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Dennis S C Lam

Publications and source records attributed to Dennis S C Lam.

At least 19 recordsLinked to original sources
PubMed2007

Results of high-density silicone oil as a tamponade agent in macular hole retinal detachment in patients with high myopia.

BACKGROUND: To evaluate the use of high-density silicone oil (HDSO) as a tamponade agent for retinal detachment secondary to myopic macular hole. METHODS: 12 eyes of 12 patients with macular hole retinal detachment underwent pars plana vitrectomy, internal limiting membrane peeling and HDSO tamponade. No posturing was required postoperatively and HDSO was removed 3-4 months later. Outcome measures included macular hole closure and retinal attachment rates, best-corrected visual acuity (BCVA), and intraoperative and postoperative complications. RESULTS: The mean age of the patients was 67.8 years and the mean spherical equivalent refractive error was -13.4 diopters. After the removal of HDSO, 10 (83%) eyes had macular hole closure with retinal reattachment without any tamponade. One eye had retinal reattachment after re-operation and the other refused further surgery. At the last follow-up, the median BCVA improved from 20/800 to 20/600 (p = 0.046). A transient increase in intraocular pressure was observed in 5 (42%) eyes and one eye each developed mild oil emulsification and transient peripheral choroidal detachment. None of the eyes was found to have severe intraocular inflammation postoperatively. CONCLUSIONS: HDSO seemed to be an effective tamponade agent for myopic macular hole retinal detachment. Further prospective controlled studies seem warranted.

Aged↗
PubMed2007

Safety and efficacy of micro-incisional cataract surgery with bimanual phacoemulsification for white mature cataract.

BACKGROUND: To evaluate the safety and efficacy of micro-incisional cataract surgery (MICS) with bimanual phacoemulsification for the management of white mature cataract. METHODS: Twenty-five eyes in 25 patients with mature cataract were prospectively recruited to undergo MICS with bimanual phacoemulsification. Serial changes in best-corrected visual acuity (BCVA), central corneal thickness (CCT) and endothelial cell density (ECD) were compared using the Wilcoxon signed-rank test. RESULTS: MICS was successfully performed in 24 (96%) of the 25 eyes, with 1 eye requiring conversion to extracapsular cataract extraction due to radial tear during continuous curvilinear capsulorhexis. The median preoperative BCVA was hand movement. On day 1 postoperatively, the median BCVA improved to 0.6 (p < 0.001 compared with baseline). All patients had BCVA of 0.6 or better at 3 months after surgery (p < 0.001 compared with baseline). The mean increase in CCT at day 1 and week 1 postoperatively was 11.5 and 7.1%, respectively. The change in mean CCT was no longer significant at month 3 postoperatively (p = 0.82). The mean reduction in ECD at 3 months postoperatively was 7.8% (p = 0.037). None of the patients developed any postoperative complications. CONCLUSIONS: MICS with bimanual phacoemulsification appeared to be a promising alterative for the management of white mature cataract.

Aged↗
PubMed2006

Association of complement factor H polymorphisms with exudative age-related macular degeneration.

PURPOSE: Variants in the complement factor H (CFH) gene have been reported to be associated with age-related macular degeneration (AMD). We conducted a case-control association study to investigate the association of 6 single nucleotide polymorphisms (SNPs) in CFH with exudative AMD in the Chinese population. METHODS: We recruited 163 cases and 244 controls, all ethnic Chinese, with complete ophthalmic examination including fundus investigation. Cigarette smoking was recorded. Six SNPs (dbSNP ID: rs3753394, rs800292, rs1061147, rs1061170, rs380390, and rs1329428) in the CFH gene were genotyped by Taqman assays. RESULTS: Y402H (1277 T>C) has low frequencies in our study population, 5.8% in patients and 3.9% in controls. It was not associated with exudative AMD adjusted for age, gender and smoking. Significant associations were detected for AMD with rs3753394 (p=0.003, p(corr)=0.018), rs800292 (p=0.00053, p(corr)=0.0032), and rs1329428 (p=0.00092, p(corr)=0.0028), p(corr) values obtained after adjustment for multicomparison. A haplotype containing these four SNPs (TGTC) was found to confer a significantly increased likelihood of exudative AMD with an odds ratio of 1.68 (95% CI: 1.26-2.23) p=0.0003 (p(corr)=0.0026 after correction by permutation test). Logistic regression analysis detected no interactions between the SNPs and age, gender or smoking. CONCLUSIONS: We have found differences in the association between the CFH gene and exudative AMD in Chinese from Caucasians and Japanese. We detected SNP rs3753394 in the CFH promoter carrying a significantly increased risk for exudative AMD.

Aged↗
PubMed2006

Effects of triamcinolone on the expression of VEGF and PEDF in human retinal pigment epithelial and human umbilical vein endothelial cells.

PURPOSE: To investigate whether triamcinolone acetonide (TA) affects the expression of vascular endothelial growth factor (VEGF) and pigment epithelial derived factor (PEDF) in human retinal pigment epithelium (ARPE19) and human umbilical vein endothelial (HUVE) cells. Study the time course of the effects of TA on VEGF and PEDF expressions in cultured cells. METHODS: ARPE19 and HUVE cells were grown to subconfluence and treated with TA (0.1 mg/ml, 1 mg/ml). The mRNA expressions of VEGF and PEDF were determined from 10 min to three days using real-time RT-PCR. Concurrently, the protein levels of VEGF and PEDF in ARPE cells were detected with ELISA. RESULTS: Real-time RT-PCR showed TA affected a 0.5 fold decrease in VEGF(165) level and about a 2.5 fold increase in PEDF level at both TA concentrations. The effect was maintained at 12 h at 0.1 mg/ml TA and 24 h at 1 mg/ml TA. Similar changes were observed in the respective protein concentrations. The effects of TA on VEGF and PEDF transcript levels were similar in HUVE and ARPE19 cells. VEGF and PEDF protein productions in HUVE cells were too low for statistical analysis. CONCLUSIONS: TA reduces the expression of VEGF but increases the expression of PEDF in ARPE19 and HUVE cells. These observations suggest TA may influence the inhibition of neovascularization and macular edema through differential VEGF and PEDF expressions.

Cell Line↗
PubMed2006

Comparison of outcomes of primary scleral-fixated versus primary anterior chamber intraocular lens implantation in complicated cataract surgeries.

OBJECTIVE: To compare the visual outcomes and complication profiles of primary scleral-fixated intraocular lens (SFIOL) versus primary anterior chamber intraocular lens (ACIOL) implantation in cataract surgeries complicated by inadequate capsular support. DESIGN: Retrospective, interventional, comparative cases series. PARTICIPANTS: Thirty-six eyes of 36 patients undergoing SFIOL implantation (group 1) and 46 eyes of 46 patients undergoing ACIOL implantation (group 2). METHODS: Retrospective analysis of medical records of a consecutive series of complicated cataract surgeries with primary SFIOL or ACIOL implantation. MAIN OUTCOME MEASURES: Postoperative best-corrected visual acuity (BCVA), intraoperative and postoperative complications, if any, and postoperative corneal endothelial cell counts. A multiple linear regression model was constructed with postoperative BCVA as the dependent variable and with IOL group (SFIOL vs. ACIOL), preoperative BCVA, surgeon's operative experience, planned operation, and patient's age as independent variables. RESULTS: Fifty-eight percent (group 1) and 37% (group 2) of patients underwent phacoemulsification, whereas the rest underwent extracapsular cataract extraction. The mean postoperative follow-up was 33.4+/-17.9 months (range, 6-61 months). Postoperative Snellen BCVA of 20/40 or better was achieved in 47.2% (group 1) and 71.7% (group 2) of patients (P = 0.038). Regression analysis showed that primary ACIOL implantation was associated with a significantly better postoperative BCVA of -0.157 on the logarithm of minimum angle of resolution scale (95% confidence interval, -0.306 to -0.007; P = 0.040), compared with primary SFIOL implantation. Although both the number of eyes with complications and the total number of complications were higher in the SFIOL group, the differences in early (P = 0.073) and late (P = 0.377) complications were not statistically significant. CONCLUSIONS: The results indicate that satisfactory results are achieved with primary implantation of current open-loop ACIOLs during cataract surgery complicated by loss of posterior capsule integrity. Eyes with these IOLs fared better than a cohort of eyes undergoing SFIOL implantation in a similar situation, at intermediate-term follow-up. Further prospective clinical trials with longer follow-up may help to evaluate the long-term visual outcomes and complication profiles after primary implantation of these lenses.

Aged↗
PubMed2006

HTRA1 promoter polymorphism in wet age-related macular degeneration.

Age-related macular degeneration (AMD), the most common cause of irreversible vision loss in individuals aged older than 50 years, is classified as either wet (neovascular) or dry (nonneovascular). Inherited variation in the complement factor H gene is a major risk factor for drusen in dry AMD. Here we report that a single-nucleotide polymorphism in the promoter region of HTRA1, a serine protease gene on chromosome 10q26, is a major genetic risk factor for wet AMD. A whole-genome association mapping strategy was applied to a Chinese population, yielding a P value of <10(-11). Individuals with the risk-associated genotype were estimated to have a likelihood of developing wet AMD 10 times that of individuals with the wild-type genotype.

Aged↗
PubMed2006

Combined photodynamic therapy and intravitreal triamcinolone injection for the treatment of choroidal neovascularisation secondary to pathological myopia: a pilot study.

BACKGROUND: To assess the efficacy and safety of combined intravitreal triamcinolone (IVTA) and photodynamic therapy (PDT) with verteporfin in the treatment of choroidal neovascularisation (CNV) secondary to pathological myopia. METHODS: 22 eyes of 22 patients with subfoveal or juxtafoveal CNV due to pathological myopia were prospectively recruited for combined PDT with IVTA. The treatment outcomes at 1 year were compared with those in a control group of 22 eyes that received PDT monotherapy. RESULTS: At 1 year, the logMAR best-corrected visual acuity (BCVA) for the combined PDT with IVTA group changed from 0.62 to 0.61 (p = 0.74), whereas that for the monotherapy group changed from 0.61 to 0.67 (p = 0.33). The mean logMAR BCVA and proportions of patients without losing > or =3 lines at 1 year were similar between the two groups (p = 0.68 and 0.74, respectively). Subgroup analyses showed that eyes with baseline logMAR BCVA worse than 0.6 (Snellen equivalent 20/80) or CNV with greatest linear dimension > or =750 microm which received combined therapy had better mean logMAR BCVA at 1 year (p = 0.023 and 0.041, respectively), with a higher proportion of eyes gaining > or =2 lines of BCVA (p = 0.027 and 0.017, respectively) compared with PDT monotherapy. CONCLUSIONS: Combined PDT with IVTA did not seem to result in significantly better visual outcome compared with PDT monotherapy. However, combined therapy might result in better visual outcome in selected patients with worse initial visual acuity or larger myopic CNV. Further studies are warranted to investigate the role of combined PDT with IVTA in the treatment of myopic CNV, especially in patients with worse prognostic factors.

Adult↗
PubMed2006

A prospective randomised trial of different doses of intravitreal triamcinolone for diabetic macular oedema.

OBJECTIVE: To compare the safety and efficacy of different doses of intravitreal triamcinolone (ivTA) in treating clinically significant diabetic macular oedema (CSMO). METHODS: 63 eyes of 63 patients with CSMO and central foveal thickness (CFT) of > or =250 microm on optical coherence tomography were randomised to receive 4 mg (n = 23), 6 mg (n = 20) or 8 mg (n = 20) ivTA. Patients were followed up for 6 months, and changes in best-corrected visual acuity (BCVA), optical coherence tomography CFT, standardised change in macular thickness (SCMT), and side effects such as intraocular pressure and cataractogenesis were compared between the three groups. RESULTS: After ivTA injection, improvements of BCVA and CFT occurred in all groups. The mean BCVA improvement at 6 months was significantly higher for the 8 mg group compared with the 4 mg group, with 9.9 and 3.1 improvement in letters on the Early Treatment of Diabetic Retinopathy Study chart, respectively (p = 0.047). The mean SCMT at 6 months for the 4, 6 and 8 mg groups was 28.7%, 42.3% and 60.5%, respectively (p = 0.06). The proportion of eyes with SCMT > or =75% at 6 months was higher in the 8 mg group, but the difference failed to reach significance (p = 0.06). Ocular hypertensive responses (>21 mm Hg) occurred in 39%, 30% and 55% of eyes in the 4, 6, and 8 mg groups, respectively (p = 0.27). CONCLUSIONS: Higher doses of ivTA may prolong the duration of visual benefit in diabetic CSMO and seemed to result in more sustained reduction in macular oedema. Further studies are warranted to investigate the optimum dose of ivTA in treating diabetic CSMO.

Aged↗
PubMed2006

Pars plana vitrectomy and perfluoropropane (C3F8) tamponade for retinal detachment due to myopic macular hole: a prognostic factor analysis.

PURPOSE: To determine the prognostic factors associated with anatomical success in the treatment of retinal detachment (RD) due to myopic macular hole by pars plana vitrectomy (PPV) and perfluoropropane (C3F8) gas tamponade. DESIGN: Retrospective, interventional, comparative case series. METHODS: In an institutional setting, 57 eyes with myopic macular hole RDs treated by PPV and C3F8 tamponade, with or without concomitant internal limiting membrane (ILM) peeling, endolaser photocoagulation, and/or phacoemulsification, were analyzed. Outcome measures were anatomical success, defined as closure of macular hole with reattachment of the surrounding retina, and postoperative best-corrected visual acuity (BCVA). RESULTS: The mean postoperative follow-up was 26.9 +/- 16.5 months. The anatomical success rate after primary PPV and C3F8 tamponade was 63.2%. Regression analysis showed that shorter axial lengths (odds ratio [OR] = 6.73, 95% confidence interval [95% CI] 1.86 to 12.22, P = .010), concomitant ILM peeling (OR 1.59, 95% CI 1.14 to 2.38, P = .013), and shorter duration of macular hole RD (OR 0.81, 95% CI 0.67 to 0.98, P = .033) were associated with a higher anatomical success. The mean pre- and postoperative BCVAs were 1.430 +/- 0.273 (range, 0.523 to 1.700) and 1.403 +/- 0.271 (range, 0.699 to 1.800) logarithm of minimal angle of resolution units, respectively. The postoperative BCVA was significantly better in eyes with macular hole closure than in eyes without (P = .021). CONCLUSIONS: Axial length, concomitant ILM peeling, and duration were important prognostic factors for PPV and C3F8 tamponade in the treatment of myopic macular hole RDs.

Adult↗
PubMed2006

Visual field and multifocal electroretinography and their correlations in patients on hydroxychloroquine therapy.

PURPOSE: To evaluate the effects of hydroxychloroquine on visual field and multifocal electroretinography (mfERG) and their correlations in patients taking hydroxychloroquine. METHODS: This was a cross-sectional study in which patients on hydroxychloroquine therapy underwent automated 10-2 threshold static visual field examination and mfERG recordings. Non-parametric unadjusted and age-adjusted Spearman correlation coefficients rho were calculated between the cumulative dose of hydroxychloroquine and the visual field mean deviation (MD) and pattern standard deviation (PSD) values; and the mfERG response amplitudes and peak latencies. Correlation analysis was also performed between the visual field MD and PSD values and the mfERG response amplitudes and peak latencies. RESULTS: A total of 26 eyes in 13 patients were analyzed. The mean duration of hydroxychloroquine therapy was 4.9 years and the mean cumulative dose was 574 g. No significant correlation was found between the cumulative dose of hydroxychloroquine and the visual field MD and PSD values. There were significant correlations between the cumulative dose of hydroxychloroquine and mfERG N1 and P1 response amplitudes for the central rings (ring 1-3). The correlations between the dose of hydroxychloroquine and mfERG N1 and P1 response amplitudes were strongest for the paracentral ring 2 (rho =-0.63 and rho =-0.62, respectively, P = 0.001). Significant correlations were also found between the visual field MD values and mfERG response amplitudes of various ring eccentricities. CONCLUSIONS: In patients on hydroxychloroquine, mfERG response amplitude correlated with both the 10-2 visual field MD values and with the cumulative dose of hydroxychloroquine used. The use of mfERG can provide objective measurement of retinal function in patients on hydroxychloroquine and may provide supplementary quantitative information to visual field findings.

Adult↗
PubMed2006

Assessment of macular function by multifocal electroretinography following epiretinal membrane surgery with indocyanine green-assisted internal limiting membrane peeling.

PURPOSE: To evaluate the changes in macular function and potential retinal toxicity in epiretinal membrane (ERM) surgery with indocyanine green (ICG)-assisted internal limiting membrane (ILM) peeling using multifocal electroretinography (mfERG). METHODS: Thirteen eyes of 13 patients were randomly assigned to have ERM surgery with ILM peeling using 0.5 mg/ml or 1.25 mg/ml ICG staining. Patients were examined at baseline and at 3 and 6 months postoperatively. The postoperative mfERG N1 and P1 response amplitudes and peak latencies of various ring eccentricities were assessed and compared with baseline to determine any serial changes. RESULTS: After surgery, the median best-corrected visual acuity improved from 20/70 at baseline to 20/30 at 6 months postoperatively (Wilcoxon signed-ranks test, P=0.004). At 3 months postoperatively, the 0.5 mg/ml group showed no significant changes in N1 and P1 response amplitudes and peak latencies, whereas the 1.25 mg/ml ICG group showed significant reductions in N1 and P1 response amplitudes compared with baseline. No significant changes in mfERG responses were observed in either group at 6 months after surgery. CONCLUSIONS: Our mfERG findings suggested that the use of a higher concentration of ICG for ILM staining might result in transient retinal functional impairment postoperatively. The lowest possible concentration of ICG should be used intraoperatively to minimize potential retinal toxicity.

Aged↗
PubMed2006

Novel myocilin mutation in a Chinese family with juvenile-onset open-angle glaucoma.

OBJECTIVE: To search for the genetic cause of juvenile-onset open-angle glaucoma (JOAG) in a Chinese family. METHODS: In a 3-generation glaucoma family affected with JOAG or ocular hypertension, we screened myocilin (MYOC) and optineurin (OPTN) for mutations and investigated apolipoprotein E (APOE) polymorphisms in 6 family members, 2 of them patients with JOAG, 2 patients with ocular hypertension, and 2 patients who were asymptomatic. Normal controls included 200 unrelated Chinese subjects. The COS-7 cell line was transfected with expression vectors encoding wild-type or mutated MYOC complementary DNA. Cellular and secreted MYOC proteins were characterized by Western blotting. RESULTS: One missense MYOC mutation, 734G>A: Cys245Tyr, was identified. It occurred in all 4 family members afflicted with JOAG or ocular hypertension but not in asymptomatic family members. No OPTN variations were observed. APOE polymorphism frequencies were similar to those for controls. The Cys245Tyr MYOC mutation cosegregated with the disorder within the family. It was absent in the 200 control subjects. The Cys245Tyr mutant MYOC protein formed homomultimeric complexes that migrated at molecular weights larger than their wild-type counterparts. These mutant complexes remained sequestered intracellularly in COS-7 cells. CONCLUSIONS: The Cys245Tyr MYOC mutation was the genetic cause of JOAG in this Chinese family. This mutation may alter covalent bonds that formed between MYOC cysteines. Clinical Relevance Genetic tests of MYOC mutations may be beneficial to predict new cases of the disease in families with JOAG.

Adolescent↗
PubMed2006

Aqueous humor levels of vascular endothelial growth factor and pigment epithelium-derived factor in polypoidal choroidal vasculopathy and choroidal neovascularization.

PURPOSE: To determine the aqueous levels of vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in patients with active polypoidal choroidal vasculopathy (PCV) and choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) and pathologic myopia. DESIGN: Prospective, comparative control study. METHODS: Aqueous humors were collected from 32 eyes of 32 patients for either active PCV or CNV. Among them, 11 eyes had active and symptomatic PCV, 12 eyes had active CNV secondary to AMD, and nine eyes had active CNV of pathologic myopia. Levels of VEGF and PEDF were determined by commercially available enzyme-linked immunosorbent assay kits. A group of 10 aqueous samples from 10 patients who underwent cataract surgery without other ocular or systemic diseases comprised the controls. RESULTS: VEGF concentrations in aqueous humor were markedly increased in patients with PCV, CNV of AMD, and CNV of myopia when compared with the controls (analysis of variance [ANOVA], P < .001). VEGF levels in eyes with PCV were, however, significantly lower than those of exudative AMD (P = .045). The PEDF levels were also significantly different among the groups (ANOVA, P = .001), and we observed increased levels in PCV, CNV of AMD, and CNV of myopia. CONCLUSIONS: VEGF and PEDF factors were coexpressed and increased with positive correlation in aqueous humor of eyes with active PCV. The different levels of both factors in eyes of PCV and AMD might suggest distinct clinical entities or different angiogenesis courses between PCV and AMD.

Adult↗