Anna M Tan

National University Health System, Singapore

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Publications (5)11.47 Total impact

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    ABSTRACT: Background The aim of this study was to compare the efficacy and safety of micropulse and continuous-wave diode trans-scleral cyclophotocoagulation in refractory glaucoma.DesignRandomised, comparative, exploratory study in a tertiary hospital settingParticipantsPatients with refractory, end-stage glaucomaMethods48 patients were randomised to either treatment. The intraocular pressure, visual acuity, number of medicines and repeat treatment were monitored for 18 months. Complications that include visual acuity decline, prolonged anterior chamber inflammation, phthisis bulbi, scleral thinning and ocular pain were noted.Main Outcome MeasureIntraocular pressure between 6–21mmHg and at least a 30% reduction with or without anti-glaucoma medications after 18 months.ResultsA successful primary outcome was achieved in 75% of patients who underwent micropulse cyclophotocoagulation and 29% of patients who received continuous wave cyclophotocoagulation after 12 months (p<0.01). At 18 months, successful outcome was 52% and 30% (p=0.13) respectively. The mean intraocular pressure was reduced by 45% in both groups (p=0.70) from a baseline of 36.5 mmHg and 35.0 mmHg (p=0.50) after 17.5 ± 1.6 months (range 16-19) follow-up. No significant difference in retreatment rates or number of intraocular pressure lowering medications was noted. The ocular complication rate was higher in continuous wave treated eyes (p=0.01).Conclusion Diode trans-scleral cyclophotocoagulation in both micropulse and continuous modes was effective in lowering intraocular pressure. The micropulse mode provided a more consistent and predictable effect in lowering intraocular pressure with minimal ocular complications.
    Clinical and Experimental Ophthalmology 05/2014; 43(1). DOI:10.1111/ceo.12360 · 2.35 Impact Factor
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    ABSTRACT: Background: To evaluate different mechanisms of primary angle closure and to quantify anterior chamber parameters in these mechanisms using anterior segment optical coherence tomography in an Asian population. Design: Hospital-based cross-sectional observational study. Participants: Forty-eight consecutive patients with primary angle closure glaucoma. Methods: Patients underwent complete ophthalmic examination and imaging of nasal-temporal angles with anterior segment optical coherence tomography. Images were categorized into four primary angle closure mechanisms: pupil block, plateau iris configuration, Thick peripheral iris roll and exaggerated lens vault. Parameters computed: anterior chamber depth central, anterior chamber depth at 1000 µm and 2000 µm anterior to scleral spur, lens vault, anterior chamber area, angle opening distance, trabecular iris space area and iris thickness. Main Outcome Measure: Anterior chamber parameters and primary angle closure mechanisms. Results: Mean values of anterior chamber depths: central (P < 0.001), at 2000 µm (P < 0.001), 1000 µm (P < 0.001), lens vault (P < 0.001), anterior chamber area (P < 0.001), were significantly different among the four groups. Multivariate analysis showed anterior chamber depths: central, and anterior chamber depth at 2000 µm and anterior chamber area were higher in plateau iris and Thick peripheral iris roll and lower in exaggerated lens vault (P < 0.001) as compared to pupil block mechanism, lens vault was greater in exaggerated lens vault (P < 0.001) and lesser in plateau iris and Thick peripheral iris roll as compared to pupil block mechanism. Conclusion: Anterior segment optical coherence tomography may be used for evaluation of underlying primary angle closure mechanism(s) in a patient and tailor the treatment accordingly.
    Clinical and Experimental Ophthalmology 05/2012; 40(8). DOI:10.1111/j.1442-9071.2012.02805.x · 2.35 Impact Factor
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    ABSTRACT: AIMS/PURPOSE: To determine and correlate the long-term changes in retinal nerve fibre layer (RNFL) thickness, optic nerve head (ONH) morphology, and visual fields after a single episode of acute primary angle closure (APAC). This was a cross-sectional comparative study of patients at National University Hospital (Singapore) from 2000 to 2006 after an episode of unilateral APAC. The peripapillary and macular RNFL were measured using Stratus optical coherence tomography (OCT) and ONH configuration was assessed using Heidelberg Retina Tomography (HRT)-III. Humphrey perimetry was also performed, and the presence of disc pallor was noted. APAC eyes were compared with fellow eyes as matched controls. Twenty-five patients were assessed at a median of 33 months (range, 11-85 months) after APAC. OCT showed that there was a reduction in the peripapillary and outer macular RNFL thickness in APAC eyes compared with controls. Humphrey perimetry revealed significantly reduced mean deviation (P=0.006) and increased pattern standard deviation (P=0.045) in APAC eyes compared with controls. HRT-III showed no difference in mean rim area, rim volume, or cup-disc ratio between APAC eyes and controls. Disc pallor was present in nine APAC eyes (36%) but was absent in fellow eyes (P=0.002), and was associated with peripapillary RNFL thinning, visual field loss, and an increased interval between the onset of symptoms and normalization of intraocular pressure (P=0.023). APAC results in peripapillary and outer macular RNFL loss, visual field defects, and optic disc pallor, even in cases in which the ONH configuration remains unchanged.
    Eye (London, England) 03/2011; 25(5):619-25. DOI:10.1038/eye.2011.31 · 2.08 Impact Factor
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    ABSTRACT: Transscleral diode laser cyclophotocoagulation (TSCPC) is an established method of treatment for refractory glaucoma, but is associated with significant complications. This study evaluates the efficacy and safety of a new form of TSCPC using micropulse diode laser and trans-pars plana treatment with a novel contact probe. Prospective interventional case series of 40 eyes of 38 consecutive patients with refractory glaucoma treated with micropulse TSCPC with a novel probe. Outcomes measured were success, hypotony and response rates. The mean age of patients was 63.2 +/- 16.0 years. The mean follow-up period was 16.3 +/- 4.5 months. The mean intraocular pressure (IOP) before micropulse TSCPC was 39.3 +/- 12.6 mmHg. Mean IOP decreased to 31.1 +/- 13.4 mmHg at 1 day, 28.0 +/- 12.0 mmHg at 1 week, 27.4 +/- 12.7 mmHg at 1 month, 27.1 +/- 13.6 mmHg at 3 months, 25.8 +/- 14.5 mmHg at 6 months, 26.6 +/- 14.7 mmHg at 12 months and 26.2 +/- 14.3 mmHg at 18 months (P < 0.001 at all time points). No patient had hypotony or loss of best-corrected visual acuity. The overall success rate after a mean of 1.3 treatment sessions was 72.7%. Micropulse TSCPC is a safe and effective method of lowering IOP in cases of refractory glaucoma and is comparable with conventional TSCPC.
    Clinical and Experimental Ophthalmology 04/2010; 38(3):266-72. DOI:10.1111/j.1442-9071.2010.02238.x · 2.35 Impact Factor
  • Anna M Tan · Seng C Loon · Paul T K Chew ·
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    ABSTRACT: Data regarding development of primary angle closure glaucoma (PACG) following acute primary angle closure (APAC) is conflicting. This study looks at outcomes after an APAC episode with a secondary aim to identify any risk factors that could predict progression to PACG. This is a retrospective review of the charts of consecutive patients who were diagnosed with APAC from December 2003 to June 2006. All were treated in a standard manner with initial intensive medical therapy or laser iridoplasty followed by early laser peripheral iridotomy within 24 h of presentation. Forty-two eyes of 41 patients were analysed. The mean follow-up period was 27.3 +/- 16.2 months. Nine eyes (21.4%) developed an increase in intraocular pressure (IOP) within a mean of 11.9 months (median 5 months) after resolution of APAC. Eight eyes went on to have trabeculectomy or glaucoma drainage device. At final follow up, the mean IOP of attack eye was 13.3 +/- 2.92 mmHg. None of the eyes, including those that underwent surgery, required topical medication to control IOP. Thirty-eight eyes (90.5%) have BCVA of 6/6 to 6/12. The duration of symptoms before presentation (P = 0.00) and duration taken to abort the acute attack (P = 0.01) were found to be significantly associated with development of PACG. The results of this study suggest that outcomes following successful treatment of APAC may not be as poor as described previously. Early aggressive management of the acute episode may have a role to play in preventing development of PACG after APAC.
    Clinical and Experimental Ophthalmology 08/2009; 37(5):467-72. DOI:10.1111/j.1442-9071.2009.02060.x · 2.35 Impact Factor

Publication Stats

45 Citations
11.47 Total Impact Points


  • 2009-2014
    • National University Health System