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Biomedical subjects

David S Friedman

Publications and source records attributed to David S Friedman.

At least 19 recordsLinked to original sources
PubMed2006

Laser peripheral iridotomy in primary angle-closure suspects: biometric and gonioscopic outcomes: the Liwan Eye Study.

PURPOSE: To assess the immediate effect of laser peripheral iridotomy (LPI) and mechanisms of angle closure in a population-based study of primary angle closure (PAC) suspects. DESIGN: Prospective interventional study. PARTICIPANTS: People identified as PAC suspects aged 50 to 79 years from a population-based survey in Guangzhou, China. INTERVENTION: Laser peripheral iridotomy was performed in 1 randomly selected eye. Examinations were carried out before and 2 weeks after the intervention. MAIN OUTCOME MEASURES: Intraocular pressure (IOP), ultrasound biometry, optical pachymetry, and gonioscopy. RESULTS: A total of 72 people with bilateral suspected PAC participated in the study. Mean IOP decreased by 3 mmHg (P<0.001), but axial anterior chamber depth did not change significantly (P = 0.784) after LPI. Median limbal anterior chamber depth increased from 15% to 25% of peripheral corneal thickness (P<0.001, Wilcoxon signed-rank test). Median iridotrabecular angle width increased from 0 degrees to 10 degrees in the superior quadrant and from 10 degrees to 30 degrees in the inferior quadrant (P<0.001). Nevertheless, 14 eyes (19.4%) still had 3 or more quadrants in which the posterior (usually pigmented) trabecular meshwork could not be seen after laser iridotomy. CONCLUSIONS: This study confirms that LPI results in a significant increase in the angle width in Chinese people with narrow angles. However, one fifth of eyes had residual angle closure after LPI. Although this report confirms that iridotomy widens the anterior chamber angle in most PAC suspects, long-term prospective studies with a larger sample size are required to determine if the risks of PAC glaucoma and other related pathologic sequelae are reduced after prophylactic LPI and to investigate the risk-to-benefit ratio before recommending widespread use of prophylactic LPI in this population.

Aged↗
PubMed2006

Detection of primary angle closure using anterior segment optical coherence tomography in Asian eyes.

OBJECTIVE: To evaluate noncontact anterior segment optical coherence technology (AS-OCT) as a qualitative method of imaging the anterior chamber angle and to determine its ability to detect primary angle closure when compared with gonioscopy in Asian subjects. DESIGN: Prospective observational case series. PARTICIPANTS: Two hundred three subjects were recruited from glaucoma clinics in Singapore with diagnoses of primary angle closure, primary open-angle glaucoma, ocular hypertension, or cataract. Both eyes (if eligible) of each patient were included in the study. Exclusion criteria were pseudophakia or previous glaucoma surgery. METHODS: Images of the nasal, temporal, and inferior angles were obtained with AS-OCT in dark and then light conditions. Gonioscopic angle width was graded using the Spaeth classification for each quadrant in low lighting conditions. MAIN OUTCOME MEASURES: Angle closure was defined by AS-OCT as contact between the peripheral iris and angle wall anterior to the scleral spur and by gonioscopy as a Spaeth grade of 0 degree (posterior trabecular meshwork not visible). Comparison of the 2 methods in detecting angle closure was done by eye and by individual. Sensitivities and specificities of AS-OCT were calculated using gonioscopy as the reference standard. RESULTS: Complete data were available for 342 eyes of 200 patients. Of the patients, 70.9% had a clinical diagnosis of treated or untreated primary angle closure. Angle closure in > or =1 quadrants was detected by AS-OCT in 142 (71%) patients (228 [66.7%] eyes) and by gonioscopy in 99 (49.5%) patients (152 [44.4%] eyes). The inferior angle was closed more frequently than the nasal or temporal quadrants using both AS-OCT and gonioscopy. When performed under dark conditions, AS-OCT identified 98% of those subjects found to have angle closure on gonioscopy (95% confidence interval [CI], 92.2-99.6) and led to the characterization of 44.6% of those found to have open angles on gonioscopy to have angle closure as well. With gonioscopy as the reference standard, specificity of AS-OCT in the dark was 55.4% (95% CI, 45.2-65.2) for detecting individuals with angle closure. CONCLUSION: Anterior segment OCT is a rapid noncontact method of imaging angle structures. It is highly sensitive in detecting angle closure when compared with gonioscopy. More persons are found to have closed angles with AS-OCT than with gonioscopy.

Adult↗
PubMed2006

Imaging of trabeculectomy blebs using anterior segment optical coherence tomography.

OBJECTIVE: To image trabeculectomy blebs using anterior segment optical coherence tomography (AS-OCT). DESIGN: Prospective cross-sectional study. PARTICIPANTS: Fifty-five patients who had previously undergone trabeculectomy surgery. METHODS: All blebs were imaged with a prototype of the AS-OCT. Standardized color monophotographs of blebs were also obtained. Blebs were assessed for the following qualitative features: bleb height, thickness of the conjunctiva in the bleb wall, presence of cystic spaces within the bleb wall, apposition of the scleral flap to underlying sclera, and patency of the internal ostium. MAIN OUTCOME MEASURES: For blebs with preoperative intraocular pressure (IOP) > 18 mmHg with or without ocular hypotensive medication, success was defined as last recorded IOP< or =18 mmHg without topical glaucoma medication. For blebs with preoperative IOP< or =18 mmHg with ocular hypotensive medication, success was defined last recorded IOP< or =18 mmHg with cessation of ocular hypotensive medication. For blebs with preoperative IOP< or =18 mmHg without ocular hypotensive medication, a 20% drop in IOP with no ocular hypotensive medication was accepted as success. RESULTS: Seventy-eight blebs in eyes of 55 patients were imaged. There were 32 (58.2%) men and the mean age was 68.9+/-11.5 years. Fifty-seven (73.1%) blebs were classified as successful. Anterior segment optical coherence tomography identified the following bleb characteristics: total bleb height, bleb cavity, bleb wall thickness, tangential and radial dimensions, scleral flap thickness, and patency of the internal ostium. The majority of successful blebs displayed thickening of the bleb wall. Failed blebs were mostly low and were characterized by ostial occlusion, apposition of conjunctiva-episclera to sclera or apposition of the scleral flap to its bed. Thickening of the bleb wall was typically absent. CONCLUSIONS: AS-OCT is a promising tool to image trabeculectomy blebs. It was able to demonstrate features of bleb morphology not visible with the slit lamp.

Aged↗
PubMed2006

The prevalence of open-angle glaucoma among blacks and whites 73 years and older: the Salisbury Eye Evaluation Glaucoma Study.

OBJECTIVE: To determine the prevalence of glaucoma among black and white persons 73 years and older. DESIGN: Participants in the fourth round of a population-based study, the Salisbury Eye Evaluation, were examined. The main outcome measure was glaucoma, based on optic nerve damage and visual field loss or obvious glaucomatous optic neuropathy without an available, reliable, reproducible visual field. RESULTS: A total of 1250 individuals (95.9% of those eligible) participated, 1233 (98.6%) of whom agreed to screening and an eye examination. The prevalence (95% confidence interval) of open-angle glaucoma was 3.4% (0.5%-6.4%) for white individuals aged 73 and 74 years, increasing to 9.4% (7.4%-11.5%) for those 75 years and older. There was no increasing prevalence in those older than 75 years. Among black persons, the prevalence (95% confidence interval) was 5.7% (0%-11.9%) in those aged 73 and 74 years and 23.2% (17.8%-28.5%) in those 75 years and older. CONCLUSIONS: Many older individuals have open-angle glaucoma, and black persons 75 years and older have substantially higher rates than whites. These findings have important implications for public health initiatives, in which screening programs may be of benefit.

Aged↗
PubMed2006

HIPAA and research: how have the first two years gone?

PURPOSE: To assess the impact of the Health Insurance Portability and Accountability Act (HIPAA) on research in ophthalmology. DESIGN: A personal perspective with a review of relevant publications. METHODS: Review of experience at a single institution as it transitioned to enforcing HIPAA guidelines. RESULTS: HIPAA has been costly to institutions and will continue to be so. At Johns Hopkins alone, nearly 26,000 employees have had to take HIPAA compliance training and pass examinations with an overall estimated cost of nearly $2 million in the first year. At the same time, complying with HIPAA regulations has increased institutional awareness of privacy issues. CONCLUSIONS: HIPAA has added a layer of regulation to research that has increased the burden of researchers but is unlikely to prevent most research from taking place. Although there are clear benefits to the heightened awareness of the implications of research on study subjects' privacy, the costs of implementing HIPAA have been very high, and further refinements are likely necessary.

Biomedical Research↗
PubMed2006

Long-term outcomes in fellow eyes after acute primary angle closure in the contralateral eye.

PURPOSE: To determine the long-term outcome of the contralateral eye in Asian persons with a unilateral attack of acute primary angle closure (APAC). DESIGN: Cross-sectional observational case series. PARTICIPANTS: Seventy-nine individuals who were examined from 4 to 10 years after a unilateral episode of APAC at 2 Singapore hospitals. METHODS: All subjects underwent a complete eye examination. The optic discs were graded clinically and photographically for the presence of glaucomatous optic neuropathy, and automated visual field tests were assessed for damage. All visual fields and optic nerve photographs (when available) underwent a second evaluation by a masked glaucoma specialist, who assessed whether the changes were compatible with glaucoma. MAIN OUTCOME MEASURES: Glaucomatous optic neuropathy, intraocular pressure (IOP), and visual impairment (defined as best-corrected visual acuity of worse than 6/12). RESULTS: Ninety of 138 eligible patients (65.2%) with APAC were examined, 79 with unilateral attacks. Subjects were predominantly Chinese (n = 68; 86%). There were 54 females (68%), and mean age was 68.5+/-8.9 years (standard deviation) at the time of APAC, with a mean duration of 6.3+/-1.5 years from the time of the APAC episode to the study examination. The contralateral eyes of 7 patients (8.9%) had definite or probable glaucoma, 2 of whom were felt to have glaucoma in that eye at the time of the attack. Three eyes had markedly cupped optic discs (cup-to-disc ratio > or = 0.9). Thirteen eyes (16.9%) had best-corrected vision worse than 6/12, due to cataract in almost half the cases. Only 1 eye had vision < 6/60, the cause of which was corneal decompensation. One other patient had only a central island remaining with vision of 6/12. Mean IOP of the study participants was 15.7+/-4.7 mmHg, with 6 subjects (7.6%) having undergone trabeculectomy. CONCLUSIONS: Definite or probable glaucoma was present at the time of diagnosis in 2 (2.5%) fellow eyes and developed in an additional 5 (6.5%) with a mean follow-up of 6 years. More than 80% of this cohort retained good vision in the contralateral eye, in contrast to the eye that underwent APAC. Unoperated cataract accounted for most of the visual impairment in this group.

Acute Disease↗
PubMed2006

Prevalence and clinical characteristics of glaucoma in adult Chinese: a population-based study in Liwan District, Guangzhou.

PURPOSE: To assess the prevalence and mechanism of glaucoma in adults living in an urban area of southern China. METHODS: Random clustering sampling was used to identify adults aged 50 years and over in Liwan District, Guangzhou. Glaucoma was diagnosed with the ISGEO (International Society of Geographical and Epidemiological Ophthalmology) classification scheme. All subjects underwent gonioscopy. RESULTS: In the study, 1504 subjects (75.3% participation rate) were examined, with a crude prevalence of all glaucoma of 3.8% (95% confidence interval [CI], 2.8%-4.8%). Primary open-angle glaucoma (POAG) was found in 2.1% (95% CI, 1.4%-2.8%) and primary angle-closure glaucoma (PACG) in 1.5% (95% CI, 0.8%-2.1%). The prevalence of all glaucoma was significantly higher in older people and men. CONCLUSIONS: POAG was more common than PACG in this southern Chinese population, with rates similar to those reported in Chinese Singaporeans. The age-adjusted rate of POAG was similar to that found in European-derived populations, but PACG was more common among Chinese, indicating that there is a large burden of glaucoma in the Chinese people.

Age Distribution↗
PubMed2006

Gonioscopy in adult Chinese: the Liwan Eye Study.

PURPOSE: To assess gonioscopic characteristics of the drainage angle in adult Chinese in an urban area of southern China. METHODS: Clustered random sampling was used to select adults aged 50 years and older in Liwan District, Guangzhou. Gonioscopy was performed on all the subjects. The geometric angle width was graded in the superior and inferior quadrants, according to the Spaeth system. In addition, apparent and true iris insertion was classified in four quadrants with static and dynamic gonioscopy. The peripheral iris profile was described as steep, regular, concave, and plateau. Data are presented for all phakic right eyes. Secondary or iatrogenic cases were excluded in the analysis of peripheral anterior synechiae (PAS). RESULTS: Among 1405 participants in the study, data from 1330 (95%) right eyes were available for analysis. Iridotrabecular angles (ITA) < or =20 degrees were present in 36.9% (95% CI: 34.3%-40.0%) of eyes superiorly and in 27.9% (95% CI: 25.5%-30.4%) inferiorly. Narrower ITAs were more common in the older people (sex-adjusted odds ratio [OR] = 1.1 per year of life; P < 0.001) and the women (age-adjusted OR = 2.5, P < 0.001). Apparent iris insertion of grade A or B (with pigmented trabecular meshwork not visible) by quadrant was observed in 27.2% superiorly, 12.0% nasally, 7.7% inferiorly, and 14.2% temporally. Narrow angles (in which pigmented trabecular meshwork was not visible in three or more quadrants) were identified in 11.0% (95% CI: 9.3%-12.7%) of right eyes. Overall, 33.3% of eyes had a steep iris profile, 54.2% were normal, 2.7% were concave, and 10.1% were graded plateau. PAS were seen in 30 of 146 (20.5%) eyes with narrow angles and in 7 (0.6%) of 1184 eyes with angles that did not meet criteria for narrow angles. PAS were more likely with narrower angles, with 0%, 0.3%, and 1.9% of eyes with a mean ITA of 40 degrees, 30 degrees, and 20 degrees, respectively, having PAS as opposed to 12.6% and 27.5% for those with ITA 10 degrees and 0 degrees , respectively. CONCLUSIONS: Ten percent of this population of southern Chinese persons 50 years of age and older had narrow angles. PAS were present in one fifth of these people. From these cross-sectional data, it is unclear which of these individuals are at highest risk of the development of primary angle-closure (PAC) glaucoma. Longitudinal studies are necessary to determine appropriate strategies for preventing this potentially blinding outcome.

Aged↗
PubMed2005

Poor uptake of cataract surgery in nursing home residents: the Salisbury Eye Evaluation in Nursing Home Groups study.

OBJECTIVE: To compare the uptake of cataract surgery in nursing homes in which assistance was provided in obtaining services with that in control homes. METHODS: The Salisbury Eye Evaluation in Nursing Home Groups (SEEING) project is a randomized clinical trial studying the effect of a comprehensive vision restoration-rehabilitation program, including the provision of cataract surgery services when needed. Twenty-eight nursing homes in the Eastern Shore area of Maryland and Delaware were matched in pairs by size and payment type. Nursing homes within each pair were randomized to usual care or targeted intervention. Persons with cataract causing visual acuity in the better eye to be worse than 20/40 were informed of the possible benefit of cataract surgery. For those in intervention homes, additional support was provided in obtaining cataract surgery. RESULTS: Of residents with vision-impairing cataract in intervention homes, 31% underwent cataract surgery vs 2% in usual-care facilities. Residents with cataract compared with all residents without visual impairment, regardless of nursing home assignment, tended to be older (mean age, 86.7 vs 82.1 years; P<.001), were more likely to be black (age-adjusted P<.001), had lower Mini-Mental State Examination scores (mean, 11.7 vs 16.2; age-adjusted P<.001), and longer length of stay (mean, 42.3 vs 24.4 months; P<.001). Furthermore, cataract was associated with significant visual impairment and with functional limitations, with 20% of those recommended for surgery having a visual acuity of 20/100 or worse in the better-seeing eye. CONCLUSIONS: Screening for and identifying cataracts as a cause of vision loss rarely results in uptake of cataract surgery services in nursing homes. The addition of a support system to facilitate the process of scheduling surgery and getting to and from the hospital dramatically increases uptake rates.

Aged↗
PubMed2005

Persistence and adherence with topical glaucoma therapy.

PURPOSE: The present study describes the patterns and predictors of treatment persistence and adherence among patients who are diagnosed with glaucoma or as glaucoma suspects (based on claims codes). DESIGN: A retrospective cohort study using health insurance claims data. METHODS: Newly treated individuals with diagnosed glaucoma (n = 3623) and suspect glaucoma (n = 1677) were obtained from healthcare claims data in the Ingenix Research Database. For each of these two diagnostic groups, we calculated the duration of continuous treatment with the initially prescribed medication (persistence) and the prevalence of use of the initial medication at various time points (adherence). Four drug classes were included: beta-blockers, alpha-agonists, carbonic anhydrase inhibitors, and prostaglandin analogs. RESULTS: Nearly one half of the individuals who had filled a glaucoma prescription discontinued all topical ocular hypotensive therapy within six months, and just 37% of these individuals recently had refilled their initial medication at three years after the first dispensing. Prostaglandins were associated with better persistence than any other drug class, which was indicated by hazard ratios for discontinuation of prostaglandins compared with beta-blockers of 0.40 (95% confidence interval, 0.35-0.44) for diagnosed patients and 0.44 (95% confidence interval, 0.37-0.52) for patients with suspect glaucoma. Prostaglandins showed a similar advantage in adherence. Furthermore, patients with diagnosed glaucoma were more likely to adhere to therapy than patients with suspect glaucoma (relative risk = 1.11; 95% confidence interval, 1.05-1.18). CONCLUSION: Persistence and adherence were substantially better with prostaglandins than with other drug classes, and patients with diagnosed open-angle glaucoma were more likely to adhere to treatment than suspected glaucoma.

Administration, Topical↗
PubMed2005

Rapid, objective detection of cataract-induced blur using a bull's eye photodetector.

PURPOSE: To determine whether optical aberrations caused by cataract can be detected and quantified objectively using a newly described focus detection system (FDS). SETTING: The Wilmer Opthalmological Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. METHODS: The FDS uses a bull's eye photodetector to measure the double-pass blur produced from a point source of light. To determine the range and level of focus, signals are measured with a series of trial lenses in the light path selected to span the point of best focus to generate focus curves. The best corrected visual acuity (BCVA), refractive error, lens photograph grades, and FDS signals were obtained in 18 patients scheduled to have cataract surgery. The tests were repeated 6 weeks after surgery. RESULTS: The mean FDS outcome measures improved after cataract surgery, with increased peak height (P=.001) and decreased peak width (P=.001). Improvement in signal strength (integral of signal within +/-1.5 diopters of the point of best focus) strongly correlated with improvement in peak height (R(2)=.88, P<.0001) and photographic cataract grade (R(2)=.72, P<.0001). The mean BCVA improved from 20/50 to 20/26 (P<.0001). The improvement in BCVA correlated more closely with FDS signal strength (R(2)=.44, P=.001) than with cataract grade (R(2)=.25, P=.06). CONCLUSIONS: Improvement in FDS outcome measures correlated with cataract severity and improvement in visual acuity. This objective approach may be useful in long-term studies of cataract progression.

Aged↗
PubMed2005

Variations in treatment among adult-onset open-angle glaucoma patients.

OBJECTIVE: To determine the predictors of treatment for glaucoma and suspect glaucoma in a nationally representative sample of diagnosed persons. DESIGN: Retrospective cohort study of persons enrolled in a large managed care organization. PARTICIPANTS: Thirty-five thousand seven hundred fifty-four diagnosed suspects, 5265 diagnosed glaucoma persons, and 2633 individuals coded as having cupping of the optic disc. METHODS: Linked pharmacy and patient care information were used to examine the predictors of initiating glaucoma treatment in this cohort of persons insured by a single managed care organization. Predictors entered into logistic regression models included diagnostic group (suspect vs. diagnosed), age group, gender, region of the country, provider type at the initial visit (optometrist or ophthalmologist), diagnosis index date divided into 2 periods (1995-1998 and 1999-2001), and health plan enrollment duration after the initial diagnosis. MAIN OUTCOME MEASURES: Occurrence of and factors associated with treatment for glaucoma (argon laser trabeculoplasty [ALT], surgery, or topical ocular hypotensives). RESULTS: A logistic regression model adjusting for glaucoma status, age, region, clinician seen at initial visit, and index date found that women were less likely to undergo treatment (topical ocular hypotensives, ALT, or surgery) than men (odds ratio, 0.76; 95% confidence interval, 0.71-0.80). Factors other than gender that were associated with greater likelihood of treatment were glaucoma diagnosis, older age, region, and longer follow-up. CONCLUSIONS: We have documented wide variation in treatment among individuals diagnosed as having glaucoma or as glaucoma suspects. Women were 24% less likely to be treated than men, and younger individuals were far less likely to be treated than older ones. Furthermore, treatment varied by region of the country. Understanding the sources of these variations will help in determining how to arrive at better management strategies for individuals with glaucoma and suspect glaucoma.

Adult↗
PubMed2005

Glaucoma management among individuals enrolled in a single comprehensive insurance plan.

OBJECTIVE: To determine the management patterns for glaucoma and suspect glaucoma in a nationally representative sample of newly treated persons. DESIGN: Retrospective cohort study of persons enrolled in a large managed care organization. PARTICIPANTS: One thousand seven hundred twelve diagnosed suspects and 3623 diagnosed glaucoma patients. METHODS: Linked pharmacy and patient care data were used to examine the glaucoma management and treatment patterns in this cohort of persons insured by a single managed care organization. Rates of monitoring and treatment were calculated for the 3 study groups. MAIN OUTCOME MEASURES: Probability of monitoring (return visits, visual fields [VFs], and optic nerve head imaging or photography) and treatment (argon laser trabeculoplasty [ALT] and surgery) for newly treated persons with suspect and glaucoma diagnoses. RESULTS: After a median follow-up of 440 days, 83% of treated diagnosed suspects had had a billed follow-up office visit to either an optometrist or an ophthalmologist at any time during follow-up, 46% had had at least one billed VF, and 13% had had some form of optic nerve head imaging. Rates were slightly higher for those with diagnosed glaucoma (P>0.05). Surgery and ALT were performed rarely in this treated population (1%-6% at 2 years). CONCLUSIONS: This study suggests that a large proportion of individuals felt to require treatment for glaucoma or suspect glaucoma are falling out of care and are being monitored at rates lower than expected from recommendations of published guidelines. More research is needed to confirm these findings and to determine the reasons for loss to follow-up and low monitoring rates.

Adult↗
PubMed2005

Determinants and heritability of intraocular pressure and cup-to-disc ratio in a defined older population.

PURPOSE: To investigate the heritability of intraocular pressure (IOP) and cup-to-disc ratio (CDR) in an older well-defined population. DESIGN: Family-based cohort study. PARTICIPANTS: Through the population-based Salisbury Eye Evaluation study, we recruited 726 siblings (mean age, 74.7 years) in 284 sibships. METHODS: Intraocular pressure and CDR were measured bilaterally for all participants. The presence or absence of glaucoma was determined by a glaucoma specialist for all probands on the basis of visual field, optic nerve appearance, and history. The heritability of IOP was calculated as twice the residual between-sibling correlation of IOP using linear regression and generalized estimating equations after adjusting for age, gender, mean arterial pressure, race, self-reported diabetes status, and history of systemic steroid use. The heritability of CDR was calculated using the same model and adjustments as above, while also adjusting for IOP. MAIN OUTCOME MEASURES: Heritability and determinants of IOP and CDR, and impact of siblings' glaucoma status on IOP and CDR. RESULTS: We estimated the heritability to be 0.29 (95% confidence interval [CI], 0.12-0.46) for IOP and 0.56 (95% CI, 0.35-0.76) for CDR in this population. Mean IOP in siblings of glaucomatous probands was statistically significantly higher than in siblings of normal probands (mean difference, 1.02 mmHg; P = 0.017). The mean CDR in siblings of glaucomatous probands was 0.07 (or 19%) larger than in siblings of glaucoma suspect referrals (P = 0.045) and siblings of normal probands (P = 0.004). CONCLUSIONS: In this elderly population, we found CDR to be highly heritable and IOP to be moderately heritable. On average, siblings of glaucoma patients had higher IOPs and larger CDRs than siblings of nonglaucomatous probands.

Aged↗
PubMed2004

Causes and prevalence of visual impairment among adults in the United States.

OBJECTIVES: To estimate the cause-specific prevalence and distribution of blindness and low vision in the United States by age, race/ethnicity, and gender, and to estimate the change in these prevalence figures over the next 20 years. METHODS: Summary prevalence estimates of blindness (both according to the US definition of < or =6/60 [< or =20/200] best-corrected visual acuity in the better-seeing eye and the World Health Organization standard of < 6/120 [< 20/400]) and low vision (< 6/12 [< 20/40] best-corrected vision in the better-seeing eye) were prepared separately for black, Hispanic, and white persons in 5-year age intervals starting at 40 years. The estimated prevalences were based on recent population-based studies in the United States, Australia, and Europe. These estimates were applied to 2000 US Census data, and to projected US population figures for 2020, to estimate the number of Americans with visual impairment. Cause-specific prevalences of blindness and low vision were also estimated for the different racial/ethnic groups. RESULTS: Based on demographics from the 2000 US Census, an estimated 937 000 (0.78%) Americans older than 40 years were blind (US definition). An additional 2.4 million Americans (1.98%) had low vision. The leading cause of blindness among white persons was age-related macular degeneration (54.4% of the cases), while among black persons, cataract and glaucoma accounted for more than 60% of blindness. Cataract was the leading cause of low vision, responsible for approximately 50% of bilateral vision worse than 6/12 (20/40) among white, black, and Hispanic persons. The number of blind persons in the US is projected to increase by 70% to 1.6 million by 2020, with a similar rise projected for low vision. CONCLUSIONS: Blindness or low vision affects approximately 1 in 28 Americans older than 40 years. The specific causes of visual impairment, and especially blindness, vary greatly by race/ethnicity. The prevalence of visual disabilities will increase markedly during the next 20 years, owing largely to the aging of the US population.

Adult↗