National Healthcare Group Eye Institute

Singapore, Singapore

National Healthcare Group Eye Institute

Singapore, Singapore
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Singer M.,Medical Center Ophthalmology | Tan C.S.,Tan Tock Seng Hospital | Tan C.S.,National Healthcare Group Eye Institute | Tan C.S.,Doheny Eye Institute | And 2 more authors.
Retina | Year: 2014

PURPOSE:: To evaluate the extent of peripheral retinal nonperfusion in retinal vein occlusion and to determine its effect on the severity of macular edema and response to treatment. METHODS:: This prospective clinic-based cohort study included 32 consecutive patients with retinal vein occlusion and refractory macular edema evaluated using spectral domain optical coherence tomography and wide-field fluorescein angiography. Areas of ischemia were calculated as a percentage of the total visible retina (ischemic index), which was evaluated when macular edema was present (foveal central subfield >300 μm) and when edema had resolved (foveal central subfield ≤300 μm). Ischemic index was the main outcome measure. RESULTS:: The mean ischemic index at study enrollment was 14.8% and was larger when macular edema was present compared with when edema had resolved (14.8 vs. 10.3%, P < 0.001). Compared with those with less nonperfusion, patients with ischemic index >10% had thicker mean foveal central subfield on optical coherence tomography (520.8 vs. 424.5 μm, P = 0.029) and worse visual acuity (56.3 vs. 59 letters) with the presence of macular edema and experienced greater decrease in optical coherence tomography (296.1 vs. 165.3 μm, P = 0.019) and gain in visual acuity (12.4 vs. 0.9 letters, P = 0.036) in response to treatment. CONCLUSION:: The area of peripheral retinal nonperfusion is variable in patients with retinal vein occlusion and affects its clinical course and response to treatment. Copyright © by Ophthalmic Communications Society, Inc.


Heussen F.M.,Doheny Eye Institute | Heussen F.M.,Charité - Medical University of Berlin | Tan C.S.,Doheny Eye Institute | Tan C.S.,National Healthcare Group Eye Institute | And 2 more authors.
Investigative Ophthalmology and Visual Science | Year: 2012

Purpose. To assess the prevalence of peripheral fundus autofluorescence (FAF) abnormalities in a variety of diseases seen at a tertiary retina clinic. Methods. We conducted a retrospective review of cases seen at the Doheny Eye Institute between November 2009 and May 2011, who had ultra-widefield FAF and pseudocolor imaging performed on new models of scanning laser ophthalmoscopes. Patients with a history of previous therapies that could alter the FAF findings, including vitrectomy, cryotherapy, laser photocoagulation, or photodynamic therapy, were excluded from the analysis. Based on their primary diagnosis the eyes were grouped into nine disease categories: age-related macular degeneration, central serous retinopathy, dystrophy, inflammatory disorders, ocular tumor, retinal vascular disorders, other, normal, and unknown. All FAF and accompanying pseudocolor images were reviewed independently by two reading center-certified graders. Results. A total of 470 eyes of 248 patients were included for analysis of which 461 eyes had images of sufficient quality for grading. The prevalence of peripheral findings was 65.5% (n = 302) for FAF images and 68.5% (n = 316) for the pseudocolor images (P < 0.001). The prevalence of peripheral abnormalities differed significantly between the disease categories ranging from 18.5% to 82.2% for FAF and 18.5% to 82.4% for pseudocolor images. Conclusions. Peripheral FAF abnormalities are frequent and readily revealed by FAF imaging. Interestingly, even cases with presumably macular disease demonstrated a high prevalence of peripheral findings. Further investigation in prospective studies is warranted. © 2012 The Association for Research in Vision and Ophthalmology, Inc.


Tan C.S.H.,Tan Tock Seng Hospital | Tan C.S.H.,National Healthcare Group Eye Institute | Ngo W.K.,Tan Tock Seng Hospital | Cheong K.X.,Tan Tock Seng Hospital
British Journal of Ophthalmology | Year: 2015

Background/aims: Choroidal thickness measurements are reported to differ between swept source optical coherence tomography (SS-OCT) and spectral domain OCT (SD-OCT). This study aimed to assess the comparability of choroidal thickness measurements using SS-OCT and SD-OCT devices among patients with retinal diseases and normal participants. Methods: In a prospective cohort study of 100 subjects, comprising patients with retinal disease and normal volunteers, OCT scans were performed sequentially with the DRI OCT-1 and Spectralis OCT using standardised imaging protocols. Subfoveal choroidal thicknesses were independently measured by masked reading-centre certified graders. Paired t tests and intraclass correlation coefficients (ICCs) were used to compare the measurements. Results: Among all 100 participants, mean subfoveal choroidal thickness was 264.3 μm and 272.4 μm for DRI OCT-1 and Spectralis OCT respectively (p=0.001), with ICC of 0.989. The mean difference in choroidal thickness between OCT devices was larger among eyes with retinal diseases compared with normal eyes (8.4 μm vs 7.3 μm). Eyes with choroidal thickness ≤200 μm had smaller differences between OCT devices compared with those with thicker choroids (mean 3.6 μm vs 10.0 μm, p=0.021). Conclusions: Subfoveal choroidal thickness measurements are comparable between DRI OCT-1 and Spectralis OCT. The presence of retinal disease increases the variability of choroidal thickness measurements between OCT devices.


Tan C.S.H.,National Healthcare Group Eye Institute | Tan C.S.H.,Tan Tock Seng Hospital | Li K.Z.,National Healthcare Group Eye Institute | Lim T.H.,National Healthcare Group Eye Institute | Lim T.H.,Tan Tock Seng Hospital
Investigative Ophthalmology and Visual Science | Year: 2012

Purpose. The quantitative assessment of retinal thickness and volume varies according to the optical coherence tomography (OCT) machine used due to differences in segmentation lines. We describe a novel method of adjusting the segmentation lines of spectral-domain OCT (SD-OCT) to enable comparison with time-domain OCT (TD-OCT), and assess factors affecting its accuracy. Methods. In a prospective study, SD-OCT (Spectralis OCT) and TD-OCT (Stratus OCT) were sequentially performed on 200 eyes of 100 healthy individuals. Central retinal thickness (CRT), central point thickness (CPT), and 1-mm volume of the Early Treatment Diabetic Retinopathy Study grid were compared between the two machines. The segmentation lines on SD-OCT were manually adjusted by a trained operator and the parameters compared again with TD-OCT. Results. The mean CRTs of Spectralis and Stratus were significantly different (268.2 μm vs. 193.9 μm, P < 0.001). After adjustment of segmentation lines, the mean adjusted Spectralis CRT was 197.3 μm, with the difference between SD-OCT and TD-OCT measurements decreasing from 74.3 μm to 3.4 μm (P < 0.001). The difference between the adjusted Spectralis and Stratus CRTs was smallest for high myopes (≤ -6.0 diopters [D]) compared with those with moderate and low myopia (1.5 μm vs. 3.5 μm and 4.6 μm, respectively; P < 0.001). Similar trends were obtained for central 1-mm volumes and CPT. Interoperator and intraoperator repeatability for adjustment of the segmentation lines were good, with an intraclass correlation of 0.99 for both. Conclusions. Manual adjustment of SD-OCT segmentation lines reliably achieves retinal thickness and volume measurements that are comparable to that of TD-OCT. This is valuable to allow comparisons in multicenter clinical trials where different OCT machines may be used. © 2012 The Association for Research in Vision and Ophthalmology, Inc.


Tan C.S.,Doheny Eye Institute | Tan C.S.,National Healthcare Group Eye Institute | Tan C.S.,Tan Tock Seng Hospital | Ouyang Y.,Doheny Eye Institute | And 2 more authors.
Investigative Ophthalmology and Visual Science | Year: 2012

PURPOSE. To describe the pattern and magnitude of diurnal variation of choroidal thickness (CT), its relation to systemic and ocular factors, and to determine the intervisit reproducibility of diurnal patterns. METHODS. A prospective study was conducted on 12 healthy volunteers who each underwent sequential ocular imaging on two separate days at five fixed, 2-hour time intervals. Spectral domain optical coherence tomography (OCT) with enhanced depth imaging and image tracking was performed using a standardized protocol. Choroidal and retinal thicknesses were independently assessed by two masked graders. CT diurnal variation was assessed using repeated-measures ANOVA. RESULTS. A significant diurnal variation in CT was observed, with mean maximum CT of 372.2 μm, minimum of 340.6 μm (P < 0.001), and mean diurnal amplitude of 33.7 μm. Retinal thickness (mean, 235.0 μm) did not exhibit significant diurnal variation (P = 0.621). The amplitude of CT variation was significantly greater for subjects with thicker morning baseline CT compared with those with thin choroids (43.1 vs. 10.5 μm, P < 0.001). There were significant correlations between amplitude of CT and age (P = 0.032), axial length (P < 0.001), and spherical equivalent (P < 0.001). The change in CT also correlated with change in systolic blood pressure (P = 0.031). Comparing CT on two different days, a similar diurnal pattern was observed, with no significant difference between corresponding measurements at the same time points (P = 0.180). CONCLUSIONS. There is significant diurnal variation of CT, with good intervisit reproducibility of diurnal patterns on two different days. The amplitude of variation varies with morning baseline CT, and is correlated with age, axial length, refractive error, and change in systolic blood pressure. © 2012 The Association for Research in Vision and Ophthalmology, Inc.


Tan C.S.H.,Tan Tock Seng Hospital | Tan C.S.H.,National Healthcare Group Eye Institute | Cheong K.X.,Tan Tock Seng Hospital
Investigative Ophthalmology and Visual Science | Year: 2014

PURPOSE: To determine the differences in choroidal thickness (CT) among different groups of refractive errors and axial lengths, and to describe the rates of change of CT with ocular and demographic factors in various regions of the macula.METHODS: Prospective cohort study of 150 healthy volunteers. Spectral-domain optical coherence tomography was performed on both eyes using a standardized imaging protocol. Manual grading of the choroidal boundaries was independently performed by trained graders to determine Early Treatment Diabetic Retinopathy Study (ETDRS) subfield choroidal thickness. Multiple linear regression analyses were performed to determine the effects of spherical equivalent, axial length and age on choroidal thickness in each subfield.RESULTS: The mean central subfield CT was 324.9 μm (range, 123-566 μm) and varied significantly with both spherical equivalent (P < 0.001) and axial length (P < 0.001), but not age or sex. On multiple linear regression analysis using spherical equivalent, the coefficients were 20.0 for the central subfield, ranged from 16.9 to 19.9 for the inner subfields, and decreased to 13.9 to 16.2 for the outer subfields. Performing regression analysis using axial length, the coefficients were -36.4 for the central subfield, -30.5 to -34.5 for the inner subfields, and -24.6 to -27.3 for the outer subfields.CONCLUSIONS: Choroidal thickness varies significantly with spherical equivalent and axial length in all regions of the macula, but exhibits different rates of change among different subfields. The rates of change were greater in the central and inner subfields compared with the outer subfields. © 2014 The Association for Research in Vision and Ophthalmology, Inc.


Tan C.S.H.,Tan Tock Seng Hospital | Tan C.S.H.,National Healthcare Group Eye Institute | Cheong K.X.,Tan Tock Seng Hospital | Lim L.W.,Tan Tock Seng Hospital | Li K.Z.,Tan Tock Seng Hospital
British Journal of Ophthalmology | Year: 2014

Background/aims: To determine the topographic variation of macular choroidal and retinal thicknesses (RTs) in normal eyes and their relationship with refractive error. Methods: Spectral domain optical coherence tomography with enhanced depth imaging was performed on 124 healthy participants using a standardised imaging protocol. Manual segmentation of choroidal boundaries was performed by trained graders, and mean choroidal thickness (CT) was compared with mean RT in corresponding sectors of the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. Results: Mean central subfield CT was 322.2 μm. The choroid was thickest at the temporal and superior sectors (323.1-338.1 μm), followed by inferior sectors (314.0-321.8 μm), and thinnest at the nasal sectors (232.8-287.8 μm). In contrast, the retina was thicker nasally (343.4 μm) and thinner temporally (287.1 μm). CT was thickest among emmetropes in all ETDRS subfields and became thinner progressively among low, moderate and high myopes ( p<0.001). The variation of both choroidal and RTs among refractive error groups resulted in different topographic patterns at the macula. Conclusion There is significant topographic variation of choroidal and RTs at different regions of the macula, with progressive change of choroidal thickness in all sectors based on the refractive status of the eye.


Tan C.S.H.,Tan Tock Seng Hospital | Tan C.S.H.,National Healthcare Group Eye Institute | Ngo W.K.,Tan Tock Seng Hospital | Lim L.W.,Tan Tock Seng Hospital | And 2 more authors.
British Journal of Ophthalmology | Year: 2014

Purpose: To propose a novel classification system for polypoidal choroidal vasculopathy (PCV), and compare the clinical outcomes among PCV subtypes. Methods: Consecutive treatment-naive patients with symptomatic PCV were managed over 5 years. PCV subtypes were classified based on indocyanine green angiography (ICGA) and fluorescein angiography (FA) characteristics. Results: Among 107 patients, 3 PCV subtypes were seen: Type A (interconnecting channels on ICGA) -22.4%; Type B (branching vascular network with no leakage) -24.3%; Type C (branching vascular network with late leakage on FA) -53.3%. The proportion of patients with bestcorrected visual acuity (BCVA) ≥20/40 was highest in Type A, intermediate in Type B and lowest in Type C at all time points (80% vs 66.7% vs 7.7% at 5 years, p<0.001). The highest rate of moderate visual loss (loss of ≥ 3 lines) occurred in Type C PCV (57.7% vs 0% for Types B and A at 5 years, p<0.001). Risk factors for poor visual outcomes were PCV subtype (OR 53.7, p<0.001 for Type C and OR 13.7, p=0.023 for Type B compared to Type A) and age (OR 1.06, 95% CI 1.002 to 1.125, p=0.044). Conclusions: The PCV subtype seen on initial presentation affects the long-term visual outcomes over a 5-year period.


Tan C.S.,Doheny Eye Institute | Tan C.S.,Tan Tock Seng Hospital | Tan C.S.,National Healthcare Group Eye Institute | Heussen F.,Doheny Eye Institute | Sadda S.R.,Doheny Eye Institute
Ophthalmology | Year: 2013

Purpose: To characterize peripheral fundus autofluorescence (FAF) abnormalities in patients with age-related macular degeneration (AMD), correlate these with clinical findings, and identify risk factors associated with these FAF abnormalities. Design: Clinic-based, cross-sectional study. Participants: A total of 119 consecutive patients: 100 patients with AMD (200 eyes) and 19 patients without AMD (38 eyes). Methods: In a prospective study performed at the Doheny Eye Institute, University of Southern California, widefield 200-degree FAF and color images were obtained by the Optos 200Tx Ultra-Widefield device (Optos, Dunfermline, Scotland) using a standardized imaging protocol. The FAF images were captured centered on the fovea, and additional images were captured after steering the field of view inferiorly and superiorly. All FAF and color images were graded independently by 2 masked ophthalmologists with respect to the presence, location, extent, and type of peripheral (defined as outside the central 30 degrees) FAF abnormality. Main Outcome Measures: Presence and type of peripheral FAF abnormalities. Results: Peripheral FAF abnormalities were evident in 164 eyes (68.9%), with several distinct FAF patterns identified: granular (46.2%), mottled (34.0%), and nummular (18.1%). A 90% concordance of FAF patterns was observed between both eyes. Abnormal FAF occurred more frequently in neovascular compared with non-neovascular AMD or normal eyes (86% vs. 72.8% vs. 18.4%, respectively, P<0.001). Significant risk factors for peripheral FAF abnormalities were AMD type (neovascular AMD odds ratio [OR], 12.7 and non-neovascular AMD OR, 6.2 compared with normal eyes, P<0.001), older age (OR, 6.5; 95% confidence interval [CI], 2.4-17.8; P<0.001 for the oldest quartile compared with the youngest), and female sex (OR, 4.1; 95% CI, 1.9-8.9; P<0.001). Clinical features on color photography were detected in 174 eyes (73.1%): peripheral drusen (51.7%), retinal pigment epithelium (RPE) depigmentation (34.9%), RPE hyperpigmentation (branching reticular pigmentation) (22.7%), and atrophic patches (16.8%). There was a high correlation between specific FAF and clinical findings: granular FAF with peripheral drusen (P<0.001) and mottled FAF with RPE depigmentation (P<0.001). Conclusions: Several distinct patterns of peripheral FAF abnormalities were observed in 68.9% of patients, with AMD type, female sex, and age being independent risk factors. The peripheral FAF patterns correlate strongly with specific clinical features seen in eyes with AMD. Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references. © 2013 American Academy of Ophthalmology.


Tan C.S.,Tan Tock Seng Hospital | Tan C.S.,National Healthcare Group Eye Institute | Chew M.C.,Tan Tock Seng Hospital | Lim T.H.,Tan Tock Seng Hospital | Lim T.H.,National Healthcare Group Eye Institute
Eye (Basingstoke) | Year: 2014

PurposeTo evaluate the visual outcomes of choroidal neovascularization (CNV) secondary to pathological myopia in eyes treated with photodynamic therapy (PDT), and to determine the effect of lesion location and foveal involvement on visual prognosis.MethodsInterventional case series of 24 consecutive patients with myopic CNV treated with PDT. The main outcome measure was final LogMAR visual acuity (VA).ResultsOf 24 eyes, the CNV lesion was subfoveal in 11 and extrafoveal in 13. Overall, the mean LogMAR VA at 24 months was 0.72. Extrafoveal CNV lesions achieved significantly better final VA compared with subfoveal CNV (LogMAR 0.45 vs 1.05, P=0.012). Eyes with extrafoveal CNV lesions were subdivided into foveal-sparing PDT (where the PDT laser spot did not involve the foveal center) and foveal-involved PDT (where the PDT laser covered the fovea). At all time points, the group with foveal-sparing PDT had significantly better VA compared with the foveal-involved group. The final LogMAR VA for the foveal-sparing PDT group was 0.26 compared with 1.00 for the foveal-involved PDT group (P=0.003). At 24 months, 77.8% of foveal-sparing PDT cases achieved VA of ≥20/40, compared with 25% of foveal-involved PDT cases and 9.1% of subfoveal CNV lesions (P=0.006).ConclusionFor patients with myopic CNV, foveal-sparing PDT results in significantly better long-term visual outcomes compared with those with foveal-involved PDT. Foveal-sparing PDT may be of value for treatment of myopic CNV patients who are not suitable for treatment with anti-vascular endothelial growth factor injections. © 2014 Macmillan Publishers Limited All rights reserved.

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