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Biomedical subjects

D S Lam

Publications and source records attributed to D S Lam.

At least 91 records · Page 5Linked to original sources
PubMed2000

Temporal variations in myopia progression in Singaporean children within an academic year.

PURPOSE: Excessive nearwork is believed to be associated with myopia development and progression. To investigate this further, we studied refractive error changes and their correlation with nearwork in a cohort of grade school children in Singapore. METHODS: Cycloplegic autorefraction was performed 5 times over 10 months on 168 children aged 7, 9, and 12 years who were further divided into myopic and nonmyopic subgroups based in their initial refractive errors. Information about nearwork was obtained through diaries filled out over 24 h at the commencement of the study. RESULTS: Myopia progression was high (overall mean: -0.87 D per year) and largely linear throughout the year, but significantly higher rates were seen after the final school examinations in 7-year-old myopes and nonmyopes. Overall, myopic groups exhibited higher progression rates than nonmyopic groups, although 33.6% of subjects from the latter groups had become myopic by the end of the study. Nearwork scores derived from the diaries were generally not well correlated with overall myopia progression. CONCLUSIONS: The tendency for myopia progression rates to increase after the final school examinations in 7-year-olds is interpreted as a delayed effect of the intense nearwork associated with preparing for them. The timing of nearwork-diary data collection at the beginning of the study could be responsible for the poor correlation between these data and overall myopia progression rates.

Child↗
PubMed2000

Endolaser around macular hole in the management of associated retinal detachment in highly myopic eyes.

PURPOSE: To analyze the role of endolaser around macular hole in managing associated retinal detachment in patients with high myopia. METHODS: Review of medical records of 25 consecutive eyes of 25 patients with at least 5.00 diopters of myopia who underwent primary pars plana vitrectomy and fluid-gas exchange. In the first half of the study period, one row of contiguous argon green endolaser was routinely applied over the retinal edge of the macular hole (EL group). In the second half of the study period, endolaser was not applied around any macular hole (NEL group). Demographic information, intraoperative and postoperative complications, and final visual acuities and retinal reattachment rates were studied. RESULTS: The mean (+/-SD) refractive error was -11.8 +/- -3.5 diopters (D) for the EL group and -11.6 +/- -5.4 D for the NEL group. The mean axial length was 29.0 +/- 1.8 mm for the EL group and 28.3 +/- 1.7 mm for the NEL group. The primary anatomic success was 62.5% (10/16) and 77.8% (7/9) in the EL and NEL groups, respectively. No statistically significant difference was found in preoperative, postoperative, or change in best-corrected visual acuities between the two groups. CONCLUSION: Endolaser around the macular hole after pars plana vitrectomy and internal gas tamponade may not affect the anatomic or visual outcome in primary retinal detachment secondary to a highly myopic macular hole.

Adult↗
PubMed2000

Efficacy and safety of inferior 180 degrees goniosynechialysis followed by diode laser peripheral iridoplasty in the treatment of chronic angle-closure glaucoma.

PURPOSE: To report the efficacy and safety of inferior 180 degrees goniosynechialysis followed by diode laser peripheral iridoplasty in the treatment of chronic angle-closure glaucoma with total synechial angle closure. METHODS: Five patients with chronic angle-closure glaucoma and total synechial angle closure whose intraocular pressures were higher than 21 mm Hg while taking maximally tolerated medications underwent goniosynechialysis followed by diode laser peripheral iridoplasty to the inferior half of the angle. Intraoperative complications, postoperative visual acuity, intraocular pressures, and complications were evaluated. RESULTS: Five eyes of five patients received the operation and the mean follow-up was 7.6 months (range, 6-12 months). The mean preoperative intraocular pressure was 33.8 +/- 5.8 mm Hg. The mean postoperative intraocular pressure at most recent follow-up was 15.8 +/- 2.2 mm Hg. Postoperative complications included transient increase in intraocular pressure, hyphema, and cataract. The success rate (intraocular pressure less than 20 mm Hg with or without medication) was 80.0%. CONCLUSION: It appears that 180 degrees goniosynechialysis followed by diode laser peripheral iridoplasty is an effective and safe surgical procedure for treating chronic angle-closure glaucoma with total synechial angle closure.

Aged↗
PubMed2000

Efficacy and safety of the Ahmed glaucoma valve implant in Chinese eyes with complicated glaucoma.

AIMS: To evaluate the efficacy and safety of the Ahmed glaucoma valve implant in Chinese eyes with complicated glaucomas. METHODS: This retrospective study reviewed the final intraocular pressure, visual outcome, and incidence of complications in all patients with the Ahmed glaucoma valve implant performed at the Prince of Wales Hospital, Hong Kong, between June 1996 and November 1998. RESULTS: A total of 65 eyes from 60 patients were treated with the Ahmed glaucoma implant. At a mean follow up (SD, median) of 21.8 (9.2, 28. 0) months (range 6-37 months), the mean intraocular pressure was reduced from 37.0 (SD 12.1) mm Hg before the implant surgery to 16.1 (12.4) mm Hg at the last follow up after surgery. The success rate of intraocular pressure control of <22 mm Hg was achieved in 73.8% of operated eyes. Transient postoperative hypotony with shallow anterior chamber occurred in 10.8% of cases. The most common postoperative complication was the formation of encapsulated bleb (24.6%). CONCLUSIONS: The Ahmed glaucoma valve implant appears to be effective and relatively safe for treating complicated glaucomas in Chinese eyes. The success rate is comparable with those reported in non-Asian eyes. Formation of postoperative encapsulated bleb is, however, more commonly encountered.

Adolescent↗
PubMed2000

The apolipoprotein E epsilon4 allele is unlikely to be a major risk factor of age-related macular degeneration in Chinese.

Apolipoprotein E (ApoE) is a major transporter of lipids and cholesterol in the nervous system. Age-related macular degeneration (ARMD), characterized by drusen containing lipids, was reported to show a lower frequency of the ApoE epsilon4 allele than control subjects. We sought to examine the association of this polymorphism with ARMD in Hong Kong Chinese. Among 98 ARMD subjects, the frequency of epsilon4 carriers showed a trend toward a decrease compared to controls, but it was not significant (11.2 vs. 15.0%, p < 0.52). The association of epsilon4 with an apparent reduced risk of ARMD was reported previously in the exudative form of the disease, however among 39 exudative ARMD patients there was also no significant difference in epsilon4 frequency (12.8%, p < 0.93). The lack of a statistically significant effect of epsilon4 may be due to the lower frequency of epsilon4 in Chinese than Europeans. Thus we cannot exclude a possible effect of this allele on ARMD risk, but we can conclude that this allele is likely not a major factor influencing ARMD risk in the Chinese.

Adult↗
PubMed2000

Hunting for disease genes in multi-functional diseases.

Disease genes may be identified through functional, positional, and candidate gene approaches. Although extensive and often labor-intensive studies such as family linkage analysis, functional investigation of gene products and genome database searches are usually involved, thousands of human disease genes, especially for monogenic diseases with Mendelian transmission, have been identified. However, in diseases caused by more than one gene, or by a combination of genetic and environmental factors, identification of the genes is even more difficult. Common examples include atherosclerosis, cancer, Alzheimer's disease, asthma, diabetes, glaucoma, and age-related macular degeneration. There have been conflicting reports on the roles of associated genes. Even with population-based case-control studies and new statistical methods such as the sib-ship disequilibrium test and the discordant alleles test, there is no agreement on whether alpha2-macroglobulin (A2M) is a gene for Alzheimer's disease. Another example is the inconsistent association between age-related macular degeneration and ATP-binding cassette transporter (ABCR). Ethnic variation causes further complications. In our investigation of LDL-receptor variants in familial hypercholesterolemia, and the trabecular meshwork inducible glucocorticoid response protein, or myocillin (TIGR-MYOC) mutation pattern in primary open angle glaucoma, we did find dissimilar results in Chinese compared to Caucasians. New information from the Human Genome Project and advancements in technologies will aid the search for and confirm identification of disease genes despite such challenges.

ATP-Binding Cassette Transporters↗
PubMed2000

Truncations in the TIGR gene in individuals with and without primary open-angle glaucoma.

PURPOSE: To investigate the coding exons in the trabecular meshwork-induced glucocorticoid response protein (TIGR) gene for mutations in primary open-angle glaucoma (POAG) in Chinese subjects. METHODS: Ninety-one Chinese patients with POAG and 113 of their family members without glaucoma were screened for sequence alterations in the TIGR gene by polymerase chain reaction, conformation-sensitive gel electrophoresis, and DNA sequencing. One hundred thirty-two unrelated individuals without glaucoma, aged 50 years or more, were studied as control subjects. RESULTS: Five sequence variants that lead to amino acid changes were identified. One was novel: Arg91Stop in one patient with POAG. Four had been reported: Arg46Stop in subjects with and without POAG, including an unaffected 77-year-old woman homozygous for Arg46Stop; Gly12Arg in subjects without glaucoma; and Asp208Glu and Thr353Ile in subjects with and without POAG. The previously reported 1-83(G-->A) and Arg76Lys polymorphisms were detected in both patients and controls and always occurred together. CONCLUSIONS: A different pattern of TIGR sequence variants exists in the Chinese than in non-Chinese populations. No common TIGR mutation that causes POAG was found. The occurrence of subjects without glaucoma who are heterozygous or homozygous for Arg46Stop suggests that reduction in the amount of TIGR protein does not cause glaucoma. Thus, the TIGR missense mutations known to cause POAG probably do not cause glaucoma by inactivating a normal TIGR function, but rather through the gain of a pathologic function.

Adolescent↗