Publications by authors named "Tock Han Lim"

Article Synopsis
  • Structural variants (SVs) play a crucial role in genetic differences that relate to traits and diseases, but most research has focused on European populations.
  • This study compiles a catalogue of over 73,000 SVs from a diverse group of 8,392 Singaporeans, revealing that about 65% of these SVs are novel and specific to Asian ancestry groups.
  • The findings help identify clinically relevant SVs and improve genetic research by addressing biases related to ancestry, which is important for equity and diversity in the field.
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Purpose: To develop and validate a deep learning system (DLS) for estimation of vertical cup-to-disc ratio (vCDR) in ultra-widefield (UWF) and smartphone-based fundus images.

Methods: A DLS consisting of two sequential convolutional neural networks (CNNs) to delineate optic disc (OD) and optic cup (OC) boundaries was developed using 800 standard fundus images from the public REFUGE data set. The CNNs were tested on 400 test images from the REFUGE data set and 296 UWF and 300 smartphone-based images from a teleophthalmology clinic.

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Purpose: To present three cases of acute endophthalmitis following intravitreal sustained-release dexamethasone (Ozurdex) with atypical presentation and to discuss the management of these patients.

Methods: A retrospective case series of three patients with endophthalmitis following intravitreal sustained-release dexamethasone (Ozurdex) implantation who presented between July 2020 and August 2020.

Results: Two of three patients who were treated with topical steroid and antibiotic therapy alone showed favorable outcomes and were managed without the need for intravitreal antibiotics or implant removal.

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Purpose: To evaluate the predictors of complete polypoidal lesion regression (CPREG) in polypoidal choroidal vasculopathy.

Methods: Post hoc analysis of EVEREST II-a 24-month, multicenter, randomized, controlled clinical trial of 322 patients with polypoidal choroidal vasculopathy, randomized to receive ranibizumab with or without photodynamic therapy. Images of indocyanine green angiography (ICGA) were graded by a central reading center.

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Background: Longitudinal evidence on retinal microvasculature and subsequent systemic inflammatory alteration is lacking. We investigated the association between retinal microvasculature and immune response among patients with HIV/AIDS over a 9-month antiretroviral therapy.

Methods: We conducted a prospective cohort study on patients with HIV/AIDS at Singapore Communicable Disease Centre since June 2011.

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Purpose: A training exercise was performed to study the ability of graders to reliably identify precursor lesions to geographic atrophy (GA), known as persistent choroidal hypertransmission defects (hyperTDs), using en face OCT images from eyes with nonexudative age-related macular degeneration (AMD).

Design: Intergrader agreement study.

Participants: Eleven graders participated in this exercise.

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Background: The EVEREST II study reported superior polyp closure rates and visual outcomes using combination standard photodynamic therapy (PDT) with intravitreal ranibizumab in the treatment of polypoidal choroidal vasculopathy (PCV). The optimal PDT protocol remains controversial and it is postulated that less intensive PDT strategies may reduce complications. We aimed to compare the efficacy of reduced and standard-fluence PDT.

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Purpose: To describe the defining features of incomplete retinal pigment epithelium (RPE) and outer retinal atrophy (iRORA), a consensus term referring to the OCT-based anatomic changes often identified before the development of complete RPE and outer retinal atrophy (cRORA) in age-related macular degeneration (AMD). We provide descriptive OCT and histologic examples of disease progression.

Design: Consensus meeting.

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Low vision rehabilitation is an important step towards individuals with Age-related macular degeneration (AMD) regaining useful functional vision and quality of life. One of the key steps in low vision rehabilitation is the determination of the preferred retinal locus (PRL). Currently, localization of PRL is performed manually though the guidance of a low vision therapist and the process is highly time-consuming, labour-intensive and subjective.

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Background: While the aetiology of age-related macular degeneration (AMD)-a major blinding disease-remains unknown, the disease is strongly associated with variants in the complement factor H (CFH) gene. CFH variants also confer susceptibility to invasive infection with several bacterial colonizers of the nasopharyngeal mucosa. This shared susceptibility locus implicates complement deregulation as a common disease mechanism, and suggests the possibility that microbial interactions with host complement may trigger AMD.

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Purpose: The purpose of this study was to describe the characteristics of polypoidal choroidal vasculopathy (PCV) subtypes among patients from a multicenter randomized controlled trial and to determine the impact of PCV subtypes on clinical outcomes.

Methods: This was a prospective cohort study of 61 patients with macular PCV from the EVEREST study. Indocyanine green (ICGA) and fluorescein angiography (FA) obtained using standardized imaging protocols were graded to classify PCV into three subtypes.

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Age Related Macular Degeneration (AMD) is the third leading cause of blindness and the first one in the elderly. AMD usually causes central blindness due to loss of photoreceptor cell . In this paper, we propose to detect AMD caused vision impairment from gaze data.

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Visual impairment associated with Age-related Macular Degeneration (AMD) often results in a central scotoma which is an alteration in the central vision, leading to distortion or loss of vision. Current methods for assessing visual performance such as Amsler grid and Microperimetry are typically manual and have limitations as an indicator of visual field. In this paper, we present an automated system for detecting visual impairment through gaze tracking (AVIGA).

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Background: Dyslipidemia, particularly high-density lipoprotein cholesterol (HDL-C), has recently been implicated in the pathogenesis of age-related macular degeneration (AMD), the leading cause of vision loss. However, epidemiological studies have yielded conflicting results.

Methods: We investigated the causal role of plasma lipid levels in AMD in multiethnic populations comprising 16 144 advanced AMD cases and 17 832 controls of European descent, together with 2219 cases and 5275 controls of Asian descent, using Mendelian randomization in three models.

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Polypoidal choroidal vasculopathy (PCV), a subtype of age-related macular degeneration (AMD) more frequently seen in East Asians, has both common and distinct clinical manifestations with typical neovascular AMD (tAMD). We aim to examine the extent to which common genetic variants are shared between these two subtypes. We performed the meta-analysis of association in a total of 1062 PCV patients, 1157 tAMD patients and 5275 controls of East Asian descent from the Genetics of AMD in Asians Consortium at the 34 known AMD loci.

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Age-related Macular Degeneration (AMD) is one of the leading causes of blindness in the elderly. Visual loss associated with AMD often results in a central scotoma which is an alteration in the central vision, leading to distortion or loss of vision. Current methods of detecting AMD are typically manual, require holding fixation and an external response trigger.

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To examine the association of systemic, ocular and genetic risk factors in neovascular age-related macular degeneration (nAMD) in a large cohort of Asian patients, and to further compare risk factors between those with typical AMD and polypoidal choroidal vasculoapthy (PCV) subtypes. We recruited 456 cases and 1,824 controls matched for age, gender and ethnicity. Data on systemic and ocular risk factors were collected on questionnaires.

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Diabetic Retinopathy (DR) is one of the most common causes of blindness among the working population worldwide. Clearly, there is an unmet clinical need to find better treatment options for DR. Areas covered: The literature search was conducted on PubMed with no limitation on language or year of publication.

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This paper presents a novel augmented reality assistance platform for eye laser surgery. The aims of the proposed system are for the application of assisting eye doctors in pre-planning as well as providing guidance and protection during laser surgery. We developed algorithms to automatically register multi-modal images, detect macula and optic disc regions, and demarcate these as protected areas from laser surgery.

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Background: The introduction of fundus photography has impacted retinal imaging and retinal screening programs significantly.

Literature Review: Fundus cameras play a vital role in addressing the cause of preventive blindness. More attention is being turned to developing countries, where infrastructure and access to healthcare are limited.

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Purpose: To determine if providing high dose anti-oxidant vitamins and zinc treatment age-related eye disease study (AREDS formulation) to patients with intermediate age-related macular degeneration (AMD) aged 40-79 years from Singapore is cost-effective in preventing progression to wet AMD.

Methods: A hypothetical cohort of category 3 and 4 AMD patients from Singapore was followed for 5 calendar years to determine the number of patients who would progress to wet AMD given the following treatment scenarios: (a) AREDS formulation or placebo followed by ranibizumab (as needed) for wet AMD. (b) AREDS formulation or placebo followed by bevacizumab (monthly) for wet AMD.

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Purpose: To evaluate the performance of polypoidal choroidal vasculopathy (PCV) diagnosis using fundus camera-based indocyanine green angiography, comparing a single sign of "subretinal focal hyperfluorescence" on indocyanine green angiography with a modification of the EVEREST criteria.

Methods: Color fundus photograph, flash fundus camera-based fluorescein angiography, and indocyanine green angiography of 241 eyes of 230 consecutive patients with exudative maculopathy due to PCV or typical age-related macular degeneration were graded independently by 2 retinal specialists using a modified EVEREST criteria, which requires the presence of subretinal focal hyperfluorescence plus any 1 of 5 additional criteria. Discordant cases were adjudicated by a senior retinal specialist to arrive at the final diagnosis.

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