Methods for the Hong Kong Vision Study: a pilot assessment of visual impairment in adults.

INTRODUCTION: The Hong Kong Vision Study (HKVS) was a pilot study to collect data on the prevalence of eye diseases and risk factors in Hong Kong using methodology comparable to that developed in America and Australia. AIM: The main goal was: to evaluate the application of the methodology in a different culture and language; and to determine the prevalence and risk factors of eye diseases in order to design a larger study of an ethnic Chinese population. METHOD: This study was patterned after the Melbourne Visual Impairment Project using the Chinese language in data collection and examinations. CONCLUSION: Well-designed methodology is transferable to different cultures, languages and continents. Use of similar methodology will enable better comparisons and analyses to be made from population-based data.

A population-based study of xerophthalmia in the extreme North Province of Cameroon, West Africa.

OBJECTIVE: To obtain cross-sectional data on clinical and nutritional vitamin A deficiency from which to design appropriate intervention strategies. DESIGN: A population-based survey using multistage, cluster sampling. SETTING: Extreme North Province of Cameroon, West Africa. PARTICIPANTS: Children aged 0 to 5 years. MAIN OUTCOME MEASURES: Clinical signs of active xerophthalmia and dietary vitamin A intake. RESULTS: Of 5352 children examined, signs of active xerophthalmia were noted in 0.62%. Bitot's spots, corneal xerosis, and corneal ulceration were noted in 0.47%, 0.06%, and 0.12% of the subjects, respectively. Children with xerophthalmia had lower vitamin A intake scores when compared with age-matched controls and with a 20% systematic subsample of children. CONCLUSION: Xerophthalmia is a major public health problem in this region.

Prevalence and causes of low vision and blindness in the Extreme North Province of Cameroon, West Africa.

A survey to determine the prevalence and causes of blindness and visual impairment in the Extreme North Province of Cameroon was conducted in the Spring of 1992. A total of 10,647 people age 6 years and older was selected from a multi-stage, clustered sample stratified by ecological zone. The subjects were examined by ophthalmologist-led teams for visual acuity and ocular diseases. Approximately 1.2% of the sample was bilaterally blind by the World Health Organization classification (Category 3) of vision less than the ability to count fingers at 3 meters. Similarly to results found in other developing countries, senile cataract was the most common diagnosis encountered and the most frequent principal cause of low vision and blindness.

Intermediate-term results of a randomized clinical trial of the 350- versus the 500-mm2 Baerveldt implant.

BACKGROUND: The Baerveldt glaucoma implant is a large equatorial aqueous shunting device that is installed through a single-quadrant conjunctival incision. The intermediate-term results of a randomized study comparing the 350- and 500-mm2 Baerveldt implants are reported. METHODS: Seventy-three patients with medically uncontrollable, nonneovascular glaucomas associated with aphakia, pseudophakia, or failed filters were enrolled in a randomized, prospective study comparing 350- and 500-mm2 Baerveldt implants. Surgical success was defined as 6 mmHg < or = final intraocular pressure < or = 21 mmHg without glaucoma reoperation or devastating complication. RESULTS: Of patients with 350- and 500-mm2 implants, 93% and 88%, respectively, achieved surgical success (18-month life-table analysis, P = 0.93). The 500-mm2 implants afforded intraocular pressure control with significantly fewer medications (0.7 versus 1.3; P = 0.006). The postoperative visual acuities remained within one line of the preoperative visual acuities or improved in 62% and 66% of patients in the 350- and 500-mm2 groups, respectively (P = 0.93). Complication rates were statistically similar. The most frequent ones in the 350- and 500-mm2 groups, respectively, were serous choroidal effusion (16% and 32%), strabismus (16% and 19%), anterior uveitis (14% and 11%), and corneal or corneal graft edema (11% each). CONCLUSION: The intermediate-term results of the 350- and 500-mm2 Baerveldt implants were statistically comparable with respect to surgical and visual outcomes, as well as complications, although the larger implant was associated with a higher rate of some complications. However, the 500-mm2 Baerveldt implant afforded intraocular pressure control with fewer medications than the 350-mm2 implant.

Epidemic optic neuropathy in Cuba. Eye findings.

OBJECTIVE: To characterize and establish a clinical definition of the optic neuropathy that appeared in epidemic form in Cuba in 1992 and 1993. METHODS: At the invitation of the Cuban Ministry of Health, Havana, members of ORBIS International and the Pan American Health Organization, assembled teams that traveled to Cuba in May 1993. We were initially briefed by Cuban national experts in the areas of virology, nutrition, toxicology, ophthalmology, neurology, and public health. We then examined 20 patients on our own. Thirteen of these patients underwent a comprehensive neuro-ophthalmologic examination, including neurologic examination, ophthalmologic examination, visual fields, optic nerve function studies, contrast sensitivity studies, and funduscopy. We returned 4 months later to perform an additional 12 comprehensive neuro-ophthalmologic and follow-up examinations. RESULTS: Only seven of the 13 patients who were alleged to have the optic form of the epidemic and who were rigorously and systematically examined on the first visit demonstrated a bilateral optic neuropathy. These seven patients had several features that included decreased visual acuity, poor color vision, central scotomas, decreased contrast sensitivity, saccadic eye movements, and most prominent and distinctive of all, nerve fiber layer wedge defects of the papillomacular bundle. Our clinical definition was then implemented by the Cuban ophthalmologists and epidemiologists. On returning 4 months later, we found that all newly presented patients were correctly diagnosed to have the epidemic disease. With the new case definition and the application of a few simple psychophysical tests, the false-positive rate of diagnosis became much lower. After vitamin therapy, we reexamined the patients seen on our initial visit, and all showed marked improvement. CONCLUSIONS: The Cuban epidemic was characterized by an optic neuropathy with features that were similar to those of tobacco/alcohol amblyopia and Leber's optic atrophy. Recent political, economic, and social changes in Cuba may have contributed to the nutritional and/or toxic compromise of mitochondrial function of an acquired nature, which led to selective retinal ganglion cell damage. We have termed this condition Cuban epidemic optic neuropathy.

Initial clinical experience with the baerveldt implant in complicated glaucomas.

BACKGROUND: The Baerveldt glaucoma implant is an aqueous shunting device with a large surface area that is installed through a conjunctival incision in one quadrant of the eye. This study presents the initial results of the first 13 patients who underwent Baerveldt implantation as part of the Food and Drug Administration approval process. METHODS: Thirteen patients with medically uncontrollable complicated glaucomas underwent one-stage implantation of either a 200- or 350-mm2 Baerveldt implant without postoperative systemic antifibrosis therapy. Surgical success was defined as intraocular pressure greater than or equal to 6 and less than or equal to 21 mmHg without glaucoma reoperation or devastating complication. RESULTS: Eight patients (62%) had successful surgical outcomes, with a mean follow-up of 17.3 +/- 7.0 months (+/- standard deviation) (range, 6-24 months). Seven (70%) of the ten patients with glaucomas associated with aphakia or pseudophakia had successful outcomes, whereas only one (50%) of the two patients with neovascular glaucomas had a successful outcome. One patient with glaucoma associated with nanophthalmos and an unsuccessful filtering procedure had a failed outcome. The postoperative visual acuities remained within one line of the preoperative visual acuities or improved in 62% of the patients. The most frequent complications among all patients were transient serous choroidal effusion (23%) and hyphema (15%). CONCLUSION: Initial results of the Baerveldt implant generally are comparable with other implants. It is easier to install and requires less extensive conjunctival dissection than other large implants. Additional studies are needed to evaluate the effectiveness of the Baerveldt implant in affording long-term intraocular pressure control.

Cuba: response of medical science to a crisis of optic and peripheral neuropathy.

We made two trips to Cuba, as part of an invited international delegation, to investigate an epidemic of optic neuropathy-induced blindness. We worked closely with Cuban scientists and clinicians in their efforts to understand and then deal with 50,000 cases of blindness and an entire population at risk. This gave an unparalleled opportunity to understand the Cuban system of ophthalmologic health care and, in particular, to appreciate the responses of the scientific and health care communities to this crisis. Several features of the very different Cuban medical and scientific infrastructure were both problematic and advantageous as they affected the Cuban efforts to understand, contain and treat this remarkable epidemic.

Which is better? One or two? A randomized clinical trial of single-plate versus double-plate Molteno implantation for glaucomas in aphakia and pseudophakia.

PURPOSE: Previous studies have suggested that primary double-plate Molteno implantation may be beneficial. Therefore, the authors performed a randomized clinical trial to evaluate the relative effectiveness and safety of single- versus double-plate Molteno implantation. METHODS: From March 1988 to February 1990, 132 patients who underwent Molteno implantation for medically uncontrollable non-neovascular glaucomas in aphakia or pseudophakia were randomly assigned to receive either single- or double-plate implants. RESULTS: The 1- and 2-year life-table success rates (success [survival] defined as 6 mmHg < or = final intraocular pressure [IOP] < or = 21 mmHg without additional glaucoma surgery or devastating complication) were 55% and 46% with single-plate implantation and 86% and 71% with double-plate implantation, respectively. The final postoperative visual acuities were within one line of the preoperative visual acuities or had improved in 73% and 80% of patients, respectively. Choroidal hemorrhages and/or effusions, corneal decompensation, flat anterior chambers, and phthisis bulbi were more common in the patients who had undergone double-plate Molteno implantation; however, transient elevations of IOP during the first few postoperative months were more common in the patients who had undergone single-plate Molteno implantation. CONCLUSIONS: Double-plate Molteno implantation more frequently affords IOP control than single-plate Molteno implantation; however, double plates are associated with greater risks of choroidal hemorrhages and/or effusions, corneal decompensation, flat anterior chambers, and phthisis bulbi.

Worldwide blindness.

Blindness affects approximately 42 to 52 million people worldwide. This article examines the major causes of blindness, including cataract, trachoma, glaucoma, onchocerciasis, nutritional deficiencies, and ocular trauma. Numerous case studies supplement the text.

Clinical experience with the single-plate Molteno implant in complicated glaucomas. Update of a pilot study.

Ninety-six patients who had undergone single-plate Molteno implantation for glaucomas with poor surgical prognoses were re-evaluated for long-term results. Control of intraocular pressure was achieved with one single-plate implant to a level less than 22 mmHg (but greater than 5 mmHg) without reoperation or devastating complications in 46% of the aphakic/pseudophakic eyes, 25% of eyes after failed filters, 25% of eyes with neovascular glaucomas, and 26% of eyes in patients younger than 13 years of age (life-table analysis at 5 years). Five-year success rates improved to 53%, 71%, 40%, and 56%, respectively, when data from second plates were included. Visual acuities improved or remained the same after one or two plates were implanted in 47% of aphakic/pseudophakic eyes, 17% of eyes after failed filters, 65% of eyes with neovascular glaucomas, and 63% of eyes in patients younger than 13 years of age on whom Snellen acuity was available. The most frequent overall complications after implantation of one or two plates included: corneal edema (19%), corneal graft decompensation (13%), and cornea-tube touch, retinal detachment, and cataract (8% each).

Racial differences in the cause-specific prevalence of blindness in east Baltimore.

BACKGROUND: Bilateral blindness unrelated to simple refractive error is twice as prevalent among blacks as among whites, although the difference narrows among the elderly. The reasons for this race- and age-related pattern are uncertain. METHODS AND RESULTS: A randomly selected, stratified, multistage cluster sample of 2395 blacks and 2913 whites 40 years of age and older in East Baltimore underwent detailed ophthalmic examinations by a single team. We identified 64 subjects who were blind in both eyes. The leading causes of blindness were unoperated senile cataract (accounting for blindness in 27 of the total of 128 eyes), primary open-angle glaucoma (17 eyes), and age-related macular degeneration (16 eyes). Together, these three disorders accounted for 47 percent of all blindness in this sample. Unoperated cataract accounted for 27 percent of all blindness among blacks, among whom it was four times more common than among whites; whites were almost 50 percent more likely than blacks to have undergone cataract extraction before the age of 80 (P less than 0.002). Primary open-angle glaucoma accounted for 19 percent of all blindness among blacks; it was six times as frequent among blacks as among whites and began 10 years earlier, on average. By contrast, age-related macular degeneration resulting in blindness was limited to whites, among whom it was the leading cause of blindness (prevalence, 2.7 per 1000; 95 percent confidence interval, 1.2 to 5.4); it affected 3 percent of all white subjects 80 years of age or older. CONCLUSIONS: The pattern of blindness in urban Baltimore appears to be different among blacks and whites. Whites are far more likely to have age-related macular degeneration, and blacks to have primary open-angle glaucoma. The high rate of unoperated cataracts among younger blacks and among elderly subjects of both races suggests that health services are underused. Half of all blindness in this urban population is probably preventable or reversible.

Combined Molteno implantation and pars plana vitrectomy for neovascular glaucomas.

Ten patients underwent combined Molteno implantation and pars plana vitrectomy as the primary nonlaser surgical treatment of neovascular glaucoma associated with diabetic retinopathy (9 patients) or central retinal vein occlusion (1 patient). Combined surgery was performed most frequently because media opacities precluded adequate preoperative retinal ablation. Follow-up ranged from 3 to 43 (mean +/- standard deviation, 18.0 +/- 13.2) months. Six patients achieved final intraocular pressures less than 22 mmHg. Visual acuities remained the same or improved in four patients. Four patients had uncomplicated courses. Among the other patients, complications included: recurrent vitreous hemorrhage and retinal detachment (3 patients each); hyphema (2 patients); and tube block, extensive fibrin formation, epiretinal membrane, and total retinal necrosis (1 patient each).

Association of Vistech contrast sensitivity and visual field findings in glaucoma.

Single eye visual fields and contrast sensitivity were assessed in 60 subjects, who were being followed up in a glaucoma clinic for manifest glaucoma or a suspicion of glaucoma because of raised intraocular pressure. The Fieldmaster 5000 (static/kinetic perimeter) was used for the visual fields, and a Vistech wall chart sine wave grating test was used for contrast sensitivity measurements. The subjects were divided into three groups--defect (D), suspect (S) and normal (N)--on the basis of their perimetric findings by subjective grading of 16 perimetric scoring categories for each visual field. The mean Vistech sensitivity levels were not found to be significantly different between the D, S, and N field subgroups at any of the five spatial frequencies provided on the test charts (1.5, 3, 6, 12, and 18 cycles per degree). Complex algorithms combining results from two or more spatial frequencies also failed to yield any significant differences between the groups. Diagnostic sensitivity and specificities relating Vistech contrast sensitivity findings to groups N and D never concomitantly exceeded 60%.

Molteno implantation for glaucoma in young patients.

Seventy patients younger than 21 years of age underwent Molteno implantation for nonneovascular glaucoma. Fifty-three (76%) patients had failed angle and/or conventional filtering surgery. Final intraocular pressure less than 22 mmHg (but over 5 mmHg) was achieved in 40 (62%) of the 65 patients with at least 6-month follow-up (range, 6 to 59 months; mean +/- standard deviation, 22.7 +/- 14.1 months); however, only 22 (34%) were controlled after the initial Molteno implantation procedure, and 54 (83%) patients underwent further glaucoma and/or nonglaucoma surgical procedures. The visual acuities remained within one line of their preoperative levels or improved in 25 (68%) of the 37 patients on whom Snellen acuities were available. The most frequent complications included: tube-cornea touch (20%, transient in 3%), corneal edema (17%), retinal detachment (16%), tube block (10%), cataract (9%), chronic hypotony or phthisis (9%), pupillary or cyclitic membrane (9%), hyphema (7%), flat anterior chamber (6%), and large postoperative choroidal effusion (6%). Despite the high rates of subsequent surgical interventions and complications, Molteno implantation has been a useful approach for achieving intraocular pressure reduction in young patients with glucoma.

Apraclonidine prophylaxis for postcycloplegic intraocular pressure spikes.

A randomized, prospective, double-masked study was undertaken to determine the risk of postcycloplegic intraocular pressure spikes in patients with open-angle glaucoma and to evaluate apraclonidine prophylaxis in minimizing these spikes. Patients were stratified as miotic treated or untreated and each group was randomized to receive either placebo (artificial tears) or apraclonidine in both eyes before instillation of tropicamide. In both the miotic treated and untreated groups that received placebo, there was a high incidence, (37% and 38%, respectively) of clinically significant (greater than or equal to 6 mmHg) intraocular pressure spikes after instillation of tropicamide. In both the miotic treated and untreated groups, there was a statistically significant difference in postcycloplegic intraocular pressure between the subgroup that received placebo and the group that received apraclonidine prophylaxis (P = 0.003 and P = 0.006, respectively). Additionally, four eyes that received placebo had a spike of over 10 mmHg (range, 12 to 27 mmHg), while only one eye had an increase of greater than 10 mmHg (12 mmHg) in the apraclonidine group. Thus, apraclonidine appears to be a useful agent for minimizing precipitous increases in intraocular pressure after cycloplegia in eyes of open-angle glaucoma patients prone to this complication of cycloplegia.

National survey of the prevalence and risk factors of glaucoma in St. Lucia, West Indies. Part I. Prevalence findings.

Although blacks appear to be at higher risk for blindness from glaucoma, there is little information available on the epidemiology of this disease in this population. Using a cluster sampling technique with systematic allocation of clusters, the authors conducted a national survey of black individuals 30 years of age and older, in St. Lucia. A total of 1679 individuals underwent a screening examination that included visual acuity, intraocular pressure (IOP) measurement, and cup/disc (C/D) evaluation. Every third person had a screening field on the Humphrey field analyzer. Individuals with either elevated IOP, abnormal C/D ratio, or an abnormal screening visual field were referred for a definitive examination and threshold visual fields. A total of 520 people were referred. Identified by stringent criteria for the diagnosis of glaucoma, which required reliable threshold visual fields abnormal by the mirror image method, 147 individuals had glaucoma for a prevalence of 8.8% in the 30 years of age and older population.

Reproducibility of topographic measurements with the optic nerve head analyzer.

We evaluated the reproducibility of optic nerve head contour mapping by the Optic Nerve Head Analyzer with ten recordings and analyses of one eye each in ten normal volunteers and ten analyses of a single recording in three of the eyes. Reproducibility was good for cup-to-disk ratio and neural rim area. Reproducibility was poor for cup volume, which was inversely related to cup size. Instrument and operator error were low for cup-to-disk ratio and neural rim area, but high for cup volume. Subjective comparisons of contour lines from five recordings of six eyes implied good reproducibility of this measurement.