeys. This pathophysiology, called presbyopia, is poorly understood.
PURPOSE: To describe the system for grading cataracts from photographs in the Age-Related Eye Disease Study (AREDS).
METHODS: The system for grading cataracts in AREDS uses photographs taken in a ...standardized fashion with specially modified cameras at 11 clinical centers. The photographs are evaluated by graders for quality and cataract severity at a central reading center. The area of lens involvement is used to assess the severity of cortical and posterior subcapsular opacities. Optical density of nuclear opacity is graded against a series of seven standard photographs. Contemporaneous variability in grading is evaluated periodically by having a second examiner regrade a subset of the photographs. Temporal variability is assessed by annually regrading a subset of photographs.
RESULTS: Photographs of 925 eyes, most with no or early lens opacities, were regraded to assess intergrader reliability. For cortical opacities, there was an absolute difference of 10% or greater of area involved in 1.9% of the replicate gradings. For posterior subcapsular opacities an absolute difference of 5% of area involved was noted in 2.8% of the regraded photographs. For nuclear opacities, absolute differences of 1.5 or more steps were observed in 0.6% of eyes. There was little evidence of temporal drift in grading any of the three types of opacity during four annual regrades.
CONCLUSIONS: We have demonstrated a high degree of reliability in grading the severity of lens opacities in a large study cohort with mostly early lens changes, the type of cohort most likely to be entered in clinical trials involving cataract prevention. The Age-Related Eye Disease Study System for Classifying Cataracts From Photographs could be useful in studies where there is a need to standardize data collection over time and across different data collection sites. Limitations of the system include the cost of implementation and, currently, the limited amount of data on grading reproducibility for more advanced lens opacities.
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