Donald T H Tan

Singapore National Eye Centre, Tumasik, Singapore

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Publications (214)717.97 Total impact

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    ABSTRACT: To analyze graft survival of endothelial keratoplasty (EK) under a previous failed penetrating keratoplasty (PK) compared to repeat PK.
    American journal of ophthalmology. 08/2014;
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    ABSTRACT: To evaluate the long-term corneal graft survival and risk factors for graft failure in pediatric eyes.
    American journal of ophthalmology. 05/2014;
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    ABSTRACT: To determine whether changes in cornea nerve growth factor (NGF) protein and gene expression correlate with corneal nerve regeneration after LASIK in rhesus monkeys. Ten rhesus monkeys underwent randomly assigned LASIK procedures to correct -8.0 diopters of myopia in both eyes and two additional monkeys (with no surgery) served as controls. The central corneas of the experimental animals were excised 3 and 7 days and 1, 3, and 6 months after the surgery. Nerve regeneration, NGF mRNA, and protein expression were analyzed by gold chloride staining, real-time polymerase chain reaction, and enzyme-linked immune sorbent assay analysis, respectively. Compared to controls, the LASIK-treated animals had a significantly diminished nerve plexus in the sub-basal region of the cornea at all times after the surgery (P < .001). NGF protein levels decreased significantly on days 3 and 7 after LASIK (P < .001), but returned to control levels 1 month later. NGF mRNA levels increased 5.4-fold on day 3 after the surgery (P < .001), then reduced to two-fold (P < .05) above control levels on day 7 and were back to normal at 3 months and beyond. After LASIK, the changes of early NGF protein and NGF mRNA levels correlated with the density of the corneal nerve plexuses. The results showed that the LASIK procedure in non-human primates was associated with changes in NGF protein and mRNA levels in the cornea. Such changes may be related to the initiation of nerve regeneration and the final recovery of nerve plexuses in the cornea. [J Refract Surg. 2014;30(2):134-139.].
    Journal of refractive surgery (Thorofare, N.J.: 1995) 02/2014; 30(2):134-9. · 2.47 Impact Factor
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    ABSTRACT: To describe the subjective experience of patients and surgeons during laser in situ keratomileusis (LASIK) using the Intralase 60 kHz or the Visumax 500 kHz femtosecond laser. Singapore National Eye Centre, Singapore. Prospective randomized clinical study. In myopic patients, LASIK was performed with the corneal flap created using the 60 kHz laser in 1 eye and the 500 kHz laser in the contralateral eye. Postoperatively, patients completed a standardized validated questionnaire about their subjective intraoperative experiences (eg, light perception, pain, fear). Surgeons reported their intraoperative experiences and preferences. Loss of light perception occurred in 50.0% of 60 kHz laser cases and 0% of 500 kHz laser cases during docking and in 63.0% and 0% of cases, respectively, during laser flap creation (P < .0001). The mean pain score with the 60 kHz laser was significantly higher during docking (P < .0001) but not during laser flap cutting (P = .006). Subconjunctival hemorrhage occurred in 67.4% of eyes with the 60 kHz laser and in 2.2% of eyes with the 500 kHz laser (P < .0001). The 500 kHz laser was preferred by 78.3% of patients, while 21.7% preferred the 60 kHz laser (P < .0001). The surgeons preferred the 60 kHz laser in 50.0% of cases and the 500 kHz laser in 8.7% (P < .0001); 41.3% had no preference. Patients preferred surgery with the 500 kHz laser with no loss of light perception, less pain, less fear, and less subconjunctival hemorrhage. Surgeons preferred the 60 kHz laser. No author has a financial or proprietary interest in any material or method mentioned.
    Journal of Cataract and Refractive Surgery 01/2014; · 2.75 Impact Factor
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    ABSTRACT: To describe the indications for and approaches to vitreoretinal surgery in patients with osteo-odonto-keratoprosthesis (OOKP). Retrospective case series. This was a retrospective review of all patients who had undergone OOKP surgery between 2003 and 2012 at our center. OOKP procedures were performed for severe ocular surface disease according to the indications and techniques described in the patient demographics of the Rome-Vienna Protocol. Indications for retinal surgery, surgical outcomes, and intraoperative and postoperative complications were documented. Operative techniques were reviewed from the surgical records, and any subsequent surgeries were also recorded. Thirty-six patients underwent OOKP, and retinal surgery was indicated in 13 (36%). The indications for and approaches to surgery were retinal detachment repair using an Eckardt temporary keratoprosthesis; assessment of retina and optic nerve health prior to OOKP surgery, using either a temporary keratoprosthesis or an endoscope; endoscopic cyclophotocoagulation for intractable glaucoma; endoscopic trimming of a retroprosthetic membrane; or vitrectomy for endophthalmitis with visualization through the OOKP optic using the binocular indirect viewing system. In all cases, retinal surgical aims were achieved with a single procedure. Postoperative vitreous hemorrhage occurred in 16 patients (44%), but all resolved spontaneously. OOKPs represent the last hope for restoration of vision in severe ocular surface disease, and the retinal surgeon is frequently called upon in the assessment and management of these patients. Temporary keratoprostheses and endoscopic vitrectomies are valuable surgical tools in these challenging cases, improving functional outcomes without compromising OOKP success.
    American journal of ophthalmology 10/2013; · 3.83 Impact Factor
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    ABSTRACT: To describe the use of high-resolution anterior segment optical coherence tomography (AS-OCT) during deep anterior lamellar keratoplasty (DALK). Prospective case series. At the Singapore National Eye Centre we performed sequential intraoperative AS-OCT scans using iVue 100-2 (Optovue, Fremont, CA, USA) during various DALK techniques. In case 1 (corneal scarring) the OCT images helped to guide manual dissection, showed the depth of the needle track before air injection, and identified the location of a small bubble when the big bubble failed. In cases 2 (macular dystrophy) and 3 (lattice), viscodissection was undertaken, but in case 2 the OCT showed the viscoelastic trapped intrastromally, compared to case 3, in which the viscobubble dissection was successful. In case 4 (irregular corneal thinning and scarring), AS-OCT enabled accurate decision on initial trephination and guided dissection. In case 5 (keratoconus), the OCT showed the achieved big-bubble and detached Descemet membrane. Case 6 was a repeat DALK; the OCT guided the manual dissection of the residual stroma underlying the failed graft. In case 7, the OCT showed an intrastromal retention of fluid that was not detectable by the operating microscope due to diffuse scarring following alkaline injury. The OCT helped to assess the location of the Descemet membrane and guided the manual dissection. Intraoperative high-definition AS-OCT obtained good-quality images of the cornea during DALK and proved useful in various cases of DALK to help the surgeon decide on a number of surgical steps.
    American journal of ophthalmology 10/2013; · 3.83 Impact Factor
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    ABSTRACT: To study the clinical outcomes of Descemet stripping automated endothelial keratoplasty (DSAEK) with the EndoGlide donor insertion device. Retrospective interventional case series. We included 100 eyes that underwent DSAEK for Fuchs endothelial dystrophy or pseudophakic bullous keratopathy (PBK) at a single institution. Eyes with anterior segment pathology or previous intraocular surgery (except for uncomplicated cataract surgery) were excluded. Preoperative data included visual acuity and donor endothelial cell density by specular microscopy. The main outcome measures were postoperative best spectacle-corrected visual acuity (BSCVA) and endothelial cell loss at 3, 6, and 12 months. There were 59 eyes with Fuchs dystrophy and 41 eyes with PBK. In eyes without vision-limiting pathology, the median postoperative BSCVA was consistently 20/40 (range 20/20-20/400) at 3 months (n = 61 eyes), 6 months (n = 55 eyes), and 12 months (n = 48 eyes). Endothelial cell loss was 13.7% at 3 months (n = 57), 13.5% at 6 months (n = 61), and 14.9% at 12 months (n = 53). Primary graft failure occurred in 1 eye, attributable to incorrect use of the insertion device. Two eyes with complete donor dislocation were rebubbled successfully. The most common complication was glaucoma/ocular hypertension in 29 eyes (34.1%) without prior glaucoma and treatment escalation in 6 eyes (40.0%) with prior glaucoma. Of the 78 eyes with 12 months follow-up, 2 (2.6%) developed endothelial rejection, and 1 (1.3%) subsequently failed. The use of this donor insertion device during DSAEK demonstrates good outcomes and potentially low endothelial cell loss at up to 12 months after surgery.
    American journal of ophthalmology 07/2013; · 3.83 Impact Factor
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    ABSTRACT: PURPOSE: To compare the efficacy, predictability, and refractive outcomes of laser in situ keratomileusis (LASIK) using 2 femtosecond platforms for flap creation. SETTING: Multisurgeon single center. DESIGN: Clinical trial. METHODS: Bilateral femtosecond LASIK was performed using the Wavelight Allegretto Eye-Q 400 Hz excimer laser system. The Visumax femtosecond platform (Group 1) was used to create the LASIK flap in 1 eye, while the Intralase femtosecond platform (Group 2) was used to create the LASIK flap in the contralateral eye. The preoperative, 1-month, and 3-month postoperative visual acuities, refraction, and contrast sensitivity in the 2 groups were compared. RESULTS: The study enrolled 45 patients. Three months after femtosecond LASIK, 79.5% of eyes in Group 1 and 82.1% in Group 2 achieved an uncorrected distance visual acuity of 20/20 (P=.808). The mean efficacy index was 0.97 in Group 1 and 0.98 in Group 2 at 3 months (P=.735); 89.7% of eyes in Group 1 and 84.6% of eyes in Group 2 were within ±0.50 diopter of emmetropia at 3 months (P=.498). No eye in either group lost more than 2 lines of corrected distance visual acuity. The mean safety index at 3 months was 1.11 in Group 1 and 1.10 in Group 2 (P=.570). CONCLUSION: The results of LASIK with both femtosecond lasers were similar, and both platforms produced efficacious and predictable LASIK outcomes. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.
    Journal of Cataract and Refractive Surgery 05/2013; · 2.75 Impact Factor
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    ABSTRACT: This work describes how to tune the amphiphilic conformation of α-mangostin, a natural compound that contains a hydrophobic xanthone scaffold, to improve its antimicrobial activity and selectivity for Gram-positive bacteria. A series of xanthone derivatives was obtained by cationic modification of the free C3 and C6 hydroxyl groups of α-mangostin with amine groups of different pKa values. Modified structures using moieties with high pKa values, such as AM-0016 (3b), exhibited potent antimicrobial properties against Gram-positive bacteria. Compound 3b also killed bacteria rapidly without inducing drug resistance and was nontoxic when applied topically. Biophysical studies and molecular dynamics simulations revealed that 3b targets the bacterial inner membrane, forming an amphiphilic conformation at the hydrophobic–water interface. In contrast, moieties with low pKa values reduced the antimicrobial activity of the parent compound when conjugated to the xanthone scaffold. This strategy provides a new way to improve “hits” for the development of membrane-active antibiotics that target drug-resistant pathogens.
    Journal of Medicinal Chemistry 04/2013; · 5.61 Impact Factor
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    ABSTRACT: PURPOSE: To describe outcomes of corneal transplantation for irreversible corneal decompensation from corneal endotheliitis in Asian eyes. DESIGN: Retrospective, observational case series. METHODS: We reviewed consecutive patients with corneal endotheliitis (32 eyes of 31 subjects) who underwent keratoplasty (January 1, 2008-December 1, 2009). All eyes had preoperative aqueous polymerase chain reaction (PCR) analysis for viruses, including cytomegalovirus (CMV). CMV-positive patients were treated preoperatively with topical corticosteroids and anti-CMV treatment (oral valganciclovir 900 mg twice daily, topical ganciclovir 0.15% 5 applications per day, for 6 weeks) with complete resolution of ocular inflammation, and quiescence for at least 6 months before corneal transplantation. Our main outcome measure was recurrence of endotheliitis within 1 year after corneal transplantation. RESULTS: Five eyes were CMV positive; the remaining 27 eyes were negative for all viruses on PCR analysis. CMV-positive patients had a higher rate of recurrence of endotheliitis within 1 year after corneal transplantation, compared with CMV-negative eyes (60% vs 7.4%, P = .01). The CMV-positive eyes had recurrent endotheliitis at a median of 10 months (range 3-11 months) after corneal transplantation. After successful anti-CMV treatment, all 5 CMV-positive eyes then continued to have clear grafts for a median duration of 21 months (range 13-44 months). CONCLUSION: Our study suggests that Asian patients with corneal endotheliitis may benefit from preoperative aqueous PCR analysis before corneal transplantation. Such patients were more likely to have a recurrence of endothelial inflammation if they were CMV positive preoperatively, despite successful anti-CMV treatment before surgery.
    American journal of ophthalmology 04/2013; · 3.83 Impact Factor
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    ABSTRACT: To develop a mouse model of bullous keratoplasty and evaluate the safety and efficacy of cryoinjury-induced corneal endothelial decompensation. Transcorneal freezing was performed on the right eye of each mouse. One cycle of cryoinjury was performed in 18 eyes (group A), and three cycles were performed in 17 eyes (group B). Pachymetry and intraocular pressure (IOP) measurements were done preoperatively, as well as at 1, 3, 7, 14, and 21 days after cryoinjury. At each post-cryoinjury time point, three mice from each group were euthanized, and the corneas underwent histology and electron microscopy. In both groups, significant corneal edema was noted at post-cryoinjury day 1, which was maintained throughout the study period. IOP remained within normal range in group A, but increased significantly with time in group B (p=0.011 at day 1, 0.038 at day 3, 0.026 at day 14, and 0.008 at day 21). In group B, serious complications including hyphema (one case), severe iridocorneal adhesion (15 cases), and total cataract (three cases) were detected, while only mild iridocorneal adhesion (four cases) and cataract (three cases) were noted in group A. Live/dead cell assay, hematoxylin and eosin staining, and scanning electron microscopy revealed successful ablation of corneal endothelial cells and absence of regeneration in both groups. Hematoxylin and eosin staining and terminal deoxynucleotidyl transferase-mediated nick end labeling assay showed that apoptosis was mainly confined to the posterior stroma and endothelium in group A, while severe apoptosis was observed throughout all layers of the cornea in group B. One cycle of cryoinjury was safer than three, while both were equally effective in inducing bullous keratopathy. This cryoinjury mouse model of bullous keratopathy was a consistently reproducible model that can be used for further studies on endothelial cell damage and rescue therapy.
    Molecular vision 01/2013; 19:1222-30. · 1.99 Impact Factor
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    ABSTRACT: The emergence of methicillin-resistant Staphylococcus aureus (MRSA) has created the need for better therapeutic options. In this study, five natural xanthones were extracted and purified from the fruit hull of Garcinia mangostana and their antimicrobial properties were investigated. α-Mangostin was identified as the most potent among them against Gram-positive pathogens (MIC=0.78-1.56μg/mL) which included two MRSA isolates. α-Mangostin also exhibited rapid in vitro bactericidal activity (3-log reduction within 5min). In a multistep (20 passage) resistance selection study using a MRSA isolated from the eye, no resistance against α-mangostin in the strains tested was observed. Biophysical studies using fluorescence probes for membrane potential and permeability, calcein encapsulated large unilamellar vesicles and scanning electron microscopy showed that α-mangostin rapidly disrupted the integrity of the cytoplasmic membrane leading to loss of intracellular components in a concentration-dependent manner. Molecular dynamic simulations revealed that isoprenyl groups were important to reduce the free energy for the burial of the hydrophobic phenyl ring of α-mangostin into the lipid bilayer of the membrane resulting in membrane breakdown and increased permeability. Thus, we suggest that direct interactions of α-mangostin with the bacterial membrane are responsible for the rapid concentration-dependent membrane disruption and bactericidal action.
    Biochimica et Biophysica Acta 09/2012; · 4.66 Impact Factor
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    American journal of ophthalmology 07/2012; 154(1):210-1. · 3.83 Impact Factor
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    ABSTRACT: We provided normative data of corneal and anterior segment dimensions, and a novel parameter, posterior corneal arc length (PCAL), in an adult Malay population. The current analysis is a substudy of the Singapore Malay Eye Study (SiMES), a population-based, cross-sectional study of urban Malay adults aged 40 to 80. Subjects underwent ophthalmic and systemic examination, including imaging with anterior segment optical coherence tomography (AS-OCT). Ocular parameters subsequently were measured with the Zhongshan Assessment Program (ZAP), and included anterior chamber depth (ACD), central corneal thickness (CCT), anterior and posterior corneal curvature (ACC and PCC, respectively), and PCAL, which is a novel parameter defined as the arc-distance of the posterior corneal border between the scleral spurs. Age- and sex-adjusted analyses, and multivariate analyses were performed to determine correlations of PCAL with other ocular and systemic components. We studied 237 subjects, among whom the mean age was 56.6 ± 10.4 years and 50.2% were women. Ocular parameters (mean ± SD) included central ACD 2.78 ± 0.34 mm, CCT 550.23 ± 37.12 mm, ACC 7.43 ± 0.37 mm, PCC 6.75 ± 0.37 mm, and PCAL 13.95 ± 0.51 mm. There was moderate correlation between PCAL and ACD (r = 0.476, P < 0.001), but poor correlation with PCC (r = 0.243, P < 0.001), ACC (r = 0.251, P < 0.001), and systemic parameters, like age, body mass index (BMI), blood pressure, blood glucose levels, hemoglobin A1c (HbA1c), and refractive parameters. Multivariate analysis showed a significant association between PCAL and ACD (P < 0.001), PCC (P < 0.001), and height (P < 0.05). Our study, to our knowledge, provides the largest baseline anterior segment parameters in an adult Asian Malay population. PCAL correlated moderately with ACD. These data are applicable clinically for assessment and surgical management of patients requiring anterior segment or corneal surgery.
    Investigative ophthalmology & visual science 06/2012; 53(8):4860-7. · 3.43 Impact Factor
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    ABSTRACT: Corneal transplantation or keratoplasty has developed rapidly in the past 10 years. Penetrating keratoplasty, a procedure consisting of full-thickness replacement of the cornea, has been the dominant procedure for more than half a century, and successfully caters to most causes of corneal blindness. The adoption by specialist surgeons of newer forms of lamellar transplantation surgery, which selectively replace only diseased layers of the cornea, has been a fundamental change in recent years. Deep anterior lamellar keratoplasty is replacing penetrating keratoplasty for disorders affecting the corneal stromal layers, while eliminating the risk of endothelial rejection. Endothelial keratoplasty, which selectively replaces the corneal endothelium in patients with endothelial disease, has resulted in more rapid and predictable visual outcomes. Other emerging therapies are ocular surface reconstruction and artificial cornea (keratoprosthesis) surgery, which have become more widely available because of rapid advances in these techniques. Collectively, these advances have resulted in improved outcomes, and have expanded the number of cases of corneal blindness, which can now be treated successfully. Femtosecond-laser-assisted surgery, bioengineered corneas, and medical treatment for endothelial disease are also likely to play a part in the future.
    The Lancet 05/2012; 379(9827):1749-61. · 39.06 Impact Factor
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    ABSTRACT: PURPOSE:: To evaluate the efficacy of air bubble (AB) tamponade for Descemet membrane detachment (DMD) after clear corneal incision phacoemulsification surgery and to evaluate the risk factors for DMD. METHODS:: This is a retrospective analysis of patients with DMD managed with AB tamponade, within 42 postoperative days (PODs), over a 4-year period. Data collected were as follows: demographics, cataract density (Lens Opacities Classification System III), visual acuity, AB technique, clinical outcome, and total surgeries over the time period. Successful end points were DM reattachment and corneal clarity. Risk factors were assessed using a case-control study, with univariate and multivariate logistic regression analyses (significance at P < 0.05). RESULTS:: Incidence rate of DMD was 0.044% per year. Sixteen patients (mean age of 76 years) had AB tamponade for DMD, with corneal clarity restored in 14 cases (87.5%; n = 11 with 1 AB procedure, n = 3 with 2 AB procedures). The main clear corneal incision was the major site of DMD (n = 14, 87.5%). Pre-AB visual acuity was 20/100 and at 1 month, 20/40. Corneal clarity occurred by 30 days (range: 4-82 days) and remained clear throughout the median follow-up of 12.9 months. Significant univariate factors were as follows: age >65 years, nuclear sclerosis grade ≥4 (Lens Opacities Classification System III), preexisting endothelial disease, and first POD corneal edema. Multivariate logistic regression analyses revealed endothelial disease (odds ratio = 18.66) and first POD edema (odds ratio = 7.88) as significant independent risk factors for DMD occurrence (P < 0.05). CONCLUSIONS:: AB tamponade for DMD effectively restored corneal clarity in 87.5% of cases (14 of 16 eyes). Significant risk factors included endothelial disease and first POD corneal edema.
    Cornea 05/2012; · 1.75 Impact Factor
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    ABSTRACT: Endothelial keratoplasty (EK) is continually evolving both in surgical technique and clinical outcomes. Descemet's stripping endothelial keratoplasty (DSEK) has replaced penetrating keratoplasty (PK) as the treatment of choice for corneal endothelial dysfunction. It is safe and predictable and offers early visual rehabilitation. Newer iterations include Descemet's membrane endothelial keratoplasty, Descemet's membrane automated endothelial keratoplasty, and other hybrid techniques. Early data on these newer EK techniques suggests that they provide significantly better visual outcomes compared to DSEK. Initial 5-year survival data indicates that EK is at least comparable to PK, and more widespread survival data is anticipated. Further work is needed to simultaneously optimize visual outcomes, refractive predictability, and endothelial cell survival, as well as surgical techniques of donor preparation and insertion.
    Survey of Ophthalmology 05/2012; 57(3):236-52. · 2.86 Impact Factor
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    ABSTRACT: Outcomes of corneal transplantation for tectonic indications and risk factors for (tectonic and physiologic) graft failure. Retrospective cohort study. Consecutive patients who underwent keratoplasty for tectonic indications at the Singapore National Eye Centre (SNEC) between January 1, 1991, and December 1, 2009. Clinical data and donor and recipient characteristics were recorded and analyzed from subjects in the prospective Singapore Corneal Transplant Study. (1) Tectonic (anatomic) failure defined as recurrence of corneal melt threatening tectonic integrity and requiring additional corneal grafting within 3 months of the primary procedure. (2) Physiologic failure defined as irreversible change in graft clarity preventing recovery in useful vision in grafts initially clear 2 weeks postoperatively. The mean age of the study cohort (n = 362, 193 male and 169 female subjects) was 51.5 ± 20.2 years, with a mean follow-up of 25.8 ± 18.7 months. Patients underwent penetrating keratoplasty (PK) (n = 142, 39.2%), anterior lamellar keratoplasty (ALK) (n = 127, 35.1%), or a peripheral corneoscleral patch graft (n = 93, 25.7%) most commonly for inflammation (n = 68, 18.8%), trauma (n = 66, 18.2%), or infection (n = 66, 18.2%). Risk factors for tectonic failure (18/362 eyes, 5.0%) were severe lid disease (odds ratio [OR], 6.1; 95% confidence interval [CI], 1.7-22.1; P = 0.006), central ALK (OR, 7.5; 95% CI, 1.8-32.4; P = 0.007), and peripheral grafts (OR, 5.7; 95% CI, 1.1-28.3; P = 0.035). Among anatomically successful central grafts (n = 223), the mean physiological graft survival was 96 months (95% CI, 83-110); Kaplan-Meier probabilities for survival at 10 years were 66.8% for ALK and 44.2% for PK. Active corneal inflammation (hazard ratio [HR], 2.5; 95% CI, 1.4-4.4; P = 0.003) and larger donor and recipient graft sizes of ≥ 9 mm (HR, 17.9; 95% CI, 2.3-140.3; P = 0.006) were risk factors for physiologic graft failure in anatomically successful eyes with central tectonic grafts. Patients with lid disease, central ALK, and peripheral grafts were at higher risk of anatomic failure. For anatomically successful cases with central tectonic grafts, active corneal inflammation and donor size ≥ 9 mm were risk factors for physiologic failure. In these cases, our results suggest that ALK had better physiologic graft survival outcomes than PK.
    Ophthalmology 04/2012; 119(7):1311-9. · 5.56 Impact Factor
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    ABSTRACT: To describe the prevalence and risk factors of pterygium in a multiethnic Asian population and to examine racial differences. Population-based study in Singapore, located 1° north of the equator. Data were analyzed from 8906 participants from 3 population-based studies of Malays, Indians, and Chinese persons 40 years of age and older conducted between 2004 and 2011. Standardized slit-lamp examinations were performed by trained study ophthalmologists to examine the anterior segment for evidence of pterygium. Every subject underwent standardized systemic and ocular examinations, interviewer-administered questionnaires, and blood investigations for risk factor assessment. Regression and principle component analysis models were constructed to study the relationship of race and other factors to pterygium. Any pterygium and severe (grade 3 or opaque) pterygium. The overall prevalence of any pterygium was 10.1% (n = 900), of which severe pterygium was seen in 1.6% (n = 142). The prevalence of any pterygium was more common in Malays (15.5%) than Chinese (7.0%; P<0.001) or Indians (7.0%; P<0.001). Multivariate analysis revealed increasing age (P<0.001), male gender (P<0.001), Malay race (P<0.001), and having a poorer education level (P<0.001) as significant factors for any pterygium. Race contributed significantly to presence of any pterygium (41%; P<0.001) or presence in both eyes (33%; P<0.001) compared with other risk factors. Severe pterygium was associated with outdoor occupation (P = 0.02), but race was not a significant risk factor in multivariate analysis. This population-based study in Asian persons of different races living in the same geographical location at the equator indicated that race is a significant risk factor for pterygium, with Malays having higher prevalence than Indians and Chinese, while controlling for other risk factors.
    Ophthalmology 04/2012; 119(8):1509-15. · 5.56 Impact Factor
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    ABSTRACT: To compare the outcomes of trabeculectomy surgery after Descemet stripping automated endothelial keratoplasty (DSAEK) to penetrating keratoplasty (PK). Retrospective case-control study. Patients within an institutional setting who underwent trabeculectomy with mitomycin C (MMC) for uncontrolled elevated intraocular pressure (IOP) after corneal graft surgery were included. Patients with pre-existing glaucoma were excluded. Twenty patients with trabeculectomy after DSAEK and 41 patients with trabeculectomy after PK were analyzed. The main outcome measure was IOP control at 12 months. Secondary outcome measures were postoperative interventions including reinstatement of IOP-lowering medications, bleb needling with 5-fluorouracil (5FU) or further glaucoma surgery, and the incidence of complications related to trabeculectomy and/or corneal graft surgery. There was no difference in pre-trabeculectomy IOP between DSAEK vs PK group (35.5 ± 10.1 vs 32.9 ± 8.9, P = .31). At 12 months after trabeculectomy, mean IOP in the DSAEK group was lower compared to the PK controls (10.6 ± 3.2 vs 14.6 ± 8.5, P = .04). The proportion of patients who achieved an IOP less than 12 mm Hg was significantly higher in the DSAEK group (80.0% vs 48.6%, P = .03). The proportions of eyes that required intervention after trabeculectomy were comparable between the 2 groups (DSAEK vs PK, all interventions: 20.0% vs 39.5%, P = .15; IOP-lowering medications required: 15.0% vs 39.5%, P = .08; needling with 5FU: 20.0% vs 23.7%, P > .99; further glaucoma surgery: 0% vs 13.2%, P = .15). Corneal graft failure arising after trabeculectomy was seen in 10.0% of DSAEK cases and in 10.5% of PK controls (P = 1.0). Compared to trabeculectomy after PK, trabeculectomy after DSAEK achieved lower mean IOP at 12 months, and a larger proportion of DSAEK patients achieved an IOP of less than 12 mm Hg. There was no difference in the need for intervention after trabeculectomy, or incidence of other complications. Trabeculectomy is an effective surgical procedure for the management of postgraft ocular hypertension in DSAEK patients, and DSAEK may have an advantage in terms of success of trabeculectomy surgery over PK.
    American journal of ophthalmology 03/2012; 153(6):1091-8.e2. · 3.83 Impact Factor

Publication Stats

4k Citations
717.97 Total Impact Points


  • 1995–2014
    • Singapore National Eye Centre
      Tumasik, Singapore
  • 2001–2012
    • Singapore Eye Research Institute
      Tumasik, Singapore
  • 2011
    • Shanghai Jiao Tong University
      • Department of Ophthalmology
      Shanghai, Shanghai Shi, China
    • Duke-NUS Graduate Medical School Singapore
      Tumasik, Singapore
  • 2006–2011
    • Tianjin Eye Hospital
      T’ien-ching-shih, Tianjin Shi, China
  • 1998–2011
    • National University of Singapore
      • • Singapore Eye Research Institute
      • • Department of Ophthalmology
      • • Saw Swee Hock School of Public Health
      Singapore, Singapore
  • 2008
    • University of Melbourne
      • Department of Ophthalmology
      Melbourne, Victoria, Australia
  • 2004
    • Queensland University of Technology
      • School of Optometry and Vision Science
      Brisbane, Queensland, Australia