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G J Johnson

Publications and source records attributed to G J Johnson.

At least 55 records · Page 3Linked to original sources
PubMed2001

Postoperative astigmatism after intracapsular cataract surgery: results of a randomised controlled trial in Nepal.

PURPOSE: Postoperative astigmatism following intracapsular cataract extraction with or without anterior chamber intraocular lens implantation is reported as an outcome from a randomised controlled trial. METHODS: Five hundred and two of 1002 eyes randomised to intracapsular cataract extraction with anterior chamber intraocular lens (ICCE/AC IOL) and 417 of 998 eyes to intracapsular cataract extraction with aphakic spectacles (ICCE/AS) were seen for objective refraction one year after surgery. The prevalence and axis of astigmatism were evaluated using univariate analysis. Logistic regression was used to compare the postoperative astigmatism between the groups. RESULTS: Acceptable astigmatism (-0.5 to 0.0 DCyl) in the AC IOL group was found in 60 (12.0%) patients (95% CI 9.1%-14.9%) and in the aphakic spectacles group (AS) in 69 (16.5%) patients (95% CI 12.9%-20.1%), moderate astigmatism (-1.0 to-1.5 DCyl) was found in 153 (30.4%) patients (95% CI 26.4-34.6%) in ACIOL group and in 288 (69.1%) patients (95% CI 64.6%-73.6%) in AS group; and large astigmatism (-2.0 to - 8.0 D Cyl) was found in 289 (57.6%) patients (95% CI 53.1%-61.6%) in ACIOL group and in 60 (14.4%) patients (95% CI 11.0% 17.8%) in AS group. Large astigmatism was approximately four times more common in the ICCE/AC IOL group compared to ICCE/AS group. In both groups, most patients had "against-the-rule" astigmatism, 446 (88.8%) (95%CI 86.0%-91.6%) in AC IOL group and 348 (83.5%) (95%CI 79.9%-87.1%) in AS group. CONCLUSION: Astigmatism is common after intracapsular cataract extraction. Insertion of an anterior chamber IOL increases the risk of astigmatism.

Adolescent↗
PubMed2000

Anterior chamber depth measurement as a screening tool for primary angle-closure glaucoma in an East Asian population.

OBJECTIVE: To evaluate anterior chamber depth measurement as a method of screening for primary angle-closure glaucoma in an East Asian population. DESIGN: Two-phase, cross-sectional, community-based study. SETTING: Rural and urban locations in the Hovsgol and Omnogobi provinces, Mongolia. PARTICIPANTS: Nine hundred forty-two (94.2%) of 1000 individuals in Hovsgol(1995) and 775 (96.9%) of 1000 individuals in Omnogobi (1997) aged 40 years or older were examined. MAIN OUTCOME MEASURES: Anterior chamber depth was measured by optical pachymetry, slitlamp-mounted A-mode ultrasound, and handheld ultrasound. Gonioscopy was used to detect occludable angles, defined as one in which the trabecular meshwork was visible for less than 90 degrees of angle circumference. Primary open-angle glaucoma was diagnosed in subjects with an occludable angle and glaucomatous optic neuropathy with visual morbidity. The area under the curve in a receiver operating characteristic plot was used to compare test performance. RESULTS: Optical pachymetry outperformed the slitlamp-mounted ultrasound method of anterior chamber depth measurement (area under the curve, 0.93 and 0.90, respectively; z test, P = .001). Handheld ultrasound (area under the curve, 0.86) was inferior to optical measurement (z test, P = .001) but did not differ significantly from slitlamp ultrasound (z test, P = .06). The optical method gave sensitivity of 85% and specificity of 84% at a screening cutoff of less than 2.22 mm for detecting occludable angles. CONCLUSIONS: Measurement of axial anterior chamber depth can detect occludable angles in this Asian population and therefore may have a role in population screening for primary angle-closure glaucoma.

Adult↗
PubMed2000

The prevalence of glaucoma in Chinese residents of Singapore: a cross-sectional population survey of the Tanjong Pagar district.

BACKGROUND: Data on prevalence of glaucoma in East Asia are scarce. OBJECTIVE: To determine the prevalence and clinical characteristics of glaucoma in adult Chinese Singaporeans. METHODS: A group of 2000 Chinese people, aged 40 to 79 years, were selected from the electoral register of Tanjong Pagar district in Singapore using a disproportionate, stratified, clustered, random-sampling procedure. Glaucoma was diagnosed in people with an excavated optic neuropathy and a reproducible visual field defect or on the basis of severe structural disc abnormality alone, if reliable field results could not be obtained. The diagnosis was also made in blind subjects with raised intraocular pressure or previous glaucoma surgery. RESULTS: Of 1717 eligible subjects, 1232 were examined, with a response rate of 71.8%. There were 45 cases of glaucoma: 27 were men and 18 were women. The main diagnoses were primary open-angle glaucoma (n = 22 [49%]), primary angle-closure glaucoma (n = 14 [31%]), and secondary glaucoma (n = 7 [16%]). It was not possible to determine the mechanism in 2 (4%). CONCLUSIONS: The age-standardized prevalence of glaucoma was 3.2% (95% confidence interval, 2.3-4.1) in the population 40 years and older. Glaucoma was the leading cause of blindness. Primary angle-closure glaucoma and secondary glaucoma were the most visually destructive forms of the disease. Our findings suggest current projections of glaucoma prevalence among ethnic Chinese are a substantial underestimate. Arch Ophthalmol. 2000;118:1105-1111

Adult↗
PubMed2000

Long-term follow-up of lid surgery for trichiasis in the Gambia: surgical success and patient perceptions.

BACKGROUND: Surgery is an important component of the SAFE strategy which has been shown to improve visual acuity. There are limited data on long-term surgical success and patient perceptions and satisfaction. A sample of patients from the Gambia who had undergone previous lid surgery for trichiasis were therefore examined for recurrence of trichiasis and interviewed for patient satisfaction. METHODS: Health centre surgical records and community screening were used to identify patients who had undergone previous lid surgery. Consenting patients were examined and a questionnaire administered. Kaplan-Meier survival plots were constructed for recurrence of trichiasis. RESULTS: Sixty-five subjects were recruited. Median age at surgery was 50 years. Median time since surgery was 7 years. Fifty-two of 115 (45%) operated eyes were free of trichiasis at follow-up and 23 of 65 (35%) patients had not suffered recurrent trichiasis in an operated eye. Median time from surgery to recurrence of trichiasis was estimated as 10.0 years (95% CI 3.7-16.3). Recurrent trichiasis was not significantly associated with visual impairment or blindness at follow-up. The following patient perceptions were reported: satisfaction with surgery (88%), less discomfort than before surgery (93%), improved vision (83%), work easier (38%), worth the expenditure (94%), would recommend it to others (93%), had recommended it to others (38%), experienced intra-operative pain (26%) and experienced post-operative pain (26%). CONCLUSION: Factors affecting surgical success, including surgical technique and re-exposure to infection, are discussed. This study provides important preliminary data for programme planners but larger prospective studies are required.

Adolescent↗
PubMed2000

Should trichiasis surgery be offered in the village? A community randomised trial of village vs. health centre-based surgery.

INTRODUCTION: Surgery for trachomatous trichiasis prevents blindness and is advocated by the WHO as part of the SAFE strategy for the global elimination of trachoma. We conducted a randomised community trial to investigate the effect of providing surgery in villages on surgical uptake in The Gambia. METHODS: 56 villages from two divisions were assigned to eight pairs of clusters matched by geographical division and proximity. One cluster from each pair was randomly assigned to receive village-based surgery and the other cluster health centre-based surgery. Outcome measures were uptake rates and surgical results after 1 week and 3 months. The paired t-test was used to analyse the results. RESULTS: Overall uptake was 66% in the village-based clusters and 44% in the health centre-based clusters. Subjects in the village-based surgery arm had significantly shorter journey times (P = 0.01) and lower costs (P = 0.002). The mean difference in absolute acceptance rates of surgery was 20% better in village-based clusters (95% CI -9 to + 49%, P = 0.15), which would equate to an improvement of 45% (95% CI -20% to 120%) on the average acceptance rates of 44% in the health centre-based group. CONCLUSION: These results strongly suggest better surgical uptake when surgery is provided in patients' villages due to lower cost to the patient, time saved and less fear of the operation.

Blindness↗
PubMed2000

Perceived overqualification and dimensions of job satisfaction: a longitudinal analysis.

The present study is an investigation of the effects of perceived overqualification on dimensions of job satisfaction. The data for this study came from a two-wave panel study of members of a midwestern American Postal Workers Union local. Job satisfaction was operationalized with 4 subscales from the Job Descriptive Index (P. Smith, L. Kendall, & C. Hulin, 1969). The following three hypotheses were tested: (a) Perceived overqualification will be negatively related to facets of job satisfaction; (b) there is stability in the test-retest correlations of facets of job satisfaction; and (c) the effects of perceived overqualification on facets of job satisfaction will not change from Time 1 to Time 2 because of adaptation. The cross-sectional results supported the hypotheses and suggested that perceived overqualification has a negative effect on job satisfaction. However, the relationships varied by dimension of perceived overqualification and dimension of job satisfaction. Future researchers of overqualification and dimensions of job satisfaction should consider relative deprivation as a source of work-related deprivations.

Adult↗
PubMed2000

YAG laser iridotomy treatment for primary angle closure in east Asian eyes.

AIM: To assess the efficacy of Nd:YAG laser iridotomy as initial treatment for primary angle closure in a community setting in rural Mongolia. METHODS: Subjects with occludable drainage angles in two glaucoma prevalence surveys in Mongolia (carried out in 1995 and 1997) were treated with YAG laser iridotomy at the time of diagnosis. These patients were re-examined in 1998. Patency of iridotomy, intraocular pressure (IOP), visual acuity, and gonioscopic findings were recorded. Iridotomy was classified unsuccessful in eyes where further surgical intervention was required or in which there was a loss of visual acuity to <3/60 from glaucomatous optic neuropathy. RESULTS: 164 eyes of 98 subjects were examined. Patent peripheral iridotomies were found in 98.1% (157/160) of eyes that had not undergone surgery. Median angle width increased by two Shaffer grades following iridotomy. Iridotomy alone failed in 3% eyes with narrow drainage angles and either peripheral anterior synechiae or raised IOP, but normal optic discs and visual fields. However, in eyes with established glaucomatous optic neuropathy at diagnosis iridotomy failed in 47%. None of the eyes with occludable angles that were normal in all other respects, and underwent iridotomy, developed glaucomatous optic neuropathy or symptomatic angle closure within the follow up period. CONCLUSIONS: Nd: YAG laser iridotomy is effective in widening the drainage angle and reducing elevated IOP in east Asian people with primary angle closure. This suggests that pupil block is a significant mechanism causing closure of the angle in this population. Once glaucomatous optic neuropathy associated with synechial angle closure has occurred, iridotomy alone is less effective at controlling IOP.

Adult↗
PubMed2000

Detection of gonioscopically occludable angles and primary angle closure glaucoma by estimation of limbal chamber depth in Asians: modified grading scheme.

AIM: To evaluate the performance of limbal chamber depth estimation as a means of detecting occludable drainage angles and primary angle closure, with or without glaucoma, in an east Asian population, and determine whether an augmented grading scheme would enhance test performance. METHOD: A two phase, cross sectional, community based study was conducted on rural and urban areas of Hövsgöl and Omnögobi provinces, Mongolia. 1800 subjects aged 40 to 93 years were selected and 1717 (95%) of these were examined. Depth of the anterior chamber at the temporal limbus was graded as a percentage fraction of peripheral corneal thickness. An "occludable" angle was one in which the trabecular meshwork was seen in less than 90 degrees of the angle circumference by gonioscopy. Primary angle closure (PAC) was diagnosed in subjects with an occludable angle and either raised pressure or peripheral anterior synechiae. PAC with glaucoma (PACG) was diagnosed in cases with an occludable angle combined with glaucomatous optic neuropathy and consistent visual morbidity. RESULTS: Occludable angles were identified in 140 subjects, 28 of these had PACG. The 15% grade (equivalent to the traditional "grade 1") yielded sensitivity and specificity of 84% and 86% respectively for the detection of occludable angles. The 5% grade gave sensitivity of 91% and specificity of 93% for the detection of PACG. The interobserver agreement for this augmented grading scheme was good (weighted kappa 0.76). CONCLUSIONS: The traditional limbal chamber depth grading scheme offers good performance for detecting occludable drainage angles in this population. The augmented scheme gives enhanced performance in detection of established PACG. The augmented scheme has potential for good interobserver agreement.

Adult↗
PubMed2000

Evaluation of a national eye care programme: re-survey after 10 years.

AIM: To re-survey the Gambia after an interval of 10 years to assess the impact of a national eye care programme (NECP) on the prevalence of blindness and low vision. METHOD: Comparison of two multistage cluster random sample surveys taking into account the marked increase in population in the Gambia, west Africa. Samples of the whole population in 1986 and 1996 were taken. The definition of blindness is presenting vision less than 3/60 in the better eye, or visual fields constricted to less than 10 degrees from fixation. Low vision is less than 6/18 but 3/60 or better. Causes of blindness were determined clinically by three ophthalmologists. RESULTS: The crude prevalence of blindness fell from 0.70% to 0.42%, a relative reduction of 40%. During the same 10 year period, the population increased by 51% from 775 000 to 1 169 000. When the results were standardised for age, a west to east gradient was found for changes in risk of blindness over the 10 year period. This matched the phased west to east introduction of the NECP interventions. There was a modest but significant increase in the risk of low vision across the whole country. CONCLUSIONS: The overall reduction in risk of blindness, in those areas where the NECP has been active, appears to justify the programme and the support of donor organisations. The low vision cases due to cataract must now be addressed.

Blindness↗
PubMed2000

Epinephrine correction of impaired platelet thromboxane receptor signaling.

This study evaluated the mechanism of epinephrine potentiation of platelet secretion induced by thromboxane A(2) (TXA(2)). Dog platelets that do not secrete in response to TXA(2) alone (TXA(2)-) were compared with dog platelets that do secrete (TXA(2)+) and with human platelets. TXA(2)- platelets had impaired TXA(2) receptor (TP receptor)-G protein coupling, indicated by 1) impaired stimulated GTPase activity, 2) elevated basal guanosine 5'-O-(3-thiotriphosphate) binding, and 3) elevated Galpha(q) palmitate turnover that was corrected by preexposure to epinephrine. Kinetic agonist binding studies revealed biphasic dog and human platelet TP receptor association and dissociation. TXA(2)- and TP receptor-desensitized TXA(2)+ dog and human platelets had altered ligand binding parameters compared with untreated TXA(2)+ or human platelets. These parameters were reversed, along with impaired secretion, by epinephrine. Basal phosphorylation of TXA(2)- platelet TP receptors was elevated 60% and was normalized by epinephrine. Epinephrine potentiates platelet secretion stimulated by TXA(2) by reducing basal TP receptor phosphorylation and facilitating TP receptor-G protein coupling in TXA(2)- platelets and, probably, in normal platelets as well.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2000

Randomized controlled trial of anterior-chamber intraocular lenses in Nepal: long-term follow-up.

Most of the estimated 20 million people who are blind with cataracts live in rural areas of developing countries, where expert surgical resources are scarce. We have studied the use of multiflex open-loop anterior-chamber intraocular lenses (ACIOL) in high-volume low-cost surgery. Between 1992 and 1995, a total of 2000 people attending Lahan Eye Hospital, Nepal, with bilateral cataracts reducing vision to < or = 6/36 were randomly allocated to receive intracapsular extraction (ICCE) with aphakic spectacles, or ICCE with an ACIOL. We re-examined the cohort (1305/2000, 65%) between November 1996 and April 1997 and report the findings in this article. There were 13 new cases of poor visual outcome (best corrected vision < 6/60) arising after one year: 9 in the ACIOL group and 4 in the control group; odds ratio 2.1 (95% confidence interval, 0.59-9.55). The causes of poor outcome were as follows: ACIOL group--retinal detachment (4 cases), cystoid macular oedema (2), epiretinal membrane (1), age-related macular degeneration (1), and late endophthalmitis (1); control group--retinal detachment (2 cases), late endophthalmitis (1), and primary open-angle glaucoma with age-related macular degeneration (1). In rural areas of developing countries, well-manufactured multiflex open-loop ACIOLs can be implanted safely by experienced ophthalmologists after routine ICCE, avoiding the disadvantages of aphakic spectacle correction.

Adult↗
PubMed2000

Prevalence and risk factors for refractive errors in adult Chinese in Singapore.

PURPOSE: To determine the epidemiology of refractive errors in an adult Chinese population in Singapore. METHODS: A disproportionate, stratified, clustered, random-sampling procedure was used to select names of 2000 Chinese people aged 40 to 79 years from the 1996 Singapore electoral register in the Tanjong Pagar district in Singapore. These people were invited to a centralized clinic for a comprehensive eye examination, including refraction. Refraction was also performed on nonrespondents in their homes. Myopia, high myopia, and hyperopia were defined as a spherical equivalent (SE) in the right eye of less than -0.5 D, less than -5.0 D, and more than +0.5 D, respectively. Astigmatism was defined as less than -0.5 D of cylinder. Anisometropia was defined as a difference in SE of more than 1.0 D between the two eyes. Only phakic eyes were analyzed. RESULTS: From 1717 eligible people, 1232 (71.8%) were examined. Adjusted to the 1997 Singapore population, the overall prevalence of myopia, hyperopia, astigmatism, and anisometropia was 38.7% (95% confidence interval [CI]: 35.5, 42.1), 28.4% (95% CI: 25.3, 31.3), 37.8% (95% CI: 34.6, 41.1), and 15.9% (95% CI: 13.5, 18.4), respectively. The prevalence of high myopia was 9.1% (95% CI: 7.2, 11.2), with women having significantly higher rates than men. The age pattern of myopia was bimodal, with higher prevalence in the 40 to 49 and 70 to 81 age groups and lower prevalence between those age ranges. Prevalence was reversed in hyperopia, with a higher prevalence in subjects aged 50 to 69. There was a monotonic increase in prevalence with age for both astigmatism and anisometropia. Increasing educational levels, higher individual income, professional or office-related occupations, better housing, and greater severity of nuclear opacity were all significantly associated with higher rates of myopia, after adjustment for age and sex. CONCLUSIONS: The results indicate that whereas myopia is 1.5 to 2.5 times more prevalent in adult Chinese residing in Singapore than in similarly aged European-derived populations in the United States and Australia, the sociodemographic associations are similar.

Adult↗
PubMed2000

Rapid assessment of cataract surgical coverage in rural Zululand.

OBJECTIVE: Cataract surgical coverage (CSC) is a useful indicator of the degree of success of a cataract intervention programme. However, because previously described methods are time-consuming and labour-intensive, they are rarely performed. This study describes a simple and inexpensive assessment of CSC based on screening of pensioners at pension delivery sites in a rural district. DESIGN: Random cluster-based cross-sectional survey. SETTING: State pension distribution sites in Hlabisa, a rural district in KwaZulu-Natal, South Africa. SUBJECTS: 562 old-age pensioners. METHOD: Subjects found to be blind (visual acuity < 3/60) and those reporting a history of eye surgery were examined using a torch and direct ophthalmoscope by an ophthalmologist. OUTCOME MEASURES: Cases of blindness due to operable cataract and post-cataract surgical subjects were identified. RESULTS: CSC was found to be 38.5% (95% confidence interval 29.1-47.9%). Blindness prevalence was 10.3%, with 69.0% due to cataract.

Aged↗
PubMed2000

Operational comparison of single-dose azithromycin and topical tetracycline for trachoma.

PURPOSE: World Health Organization guidelines for antibiotic treatment of trachoma currently include a 6-week course of tetracycline eye ointment twice daily or a single dose of oral azithromycin. Previous trials have shown similar efficacy of these two alternatives when administration of the ointment was carefully supervised. It is believed, however, that azithromycin may be a more effective treatment in practice, and the purpose of this study was to test that hypothesis. METHODS: A masked randomized controlled trial was conducted to compare azithromycin and tetracycline under practical operational conditions-i.e., without supervision of the administration of the ointment. Three hundred fourteen children aged 6 months to 10 years with clinically active trachoma were recruited and individually randomized to receive one of the two treatments. Follow-up visits were conducted at 10 weeks and 6 months. The outcome was resolution of disease (clinical "cure"). RESULTS: Children allocated to azithromycin were significantly more likely to have resolved disease than those allocated to tetracycline, both at 10 weeks (68% versus 51%; cure rate ratio, 1.31; 95% confidence interval [CI], 1.08-1.59; P = 0.007) and at 6 months (88% versus 73%; cure rate ratio, 1.19; 95% CI, 1.06-1.34; P = 0.004). Azithromycin was particularly effective for intense inflammation (P = 0.023, Fisher's exact test). CONCLUSIONS: Single-dose oral azithromycin was a more effective treatment for active trachoma than tetracycline ointment as applied by caregivers. The high cure rate achieved with tetracycline in this study in the absence of supervision and the significantly higher costs of azithromycin, suggest that in the absence of donation programs, switching routine treatment from tetracycline to azithromycin would not be a good use of resources.

Administration, Topical↗
PubMed1999

Perceived overqualification and health: a longitudinal analysis.

The authors examined the effects of perceived overqualification on health and health decline by means of a 2-wave panel study of members of a midwestern American Postal Workers Union local. The 1st hypothesis was that overqualification was negatively related to health at Time 2 (T2); the second hypothesis was that overqualification was positively related to perceived health decline at T2. Neither was supported by the data. However, the relationships were in the expected direction for perceived mismatch but not for the perceived no grow dimension of overqualification. The results imply that perceived no grow may have immediate threats to health, whereas perceived mismatch may have longer term implications for health. The stability of perceived health between Time 1 (T1) and T2 could overshadow a longitudinal effect of overqualification on health and health decline at T2.

Adult↗
PubMed1999

The utility of animal models in the preclinical study of interventions to prevent human coronary artery restenosis: analysis and recommendations. On behalf of the Subcommittee on Animal, Cellular and Molecular Models of Thrombosis and Haemostasis of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis.

Small animal models have several advantageous characteristics, but those used in preclinical restenosis research have lacked efficacy in predicting the success of interventions to inhibit restenosis in humans. Large animal models have been more successful than small animal models in predicting efficacy of interventions to inhibit restenosis in humans, but the results of studies carried out with these models have not been uniformly predictive. Confirmation of the results of small animal studies in large animals has not always yielded information predictive of success in humans; however, the absence of such confirmation has had strong negative predictive value. Small animal models used for evaluation of interventions to inhibit luminal narrowing following arterial instrumentation have failed to closely simulate human atherosclerosis and the stenotic lesions subjected to instrumentation in humans. Transgenic, atherosclerotic animals hold promise for the development of more useful small animal models to study mechanisms of the response of diseased arteries to angioplasty and stents. The pig has been the most useful large animal to study stenosis/ restenosis, but more information is needed to overcome the limitations of this model.

Animals↗
PubMed1999

Overview on community ophthalmology.

Community ophthalmology requires a comprehensive approach for primary, secondary and tertiary prevention of all eye diseases like vitamin A deficiency, trachoma, measles, diabetic retinopathy, refractive errors, etc. Community ophthalmology is based on the principles of primary health care approach. Equitable distribution, community involvement, focus on prevention, appropriate technology and multisectorial approach are to name a few in primary health care approach. In India, National Programme for Trachoma Control was launched in 1963 and National Programme for Control of Blindness was launched in 1976. Prevention of blindness was included in 20-point plan in early 1980s. Increase in blindness was reassessed in 1986-89 and the strategy was changed. World Bank came to help in planning 11 million cataract operations in 7 years in 7 States where there was the highest prevalence of cataract. Departments of community ophthalmology have recently been developed in several institutions. If the problem of blindness is to be solved, extension of community-based approach including all strata of society is the need of the hour.

Blindness↗