Donald T H Tan

Singapore Eye Research Institute, Tumasik, Singapore

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Publications (296)1175.13 Total impact

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    ABSTRACT: To describe and compare graft survival and intraocular pressure (IOP) control after penetrating keratoplasty (PK) and descemet stripping automated endothelial keratoplasty (DSAEK) in eyes with iridocorneal endothelial (ICE) syndrome. Retrospective case series. Multicentred study conducted at the Singapore National Eye Centre (SNEC) and Price Vision Group. Twenty-nine consecutive eyes with ICE syndrome that underwent keratoplasty between 1991 and 2011 were identified from the SNEC transplant database and Price Vision Group patient database and the following data extracted: demographics, graft failure, IOP indices and glaucoma treatment pre and post keratoplasty. The main outcome measures were graft failure and need for additional IOP-lowering treatment after keratoplasty RESULTS: The mean follow up duration was 7.0±4.9 years in the PK group (n=17) and 4.0±2.6 years in the DSAEK group (n=12). After a mean of 4.1±3.1 years, 37.9% (11/29) of grafts failed - 7 PK compared to 4 DSAEK (P=.72). The graft failure rate was 50% in eyes with pre-keratoplasty glaucoma surgery vs 31.6% in those without, (P=.43). Additional glaucoma treatment was required in 37.9% (11/29) eyes; 41.2% of PK eyes and 50% of DSAEK eyes (P=.28) Eyes that had undergone glaucoma surgery before keratoplasty were less likely to require escalation of IOP lowering therapy post-keratoplasty (9.1% vs 50%, P=.03). One third of grafts failed after keratoplasty for ICE syndrome at a mean duration of 4 years and additional IOP lowering treatment was required in 37.9%. Both PK and DSAEK had similar outcomes with regards to graft failure and IOP control. Copyright © 2015 Elsevier Inc. All rights reserved.
    American Journal of Ophthalmology 05/2015; DOI:10.1016/j.ajo.2015.05.024 · 4.02 Impact Factor
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    ABSTRACT: Descemet membrane endothelial keratoplasty (DMEK) allows for selective replacement of damaged endothelial cells, using only donor Descemet's membrane with endothelium. However, early adoption by corneal surgeons has been limited (illustrated by graft registry reports: 0.7% all corneal transplants in the USA; 0.4% in Australia for 2011) due to challenges in donor preparation and surgical technique. Recently, innovative donor preparation techniques may improve availability of pre-stripped DMEK donors from eye banks. The refinement of donor insertion and manipulation techniques has also improved outcomes and reduced graft detachment rates-still, the most common postoperative complication following DMEK. Randomised studies are needed to compare clinical practices and surgeon preferences, such as intraoperative use of long-acting gas, early versus late intervention of graft detachments and postoperative steroid management. A review of current literature reveals that most publications to date are reports from similar study cohorts by surgeons who pioneered and advocate this technique. Thus, more long-term clinical studies in other tertiary centres are required in order to confirm if the purported advantages of DMEK such as improved visual outcomes and reduced graft rejection are replicable among most corneal surgeons. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
    The British journal of ophthalmology 05/2015; DOI:10.1136/bjophthalmol-2015-306837 · 2.81 Impact Factor
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    ABSTRACT: The global shortage of donor corneas has garnered extensive interest in the development of graft alternatives suitable for endothelial keratoplasty using cultivated primary human corneal endothelial cells (CECs). We have recently described a dual media approach for the propagation of human CECs. In this work, we characterize the effects of a Rho-kinase inhibitor Y-27632 on the cultivation of CECs propagated using the dual media culture system. Seventy donor corneas deemed unsuitable for transplantation were procured for this study. We assessed the use of Y-27632 for its effect at each stage of the cell culture process, specifically for cell attachment, cell proliferation, and during both regular passaging and cryopreservation. Lastly, comparison of donor-matched CEC-cultures expanded with or without Y-27632 was also performed. Our results showed that Y-27632 significantly improved the attachment and proliferation of primary CECs. A non-significant pro-survival effect was detected during regular cellular passage when CECs were pre-treated with Y-27632, an effect that became more evident during cryopreservation. Our study showed that the inclusion of Y-27632 was beneficial for the propagation of primary CECs expanded via the dual media approach, and was able to increase overall cell yield by between 1.96 to 3.36 fold. [http://www.nature.com/srep/2015/150316/srep09167/full/srep09167.html]
    Scientific Reports 03/2015; 5:9167. DOI:10.1038/srep09167 · 5.58 Impact Factor
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    ABSTRACT: To evaluate and compare changes in contrast sensitivity and ocular higher-order aberrations (HOAs) after femtosecond lenticule extraction (FLEx) and pseudo small-incision lenticule extraction (SMILE). Singapore National Eye Centre, Singapore. Retrospective case series. Patients had femtosecond lenticule extraction (Group 1) or pseudo small-incision lenticule extraction (Group 2) between March 2010 and December 2011. The main outcome measures were manifest refraction, HOAs, and contrast sensitivity 1, 3, 6, and 12 months postoperatively. Fifty-two consecutive patients (102 eyes) were recruited, 21 patients (42 eyes) in Group 1 and the 31 patients (60 eyes) in Group 2. The uncorrected and corrected distance visual acuities were significantly better in Group 2 than in Group 1 at 12 months (P = .032). There was no significant increase in 3rd- or 4th-order aberrations at 1 year and no significant difference between the 2 groups preoperatively or postoperatively. At 1 year, there was a significant increase in mesopic contrast sensitivity in Group 2 at 1.5 cycles per degree (cpd) (P = .008) that was not found in Group 1, and photopic contrast sensitivity at 6.0 cpd was higher in Group 2 (P = .027). These results indicate that refractive lenticule extraction is safe and effective with no significant induction of HOAs or deterioration in contrast sensitivity at 1 year. Induction of HOAs was not significantly different between both variants of refractive lenticule extraction. However, there was significant improvement in photopic contrast sensitivity after pseudo small-incision lenticule extraction, which persisted through 1 year. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.
    Journal of Cataract and Refractive Surgery 03/2015; 41(3):623-34. DOI:10.1016/j.jcrs.2014.07.032 · 2.55 Impact Factor
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    ABSTRACT: To investigate variables associated with myopic progression despite treatment in the Atropine in the Treatment of Myopia (ATOM-1) Study. Retrospective cohort study. 200 of 400 children were randomized to receive atropine 1% in one eye only in this institutional study. Children were followed up with cycloplegic autorefraction every 4 months over 2 years. Children whose myopia progressed by more than 0.5 Diopter (D) in atropine treated eye at 1 year were classified as being 'progressors'. There were 22 (12.1%) progressors amongst the 182 children still in the study at 1 year. Univariate analysis suggested these children tended to be younger (8.5±1.4years versus 9.3±1.5years, p=0.023), with higher myopic spherical equivalent (SE) at baseline (-3.6±1.3D versus -2.8±1.4D, p=0.015) and to have 2 myopic parents (77.3% versus 48.1%, p=0.012). In non-progressors, the myopia progression at 1 year was less in the atropine-treated compared to untreated fellow eyes (+0.16±0.37 D verus -0.73±0.48, p<0.001) but in progressors, progression was more similar between eyes (-0.92±0.31 versus -1.06±0.44, p=0.363). Regression analysis showed that the risk of being a progressor was 40% lower with each year of increased age, 43% lower for every 1.0 D less myopia at baseline, and 59% lower for every 1.0 D less myopic change in the untreated eyes over the first year. Doctors and parents need to be aware that there is a small group of children (younger, with higher myopia and greater tendency of myopic progression) who may still progress while on atropine treatment. Copyright © 2015 Elsevier Inc. All rights reserved.
    American Journal of Ophthalmology 01/2015; 159(5). DOI:10.1016/j.ajo.2015.01.029 · 4.02 Impact Factor
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    ABSTRACT: Purpose: To investigate the quality of the ultrathin corneal grafts prepared by femtosecond laser from the endothelial side for Descemet stripping endothelial keratoplasty. Methods: Thirty human corneoscleral buttons were cut from the endothelial side by LDV femtosecond laser with or without viscoelastic materials coating. Two cutting depths were selected: 70 μm and 90 μm. The postcut endothelial count was determined by specular microscopy, and the graft thickness was evaluated by anterior segment optical coherence tomography. The endothelial viability was determined using Trypan blue/Alizarin red staining, calcein-AM/EthD-1 live/dead cell assay, and scanning electron microscope (SEM). The graft interface smoothness was evaluated by SEM. Another eighteen corneoscleral buttons were used as controls for the comparisons. Results: The overall targeted cutting depth and achieved cutting depth were significantly highly correlated (r = 0.84). The central to peripheral corneal thickness ratio was 0.976 and 0.998 for the 70 μm and 90 μm grafts. The percentage of the damaged endothelial cells assessed by vital staining and SEM showed the 70 μm grafts had noticeably more endothelial damage compared to the 90 μm grafts. But the damage was significantly reduced, to the control corneas level, after coating the endothelium with Viscoat. The 90 μm grafts had slightly rougher graft interface than the 70 μm grafts, but all the grafts dissected by a Chansue dissector exhibited generally smooth interface. Conclusions: The corneal endothelial grafts prepared by LDV femtosecond laser with endothelial approach produced consistently ultrathin grafts in uniform shape with high accuracy and good endothelial and stromal interface quality. Copyright © 2014 by Association for Research in Vision and Ophthalmology.
    Investigative Ophthalmology &amp Visual Science 12/2014; 55(12). DOI:10.1167/iovs.14-15080 · 3.66 Impact Factor
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    ABSTRACT: Antibiotic resistance is a critical global health care crisis requiring urgent action to develop more effective antibiotics. Utilizing the hydrophobic scaffold of xanthone, we identified three components that mimicked the action of an antimicrobial cationic peptide to produce membrane-targeting antimicrobials. Compounds 5c and 6, which contain a hydrophobic xanthone core, lipophilic chains and cationic amino acids, displayed very promising antimicrobial activity against multidrug-resistant Gram-positive bacteria, including MRSA and VRE, rapid time-kill, avoidance of antibiotic resistance and low toxicity. The bacterial membrane selectivity of these molecules was comparable to that of several membrane-targeting antibiotics in clinical trials. 5c and 6 were effective in a mouse model of corneal infection by S. aureus and MRSA. Evidence is presented indicating that 5c and 6 target the negatively charged bacterial membrane via a combination of electrostatic and hydrophobic interactions. These results suggest that 5c and 6 have significant promise for combating life-threatening infections.
    Journal of Medicinal Chemistry 12/2014; 58(2). DOI:10.1021/jm501285x · 5.48 Impact Factor
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    ABSTRACT: To describe the incidence, management, and outcomes of suction loss in refractive lenticule extraction (ReLEx). Tertiary eye hospital. Retrospective case series. All patients who experienced suction loss during refractive lenticule extraction from March 9, 2010, to August 5, 2013, were evaluated preoperatively, including slitlamp biomicroscopy, fundoscopy, corneal topography, ultrasound pachymetry, manifest and cycloplegic refractions, and measurement of uncorrected (UDVA) and corrected (CDVA) distance visual acuities. Patients were followed at predetermined timepoints. At each follow-up visit, the UDVA and CDVA were measured and slitlamp biomicroscopy was performed. Manifest refraction was measured 1 and 3 months postoperatively. During the study period, 340 refractive lenticule extractions were performed. The overall cumulative incidence of suction loss was 3.2%. The incidence of suction loss was 4.3% (2/46) for femtosecond lenticule extraction, 4.4% (8/183) for small-incision lenticule extraction, and 0.9% (1/109) for pseudo small-incision lenticule extraction. Of the 11 eyes in which suction loss occurred, 8 (72.7%) had a UDVA of 20/30 or better and 9 (81.8%) had a spherical equivalent within ±0.5 diopter of emmetropia at 3 months. Suction loss occurred in 4 eyes during the posterior lenticule cut, in 5 eyes during the anterior lenticule cut, and in 2 eyes during the lamellar flap cut. In 9 of these (81.8%), suction was reapplied and the procedure was completed without further complications. The incidence of suction loss during refractive lenticule extraction was relatively low. Good visual outcomes were achieved with appropriate management. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.
    Journal of Cataract and Refractive Surgery 11/2014; DOI:10.1016/j.jcrs.2014.04.031 · 2.55 Impact Factor
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    ABSTRACT: Purpose: To test the association between the CTG18.1 trinucleotide repeat expansion of TCF4 gene and Fuchs' endothelial corneal dystrophy (FECD) in a Chinese population. Methods: The CTG18.1 trinucleotide repeat polymorphism was genotyped using short tandem repeat (STR) and triplet repeat primed polymerase chain reaction (TP-PCR) assays in 57 Chinese subjects with FECD and 121 controls. Statistical association of the expanded CTG18.1 allele and 18 single nucleotide polymorphisms (SNPs) across TCF4 with FECD was evaluated. To investigate the linkage disequilibrium structure of the TCF4 region, haplotype analysis was performed on our study subjects and compared to genotyping data of 97 Han Chinese and 85 Caucasians in the 1000 Genomes Project. Results: The expanded CTG18.1 allele was associated with FECD (P = 4.7 X 10-14) with the odds ratio of each copy of the expanded allele estimated to be 66.5 (95% confidence interval: 12.6-350.1). Five TCF4 SNPs showed association with FECD at a nominal level (P < 5.0 X 10-2); however, conditional on the expanded CTG18.1 polymorphism, none of the SNPs showed association with FECD. The only haplotype associated with the disease was the one with the expansion at the CTG18.1 locus. Conclusions: Trans-ethnic replication of the association between the CTG18.1 repeat expansion in the TCF4 gene and FECD suggests it a common, causal variant shared in Eurasian populations conferring significant risk for the development of FECD. Our data suggests that the expanded CTG18.1 allele is the main, if not sole, causal variant at this gene locus in Chinese.
    Investigative Ophthalmology &amp Visual Science 10/2014; DOI:10.1167/iovs.14-15390 · 3.66 Impact Factor
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    ABSTRACT: PURPOSE: To describe the transition and outcomes of 3 refractive lenticule extraction (ReLEx) techniques: femtosecond lenticule extraction (FLEx), small-incision lenticule extraction (SMILE), and pseudo small-incision lenticule extraction. SETTING: Singapore National Eye Center, Singapore. DESIGN: Prospective comparative case series. METHODS: Refractive lenticule extraction was performed between March 1, 2010, and November 1, 2012, using the Visumax 500 kHz femtosecond laser system. The main outcome measures were the refractive efficacy, predictability, and safety over 12 months. RESULTS: The study enrolled 88 eyes. All 3 refractive lenticule extraction techniques yielded good refractive outcomes and stability over 12 months. Three months postoperatively, the mean overall efficacy index of refractive lenticule extraction was 0.89 +/- 0.22 (SD), with 95.5% of eyes attaining an uncorrected distance visual acuity (UDVA) of better than 20/40 and 60.2% of better than 20/20. Of all eyes, 95.5% were within +/-1.00 diopter (D) and 78.4% within +/-0.50 D of the attempted correction. The mean overall safety index was 1.06 +/- 0.17. At 3 months, all small-incision lenticule extraction eyes and 96.7% of pseudo small-incision lenticule extraction eyes had a UDVA of 20/40 or better, while femtosecond lenticule extraction eyes had a lower efficacy index (87.0%). However, efficacy was comparable in all 3 groups by 12 months (mean 0.87 +/- 0.04 [standard error of the mean]; P = 1.00). CONCLUSION: The efficacy, safety, and predictability profiles of the 3 refractive lenticule extraction techniques were good over a 12-month follow-up. (C) 2014 ASCRS and ESCRS
    Journal of Cataract and Refractive Surgery 09/2014; 40(9):1415-24. DOI:10.1016/j.jcrs.2013.12.026 · 2.55 Impact Factor
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    ABSTRACT: PURPOSE: To analyze graft survival of endothelial keratoplasty (EK) under a previous failed penetrating keratoplasty (PK) compared to repeat PK. DESIGN: Retrospective, comparative case series. METHODS: Analysis involved consecutive patients who underwent either a repeat PK or EK under PK, after failed PK, whose primary surgical indication was pseudophakic bullous keratopathy at a single tertiary center. Clinical data and donor and recipient characteristics were recorded from our prospective cohort from the Singapore Corneal Transplant Study. Main outcome measure was graft survival up to 5 years follow-up. RESULTS: We included a total of 113 eyes that underwent a repeat PK (n = 81) or EK under a failed PK (n = 32). Cumulative graft survival probabilities comparing repeat PK with EK under PK were at 91.9% vs 96.2% (1 year), 82.6% vs 91.6% (2 years), 66.8% vs 86.4% (3 years), and 51.3% vs 86.4% up to 5 years follow-up, respectively (log-rank P value = .013). Multivariate Cox regression analysis was performed, which adjusted for: age, sex, risk factors for graft failure (corneal neovascularization, ocular surface disease, glaucoma, active corneal inflammation, anterior synechiae), donor endothelial cell count, and repeat donor size. Repeat PK was a significant risk factor for graft failure compared to performing an EK under PK (hazard ratio: 10.17; 95% CI 1.10-93.63; P = .041). CONCLUSION: In our study of eyes with bullous keratopathy, endothelial keratoplasty under a previously failed PK provided better graft survival outcomes than repeat PK, adjusting for potential confounders and risk factors for graft failure.
    American Journal of Ophthalmology 08/2014; 158(6). DOI:10.1016/j.ajo.2014.08.024 · 4.02 Impact Factor
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    ABSTRACT: Endothelial keratoplasty has largely replaced penetrating keratoplasty as the preferred technique to selectively replace diseased corneal endothelium. Descemet’s stripping automated endothelial keratoplasty (DSAEK) is the most common type of endothelial keratoplasty performed worldwide. One of the challenges in DSAEK is the insertion of the donor lenticule into the eye using a method so as to minimize endothelial cell loss. Various techniques have been suggested such as forceps insertion and graft insertion devices. With the trend towards using thinner DSAEK tissue and Descemet membrane endothelial keratoplasty, there are increasing challenges in inserting and manipulating even more delicate tissue. The EndoGlide Ultrathin has several new features that will enable easier insertion of thinner DSAEK tissue. This paper presents the features and surgical technique of the EndoGlide Ultrathin during DSAEK.
    Expert Review of Medical Devices 08/2014; 11(6). DOI:10.1586/17434440.2014.947273 · 1.78 Impact Factor
  • Donald Tan, Hla M Htoon, Marcus Ang
    British Journal of Ophthalmology 07/2014; 98(10). DOI:10.1136/bjophthalmol-2014-305810 · 2.81 Impact Factor
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    ABSTRACT: Titanium (Ti) is a promising candidate biomaterial for an artificial corneal skirt. Antimicrobial peptide (AMP) immobilization could improve the bactericidal effect of the Ti substrate. In this study, we tested the bactericidal efficacy of a functionalized Ti surface in a rabbit keratitis model. A corneal stromal pocket was created by a femtosecond laser. The Ti films were then inserted into the pocket and staphylococcus aureus (S. aureus) or pseudomonas aeruginosa (P. aeruginosa) were inoculated into the pocket above the implant films. The corneas with Ti-AMP implants were compared with corneas implanted with unprotected Ti by slit lamp observation and anterior segment optical coherence tomography (AS-OCT). Inflammatory response was evaluated by bacteria counting, haematoxylin and eosin staining and immunostaining. There was a lower incidence and less extent of infection on rabbit corneas implanted with Ti-AMP than those corneas with unprotected Ti implants. The bactericidal effect of AMP against S.aureus was comparable to post-operative prophylactic antibiotic treatment hence SESB2V AMP bound to the Ti implant provided functional activity in vivo but its efficacy was superior against S.aureus compared to P.aeruginosa. This work suggests that SESB2V AMP can be successfully functionalized in a rabbit keratitis model to prevent perioperative corneal infection.
    Antimicrobial Agents and Chemotherapy 06/2014; 58(9). DOI:10.1128/AAC.02859-14 · 4.45 Impact Factor
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    ABSTRACT: PURPOSE: To evaluate the long-term corneal graft survival and risk factors for graft failure in pediatric eyes. DESIGN: Retrospective, interventional consecutive case series. METHODS: Unilateral eyes of 105 patients aged 16 years and below were included from the Singapore Corneal Transplant Study between April 4, 1991 and April 4, 2011. Corneal graft survival was calculated using Kaplan-Meier survival analysis, and survival distributions were compared using log-rank test. RESULTS: Mean recipient age was 8.38 +/- 5.63 years (range 0.18-15.92 years). Mean follow-up time was 34.16 +/- 39.10 months. Main diagnoses were corneal scar (22.9%), limbal dermoid (21.9%), anterior segment dysgenesis (15.2%), and keratoconus (14.3%). Forty-four eyes (41.9%) underwent penetrating keratoplasty (PK), 37 (35.2%) underwent anterior lamellar keratoplasty (ALK), 22 (21.0%) underwent lamellar corneal patch graft, and 2 (1.9%) underwent Descemet stripping automated endothelial keratoplasty (DSAEK). Kaplan-Meier survival rates for PK were 92.8% at 1 year, 88.9% at 2-4 years, and 80.9% at 5-16 years; survival rates for ALK were 88.0% at 1 year and 84.3% at 2-7 years; survival rates for corneal patch graft were 100% at 1-3 years and 90% at 4-10 years; these were not statistically significant (P = .362). Deep corneal vascularization (P = .012), preexisting active inflammation (P = .023), preexisting glaucoma drainage device (P = .023), and preexisting ocular surface disease (P = .037) were associated with reduced graft survival in a univariate analysis. CONCLUSIONS: We report good long-term graft survival following pediatric keratoplasty for various indications. Lamellar keratoplasty, when indicated, should be the procedure of choice in high-risk keratoplasties.
    American Journal of Ophthalmology 05/2014; 158(3). DOI:10.1016/j.ajo.2014.05.020 · 4.02 Impact Factor
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    ABSTRACT: Purpose: To compare flap adhesion strength, stromal bed quality and tissue responses after flap preparation using nJ- and µJ-energy level femtosecond lasers. Methods: All corneal flaps were created by either VisuMax laser (µJ energy level) or Femto LDV (nJ energy level). Flap adhesion strength in the rabbits was measured with a tension meter 1 and 2 months post-operatively. To investigate tissue responses to laser delivery, immunofluorescence staining and TUNEL assay were performed 4 and 24 hours post-operatively. To assess flap bed smoothness, human donor corneas were used. Surface irregularities were graded based on scanning electron microscopy (SEM) results. Results: The flap adhesion strength in VisuMax group at month 1 and 2 was 16.95 ± 1.45 kPa and 18.33 ± 1.81 kPa, respectively; and 12.31 ± 4.15 kPa and 13.85 ± 4.78 kPa in LDV group, respectively. No significant difference was found between the groups. Fibronectin and apoptotic cells were largely absent at the central incision site in LDV group, but were present in VisuMax group. The smoothness of flap beds appeared similar for both groups. An observer scored VisuMax group 8.00 ± 1.00 and LDV group 7.33 ± 0.58 (p=0.387). Conclusions: The flap adhesion strength increased over time after treatment with both lasers. The nJ-energy pulses produced minimal wound healing reaction and apoptotic cells along the incision plane. The application of nJ-energy laser, which can incise the cornea without inducing significant damage to cells and wound healing reaction, offers great potential at reducing scarring following incisional laser stromal surgery.
    Investigative ophthalmology & visual science 04/2014; 55(5). DOI:10.1167/iovs.14-14434 · 3.66 Impact Factor
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    ABSTRACT: To describe outcomes and complications following Descemet's stripping automated endothelial keratoplasty (DSAEK) in eyes with pseudophakic bullous keratopathy (BK) while retaining the anterior chamber intraocular lenses (ACIOL). We included consecutive patients who underwent DSAEK for BK at a single tertiary centre from 1 January 2008 to 1 April 2010, from our prospective cohort (Singapore Corneal Transplant Study). We compared eyes with BK, which underwent DSAEK while retaining ACIOL (n=18), to those with DSAEK alone with the posterior chamber intraocular lenses left in place as a comparison group (n=114). Main outcome measures were endothelial cell (EC) loss and graft survival. The percentage EC loss at 1 year was 31.9±21.3% in the DSAEK with ACIOL group compared to 24.5±21.2% in the DSAEK group (p=0.516); however, this figure was significantly greater in the DSAEK with ACIOL group at 3 years compared to the DSAEK group (55.3±29.2% vs 33.3±20.8%; p=0.01 respectively). Graft survival was also significantly poorer in the DSAEK ACIOL group compared to the DSAEK group over 3 years (log rank p=0.002). We found that although eyes with BK and ACIOL that underwent DSAEK while retaining the ACIOL suffered EC loss which was not significantly greater at 1 year, EC loss and graft survival were significantly poorer compared to DSAEK controls at 3 years postoperatively.
    The British journal of ophthalmology 03/2014; 98(8). DOI:10.1136/bjophthalmol-2013-304622 · 2.81 Impact Factor
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    ABSTRACT: Anterior chamber depth (ACD) is a key anatomical risk factor for primary angle closure glaucoma (PACG). We conducted a genome-wide association study (GWAS) on ACD to discover novel genes for PACG on a total of 5,308 population-based individuals of Asian descent. Genome-wide significant association was observed at a sequence variant within ABCC5 (rs1401999; per-allele effect size = -0.045 mm, P = 8.17×10-9). This locus was associated with an increase in risk of PACG in a separate case-control study of 4,276 PACG cases and 18,801 controls (per-allele OR = 1.13 [95% CI: 1.06-1.22], P = 0.00046). The association was strengthened when a sub-group of controls with open angles were included in the analysis (per-allele OR = 1.30, P = 7.45×10-9; 3,458 cases vs. 3,831 controls). Our findings suggest that the increase in PACG risk could in part be mediated by genetic sequence variants influencing anterior chamber dimensions.
    PLoS Genetics 03/2014; 10(3):e1004089. DOI:10.1371/journal.pgen.1004089 · 8.17 Impact Factor
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    ABSTRACT: To compare 3-year endothelial cell loss and graft survival following Descemet stripping automated endothelial keratoplasty (DSAEK) using the EndoGlide (AngioTech, Reading, Pennsylvania, USA/Network Medical Products, North Yorkshire, UK) donor insertion device compared to donor insertion using the sheets glide technique. Retrospective comparative case series METHODS: Consecutive patients who underwent DSAEK with Fuchs endothelial dystrophy or pseudophakic bullous keratopathy at a single tertiary center. Clinical data with outcomes, donor and recipient characteristics were obtained from our ongoing prospective cohort from the Singapore Corneal Transplant Study. Main outcome measures were percent endothelial cell loss and graft survival up to 3 years. Overall percent endothelial cell loss was significantly lower in the EndoGlide group (100 eyes) compared to Sheets glide group (119 eyes) at 1 year (16.3±16.6% vs. 29.5±22.2%, P<0.001), 2 years (23.8±17.8% vs. 35.7±22.9%, P=0.001); and at 3 years (29.7±20.9% vs. 38.5±24.1%, P=0.015) post-operatively. Overall graft survival was greater in the EndoGlide compared to Sheets glide group up to 3 years (97.9% vs. 86.5%, log-rank P value=0.005). In eyes with Fuchs endothelial dystrophy, endothelial cell loss was significantly lower in the EndoGlide group (3-year: 28.2±17.9% vs. 43.4±27.1%, P=0.032). In eyes with pseudophakic bullous keratopathy, the EndoGlide group had a superior graft survival compared to Sheets glide (log-rank P=0.031). Endothelial cell loss was lower using a donor insertion device during DSAEK, compared to using the sheets glide technique for DSAEK in Asian eyes with Fuchs endothelial dystrophy, and resulted in better graft survival in eyes with pseudophakic bullous keratopathy.
    American Journal of Ophthalmology 02/2014; 157(6). DOI:10.1016/j.ajo.2014.02.049 · 4.02 Impact Factor
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    ABSTRACT: Purpose: To compare early corneal nerve changes after SMILE (small incision lenticule extraction) and LASIK (laser in situ keratomileusis). Methods: Twelve rabbits underwent LASIK in one eye and SMILE in fellow eye. Baseline and follow-up evaluations at 1, 2 and 4 weeks post-operatively were performed with in vivo confocal microscopy to evaluate 5 different areas within the treated zone: center, superior, inferior, nasal and temporal. Cryosections of the corneas and whole mount of the extracted SMILE lenticules were analyzed with immunostaining of βIII-tubulin. Results: One week post-SMILE and -LASIK, a decrease in nerve length and density was observed in all evaluated areas. A trend towards greater sub-basal nerve length and density (SLD), more eyes with sub-basal nerves (ESN), more eyes with sub-basal nerves longer than 200µm (SNL), and higher mean number of sub-basal nerves by frame (NSN) in SMILE than in LASIK groups was observed at subsequent follow-up time points. Only the SMILE group showed a recovery of SLD, ESN and NSN by week 4 (P>0.05). A trend towards more eyes with sprouting sub-basal nerves and greater mean number of sprouting nerves was observed in LASIK than in SMILE, indicating that more sub-basal nerves were disrupted and undergoing regeneration after LASIK. Immunostaining at post-operative week 4 revealed a faster stromal nerve recovery in post-SMILE eyes compared to post-LASIK eyes. Conclusions: Our findings suggest that SMILE results in less nerve damage and faster nerve recovery than LASIK.
    Investigative ophthalmology & visual science 02/2014; 55(3). DOI:10.1167/iovs.13-13324 · 3.66 Impact Factor

Publication Stats

6k Citations
1,175.13 Total Impact Points

Institutions

  • 2001–2015
    • Singapore Eye Research Institute
      Tumasik, Singapore
    • University of Wisconsin–Madison
      • Department of Ophthalmology and Visual Sciences
      Madison, Wisconsin, United States
  • 1999–2015
    • Singapore National Eye Centre
      Tumasik, Singapore
    • Bascom Palmer Eye Institute
      Miami, Florida, United States
  • 2014
    • Nanyang Technological University
      Tumasik, Singapore
  • 2013–2014
    • Duke University
      Durham, North Carolina, United States
  • 2012–2014
    • National University Health System
      Singapore
  • 2011–2014
    • Duke-NUS Graduate Medical School Singapore
      Tumasik, Singapore
  • 2007–2011
    • National University of Singapore
      • • Singapore Eye Research Institute
      • • Department of Ophthalmology
      Tumasik, Singapore
    • University of Melbourne
      Melbourne, Victoria, Australia
    • Tianjin Medical University
      T’ien-ching-shih, Tianjin Shi, China
  • 2001–2007
    • William Penn University
      Filadelfia, Pennsylvania, United States
  • 2006
    • Tianjin Eye Hospital
      T’ien-ching-shih, Tianjin Shi, China
    • Tan Tock Seng Hospital
      Tumasik, Singapore
    • Moorfields Eye Hospital NHS Foundation Trust
      Londinium, England, United Kingdom
    • University of Alberta
      • Department of Biochemistry
      Edmonton, Alberta, Canada