Dennis S C Lam

Sun Yat-Sen University, Shengcheng, Guangdong, China

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Publications (808)2725.89 Total impact

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    Shaolin Du · Wenbin Huang · Xiulan Zhang · Jiawei Wang · Wei Wang · Dennis S C Lam
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    ABSTRACT: Background: The existing literature contains no information regarding inflammatory cytokine expression in unilateral acute primary angle-closure (APAC) affected eyes and fellow eyes with primary angle closure suspect (PACS). To measure levels of various inflammatory cytokines in the aqueous humor (AH) of APAC affected eyes and fellow eyes with a diagnosis of PACS (18 unilateral APAC eyes and 18 fellow eyes with PACS), and determine the underlying correlation between them. Methods: The total levels of 12 cytokines including granulocyte colony-stimulating factor (G-CSF), interleukin (IL)-6, IL-8, monocyte chemotactic protein (MCP)-1, MCP-3, macrophage-derived chemokine (MDC), macrophage inflammatory protein (MIP)-1β, and vascular endothelial growth factor (VEGF) etc. were assessed using the multiplex bead immunoassay technique. The level of cytokines in different groups was analyzed by a 2-related-samples nonparametric test. Data on patient demographics, preoperative intraocular pressure (IOP), number of glaucoma medications, as well as several ocular biological parameters were also collected for correlation analysis. Results: The APAC patients had significantly higher levels of G-CSF, IL-6, IL-8, MCP-1, MCP-3, MDC, MIP-1β, and VEGF in the AH samples from unilateral APAC affected eyes than in fellow eyes with PACS (all P < 0.05). The cytokines showed positive correlations between each other (P < 0.0071). Conclusions: Cytokine networks in the AH may have critical roles in the progression of APAC. Thus, different cytokine expression in both eyes of the same patient may help us to understand the different pathology in APAC and PACS.
    Preview · Article · Jan 2016 · BMC Ophthalmology
  • Mary Ho · David T L Liu · Dennis S C Lam · Jost B Jonas
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    ABSTRACT: Purpose: To review the pathophysiology, diagnosis, and updated treatments of retinal vein occlusions (RVOs). Methods: A review of the literature was performed, focusing on the epidemiology, pathophysiology, diagnosis, and treatments (including both medical and surgical treatments) of RVO. Based on this review, a comprehensive overview was provided regarding the topic of RVO and focused on recent treatment updates. Results: Retinal vein occlusions have an age- and sex-standardized prevalence of 5.20 per 1,000 for any RVO, 4.42 per 1,000 for branch RVO, 0.80 per 1,000 for central RVO. Worldwide, an estimated 16.4 million adults are affected by RVOs, with 2.5 million affected by central RVO and 13.9 million affected by branch RVO. Retinal vein occlusion is recognized as an important cause of blindness and the diagnostic approaches and treatment options for RVO are reviewed and reported. The current treatment options including medical treatments (bevacizumab, ranibizumab, aflibercept, triamcinolone, and dexamethasone implants) and surgical alternatives were reviewed and reported with summaries on the corresponding strength of evidence. Conclusion: Despite the understanding of this disease entity, challenges persist in the long-term treatment of RVO-related complications and visual loss. This review provided a detailed summary on the rationality and efficacy of recently developed treatment regimes and evaluated the potential benefit of combination therapy.
    No preview · Article · Dec 2015 · Retina (Philadelphia, Pa.)
  • Timothy Y Y Lai · Shu Liu · Sudipta Das · Dennis S C Lam
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    ABSTRACT: Intravitreal (IVT) injection of therapeutic agents has become one of the most commonly performed procedures in ophthalmology. Over the past decade, a number of guidelines have been published that recommend proper techniques to increase the safety of IVT injections. Among the various complications of IVT injections, endophthalmitis can be sight threatening. The reported endophthalmitis rates after IVT injection range from 0.020% to 0.085%, which are higher than what would be expected from a simple, fast, and relatively atraumatic procedure. The 2 key issues involved in the prevention of endophthalmitis are pre-IVT injection disinfection using povidone-iodine (PVI) and the use of topical antibiotics as prophylaxis. Whereas 5% PVI for 5 minutes is most commonly used in cataract surgery for disinfection, the duration in IVT injection is much less and can be as short as 30 seconds. Further studies seem warranted to investigate whether longer duration of PVI application in IVT injection can lower the endophthalmitis rate. Recent data suggest that there is inadequate evidence to support the routine use of prophylactic pre-, peri-, or postinjection antibiotics to reduce the risk of endophthalmitis. However, as many confounding factors such as the PVI regimens were not standardized in previous studies, it is too soon to make a concrete conclusion. Despite the availability of published guidelines, considerable variations still exist in real-life clinical situations. In this article, we describe our IVT injection practice protocol and compare it with the most recent international guidelines. Finally, a summary table that shows the clinical features of true, sterile, and pseudoendophthalmitis is presented.
    No preview · Article · Dec 2015
  • Dennis S. C. Lam

    No preview · Article · Aug 2015
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    ABSTRACT: To identify clinical factors correlating with failure to control intraocular pressure (IOP) in primary angle-closure glaucoma (PACG) eyes with cataract after phacoemulsification or phacotrabeculectomy. Retrospective analysis of two prospective randomized controlled clinical trials. Primary angle-closure glaucoma eyes with cataract received phacoemulsification or phacotrabeculectomy. Failure was defined as having IOP of 21mm Hg or greater, or requiring glaucoma drugs to maintain an IOP of less than 21 mm Hg, or having had additional IOP-lowering surgery. Factors correlating with failure at 24 months after surgery were identified using logistic regression model. One hundred twenty-three PACG eyes with cataract and receiving phacoemulsification (n = 62) and phacotrabeculectomy (n = 61) were analyzed. With univariate analysis, factors associated with failure included a higher preoperative IOP, a higher preoperative requirement for glaucoma drugs, absence of plateau iris configuration, and phacoemulsification alone. With multivariate analysis, factors associated with failure included a higher preoperative IOP [odds ratio (OR), 1.732 per increase in IOP of 5 mm Hg], a higher preoperative requirement for glaucoma drugs (OR, 1.913), and performance of phacoemulsification alone (OR, 10.24). In PACG eyes with cataract, higher preoperative IOP and increased requirement for glaucoma drugs correlate with failure to control IOP after phacoemulsification or phacotrabeculectomy. Phacotrabeculectomy is more likely than phacoemulsification to achieve IOP control.
    No preview · Article · Jun 2015
  • Source
    Article: Cataract
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    ABSTRACT: Cataract is the leading cause of reversible blindness and visual impairment globally. Blindness from cataract is more common in populations with low socioeconomic status and in developing countries than in developed countries. The only treatment for cataract is surgery. Phacoemulsification is the gold standard for cataract surgery in the developed world, whereas manual small incision cataract surgery is used frequently in developing countries. In general, the outcomes of surgery are good and complications, such as endophthalmitis, often can be prevented or have good ouctomes if properly managed. Femtosecond laser-assisted cataract surgery, an advanced technology, can automate several steps; initial data show no superiority of this approach over current techniques, but the results of many large clinical trials are pending. The greatest challenge remains the growing ‘backlog’ of patients with cataract blindness in the developing world because of lack of access to affordable surgery. Efforts aimed at training additional cataract surgeons in these countries do not keep pace with the increasing demand associated with ageing population demographics. In the absence of strategie that can prevent or delay cataract formation, it is important to focus efforts and resources on developing models for efficient delivery of cataract surgical services in underserved regions. For an illustrated summary of this Primer, visit: http://go.nature.com/eQkKll
    Full-text · Article · Jun 2015
  • Vineet Ratra · Dennis S. C. Lam
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    ABSTRACT: Small pupils pose problems for cataract surgery. The pupil is dilated with topical mydriatic drugs for all cataract surgeries to improve the surgeon's access to, and visualization of, the lens nucleus, cortex, and capsular structures. Limited dilation poses a risk of surgical complications such as iris trauma or tearing of the anterior or posterior capsule. There are many ways and methods to achieve the appropriate pupil dilation, from pre-operative medications to intraoperative pharmacological and/or surgical methods. A management algorithm for small pupil will be discussed in this review. The various methods and maneuvers may work in isolation or combination to achieve adequate pupil dilation.
    No preview · Article · May 2015
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    ABSTRACT: To investigate the changes of retinal oxygen saturation (Sat O2) concentrations, choroidal thickness (CT), and retinal nerve fibre layer (RNFL) in eyes with trabeculectomy-required acute primary angle closure (APAC). Prospective, longitudinal study. Twenty-three eyes with trabeculectomy-required APAC were recruited. Retinal oximetry was performed at postoperative day one and again at approximately 1 month. CT and the RNFL were tested on the same day. A paired t test and Pearson correlation were used for analysis. Mean Sat O2 increased in retinal arterioles from 88.74% ± 14.36% at postoperative day 1 to 96.61% ± 18.42% at 1 month (p = 0.049). The mean diameter of the arterioles was statistically different between postoperative day 1 and 1 month (p = 0.044), as was the mean diameter of the venules (p = 0.027). APAC eyes at postoperative 1 month had a thinner mean CT, compared with day 1 (p = 0.002). No significant difference was found in the RNFL between postoperative day 1 and 1 month (p > 0.05). The Sat O2 in retinal arterioles correlated with the mean diameter of the arterioles at postoperative day 1 (r = -0.482, p = 0.020) and at 1 month (r = -0.463, p = 0.026). No significant correlation was found between retinal Sat O2 and other parameters. Increased Sat O2 in retinal arterioles, changed vessel diameter, and thinner CT from postoperative day 1 to 1 month suggest gradual recovery from APAC. However, the different pathophysiologies for APAC still need further study to prove. Copyright © 2015 Canadian Ophthalmological Society. Published by Elsevier Inc. All rights reserved.
    No preview · Article · Apr 2015 · Canadian Journal of Ophthalmology
  • Dennis S C Lam

    No preview · Article · Mar 2015
  • Source
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    ABSTRACT: Aims: To identify the reasons for poor uptake of cataract surgery in a program of outreach screening and low-cost surgery in Pucheng County, a rural area in northwestern China. Methods: Detailed interviews with a semi-structured questionnaire were conducted by telephone or face-to-face for participants who had been advised to attend a low-cost cataract surgery program but did not schedule the surgery within 3 months after the initial screening. Results: Among 432 eligible subjects, 355 (82.2%) were interviewed (mean age 70.6 ± 6.6 years, 73.8% female). A total of 138 subjects (38.9%) were interviewed by phone and 217 (61.1%) were interviewed face-to-face. Lack of family support (n = 106, 29.9%) and failure to understand the need for surgery (n = 96, 27.0%) were the two main reasons for not undergoing cataract surgery. Other factors included fear of surgery (n = 62, 17.5%), lack of faith in doctors (n = 36, 10.1%), financial constraints (n = 25, 7.0%) and lack of transportation (n = 4, 1.1%). Conclusion: The principal barriers to low-cost cataract surgery uptake in rural China included lack of family support and failure to understand the need for surgery. Education targeting entire families to eliminate these barriers and development of community support systems at the family level are required to achieve greater uptake of low-cost cataract surgery programs in rural China.
    Full-text · Article · Apr 2014 · Ophthalmic epidemiology
  • Mary Ho · David T L Liu · Alvin L. Young · Dennis S C Lam
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    ABSTRACT: Choroidal neovascularization (CNV) secondary to pathological myopia is an important cause of significant visual impairment in young adults. High myopia is particularly prevalent in Asian population. New scientific contributions have been made to the understanding of high myopia and myopic CNV. Treatment for myopic CNV has previously relied on photodynamic therapy, laser photocoagulation, and submacular surgery. The treatment outcomes from these modalities are, however, controversial. The introduction of antiangiogenic agents including bevacizumab and ranibizumab has brought the treatment of myopic CNV into a new era. The purpose of this review was to provide an overview of the natural history of myopic CNV, the prognostic factors, and the various treatment options including laser photocoagulation and photodynamic therapy, with particular attention on antiangiogenic agents.
    No preview · Article · Mar 2014
  • Rajvardhan Azad · Clement C.Y. Tham · Dennis S.C. Lam

    No preview · Article · Jan 2014
  • Frank H P Lai · David T L Liu · Dennis S C Lam
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    ABSTRACT: The purpose of this article is to highlight evidence about the medical and surgical management of intermediate uveitis (IU). Updated understandings of the immunopathology of IU were reviewed in this retrospective literature review. Literature selection for this review was based on the PubMed database (National Library of Medicine) and OVID database (Wolters Kluwer). Articles deemed relevant were selected and highlighted. Intermediate uveitis is most often a benign form of uveitis. Since intermediate uveitis has been described in association with different systemic disorders, the initial diagnostic evaluation should serve to exclude masquerade syndromes and infectious diseases in which immunosuppression may be ineffective or contraindicated. Although the pathogenesis of intermediate uveitis is not fully understood, identification of proinflammatory molecules involved in the IU has contributed to the development and implementation of new therapies. Studies about the use of various immunosuppressants, biological agents and surgical treatment on IU have provided more evidence for managing IU. Nevertheless, corticosteroids remain the mainstay of treatment. The treatment options of intermediate uveitis are evolving, with the development of various immunosuppressants and biological agents. The management of intermediate uveitis should be tailored individually, based on specific causes of the disease and associated complications.
    No preview · Article · Nov 2013

  • No preview · Article · Oct 2013 · Ophthalmology

  • No preview · Article · Oct 2013 · Ophthalmology

  • No preview · Article · Jul 2013 · Ophthalmology
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    ABSTRACT: OBJECTIVE: To define the prevalence of blindness and visual impairment (VI) in people in rural Hainan using the rapid assessment of avoidable blindness (RAAB) and to report the outcomes of cataract surgery among the residents. DESIGN: Population-based, cross-sectional survey. PARTICIPANTS: A total of 6482 rural residents of the Hainan province. METHODS: A total of 136 clusters, each of which consisted of 50 people aged ≥50 years, were selected through probability-proportionate-to-size sampling. Door-to-door visits were performed by 2 outreach teams. Visual acuity (VA) was measured on site, and those with VA <6/18 in either eye were examined by an ophthalmologist. Causes of blindness and VI were determined. The causes of poor visual outcome after cataract surgery were evaluated. Information regarding barriers to receiving surgery was collected by trained interviewers. MAIN OUTCOME MEASURES: Prevalence and causes of blindness (VA <3/60), severe VI (SVI) (VA <6/60 but ≥3/60), and VI (VA <6/18 but ≥6/60) based on presenting VA (PVA) were assessed. Outcomes of cataract surgery performed in public and private hospitals and charitable organizations were compared. RESULTS: A total of 6482 subjects were examined (response rate, 95.3%). The sample prevalence of blindness was 4.4% (95% confidence interval [CI], 2.0-6.8). The prevalence of SVI and VI was 1.9% (95% CI, 0-4.3) and 9.9% (95% CI, 7.6-12.2), respectively. Age and sex were associated with increased prevalence of blindness, SVI, and VI. Overall, cataract accounted for approximately 60% of blindness and SVI. Of the 524 eyes that had received cataract surgery, 87.2% had intraocular lenses implanted, 21% had a poor visual outcome (PVA <6 /60), and 20% had a borderline visual outcome (PVA <6/18 but ≥6/60). Eyes that received surgery in charitable organizations had a higher rate of intraocular lens implantation and good visual outcome (VA ≥6/18) compared with eyes that were operated on elsewhere. CONCLUSIONS: The prevalence of blindness, SVI, and VI was high among rural residents in Hainan. Cataract remained the leading cause of avoidable blindness. Outcomes of cataract surgery performed in public hospitals were suboptimal. Quality-control initiatives should be introduced to improve cataract surgery outcomes. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
    Full-text · Article · May 2013 · Ophthalmology
  • Mary Ho · David T.L. Liu · Vesta C.K. Chan · Dennis S.C. Lam
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    ABSTRACT: PURPOSE: To measure choroidal thickness (CT) in myopic eyes using enhanced depth imaging (EDI). DESIGN: A cross-sectional study. PARTICIPANTS: Fifty-six consecutive patients with spherical equivalent refractive error of at least 6 diopters (D) were evaluated. METHODS: Enhanced depth imaging optical coherence tomography (OCT) images were obtained by positioning the spectral-domain OCT device close enough to the eye to acquire an enhanced signal of the choroidal layer. Choroidal depth was measured as the distance between the outer reflective retinal pigment epithelium (RPE) layer and the inner sclera border. Measurements were made in a horizontal fashion across the fovea at 500-μm intervals of the sections. The CT was measured at the subfoveal region in a horizontal fashion, 3 mm temporal to fovea and 3 mm nasal to fovea. MAIN OUTCOME MEASURES: Correlations among CT with age, refractive error in diopters, and visual acuity in logarithm of the minimum angle of resolution (logMAR) were analyzed with linear mixed models. RESULTS: The mean age of the 56 patients was 50.4 years (±2.03 years standard deviation; interquartile range [IQR], 42-62 years), and the mean refractive error was -8.7 D (IQR, -6.1 to -11 D). The mean subfoveal CT was 118 μm (±68 μm) and correlated negatively with age (P = 0.032) and refractive error (P = 0.011). Regression analysis suggested that subfoveal CT decreased by 11.9 μm for each decade of life and by 6.205 μm for each diopter of myopia. The subfoveal CT was inversely correlated with the logMAR visual acuity (P = 0.008), and visual acuity improved by 0.02 (logMAR) in a 10-μm increase in CT. CONCLUSIONS: Choroidal thickness decreases with age and severity of myopia. Visual acuity decreases in line with decreasing subfoveal CT. A reduction in CT is related to aging and the severity of myopia, whereas visual acuity depends on subfoveal CT. Our study supports the theory that choroidal abnormality may play a key role in the pathogenesis of myopic degeneration. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
    No preview · Article · May 2013 · Ophthalmology
  • Source
    Xiao Ying Liang · Mingguang He · Dennis S C Lam

    Full-text · Article · May 2013
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    ABSTRACT: OBJECTIVE: To investigate the use of swept-source optical coherence tomography (OCT) for measuring the area and degree of peripheral anterior synechia (PAS) involvement in patients with angle-closure glaucoma. DESIGN: Cross-sectional study. PARTICIPANTS: Twenty-three eyes with PAS (detected by indentation gonioscopy) from 20 patients with angle-closure glaucoma (20 eyes had primary angle-closure glaucoma and 3 eyes had angle-closure glaucoma secondary to chronic anterior uveitis [n = 2] and Axenfeld-Rieger syndrome [n = 1]). METHODS: The anterior chamber angles were evaluated with indentation gonioscopy and imaged by swept-source OCT (Casia OCT, Tomey, Nagoya, Japan) in room light and in the dark using the "angle analysis" protocol, which was composed of 128 radial B-scans each with 512 A-scans (16-mm scan length). The area and degree of PAS involvement were measured in each eye after manual detection of the scleral spur and the anterior irido-angle adhesion by 2 masked observers. The interobserver variability of the PAS measurements was calculated. MAIN OUTCOME MEASURES: The agreement of PAS assessment by gonioscopy and OCT, the area and the degree of PAS involvement, and the intraclass correlation coefficient (ICC) of interobserver PAS measurements. RESULTS: The area of PAS (mean ± standard deviation) was 20.8±16.9 mm(2) (range, 3.9-74.9 mm(2)), and the degree of PAS involvement was 186.5±79.9 degrees (range, 42-314 degrees). There was no difference in the area of PAS (P = 0.90) and the degree of PAS involvement (P = 0.95) between images obtained in room light and in the dark. The interobserver ICCs were 0.99 (95% confidence interval [CI], 0.98-1.00) for the area of PAS and 0.99 (95% CI, 0.97-1.00) for the degree of PAS involvement. There was good agreement of PAS assessment between gonioscopy and OCT images (kappa = 0.79; 95% CI, 0.67-0.91). CONCLUSIONS: Swept-source OCT allows visualization and reproducible measurements of the area and degree of PAS involvement, providing a new paradigm for evaluation of PAS progression and risk assessment for development of angle-closure glaucoma. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
    No preview · Article · Mar 2013 · Ophthalmology

Publication Stats

15k Citations
2,725.89 Total Impact Points

Institutions

  • 2015-2016
    • Sun Yat-Sen University
      • State Key Laboratory of Oncology
      Shengcheng, Guangdong, China
  • 1994-2015
    • Prince of Wales Hospital, Hong Kong
      Chiu-lung, Kowloon City, Hong Kong
  • 1995-2014
    • The Chinese University of Hong Kong
      • • Department of Ophthalmology and Visual Sciences
      • • Department of Obstetrics and Gynaecology
      Hong Kong, Hong Kong
  • 2001-2012
    • Caritas Hong Kong
      Chiu-lung, Kowloon City, Hong Kong
  • 2003-2010
    • Shantou University
      Swatow, Guangdong, China
    • Tuen Mun Hospital
      Hong Kong, Hong Kong
  • 2007
    • Hong Kong Sanatorium & Hospital
      Hong Kong, Hong Kong
  • 2006
    • Queen Mary Hospital
      Hong Kong, Hong Kong
    • Fudan University
      Shanghai, Shanghai Shi, China
  • 2005-2006
    • Alice Ho Miu Ling Nethersole Hospital
      Ch’üan-wan, Tsuen Wan, Hong Kong
  • 2004-2006
    • Hong Kong SAR Government
      Hong Kong, Hong Kong
  • 2001-2004
    • Christian Hospital
      Saint Louis, Michigan, United States
  • 2002
    • City University London
      • Applied Vision Research Centre
      Londinium, England, United Kingdom
    • Hong Kong Hospital Authority
      Hong Kong, Hong Kong